Effect of non-metallic doping on the electronic structure of GaS monolayers and mercury adsorption performance

Effect of non-metallic doping on the electronic structure of GaS monolayers and mercury adsorption performance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of non-metallic doping on the electronic structure of GaS monolayers and mercury adsorption performance Zilian Tian, Lu Yang, Xiaotong Yang, Hang Yang, Yao Dong, Wei Zhao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6183020/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study systematically explores the optical properties of non-metallic doped single-layer GaS materials and their performance in mercury adsorption. Using first-principles calculations, the effects of different doping elements (including C, N, O, Si.) on the optical properties of GaS were investigated, with a focus on the regulatory effects of doping on the material's dielectric function, absorbance, reflectivity, and energy loss function. The results demonstrate that the doping elements induce substantial changes in the electronic structure and optical response of GaS. Notably, the Ga-doped Si system displays pronounced polarization response and light absorption capability in the low-energy region, resulting in a shift towards longer wavelengths in its absorption spectrum. The reflectivity of different doping systems in the low-energy and high-energy regions also exhibits divergent trends. Doping with elements such as Si and C shifts the absorption peak to lower energies, narrows the band gap, and enhances the material's absorption of low-energy light. In addition, energy loss function analysis elucidates the contribution of doped elements to the stability of the electronic structure in the low-energy region. The Ga-site doped N and S-site doped O systems demonstrate exceptional electronic stability. In conclusion, the findings of this study demonstrate that doping regulates the optical and electronic properties of GaS materials, thus providing novel optimisation strategies for applications such as optoelectronic devices, solar cells, and sensors. Through in-depth analysis of this study, we provide a theoretical basis for designing efficient optoelectronic materials and lay the foundation for applied research in related fields. GaS material non-metallic doping electronic structure optical properties Hg adsorption Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction Since the Industrial Revolution, with the rapid development of human society and the economy, environmental pollution problems have become increasingly severe, especially water pollution. As a key resource for maintaining human survival and development, water is threatened by various harmful substances. Among these, heavy metal ions such as mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As) have been identified as particularly problematic. These substances cause significant deterioration in water quality and accumulate in the food chain through biological absorption and enrichment, posing a serious threat to human health. Mercury, in particular, has been shown to cause significant damage to the nervous and immune systems and to pose a risk of cancer. This underscores the pressing need to develop effective adsorbent materials to remove heavy metal ions, particularly mercury, from water to address the pressing issue of water pollution [ 1 – 4 ]. In recent years, graphene has been the focus of extensive research due to its remarkable physical and chemical properties. Its high specific surface area and excellent adsorption capabilities have led to significant advancements in various fields, including adsorption [ 5 – 7 ]. The advent of graphene has prompted researchers to explore the domain of two-dimensional materials to achieve technological breakthroughs in developing novel materials [ 8 – 13 ]. Two-dimensional materials have attracted significant attention in environmental protection and energy research due to their layered structure and distinctive physicochemical properties. In a study by Yang et al. [ 14 ], it was observed that magnesium-rich zeolite exhibited a notable adsorption capacity for Pb and Cd. In contrast, its adsorption capability for Sb and Hg was less effective. Electronic structure analysis indicates that the aluminium content is the key factor determining the adsorption capacity of zeolites for heavy metals and that the interaction between heavy metals and oxygen atoms is the main adsorption force. Zhao et al. [ 15 ] used first-principles calculations to conclude that the adsorption capacity of heavy metals by kaolinite is Ni > Cu > Cd > Hg (II). Furthermore, the research delves into the intricate interplay of properties such as charge distribution, lattice relaxation, and electronic state density, elucidating their profound influence on the adsorption of heavy metals. As demonstrated by Wang et al. [ 16 ], calcite minerals have been shown to possess strong adsorption capacity for the removal of heavy metals, rendering them particularly suitable for the removal of heavy metals such as arsenic and lead. In addition, Altaf Ur Rahman et al. [ 17 ] have demonstrated that N and F doping can significantly modulate the electronic and magnetic properties of two-dimensional GaS. F doping in the Ga site has been shown to exhibit excellent p-type doping properties. At the same time, the substitution of S by F introduces magnetic moments and demonstrates defect-interaction effects. The introduction of N doping at the S and Ga sites has been observed to result in a change in the spin-polarized state and the direct band gap of GaS. GaS exhibits favourable optical properties and a substantial specific surface area as a two-dimensional material, indicating considerable potential in water pollution control [ 18 – 20 ]. The layered crystal structure of GaS [ 21 – 23 ] affords many surface active sites, a property that confers a notable advantage in the adsorption of heavy metal ions. Furthermore, the field of optoelectronics has seen GaS demonstrate excellent performance, thus opening up new horizons for multifunctional applications [ 24 – 26 ]. Despite the promising prospects of GaS in water pollution control, there are still some challenges in its optoelectronic and adsorption properties, mainly including limitations of its band structure and high carrier recombination rate. The aforementioned issues directly impact the application of GaS in domains such as photoelectric conversion and sensors. Consequently, doping technology has emerged as a pivotal method for optimisation to enhance the performance of GaS, particularly its capacity to adsorb heavy metal ions. By implementing diverse elemental doping, the electronic structure, band gap, and carrier concentration of GaS can be modified, thereby enhancing its surface activity and adsorption performance. For instance, Guler et al. [ 27 ] demonstrated that the thermoluminescence properties of Nd-doped GaS vary significantly with light temperature, and Li et al. [ 28 ] exhibited that hole-doped GaS displays substantial alterations in magneto-optical and Faraday effects. In a related study, Khan et al. [ 29 ]established that pristine monolayer GaS is an indirect bandgap non-magnetic semiconductor and that by introducing N or Cr atoms for anion/cation doping, its band gap can be adjusted and a magnetic moment induced. Despite the intensive research conducted on GaS, with many fruitful results obtained, there are still many unresolved issues in adsorption. There is a paucity of research on the adsorption of heavy metal ions on GaS, with the adsorption of mercury ions, in particular, receiving insufficient attention. The layered structure of GaS gives it a high specific surface area, providing more active sites for adsorption. Therefore, exploring the adsorption performance of GaS materials for heavy metal ions (such as mercury), especially by doping non-metallic elements to enhance their adsorption capacity, has become one of the current research hotspots. This paper systematically studies the adsorption performance of pure GaS and doped GaS systems on mercury using first-principles calculations. The potential application of GaS materials in removing mercury ions is evaluated by analysing key parameters such as adsorption energy, band structure, and density of states. At the same time, this paper also discusses the possibility of further improving the adsorption capacity of GaS by doping non-metallic elements in the Ga and S sites. The study provides a theoretical foundation for applying GaS in water pollution control and offers novel perspectives for enhancing its versatility in optoelectronics. 2. Model and calculation method This study utilized a density functional theory (DFT)-based computational approach to conduct a systematic simulation analysis using the CASTEP module in Materials Studio software. The geometry optimization utilized a super-soft pseudopotential to model the ion-electron interactions, with the PBE functional within the generalized gradient approximation (GGA) chosen for the exchange-correlation potential. The PBE function is more effective in describing the local electronic structure; however, it has certain limitations in dealing with strongly correlated electronic systems (such as systems containing transition metals or heavy elements). Therefore, when dealing with such systems, more complex functionals (such as HSE06 or LDA + U) may be required to improve the accuracy of the calculation results. In order to enhance the calculation accuracy, the Grimme-2 correction was employed in this study to reasonably consider the role of van der Waals forces in the adsorption system. The Grimme-2 correction applies to systems with long-range interactions; however, its applicability in different systems must be evaluated case by case. The self-consistent dipole correction (SCC-DFT) was employed in this study to eliminate errors in the electronic structure caused by the dipole moment, thereby enhancing the reliability of the calculation results. Additionally, since Ga and S are light elements with weak spin-orbit coupling (SOC) effects, this study's neglect of SOC effects will not significantly affect the conclusions. However, Hg has a strong SOC effect, and its effect on localized states may not be negligible in some specific cases. However, it has a negligible effect on the overall electronic structure. Therefore, this study mainly analyses the effects of adsorption behaviour on geometric structure, adsorption energy and state density without involving magnetic or spin-related effects. The atomic electronic configurations are as follows: sulfur (S) is 3s²3p⁴, and gallium (Ga) is 4s²4p¹. The positions of Ga and S atoms are (0.3333, 0.6667, 0.32645) and (0.3333, 0.6667, 0.893149), respectively. In order to systematically study the effects of doping and adsorption on material properties, a 3 × 3 × 1 supercell model was constructed [ 30 , 31 ]. Figure 1 (a–b) shows the top and side views of pure GaS, respectively. N, P and Si are frequently employed to modify semiconductors' conductivity and electronic structure. In contrast, F and Cl are primarily utilised to enhance materials' stability and surface properties. Carbon (C) has been observed to enhance conductivity or optimise the optical properties of certain novel materials. At the same time, oxygen (O) is often implicated in forming oxide layers, thereby affecting the interface properties of the material. Consequently, the doping of C, F, Cl, P, Si, N, and O at the Ga and S sites was considered in the study, as illustrated in Fig. 1(c). The impact of doping atoms on the crystal structure of GaS and its adsorption performance for Hg was investigated. It was found that doping atoms significantly affected both of these factors. Given the important impact of doping on the structural stability of the material, the study selected the three most stable doping elements in the S site and Ga site, respectively. Subsequently, adsorption analyses were performed on these six doped systems to screen for the best adsorption sites in each system. Four adsorption sites were the focus of this particular study: two top sites (TGa and TS), where Hg is located directly above Ga and S atoms; a bridging site (B), where Hg is located above GaS at the midpoint of the Ga-S bond; and a hole site (H), where Hg is located at the hole of the hexagonal atomic ring (see Fig. 1(e)). Finally, the most effective adsorption position was selected from the six doping structures to study its photoelectric properties. Figure 1(f) shows one of the doping adsorption configurations. A 20 Å vacuum layer was introduced into the model to eliminate periodic interactions between distinct atomic layers. A cut-off energy of 500 eV was chosen to ensure an optimal compromise between computational accuracy and efficiency. A 6 × 6 × 1 k-point grid was generated using the Monkhorst-Pack method for self-consistent calculations. In the structural optimization, both atomic positions and lattice parameters were iteratively adjusted to ensure that the maximum force between atoms in the final configuration was below 0.03 eV/Å, and the maximum lattice stress did not exceed 0.05 GPa. Convergence was achieved when the energy change was smaller than 1×10 − 5 eV and atomic displacement was under 0.001 Å. 3. Results and Discussion 3.1 Geometry and Stability GaS is a two-dimensional layered semiconductor material with a hexagonal lattice structure [ 32 ], in which Ga atoms form covalent bonds with four S atoms to form a single-layer GaS structure. The GaS monolayer has a honeycomb structure. Van der Waals forces bond the layers to form a 2H phase structure, in which Ga and S atoms are coordinated in a hexagonal close-packed arrangement, belonging to the P6 3 /mmc space group (No. 194). In the single-layer structure of GaS, Ga atoms are bonded to adjacent S atoms via σ bonds to form a planar structure. Following structural optimisation, the lattice constant (a = b = 3.593 Å) is obtained, which agrees well with the experimental values reported in the literature [ 33 – 35 ]. The bond length of 2.346 Å for the Ga-S bond in intrinsic GaS and the S-Ga-S bond angle of 100.5° (slightly higher than the experimental value of 99.64°). The calculation method and model are found to be feasible. The structural stability is a key factor for the experimental synthesis and practical application of two-dimensional materials. Hence, the dynamic and thermal stability of monolayer 2H-GaS were assessed through computational methods [ 36 ]. Firstly, the phonon spectrum of monolayer 2H-GaS was calculated, as shown in Fig. 2 (a). It was found that there are no virtual frequencies in the phonon spectrum throughout the Brillouin zone, indicating that the system has good dynamic stability [ 37 ]. As shown in Fig. 2 (b), the simulation at 300 K and the crystal structure after 5 ps of simulation are presented. Throughout the simulation, both energy and system temperature exhibited slight fluctuations, with all atoms oscillating around their equilibrium positions, and the two-dimensional periodic structure remained stable.These computational results demonstrate that monolayer 2H-GaS exhibits excellent thermal stability and can be expected to exist stably within the room temperature range [ 38 ]. Considering the impact of doping or Hg adsorption on the structure, the bond lengths and angles of the most stable system are enumerated in Table 1 . The alteration in the Ga-S bond length effectively reflects the degree of distortion of the crystal structure and the strength of the covalent bond. After the adsorption of Hg, particularly in the vicinity of the adsorption site, the Ga-S bond length undergoes a slight increase from 2.360 Å to 2.347 Å, signifying that the adsorption of Hg results in alterations to the chemical bond. This phenomenon suggests that the adsorption of Hg weakens the interaction of the Ga-S bond through electronic or geometric effects, consequently leading to an elongation of the bond length. Furthermore, introducing non-metals at distinct sites within the GaS lattice alters its fundamental parameters. The introduction of dopant elements further complicates the system's nature, providing a more significant number of possibilities for regulating material properties. Comprehending these alterations can provide insight into the behaviour of GaS and its doped systems during adsorption. In summary, relatively minor structural changes occur within the doped non-metallic element Hg adsorption system, with bond length changes typically amounting to approximately 0.1 Å. This indicates that the system remains stable following the processes of doping and adsorption, although there may be a significant alteration to the electronic structure. The Ga-S bond population value ranges from 0.51 to 0.54, suggesting electron sharing between Ga and S and maintaining a balanced covalent bond nature. The system exhibits high stability within this range, indicating that slight changes in the electronic distribution of the Ga-S bond in the doped adsorption system may occur. Table 1 The most stable structural parameters before and after GaS adsorption (X = S/C/N/O)(Y = Ga/C/N/Si) structure type Band length(Å) (Ga-S) Adsorption height(Å) Band Angle(°) Ga-X-Hg/S-Y-Hg Population (Ga-S) GaS supercell 2.360 — — 0.53 GaS adsorbed Hg 2.347 4.312 56.867 0.52 Ga(C) + TS-Hg 2.381 3.595 143.687 0.51 Ga(N) + TGa-Hg 2.245 4.749 103.702 0.52 Ga(Si) + TGa-Hg 2.403 4.308 63.818 0.52 S(C) + TS-Hg 2.365 2.290 106.158 0.54 S(N) + TS-Hg 2.376 2.689 106.258 0.54 S(O) + TS-Hg 2.374 3.130 103.770 0.54 The present study employs formation energy as an evaluation criterion to quantify the material structure's stability and its preparation's difficulty and investigate the stability of adsorption systems with intrinsic and doped non-metals. Formation energy reflects the change in energy required when a doped element occupies a specific position in the material compared to the undoped system. Generally, a lower formation energy means the doping process is more stable and more likely to occur. The following formula is employed to calculate formation energy [ 39 , 40 ]: $$\:{\:E}_{form}={E}_{doped}-{E}_{pure}-{E}_{dopant\:isolated}$$ 1 In the context of this study, " E doped " is defined as the total energy of the doped system, " E pure " is the total energy of the pure material (i.e. the undoped matrix material), and " E dopant isolated " is the energy of the dopant when it exists independently (i.e. the energy of the dopant in the gas phase or other environment). The formation energy of the doped system at different sites is illustrated in Fig. 3 . As demonstrated in Fig. 3 , an analysis of the formation energies of the various doping site systems reveals that the formation energies of the Ga site C (-0.603 eV) and Si (-0.022 eV) atom doping systems, In addition, the S site C (-0.753 eV), N (-1.816 eV) and O (-2.154 eV) atom doping systems exhibit negative formation energies, suggesting enhanced stability for these doping systems. This phenomenon may be attributed to the dopant elements' atomic size, electronic structure and chemical affinity. For instance, the weak interaction or good fit between the C and Si atoms and the Ga atoms means that excessive structural mismatch is not likely to occur after doping, which in turn reduces the total energy of the system and makes it easier for the doped atoms to enter the Ga sites of GaS and form a stable structure. In contrast, non-metallic elements such as C, N and O have high electron affinities and strong chemical interactions. When doped in the S site, these elements enhance the system's stability by providing additional electrons or forming specific chemical bonds. In order to facilitate a horizontal comparison, the formation energies of the Ga-doped N systems were also studied. Subsequently, the six doping systems were combined with the Hg adsorption system, and the most stable adsorption site was selected for subsequent photoelectric property research by calculating the formation energies of different adsorption sites. In order to systematically evaluate the influence of doped atoms on adsorption capacity and structural stability [ 41 – 43 ], the adsorption energies were calculated using the following method: $$\:{E}_{ads}={E}_{substrate-Hg}-\left({E}_{substrate}+{E}_{Hg}\right)$$ 2 Where E substrate−Hg is the total energy of the adsorbate and surface standard system, E substrate is the energy of the GaS substrate, and E Hg is the energy of the Hg atom. As demonstrated in Eq. ( 2 ), it can be seen that the greater the absolute value of the adsorption energy, the more stable the adsorption system. According to the second equation, the adsorption energies of the four adsorption sites of the supercell eigenstate were calculated to be TS = 0.004 eV, TGa = -0.0015 eV, H = 0.001 eV and B = -0.0018 eV, respectively. This demonstrates that the supercell is most stable when adsorbed at the B site. In order to enhance the adsorption capacity of GaS for Hg, non-metallic elements were doped in the Ga and S sites, respectively. Following structural optimisation, the adsorption energies of each doped adsorption system were obtained, and all adsorption energies were found to be negative. For comparison, the absolute values of the adsorption energies are plotted in Fig. 4 . The adsorption of doped Hg atoms on the GaS surface is a spontaneous process, and the magnitude of the adsorption energy is closely related to the ease of the adsorption process. A comparison of the adsorption energy of the doped and undoped GaS systems reveals that the doped system exhibits higher adsorption energy. The Ga-site N-doped system exhibits the most substantial adsorption strength, while the S-site O-doped system exhibits the weakest. The findings of this study demonstrate that doping significantly enhances the adsorption capacity of Hg atoms on the GaS surface, thereby promoting the formation of a more stable adsorption structure. 3.2 Electronic property In order to further study the electronic structure of the doped adsorption system, the band structure and density of states (DOS) of each system (intrinsic GaS, atomically doped and atomically doped adsorption) were calculated, with the broadening setting fixed at 0.02 eV. A horizontal red dashed line indicates the Fermi level (with an energy of 0). The band diagram and density of states of pure GaS are shown in Fig. 5 (a-b), respectively. The band gap of GaS is 2.423 eV, the highest point of the valence band is between the Gamma point and the M point, and the lowest point of the conduction band is at the Gamma point. This observation indicates that the intrinsic monolayer GaS is a typical indirect band gap semiconductor, a finding broadly consistent with the results reported in the literature [ 35 , 44 , 45 ]. The valence band is predominantly composed of S-3p states and Ga-4p states, with a minor contribution from Ga-4s states, while the conduction band is primarily constituted of S-3p states and Ga-4p and Ga-4s states. The strong hybridisation between these states forms stable covalent bonding characteristics. As demonstrated in Figs. 6 (a–c) and 7(a–c), the band structure and density of states (DOS) of the Ga-doped systems are exhibited. The three doping systems demonstrate n-type doping, which is characterised by an increase in the number of electronic states in proximity to the Fermi level. The Fermi level is near the bottom of the conduction band. Following the introduction of C or N as impurities into GaS, there is a significant change in the band structure, specifically a migration of the conduction band towards the Fermi level and a substantial reduction in the band gap width. After C and N doping, the band gaps are 0.172 eV and 1.198 eV, respectively. In the C-doped system, the conduction band is primarily composed of Ga-4p and S-3p states, limiting the contribution of C-2p states. The valence band is dominated by the S-3p state and the Ga-4p state, with the C-2p state having minimal participation in forming the valence band. Conversely, within the N-doped system, the N-2p state hybridises with the S-3p state, thereby weakly contributing to the formation of the conduction band. This disparity underscores the notion that dopant elements exert disparate influences on the band structure through their interactions with the electronic states of the GaS substrate. Specifically, the impact of C doping on the electronic state distribution of the conduction and valence bands was negligible due to the interaction's weak nature. By contrast, N doping significantly affected the formation of the conduction band, resulting from hybridisation with the S-3p state. These differences offer novel insights into regulating the electronic properties of GaS through doping elements. Following Si doping, a notable shift in the energy level of the valence band occurs, resulting in its intersection with the Fermi level. This observation signifies a substantial modification of the electronic structure of GaS, leading to the partial filling of the original band gap. This phenomenon is corroborated by the density of states diagram, which further substantiates the transition of the material from conventional semiconductor properties to metal properties, thereby significantly enhancing its conductivity. This transition not only enhances the conductivity of GaS but also opens up new research directions for its application in optoelectronic devices, sensors and catalysis. As demonstrated in Figs. 6 (d-f) and 7(d-f), the band structure and density of states (DOS) of the S-site doping system, respectively, are shown. It is evident from the figures that C and N doping are p-type doping, which may introduce localized states in the vicinity of the top of the valence band. The density of states diagram reveals that the Fermi level is near the valence band, indicating an augmentation in the number of hole states near the Fermi level. The band gap values after doping are 0.699 eV (C doping) and 1.855 eV (N doping). Although the band gap decreases, the system retains its indirect band gap nature, indicating that the energy levels of the conduction and valence bands have shifted. Nonetheless, electron transitions from the valence band to the conduction band still rely on phonon assistance rather than occurring via a direct transition. In the C-doped system, the valence band comprises S-3p states, Ga-4p states and a small amount of C-2p states, while S-3p states and Ga-4p states dominate the conduction band. In addition, significant localised states in the conduction band near the Fermi level indicate substantial changes in the material's electronic structure, which may provide additional pathways for electron transitions. In the N-doped system, the valence band comprises S-3p states, Ga-4p states and a minor amount of N-2p states, with localised states also evident in the valence band near the Fermi level. In contrast, O doping does not exhibit analogous phenomena. As demonstrated in Figs. 8 and 9 , the energy band structures and DOS of GaS doped with Ga and S are shown. Compared with pure GaS, the band gap of the doped system is reduced. In the Ga-doped system, the C-2p state hybridises with the Ga-4p state and the S-3p state to form the conduction band. The Si-doped system exhibits a similar phenomenon, and the DOS diagram demonstrates that the conduction band crosses the Fermi level, thereby proving its metallic nature. The band gaps of the three systems doped at the S site are 1.006 eV (C doping), 1.869 eV (N doping) and 1.974 eV (O doping), in that order. This change can be attributed to introducing the doping element, with the newly generated impurity energy levels close to the Fermi energy level, thereby reducing the energy of electron transitions and resulting in a narrower band gap. A comparison of the state density characteristics of the three doping systems reveals a similarity in their properties, with the valence band primarily formed by the combined contributions of the S-3p state, Ga-3d state and the 2p state of the doping element. In contrast, the Ga-4p state predominantly dominates the conduction band. In the adsorption system of C atoms doped with C in the S position, a small peak of approximately 10 eV emerges in the conduction band, primarily attributable to the 2p state of C. The emergence of this peak introduces new localised states into the material's electronic structure, providing additional channels for electron transitions and potentially enhancing the material's conductivity. Specifically, these localised states may promote the excitation of low-energy electrons, thereby reducing the excitation energy required for electrons to transition between energy bands. This, in turn, may improve the electrical conductivity and carrier mobility of the material. In contrast, no analogous localised state features were observed in the N-doped and O-doped systems, suggesting that C atoms behave differently when doped in the S position than when doped with N and O and may exert a distinct effect on the electronic structure and electrical conductivity of the material. Doping and adsorption are significant mechanisms for regulating the electronic properties of materials. Doping alters the electronic structure of a material by introducing new electronic states, changing the band gap, and adjusting the carrier concentration. Adsorption further optimises or adjusts the material's electronic properties by affecting surface states and adjusting local electronic density. The combined effect of the two mechanisms can achieve more precise regulation of the electronic and adsorption properties in material design, thereby enhancing the adsorption capacity for pollutants such as mercury. However, it is important to note that the impact of doping and adsorption on the electronic structure and adsorption properties of materials is not limited to theoretical considerations. These processes have the potential to enhance the performance of GaS materials in a variety of practical applications, particularly in the domains of optoelectronic devices, sensors, and catalysis. Specifically, doping has been shown to enhance the performance of GaS in optoelectronic devices. For instance, introducing dopants can adjust the band gap, enabling the material to absorb a broader spectrum of light and thus enhancing the photoelectric conversion efficiency. In photodetectors, doping elements can enhance the material's light response speed and sensitivity by adjusting the electron density of the conduction and valence bands. Conversely, the adsorption process can improve the surface reactivity of the material by altering the surface state, thereby optimising the response performance in sensors. In catalytic applications, doping and adsorption modify the material's electronic structure and enhance its ability to adsorb reactants and catalytic activity, further improving catalytic efficiency. Moreover, the interplay between doping and adsorption imparts distinct advantages to GaS materials. Specifically, GaS demonstrates superior sensitivity and response speed relative to conventional semiconductor materials (e.g., silicon, gallium arsenide.), particularly regarding light absorption within specific wavelength ranges. By carefully controlling the nature and degree of doping and adsorption, the performance of GaS materials in practical applications can be further optimized, thereby enhancing their competitiveness in optoelectronics, sensing, and catalysis. 3.3Adsorption properties By calculating the differential charge density map of the doped adsorption system (see Fig. 10), it can be seen that the dopant or adsorbate causes a significant charge accumulation or hole region on the surface or interface region of the material. The adsorbate (Hg) causes an increase or decrease in local electron density through interactions with matrix atoms, manifested by forming electron accumulation regions and deficient regions. This phenomenon suggests that the adsorption or doping process may have induced a transfer of electrons, thereby modifying the material's electronic structure and local charge distribution. The red area in the figure denotes a decrease in electron density near Hg, indicating that electrons have been transferred from Hg to the GaS substrate. This also suggests that Hg has lost some electrons while adsorbing onto the GaS surface. Conversely, the blue area, which corresponds to an increase in electron density, is primarily concentrated around the S atoms, suggesting that these atoms have gained electrons from the adsorbate. The results of differential charge analysis demonstrate that electron rearrangements induced by doping or adsorption can substantially modify the local charge distribution of the material, particularly within the valence and conduction band regions. The presence of dopants or adsorbates can influence the band gap width and carrier concentration of the material through their capacity to attract or release electrons. This charge rearrangement directly influences the electrical conductivity and photoelectric properties of the material. In the specific case of semiconductor materials, the presence of dopants or adsorbates has been shown to either promote electron excitation or inhibit carrier recombination, thereby leading to the effective enhancement of the electrical conductivity or the light absorption capacity of the material. Notably, the distribution of differential charge density exhibits marked differences in different doping and adsorption systems. For instance, a substantial charge accumulation is observed near the N atom in the Ga-site N-doped adsorption system. This suggests that incorporating N enhances the system's stability and augments the adsorption capacity of GaS for Hg. Consequently, this reduces the distortion field on the GaS substrate, thereby facilitating further adsorption of Hg. Conversely, in the C-doped system, the degree of charge transfer is reduced, which may be attributed to the lower electronegativity of the C atom, leading to weaker charge interactions with the substrate. In the adsorption system with C or N atoms doped in the S site, the electron density is substantially increased, manifesting as a harmful charge accumulation, indicating that the dopant has obtained electrons from the substrate. Conversely, a significant decrease in electron density is observed on the substrate surface, forming an electron depletion region, suggesting an electron transfer from the substrate to the dopant. This electron transfer effect impacts the material's local charge distribution and electronic properties, consequently leading to alterations in the adsorption performance. In order to further understand the electronic exchange between Hg and the substrate, the charge transfer of Hg adsorption in various doped systems is shown in Table 2 . Table 2 Adsorbed Hg electron transfer for doped systems Charge Ga(C) Ga(N) Ga(Si) S(C) S(N) S(O) Hg(e) -0.05 -0.06 -0.05 0.32 0.12 -0.02 As illustrated in Table 2 , the charge transfer of C-doped GaS in the S site is 0.32 e, the largest among the six doping systems. This indicates that after C atoms are doping in the S site, more electrons are lost from the GaS matrix, resulting in a harmful charge accumulation. This substantial charge transfer may be attributable to two factors: firstly, the strong interaction between C atoms and S atoms, and secondly, the higher electronegativity of C atoms compared to S atoms, making it easier for C atoms to attract electrons from their surroundings. In the Ga-site C-doped and N-doped systems, the amount of charge transfer was − 0.05 e and − 0.06 e, respectively, indicating that after C atoms and N atoms were doped into the Ga site, there was almost no significant electron accumulation, and the electronic effect on the GaS substrate was relatively limited. However, compared with the pure GaS adsorption system, the Ga-site N-doped system demonstrated a marginally enhanced adsorption capacity. These charge transfer results indicate that the position of the dopant element and the doping type significantly impact the electronic properties and, ultimately, the performance of the GaS material. 3.4 Optical property The dielectric function is a significant physical quantity that characterises the response of a material to an electric field. It is composed of a real part and an imaginary part, the former being associated with the optical properties of the material and the latter with its energy loss characteristics. The dielectric function demonstrates the polarisation capability of a solid material and the extent to which electrons are excited to jump. A thorough examination of the dielectric function is paramount for advancing efficient optoelectronic devices and comprehending the optical properties of materials.Its formula is as follows[ 11 ]: $$\:{{\rm\:E}}_{（{\omega\:}）}={\epsilon\:}_{1}+i{\epsilon\:}_{2}$$ 3 The Kramers-Kronig dispersion relation is utilised to ascertain the fundamental part of the dielectric function (ε 1 ), which indicates the strength of electron polarisation in the material under an applied electric field. Furthermore, it is associated with the material's refractive index and light propagation characteristics. The imaginary part of the dielectric function (ε 2 ) reflects the light absorption characteristics, which are associated with the material's absorption capacity and energy loss. As illustrated in Fig. 11 (a), the ε 1 of single-layer GaS and its doping system adsorbing Hg is demonstrated. The static permittivity of Hg adsorption on GaS supercells and Ga-doped C, N, Si-doped and S-doped C, N, O are enumerated in Table 3 . The intrinsic GaS adsorption system exhibits the lowest static dielectric constant, while the Ga-doped Si adsorption system demonstrates the highest. This observation signifies that the latter possesses superior and more robust polarization capacity and electric field response. Consequently, this system can effectively polarize and store more electrical energy under an external electric field. The material's electronic structure may be responsible for an increase in free carriers or a higher charge density due to polarization, thereby enhancing the response to external electric fields. As illustrated in the figure, the adsorption system of Ga-doped Si becomes negative in the low-energy region, indicating that the polarization response of the material is opposite to the direction of the applied electric field. This phenomenon may be attributed to various factors, including the material's metal-insulator transition, surface plasmon resonance, local charge accumulation, and other effects. It is particularly significant in specific material systems, such as nanomaterials, two-dimensional materials, or materials with strong electron-related effects. It may substantially impact the optoelectronic, electronic, and magnetic properties of the material. Figure 11 (b) illustrates that the ε 2 of Hg adsorption on single-layer GaS and its doping systems predominantly occurs within the 0–10 eV range. The adsorption systems of Ga-doped Si and Ga-doped C exhibit more prominent peaks in the low-energy range, suggesting the presence of local defect states or new electronic states introduced by doping in the adsorption systems of Ga-doped Si and Ga-doped C. These new electronic states result in enhanced low-energy absorption, accompanied by a shift in the position of the peaks towards the red, indicating a reduction in the material's band gap. This reduction in band gap energy indicates that the energy required for electrons to transition from the valence to the conduction band is decreased, leading to a shift in the absorption spectrum towards lower energies. In contrast, the other four doped adsorption systems exhibit the most prominent peaks in the high-energy range, with the maximum peaks all near 5.1 eV. The position of these peaks has shifted to the blue. This shift may be attributed to the introduction of doped atoms, which increases the polarization rate of the system. Among the doped systems, only the peak intensity of the N-doped Ga sites adsorption system decreased compared with the intrinsic system, with a value of 4.601, which is 0.152 lower than that of the intrinsic system. This phenomenon can be attributed to incorporating the doping element into the electronic structure and chemical bonds of the GaS substrate, resulting in alterations to the electronic transition or vibration modes. These modifications may have reduced the polarisation response of the system within a specific energy range, consequently decreasing the peak dielectric absorption intensity. Table 3 Static dielectric constant and imaginary peak coordinates System Static dielectric constan Photon energy/eV Peak coordinate Pure GaS 3.027 5.054 4.753 Ga(C) + TS-Hg 19.831 0.379 6.427 Ga(N) + TGa-Hg 3.133 5.172 4.601 Ga(Si) + TGa-Hg 78.069 0.01 29.622 S(C) + TS-Hg 3.340 5.150 4.880 S(N) + TS-Hg 3.057 5.198 4.986 S(O) + TS-Hg 3.050 5.169 4.853 The impact of doping on the optical characteristics of Hg-GaS can be further investigated by analyzing the absorption and reflection spectra of various systems. Absorbance is typically calculated from the measurement of transmitted light intensity and is a widely used parameter for characterizing a material's capacity to absorb light at a specific wavelength. It is the negative logarithm of light's transmittance (T), i.e., [ 46 , 47 ], where A is the absorbance, and T is the transmittance. The reflectance indicates the degree to which the material's surface reflects the incident light and provides more intuitive information about the optical properties. The photon frequency ( ν ) is the frequency of the photon fluctuation, and h represents Planck's constant, approximately 6.63 × 10 − 34 . It is directly related to the energy of light (E), and the two are related to each other by Planck's formula [ 46 ]: \(\:\text{E}=\text{ℎ}\times\:{\nu\:}\) The analysis results demonstrate that doping and adsorption induce alterations to the optical properties of GaS, particularly concerning light absorption and reflection behavior. Specifically, the defect states or localized electronic states instigated by doping substantially enhance the material's light absorption within a designated wavelength range. As demonstrated in Fig. 12 (a), the absorption coefficients of the six doped and adsorbed systems exhibit a gradual increase in the photon frequency range from 1.21×10 15 Hz to 1.93×10 15 Hz. The Ga-position doped C and Si adsorbed systems exhibit the initial absorption peaks at 1.03 eV and 0.95 eV, respectively, suggesting that C and Si doping introduces local energy levels, thereby facilitating the absorption of low-energy light. In the S-site doped system, in particular, the formation of these localized states may be closely related to the narrowing of the band gap and the change in electron transition between the conduction band and the valence band. Doping lets the material absorb lower energy light by changing the band gap structure. Introducing defects or localized electronic states may also enhance the optical response in specific wavelength bands. Further analysis indicates that doping results in a slight red shift in the position of the material's prominent absorption peaks, for example, at 7.84 eV and 7.71 eV, which reflects changes in the band gap structure or electron transition characteristics. These changes signify that doping not only optimizes the absorption of low-energy light but may also significantly impact applications such as optoelectronic devices or solar cells. In solar cells, the local energy levels induced by doping can facilitate more efficient photoelectric conversion. At the same time, adjusting the band gap can enhance the material's light absorption in the visible or infrared regions. In summary, doping modifies the electronic structure and optical properties of GaS materials by introducing additional defect states or localized electronic states, thereby enhancing their light absorption capacity. This provides a new control strategy for further optimizing the application of GaS materials in optoelectronic devices, solar cells, and other fields. Reflectivity (R) is typically defined as a parameter that characterizes the optical properties of a material's surface reflection, indicating the proportion of incident light reflected after interacting with the surface. It is a measure of the material's surface's capacity to reflect incident light and is closely related to the position of the absorption peak because, after light interacts with the material, the energy is divided into three parts: absorption (A), transmission (T) and reflection (R).[ 48 ] High reflectivity usually means low transmittance. As demonstrated in Fig. 12 (b), when the photon energy is zero, the reflectivity of the adsorption system with Ga-site C-doping and Ga-site Si-doping increases significantly. In contrast, the other systems do not show apparent changes. These changes indicate that these two doping systems exhibit higher reflectivity in the low-energy region, which is consistent with the changes in the dielectric function and absorption coefficient. Notably, at an energy of 1.69 eV, the reflectivity of the Ga-doped Si adsorption system approaches 0, indicating that the majority of light is transmitted or absorbed, thereby enhancing the excitation efficiency of photoelectrons. This phenomenon provides a theoretical foundation for transparent materials, the design of optical devices, anti-reflective coatings, surface engineering, and nano-optics. Furthermore, the spectral changes caused by doping demonstrate that all the doping adsorption curves have shifted to the right, which may indicate that the introduction of dopant elements (such as C, N, O, and Si) causes a blue shift in the characteristic spectrum of the GaS adsorption Hg system. This blue shift may be related to the electronic structure characteristics (e.g., ionic radius, electronegativity) of the dopant elements, which affect the electronic structure of GaS and further regulate its ability to adsorb Hg. For example, the redshift and band gap change introduced by Si doping may be related to Si's small ionic radius and high electronegativity. These properties may have promoted changes in the electronic cloud, which affected the material's band gap structure and optical absorption characteristics. The reflectivity of the GaS adsorption system doped with N at the Ga site is generally lower than that of the intrinsic system. This finding may indicate that the GaS adsorption system doped with N at the Ga site has more substantial light absorption capacity, especially in the low-to-medium energy region. This is due to the effect of N doping on the band gap of the material and the optimization of its electronic structure. As demonstrated in Fig. 13 , the energy loss function of each system is exhibited. In the low-energy region, the Si-doped Hg adsorption system at the Ga site manifests a higher energy loss function, thereby indicating that the electronic structure of this system is more unstable or 'relaxed' under low-energy electron excitation. Conversely, the adsorption system doped with non-metallic elements such as C, N, and O at the S site demonstrates a substantially diminished energy loss function in the low-energy region, signifying that doping enhances the stability of the electronic structure of the system. Further analysis indicates that the adsorption system doped with N at the Ga site exhibits optimal electronic stability in the low-energy region. In contrast, the adsorption system doped with Si at the Ga site demonstrates the poorest stability within this region. In the high-energy region, the difference in the energy loss function of each doping system is minimal, suggesting that the influence of different doping elements on the electronic structure of the GaS adsorption system in this region is negligible. In the broader context of the entire spectral range, the energy loss function values of the S-site doped O and Ga-site doped N systems are predominantly low, signifying that these two types of doping exert a substantial influence on the electronic structure of the GaS adsorption system and contribute to enhancing the overall stability of the system. In summary, S-site doping with O and Ga-site doping with N effectively enhance the system's stability in the low-energy region and maintain a lower energy loss function in the high-energy region. These improvements make these two doping types an important means of optimizing the electronic structure and optical properties of the GaS adsorption system. 4. Conclusion This study employs first-principles calculations to comprehensively investigate the impact of non-metallic doping on the optical properties of single-layer GaS materials, focusing on regulating photoelectric performance during mercury adsorption. The results demonstrate that various doping elements significantly influence the electronic structure and optical response of GaS materials (e.g., C, N, O, and Si). The introduction of local defect states and new electronic states, a consequence of doping, has significantly changed the dielectric function, absorbance, and reflectivity of GaS, particularly within the low-energy and high-energy regions. The optical absorption characteristics have undergone substantial alterations, with the adsorption system of Ga-doped Si exhibiting a pronounced polarisation response and light absorption capacity in the low-energy region. The narrowing of the band gap has been evidenced to enhance the absorption of low-energy light. Moreover, the impact of doping on the energy loss function indicates that the S-site doped O and Ga-site doped N systems enhance the electronic structure's stability and optimize the material's overall photoelectric properties. Through these doping methods, the photoelectric response of GaS materials has been considerably enhanced, providing a theoretical foundation for utilizing novel optoelectronic devices, solar cells, and gas sensors. The findings of this study offer novel concepts for the regulation of performance in GaS-based optoelectronic materials. Furthermore, they establish a foundation for research on utilizing non-metallic doping in two-dimensional materials. Subsequent studies can extend this research by investigating the impact of diverse doping systems on additional physical properties of GaS materials. These properties include their stability and durability in complex environments and the interactions between dopant elements and the external environment. Declarations Author Contribution Author contributionZilian Tian: Investigation, Methodology, Validation, Visualization, Writing - original draft, Writing - review & editing. Lu Yang: Software, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision. Xiaotong Yang: Writing - review & editing. Hang Yang: Writing - review & editing. Yao Dong: Writing - review & editing. Wei Zhao: Writing - review & editing. References Qi, C., Xu, X., Chen, Q., Liu, H., Min, X., Fourie, A., Chai, L.: Ab initio calculation of the adsorption of As, Cd, Cr, and Hg heavy metal atoms onto the illite (001) surface: Implications for soil pollution and reclamation. Environ. Pollut. 312 , 120072 (2022) Tang, H., Duan, Y., Zhu, C., Cai, T., Li, C., Cai, L.: Theoretical evaluation on selective adsorption characteristics of alkali metal-based sorbents for gaseous oxidized mercury. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6183020","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":426696567,"identity":"dffaf57c-2500-4885-b9cb-70e0bbd357f4","order_by":0,"name":"Zilian Tian","email":"","orcid":"","institution":"Shenyang University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Zilian","middleName":"","lastName":"Tian","suffix":""},{"id":426696572,"identity":"700eed81-2f9f-4ed2-acd4-37913831b6ae","order_by":1,"name":"Lu 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08:53:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6183020/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6183020/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":78327988,"identity":"8f577476-e5ec-4f50-8b53-49bd5925399f","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":147573,"visible":true,"origin":"","legend":"\u003cp\u003eLattice structure of a 3×3×1 supercell of monolayer GaS\u003c/p\u003e\n\u003cp\u003e(a) Top view(b) Side view (c) The non-metallic atom X (X: C, N, O，F，Si，P，Cl) is substituted for S, or the non-metallic atom Y (Y: C, N, O，F，Si，P，Cl) is substituted for Ga(d) Brillouin zone and high-symmetry points for monolayer GaS (e) Different adsorption sites (f) Example of X doping with TGa adsorption\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/b3f183c1a8c8ce27c26aea75.png"},{"id":78328426,"identity":"4f35274f-d036-41e6-bb61-7ce911604a65","added_by":"auto","created_at":"2025-03-12 06:48:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2877468,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Phonon spectrum of single-layer GaS (b) Temperature-dependent changes in total energy and simulated structure (Temperature: 300 K, Duration: 5 ps)\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/807f913c19144bd35077f2f1.png"},{"id":78327983,"identity":"1119ceac-5c73-4e90-9156-ec7a1d24fde1","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":142221,"visible":true,"origin":"","legend":"\u003cp\u003eFormation energy of doping system (X=C, N, O, F, Si, P, Cl)\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/d9e7dcb44f3ed88c141489d9.png"},{"id":78329563,"identity":"ec39df81-ad28-41c9-95bc-ba08accffa40","added_by":"auto","created_at":"2025-03-12 06:56:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":193991,"visible":true,"origin":"","legend":"\u003cp\u003eAbsolute values of adsorption energy of GaS doped system at different adsorption sites\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/504676b40b838e604af4a7b2.png"},{"id":78327999,"identity":"3fbd5296-0e43-4ca5-8d3f-8fc98acaf263","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":3190057,"visible":true,"origin":"","legend":"\u003cp\u003eIntrinsic electronic structure of supercell (a) Intrinsic band diagram (b) Intrinsic density of states\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/d719ad1602013b39f0153829.png"},{"id":78327987,"identity":"3da8519f-a100-48a4-a4ae-6258aff65eef","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":6978415,"visible":true,"origin":"","legend":"\u003cp\u003eBand structure of GaS doped system\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/470c07fc065d7513cb8f237f.png"},{"id":78327984,"identity":"9005dd62-b532-4d9b-9f55-86ec11f7eab7","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":341346,"visible":true,"origin":"","legend":"\u003cp\u003eDensity of states diagram of doped system\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/2cc739756333ab145bb9a5a7.png"},{"id":78329565,"identity":"5d20eedb-40b9-442b-ac46-e7024f802e45","added_by":"auto","created_at":"2025-03-12 06:56:43","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":5418026,"visible":true,"origin":"","legend":"\u003cp\u003eBand structure of GaS doped system at optimal adsorption position\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/6c83542f0683b5b96e85bf52.png"},{"id":78328427,"identity":"0ba5dd0c-da97-4b2c-8be7-0739a859459e","added_by":"auto","created_at":"2025-03-12 06:48:43","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":5052213,"visible":true,"origin":"","legend":"\u003cp\u003eThe density of states of GaS doped system at the optimal adsorption position\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/ad6b518c1d74f8fd999a8af7.png"},{"id":78328429,"identity":"27023d6d-ab36-4d28-b76c-f353f785535e","added_by":"auto","created_at":"2025-03-12 06:48:43","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":285199,"visible":true,"origin":"","legend":"\u003cp\u003eDifferential Charge Diagram of GaS Adsorption System\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/192b51e7ff221379dbb7b621.png"},{"id":78328433,"identity":"d452b4f5-7f07-4e43-af3d-1c14748fef21","added_by":"auto","created_at":"2025-03-12 06:48:43","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":2426312,"visible":true,"origin":"","legend":"\u003cp\u003eReal and imaginary parts of dielectric functions for each system\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/d83a3c34435088ce49c1a8c5.png"},{"id":78328004,"identity":"beeedef9-c4c7-47e2-aa56-4fcf3d87c033","added_by":"auto","created_at":"2025-03-12 06:40:43","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":2495774,"visible":true,"origin":"","legend":"\u003cp\u003eAbsorption coefficient and reflection spectrum of adsorption system under doping\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/3de26eb46542277d9aafe1ea.png"},{"id":78329567,"identity":"1e8e74ec-73e2-4521-a627-297db9679bb7","added_by":"auto","created_at":"2025-03-12 06:56:43","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":161835,"visible":true,"origin":"","legend":"\u003cp\u003eEnergy loss function of adsorption system under doping\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/30aa393cbd764f846be76fad.png"},{"id":79016539,"identity":"1a92fbbc-b26c-4c46-8ff1-05b718259618","added_by":"auto","created_at":"2025-03-22 14:01:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":30472105,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6183020/v1/da6cf3d3-ec28-43fa-acdd-dc05500c3c78.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of non-metallic doping on the electronic structure of GaS monolayers and mercury adsorption performance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSince the Industrial Revolution, with the rapid development of human society and the economy, environmental pollution problems have become increasingly severe, especially water pollution. As a key resource for maintaining human survival and development, water is threatened by various harmful substances. Among these, heavy metal ions such as mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As) have been identified as particularly problematic. These substances cause significant deterioration in water quality and accumulate in the food chain through biological absorption and enrichment, posing a serious threat to human health. Mercury, in particular, has been shown to cause significant damage to the nervous and immune systems and to pose a risk of cancer. This underscores the pressing need to develop effective adsorbent materials to remove heavy metal ions, particularly mercury, from water to address the pressing issue of water pollution [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn recent years, graphene has been the focus of extensive research due to its remarkable physical and chemical properties. Its high specific surface area and excellent adsorption capabilities have led to significant advancements in various fields, including adsorption [\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The advent of graphene has prompted researchers to explore the domain of two-dimensional materials to achieve technological breakthroughs in developing novel materials [\u003cspan additionalcitationids=\"CR9 CR10 CR11 CR12\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Two-dimensional materials have attracted significant attention in environmental protection and energy research due to their layered structure and distinctive physicochemical properties. In a study by Yang et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], it was observed that magnesium-rich zeolite exhibited a notable adsorption capacity for Pb and Cd. In contrast, its adsorption capability for Sb and Hg was less effective. Electronic structure analysis indicates that the aluminium content is the key factor determining the adsorption capacity of zeolites for heavy metals and that the interaction between heavy metals and oxygen atoms is the main adsorption force. Zhao et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] used first-principles calculations to conclude that the adsorption capacity of heavy metals by kaolinite is Ni\u0026thinsp;\u0026gt;\u0026thinsp;Cu\u0026thinsp;\u0026gt;\u0026thinsp;Cd\u0026thinsp;\u0026gt;\u0026thinsp;Hg (II). Furthermore, the research delves into the intricate interplay of properties such as charge distribution, lattice relaxation, and electronic state density, elucidating their profound influence on the adsorption of heavy metals. As demonstrated by Wang et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], calcite minerals have been shown to possess strong adsorption capacity for the removal of heavy metals, rendering them particularly suitable for the removal of heavy metals such as arsenic and lead. In addition, Altaf Ur Rahman et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] have demonstrated that N and F doping can significantly modulate the electronic and magnetic properties of two-dimensional GaS. F doping in the Ga site has been shown to exhibit excellent p-type doping properties. At the same time, the substitution of S by F introduces magnetic moments and demonstrates defect-interaction effects. The introduction of N doping at the S and Ga sites has been observed to result in a change in the spin-polarized state and the direct band gap of GaS.\u003c/p\u003e \u003cp\u003eGaS exhibits favourable optical properties and a substantial specific surface area as a two-dimensional material, indicating considerable potential in water pollution control [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The layered crystal structure of GaS [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] affords many surface active sites, a property that confers a notable advantage in the adsorption of heavy metal ions. Furthermore, the field of optoelectronics has seen GaS demonstrate excellent performance, thus opening up new horizons for multifunctional applications [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Despite the promising prospects of GaS in water pollution control, there are still some challenges in its optoelectronic and adsorption properties, mainly including limitations of its band structure and high carrier recombination rate. The aforementioned issues directly impact the application of GaS in domains such as photoelectric conversion and sensors. Consequently, doping technology has emerged as a pivotal method for optimisation to enhance the performance of GaS, particularly its capacity to adsorb heavy metal ions. By implementing diverse elemental doping, the electronic structure, band gap, and carrier concentration of GaS can be modified, thereby enhancing its surface activity and adsorption performance. For instance, Guler et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] demonstrated that the thermoluminescence properties of Nd-doped GaS vary significantly with light temperature, and Li et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] exhibited that hole-doped GaS displays substantial alterations in magneto-optical and Faraday effects. In a related study, Khan et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]established that pristine monolayer GaS is an indirect bandgap non-magnetic semiconductor and that by introducing N or Cr atoms for anion/cation doping, its band gap can be adjusted and a magnetic moment induced. Despite the intensive research conducted on GaS, with many fruitful results obtained, there are still many unresolved issues in adsorption. There is a paucity of research on the adsorption of heavy metal ions on GaS, with the adsorption of mercury ions, in particular, receiving insufficient attention. The layered structure of GaS gives it a high specific surface area, providing more active sites for adsorption. Therefore, exploring the adsorption performance of GaS materials for heavy metal ions (such as mercury), especially by doping non-metallic elements to enhance their adsorption capacity, has become one of the current research hotspots.\u003c/p\u003e \u003cp\u003eThis paper systematically studies the adsorption performance of pure GaS and doped GaS systems on mercury using first-principles calculations. The potential application of GaS materials in removing mercury ions is evaluated by analysing key parameters such as adsorption energy, band structure, and density of states. At the same time, this paper also discusses the possibility of further improving the adsorption capacity of GaS by doping non-metallic elements in the Ga and S sites. The study provides a theoretical foundation for applying GaS in water pollution control and offers novel perspectives for enhancing its versatility in optoelectronics.\u003c/p\u003e"},{"header":"2. Model and calculation method","content":"\u003cp\u003eThis study utilized a density functional theory (DFT)-based computational approach to conduct a systematic simulation analysis using the CASTEP module in Materials Studio software. The geometry optimization utilized a super-soft pseudopotential to model the ion-electron interactions, with the PBE functional within the generalized gradient approximation (GGA) chosen for the exchange-correlation potential. The PBE function is more effective in describing the local electronic structure; however, it has certain limitations in dealing with strongly correlated electronic systems (such as systems containing transition metals or heavy elements). Therefore, when dealing with such systems, more complex functionals (such as HSE06 or LDA\u0026thinsp;+\u0026thinsp;U) may be required to improve the accuracy of the calculation results. In order to enhance the calculation accuracy, the Grimme-2 correction was employed in this study to reasonably consider the role of van der Waals forces in the adsorption system. The Grimme-2 correction applies to systems with long-range interactions; however, its applicability in different systems must be evaluated case by case. The self-consistent dipole correction (SCC-DFT) was employed in this study to eliminate errors in the electronic structure caused by the dipole moment, thereby enhancing the reliability of the calculation results. Additionally, since Ga and S are light elements with weak spin-orbit coupling (SOC) effects, this study's neglect of SOC effects will not significantly affect the conclusions. However, Hg has a strong SOC effect, and its effect on localized states may not be negligible in some specific cases. However, it has a negligible effect on the overall electronic structure. Therefore, this study mainly analyses the effects of adsorption behaviour on geometric structure, adsorption energy and state density without involving magnetic or spin-related effects.\u003c/p\u003e \u003cp\u003eThe atomic electronic configurations are as follows: sulfur (S) is 3s\u0026sup2;3p⁴, and gallium (Ga) is 4s\u0026sup2;4p\u0026sup1;. The positions of Ga and S atoms are (0.3333, 0.6667, 0.32645) and (0.3333, 0.6667, 0.893149), respectively. In order to systematically study the effects of doping and adsorption on material properties, a 3 \u0026times; 3 \u0026times; 1 supercell model was constructed [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Figure\u0026nbsp;1 (a\u0026ndash;b) shows the top and side views of pure GaS, respectively. N, P and Si are frequently employed to modify semiconductors' conductivity and electronic structure. In contrast, F and Cl are primarily utilised to enhance materials' stability and surface properties. Carbon (C) has been observed to enhance conductivity or optimise the optical properties of certain novel materials. At the same time, oxygen (O) is often implicated in forming oxide layers, thereby affecting the interface properties of the material. Consequently, the doping of C, F, Cl, P, Si, N, and O at the Ga and S sites was considered in the study, as illustrated in Fig.\u0026nbsp;1(c).\u003c/p\u003e \u003cp\u003eThe impact of doping atoms on the crystal structure of GaS and its adsorption performance for Hg was investigated. It was found that doping atoms significantly affected both of these factors. Given the important impact of doping on the structural stability of the material, the study selected the three most stable doping elements in the S site and Ga site, respectively. Subsequently, adsorption analyses were performed on these six doped systems to screen for the best adsorption sites in each system. Four adsorption sites were the focus of this particular study: two top sites (TGa and TS), where Hg is located directly above Ga and S atoms; a bridging site (B), where Hg is located above GaS at the midpoint of the Ga-S bond; and a hole site (H), where Hg is located at the hole of the hexagonal atomic ring (see Fig.\u0026nbsp;1(e)). Finally, the most effective adsorption position was selected from the six doping structures to study its photoelectric properties. Figure\u0026nbsp;1(f) shows one of the doping adsorption configurations.\u003c/p\u003e \u003cp\u003eA 20 \u0026Aring; vacuum layer was introduced into the model to eliminate periodic interactions between distinct atomic layers. A cut-off energy of 500 eV was chosen to ensure an optimal compromise between computational accuracy and efficiency. A 6 \u0026times; 6 \u0026times; 1 k-point grid was generated using the Monkhorst-Pack method for self-consistent calculations. In the structural optimization, both atomic positions and lattice parameters were iteratively adjusted to ensure that the maximum force between atoms in the final configuration was below 0.03 eV/\u0026Aring;, and the maximum lattice stress did not exceed 0.05 GPa. Convergence was achieved when the energy change was smaller than 1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e eV and atomic displacement was under 0.001 \u0026Aring;.\u003c/p\u003e "},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Geometry and Stability\u003c/h2\u003e \u003cp\u003e GaS is a two-dimensional layered semiconductor material with a hexagonal lattice structure [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], in which Ga atoms form covalent bonds with four S atoms to form a single-layer GaS structure. The GaS monolayer has a honeycomb structure. Van der Waals forces bond the layers to form a 2H phase structure, in which Ga and S atoms are coordinated in a hexagonal close-packed arrangement, belonging to the P6\u003csub\u003e3\u003c/sub\u003e/mmc space group (No. 194). In the single-layer structure of GaS, Ga atoms are bonded to adjacent S atoms via σ bonds to form a planar structure. Following structural optimisation, the lattice constant (a\u0026thinsp;=\u0026thinsp;b\u0026thinsp;=\u0026thinsp;3.593 \u0026Aring;) is obtained, which agrees well with the experimental values reported in the literature [\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The bond length of 2.346 \u0026Aring; for the Ga-S bond in intrinsic GaS and the S-Ga-S bond angle of 100.5\u0026deg; (slightly higher than the experimental value of 99.64\u0026deg;). The calculation method and model are found to be feasible.\u003c/p\u003e \u003cp\u003eThe structural stability is a key factor for the experimental synthesis and practical application of two-dimensional materials. Hence, the dynamic and thermal stability of monolayer 2H-GaS were assessed through computational methods [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Firstly, the phonon spectrum of monolayer 2H-GaS was calculated, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a). It was found that there are no virtual frequencies in the phonon spectrum throughout the Brillouin zone, indicating that the system has good dynamic stability [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b), the simulation at 300 K and the crystal structure after 5 ps of simulation are presented. Throughout the simulation, both energy and system temperature exhibited slight fluctuations, with all atoms oscillating around their equilibrium positions, and the two-dimensional periodic structure remained stable.These computational results demonstrate that monolayer 2H-GaS exhibits excellent thermal stability and can be expected to exist stably within the room temperature range [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eConsidering the impact of doping or Hg adsorption on the structure, the bond lengths and angles of the most stable system are enumerated in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The alteration in the Ga-S bond length effectively reflects the degree of distortion of the crystal structure and the strength of the covalent bond. After the adsorption of Hg, particularly in the vicinity of the adsorption site, the Ga-S bond length undergoes a slight increase from 2.360 \u0026Aring; to 2.347 \u0026Aring;, signifying that the adsorption of Hg results in alterations to the chemical bond. This phenomenon suggests that the adsorption of Hg weakens the interaction of the Ga-S bond through electronic or geometric effects, consequently leading to an elongation of the bond length. Furthermore, introducing non-metals at distinct sites within the GaS lattice alters its fundamental parameters. The introduction of dopant elements further complicates the system's nature, providing a more significant number of possibilities for regulating material properties. Comprehending these alterations can provide insight into the behaviour of GaS and its doped systems during adsorption. In summary, relatively minor structural changes occur within the doped non-metallic element Hg adsorption system, with bond length changes typically amounting to approximately 0.1 \u0026Aring;. This indicates that the system remains stable following the processes of doping and adsorption, although there may be a significant alteration to the electronic structure. The Ga-S bond population value ranges from 0.51 to 0.54, suggesting electron sharing between Ga and S and maintaining a balanced covalent bond nature. The system exhibits high stability within this range, indicating that slight changes in the electronic distribution of the Ga-S bond in the doped adsorption system may occur.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe most stable structural parameters before and after GaS adsorption (X\u0026thinsp;=\u0026thinsp;S/C/N/O)(Y\u0026thinsp;=\u0026thinsp;Ga/C/N/Si)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003estructure type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBand length(\u0026Aring;)\u003c/p\u003e \u003cp\u003e(Ga-S)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAdsorption height(\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBand Angle(\u0026deg;)\u003c/p\u003e \u003cp\u003eGa-X-Hg/S-Y-Hg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePopulation\u003c/p\u003e \u003cp\u003e(Ga-S)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGaS supercell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.360\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGaS adsorbed Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.347\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.867\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(C)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.381\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.595\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e143.687\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(N)\u0026thinsp;+\u0026thinsp;TGa-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.749\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e103.702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(Si)\u0026thinsp;+\u0026thinsp;TGa-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.403\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.308\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e63.818\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(C)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.365\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e106.158\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(N)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.376\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.689\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e106.258\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(O)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.374\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.130\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e103.770\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe present study employs formation energy as an evaluation criterion to quantify the material structure's stability and its preparation's difficulty and investigate the stability of adsorption systems with intrinsic and doped non-metals. Formation energy reflects the change in energy required when a doped element occupies a specific position in the material compared to the undoped system. Generally, a lower formation energy means the doping process is more stable and more likely to occur. The following formula is employed to calculate formation energy [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{\\:E}_{form}={E}_{doped}-{E}_{pure}-{E}_{dopant\\:isolated}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eIn the context of this study, \"\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003edoped\u003c/em\u003e\u003c/sub\u003e\" is defined as the total energy of the doped system, \"\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epure\u003c/em\u003e\u003c/sub\u003e\" is the total energy of the pure material (i.e. the undoped matrix material), and \"\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003edopant isolated\u003c/em\u003e\u003c/sub\u003e\" is the energy of the dopant when it exists independently (i.e. the energy of the dopant in the gas phase or other environment). The formation energy of the doped system at different sites is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, an analysis of the formation energies of the various doping site systems reveals that the formation energies of the Ga site C (-0.603 eV) and Si (-0.022 eV) atom doping systems, In addition, the S site C (-0.753 eV), N (-1.816 eV) and O (-2.154 eV) atom doping systems exhibit negative formation energies, suggesting enhanced stability for these doping systems. This phenomenon may be attributed to the dopant elements' atomic size, electronic structure and chemical affinity. For instance, the weak interaction or good fit between the C and Si atoms and the Ga atoms means that excessive structural mismatch is not likely to occur after doping, which in turn reduces the total energy of the system and makes it easier for the doped atoms to enter the Ga sites of GaS and form a stable structure. In contrast, non-metallic elements such as C, N and O have high electron affinities and strong chemical interactions. When doped in the S site, these elements enhance the system's stability by providing additional electrons or forming specific chemical bonds.\u003c/p\u003e \u003cp\u003eIn order to facilitate a horizontal comparison, the formation energies of the Ga-doped N systems were also studied. Subsequently, the six doping systems were combined with the Hg adsorption system, and the most stable adsorption site was selected for subsequent photoelectric property research by calculating the formation energies of different adsorption sites. In order to systematically evaluate the influence of doped atoms on adsorption capacity and structural stability [\u003cspan additionalcitationids=\"CR42\" citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], the adsorption energies were calculated using the following method:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{E}_{ads}={E}_{substrate-Hg}-\\left({E}_{substrate}+{E}_{Hg}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003esubstrate\u0026minus;Hg\u003c/em\u003e\u003c/sub\u003e is the total energy of the adsorbate and surface standard system, \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003esubstrate\u003c/em\u003e\u003c/sub\u003e is the energy of the GaS substrate, and \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eHg\u003c/em\u003e\u003c/sub\u003e is the energy of the Hg atom. As demonstrated in Eq.\u0026nbsp;(\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), it can be seen that the greater the absolute value of the adsorption energy, the more stable the adsorption system. According to the second equation, the adsorption energies of the four adsorption sites of the supercell eigenstate were calculated to be TS\u0026thinsp;=\u0026thinsp;0.004 eV, TGa = -0.0015 eV, H\u0026thinsp;=\u0026thinsp;0.001 eV and B = -0.0018 eV, respectively. This demonstrates that the supercell is most stable when adsorbed at the B site. In order to enhance the adsorption capacity of GaS for Hg, non-metallic elements were doped in the Ga and S sites, respectively. Following structural optimisation, the adsorption energies of each doped adsorption system were obtained, and all adsorption energies were found to be negative. For comparison, the absolute values of the adsorption energies are plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The adsorption of doped Hg atoms on the GaS surface is a spontaneous process, and the magnitude of the adsorption energy is closely related to the ease of the adsorption process. A comparison of the adsorption energy of the doped and undoped GaS systems reveals that the doped system exhibits higher adsorption energy. The Ga-site N-doped system exhibits the most substantial adsorption strength, while the S-site O-doped system exhibits the weakest. The findings of this study demonstrate that doping significantly enhances the adsorption capacity of Hg atoms on the GaS surface, thereby promoting the formation of a more stable adsorption structure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Electronic property\u003c/h2\u003e \u003cp\u003eIn order to further study the electronic structure of the doped adsorption system, the band structure and density of states (DOS) of each system (intrinsic GaS, atomically doped and atomically doped adsorption) were calculated, with the broadening setting fixed at 0.02 eV. A horizontal red dashed line indicates the Fermi level (with an energy of 0). The band diagram and density of states of pure GaS are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a-b), respectively. The band gap of GaS is 2.423 eV, the highest point of the valence band is between the Gamma point and the M point, and the lowest point of the conduction band is at the Gamma point. This observation indicates that the intrinsic monolayer GaS is a typical indirect band gap semiconductor, a finding broadly consistent with the results reported in the literature [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The valence band is predominantly composed of S-3p states and Ga-4p states, with a minor contribution from Ga-4s states, while the conduction band is primarily constituted of S-3p states and Ga-4p and Ga-4s states. The strong hybridisation between these states forms stable covalent bonding characteristics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs demonstrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a\u0026ndash;c) and 7(a\u0026ndash;c), the band structure and density of states (DOS) of the Ga-doped systems are exhibited. The three doping systems demonstrate n-type doping, which is characterised by an increase in the number of electronic states in proximity to the Fermi level. The Fermi level is near the bottom of the conduction band. Following the introduction of C or N as impurities into GaS, there is a significant change in the band structure, specifically a migration of the conduction band towards the Fermi level and a substantial reduction in the band gap width. After C and N doping, the band gaps are 0.172 eV and 1.198 eV, respectively. In the C-doped system, the conduction band is primarily composed of Ga-4p and S-3p states, limiting the contribution of C-2p states. The valence band is dominated by the S-3p state and the Ga-4p state, with the C-2p state having minimal participation in forming the valence band. Conversely, within the N-doped system, the N-2p state hybridises with the S-3p state, thereby weakly contributing to the formation of the conduction band. This disparity underscores the notion that dopant elements exert disparate influences on the band structure through their interactions with the electronic states of the GaS substrate. Specifically, the impact of C doping on the electronic state distribution of the conduction and valence bands was negligible due to the interaction's weak nature. By contrast, N doping significantly affected the formation of the conduction band, resulting from hybridisation with the S-3p state. These differences offer novel insights into regulating the electronic properties of GaS through doping elements. Following Si doping, a notable shift in the energy level of the valence band occurs, resulting in its intersection with the Fermi level. This observation signifies a substantial modification of the electronic structure of GaS, leading to the partial filling of the original band gap. This phenomenon is corroborated by the density of states diagram, which further substantiates the transition of the material from conventional semiconductor properties to metal properties, thereby significantly enhancing its conductivity. This transition not only enhances the conductivity of GaS but also opens up new research directions for its application in optoelectronic devices, sensors and catalysis.\u003c/p\u003e \u003cp\u003eAs demonstrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e(d-f) and 7(d-f), the band structure and density of states (DOS) of the S-site doping system, respectively, are shown. It is evident from the figures that C and N doping are p-type doping, which may introduce localized states in the vicinity of the top of the valence band. The density of states diagram reveals that the Fermi level is near the valence band, indicating an augmentation in the number of hole states near the Fermi level. The band gap values after doping are 0.699 eV (C doping) and 1.855 eV (N doping). Although the band gap decreases, the system retains its indirect band gap nature, indicating that the energy levels of the conduction and valence bands have shifted. Nonetheless, electron transitions from the valence band to the conduction band still rely on phonon assistance rather than occurring via a direct transition. In the C-doped system, the valence band comprises S-3p states, Ga-4p states and a small amount of C-2p states, while S-3p states and Ga-4p states dominate the conduction band. In addition, significant localised states in the conduction band near the Fermi level indicate substantial changes in the material's electronic structure, which may provide additional pathways for electron transitions. In the N-doped system, the valence band comprises S-3p states, Ga-4p states and a minor amount of N-2p states, with localised states also evident in the valence band near the Fermi level. In contrast, O doping does not exhibit analogous phenomena.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs demonstrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e, the energy band structures and DOS of GaS doped with Ga and S are shown. Compared with pure GaS, the band gap of the doped system is reduced. In the Ga-doped system, the C-2p state hybridises with the Ga-4p state and the S-3p state to form the conduction band. The Si-doped system exhibits a similar phenomenon, and the DOS diagram demonstrates that the conduction band crosses the Fermi level, thereby proving its metallic nature. The band gaps of the three systems doped at the S site are 1.006 eV (C doping), 1.869 eV (N doping) and 1.974 eV (O doping), in that order. This change can be attributed to introducing the doping element, with the newly generated impurity energy levels close to the Fermi energy level, thereby reducing the energy of electron transitions and resulting in a narrower band gap. A comparison of the state density characteristics of the three doping systems reveals a similarity in their properties, with the valence band primarily formed by the combined contributions of the S-3p state, Ga-3d state and the 2p state of the doping element. In contrast, the Ga-4p state predominantly dominates the conduction band. In the adsorption system of C atoms doped with C in the S position, a small peak of approximately 10 eV emerges in the conduction band, primarily attributable to the 2p state of C. The emergence of this peak introduces new localised states into the material's electronic structure, providing additional channels for electron transitions and potentially enhancing the material's conductivity. Specifically, these localised states may promote the excitation of low-energy electrons, thereby reducing the excitation energy required for electrons to transition between energy bands. This, in turn, may improve the electrical conductivity and carrier mobility of the material. In contrast, no analogous localised state features were observed in the N-doped and O-doped systems, suggesting that C atoms behave differently when doped in the S position than when doped with N and O and may exert a distinct effect on the electronic structure and electrical conductivity of the material.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDoping and adsorption are significant mechanisms for regulating the electronic properties of materials. Doping alters the electronic structure of a material by introducing new electronic states, changing the band gap, and adjusting the carrier concentration. Adsorption further optimises or adjusts the material's electronic properties by affecting surface states and adjusting local electronic density. The combined effect of the two mechanisms can achieve more precise regulation of the electronic and adsorption properties in material design, thereby enhancing the adsorption capacity for pollutants such as mercury. However, it is important to note that the impact of doping and adsorption on the electronic structure and adsorption properties of materials is not limited to theoretical considerations. These processes have the potential to enhance the performance of GaS materials in a variety of practical applications, particularly in the domains of optoelectronic devices, sensors, and catalysis. Specifically, doping has been shown to enhance the performance of GaS in optoelectronic devices. For instance, introducing dopants can adjust the band gap, enabling the material to absorb a broader spectrum of light and thus enhancing the photoelectric conversion efficiency. In photodetectors, doping elements can enhance the material's light response speed and sensitivity by adjusting the electron density of the conduction and valence bands. Conversely, the adsorption process can improve the surface reactivity of the material by altering the surface state, thereby optimising the response performance in sensors. In catalytic applications, doping and adsorption modify the material's electronic structure and enhance its ability to adsorb reactants and catalytic activity, further improving catalytic efficiency.\u003c/p\u003e \u003cp\u003eMoreover, the interplay between doping and adsorption imparts distinct advantages to GaS materials. Specifically, GaS demonstrates superior sensitivity and response speed relative to conventional semiconductor materials (e.g., silicon, gallium arsenide.), particularly regarding light absorption within specific wavelength ranges. By carefully controlling the nature and degree of doping and adsorption, the performance of GaS materials in practical applications can be further optimized, thereby enhancing their competitiveness in optoelectronics, sensing, and catalysis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3Adsorption properties\u003c/h2\u003e \u003cp\u003eBy calculating the differential charge density map of the doped adsorption system (see Fig.\u0026nbsp;10), it can be seen that the dopant or adsorbate causes a significant charge accumulation or hole region on the surface or interface region of the material. The adsorbate (Hg) causes an increase or decrease in local electron density through interactions with matrix atoms, manifested by forming electron accumulation regions and deficient regions. This phenomenon suggests that the adsorption or doping process may have induced a transfer of electrons, thereby modifying the material's electronic structure and local charge distribution. The red area in the figure denotes a decrease in electron density near Hg, indicating that electrons have been transferred from Hg to the GaS substrate. This also suggests that Hg has lost some electrons while adsorbing onto the GaS surface. Conversely, the blue area, which corresponds to an increase in electron density, is primarily concentrated around the S atoms, suggesting that these atoms have gained electrons from the adsorbate.\u003c/p\u003e \u003cp\u003eThe results of differential charge analysis demonstrate that electron rearrangements induced by doping or adsorption can substantially modify the local charge distribution of the material, particularly within the valence and conduction band regions. The presence of dopants or adsorbates can influence the band gap width and carrier concentration of the material through their capacity to attract or release electrons. This charge rearrangement directly influences the electrical conductivity and photoelectric properties of the material. In the specific case of semiconductor materials, the presence of dopants or adsorbates has been shown to either promote electron excitation or inhibit carrier recombination, thereby leading to the effective enhancement of the electrical conductivity or the light absorption capacity of the material. Notably, the distribution of differential charge density exhibits marked differences in different doping and adsorption systems. For instance, a substantial charge accumulation is observed near the N atom in the Ga-site N-doped adsorption system. This suggests that incorporating N enhances the system's stability and augments the adsorption capacity of GaS for Hg. Consequently, this reduces the distortion field on the GaS substrate, thereby facilitating further adsorption of Hg. Conversely, in the C-doped system, the degree of charge transfer is reduced, which may be attributed to the lower electronegativity of the C atom, leading to weaker charge interactions with the substrate. In the adsorption system with C or N atoms doped in the S site, the electron density is substantially increased, manifesting as a harmful charge accumulation, indicating that the dopant has obtained electrons from the substrate. Conversely, a significant decrease in electron density is observed on the substrate surface, forming an electron depletion region, suggesting an electron transfer from the substrate to the dopant. This electron transfer effect impacts the material's local charge distribution and electronic properties, consequently leading to alterations in the adsorption performance.\u003c/p\u003e \u003cp\u003eIn order to further understand the electronic exchange between Hg and the substrate, the charge transfer of Hg adsorption in various doped systems is shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAdsorbed Hg electron transfer for doped systems\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharge\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGa(C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGa(N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGa(Si)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS(C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eS(N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eS(O)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHg(e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e As illustrated in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the charge transfer of C-doped GaS in the S site is 0.32 e, the largest among the six doping systems. This indicates that after C atoms are doping in the S site, more electrons are lost from the GaS matrix, resulting in a harmful charge accumulation. This substantial charge transfer may be attributable to two factors: firstly, the strong interaction between C atoms and S atoms, and secondly, the higher electronegativity of C atoms compared to S atoms, making it easier for C atoms to attract electrons from their surroundings. In the Ga-site C-doped and N-doped systems, the amount of charge transfer was \u0026minus;\u0026thinsp;0.05 e and \u0026minus;\u0026thinsp;0.06 e, respectively, indicating that after C atoms and N atoms were doped into the Ga site, there was almost no significant electron accumulation, and the electronic effect on the GaS substrate was relatively limited. However, compared with the pure GaS adsorption system, the Ga-site N-doped system demonstrated a marginally enhanced adsorption capacity.\u003c/p\u003e \u003cp\u003eThese charge transfer results indicate that the position of the dopant element and the doping type significantly impact the electronic properties and, ultimately, the performance of the GaS material.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Optical property\u003c/h2\u003e \u003cp\u003eThe dielectric function is a significant physical quantity that characterises the response of a material to an electric field. It is composed of a real part and an imaginary part, the former being associated with the optical properties of the material and the latter with its energy loss characteristics. The dielectric function demonstrates the polarisation capability of a solid material and the extent to which electrons are excited to jump. A thorough examination of the dielectric function is paramount for advancing efficient optoelectronic devices and comprehending the optical properties of materials.Its formula is as follows[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:{{\\rm\\:E}}_{（{\\omega\\:}）}={\\epsilon\\:}_{1}+i{\\epsilon\\:}_{2}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe Kramers-Kronig dispersion relation is utilised to ascertain the fundamental part of the dielectric function (ε\u003csub\u003e1\u003c/sub\u003e), which indicates the strength of electron polarisation in the material under an applied electric field. Furthermore, it is associated with the material's refractive index and light propagation characteristics. The imaginary part of the dielectric function (ε\u003csub\u003e2\u003c/sub\u003e) reflects the light absorption characteristics, which are associated with the material's absorption capacity and energy loss. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e11\u003c/span\u003e(a), the ε\u003csub\u003e1\u003c/sub\u003e of single-layer GaS and its doping system adsorbing Hg is demonstrated. The static permittivity of Hg adsorption on GaS supercells and Ga-doped C, N, Si-doped and S-doped C, N, O are enumerated in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The intrinsic GaS adsorption system exhibits the lowest static dielectric constant, while the Ga-doped Si adsorption system demonstrates the highest. This observation signifies that the latter possesses superior and more robust polarization capacity and electric field response. Consequently, this system can effectively polarize and store more electrical energy under an external electric field. The material's electronic structure may be responsible for an increase in free carriers or a higher charge density due to polarization, thereby enhancing the response to external electric fields. As illustrated in the figure, the adsorption system of Ga-doped Si becomes negative in the low-energy region, indicating that the polarization response of the material is opposite to the direction of the applied electric field. This phenomenon may be attributed to various factors, including the material's metal-insulator transition, surface plasmon resonance, local charge accumulation, and other effects. It is particularly significant in specific material systems, such as nanomaterials, two-dimensional materials, or materials with strong electron-related effects. It may substantially impact the optoelectronic, electronic, and magnetic properties of the material.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e11\u003c/span\u003e(b) illustrates that the ε\u003csub\u003e2\u003c/sub\u003e of Hg adsorption on single-layer GaS and its doping systems predominantly occurs within the 0\u0026ndash;10 eV range. The adsorption systems of Ga-doped Si and Ga-doped C exhibit more prominent peaks in the low-energy range, suggesting the presence of local defect states or new electronic states introduced by doping in the adsorption systems of Ga-doped Si and Ga-doped C. These new electronic states result in enhanced low-energy absorption, accompanied by a shift in the position of the peaks towards the red, indicating a reduction in the material's band gap. This reduction in band gap energy indicates that the energy required for electrons to transition from the valence to the conduction band is decreased, leading to a shift in the absorption spectrum towards lower energies. In contrast, the other four doped adsorption systems exhibit the most prominent peaks in the high-energy range, with the maximum peaks all near 5.1 eV. The position of these peaks has shifted to the blue. This shift may be attributed to the introduction of doped atoms, which increases the polarization rate of the system. Among the doped systems, only the peak intensity of the N-doped Ga sites adsorption system decreased compared with the intrinsic system, with a value of 4.601, which is 0.152 lower than that of the intrinsic system. This phenomenon can be attributed to incorporating the doping element into the electronic structure and chemical bonds of the GaS substrate, resulting in alterations to the electronic transition or vibration modes. These modifications may have reduced the polarisation response of the system within a specific energy range, consequently decreasing the peak dielectric absorption intensity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStatic dielectric constant and imaginary peak coordinates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSystem\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStatic dielectric\u003c/p\u003e \u003cp\u003econstan\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePhoton energy/eV\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePeak coordinate\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePure GaS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.054\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.753\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(C)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e19.831\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.379\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.427\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(N)\u0026thinsp;+\u0026thinsp;TGa-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.172\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.601\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGa(Si)\u0026thinsp;+\u0026thinsp;TGa-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e78.069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e29.622\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(C)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.880\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(N)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.057\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.198\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.986\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS(O)\u0026thinsp;+\u0026thinsp;TS-Hg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.050\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.169\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.853\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe impact of doping on the optical characteristics of Hg-GaS can be further investigated by analyzing the absorption and reflection spectra of various systems. Absorbance is typically calculated from the measurement of transmitted light intensity and is a widely used parameter for characterizing a material's capacity to absorb light at a specific wavelength. It is the negative logarithm of light's transmittance (T), i.e., [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e], where A is the absorbance, and T is the transmittance. The reflectance indicates the degree to which the material's surface reflects the incident light and provides more intuitive information about the optical properties. The photon frequency (\u003cem\u003eν\u003c/em\u003e) is the frequency of the photon fluctuation, and \u003cem\u003eh\u003c/em\u003e represents Planck's constant, approximately 6.63 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;34\u003c/sup\u003e. It is directly related to the energy of light (E), and the two are related to each other by Planck's formula [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{E}=\\text{ℎ}\\times\\:{\\nu\\:}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003eThe analysis results demonstrate that doping and adsorption induce alterations to the optical properties of GaS, particularly concerning light absorption and reflection behavior. Specifically, the defect states or localized electronic states instigated by doping substantially enhance the material's light absorption within a designated wavelength range. As demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e(a), the absorption coefficients of the six doped and adsorbed systems exhibit a gradual increase in the photon frequency range from 1.21\u0026times;10\u003csup\u003e15\u003c/sup\u003e Hz to 1.93\u0026times;10\u003csup\u003e15\u003c/sup\u003e Hz. The Ga-position doped C and Si adsorbed systems exhibit the initial absorption peaks at 1.03 eV and 0.95 eV, respectively, suggesting that C and Si doping introduces local energy levels, thereby facilitating the absorption of low-energy light. In the S-site doped system, in particular, the formation of these localized states may be closely related to the narrowing of the band gap and the change in electron transition between the conduction band and the valence band. Doping lets the material absorb lower energy light by changing the band gap structure. Introducing defects or localized electronic states may also enhance the optical response in specific wavelength bands. Further analysis indicates that doping results in a slight red shift in the position of the material's prominent absorption peaks, for example, at 7.84 eV and 7.71 eV, which reflects changes in the band gap structure or electron transition characteristics. These changes signify that doping not only optimizes the absorption of low-energy light but may also significantly impact applications such as optoelectronic devices or solar cells. In solar cells, the local energy levels induced by doping can facilitate more efficient photoelectric conversion. At the same time, adjusting the band gap can enhance the material's light absorption in the visible or infrared regions. In summary, doping modifies the electronic structure and optical properties of GaS materials by introducing additional defect states or localized electronic states, thereby enhancing their light absorption capacity. This provides a new control strategy for further optimizing the application of GaS materials in optoelectronic devices, solar cells, and other fields.\u003c/p\u003e \u003cp\u003eReflectivity (R) is typically defined as a parameter that characterizes the optical properties of a material's surface reflection, indicating the proportion of incident light reflected after interacting with the surface. It is a measure of the material's surface's capacity to reflect incident light and is closely related to the position of the absorption peak because, after light interacts with the material, the energy is divided into three parts: absorption (A), transmission (T) and reflection (R).[\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e] High reflectivity usually means low transmittance. As demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e(b), when the photon energy is zero, the reflectivity of the adsorption system with Ga-site C-doping and Ga-site Si-doping increases significantly. In contrast, the other systems do not show apparent changes. These changes indicate that these two doping systems exhibit higher reflectivity in the low-energy region, which is consistent with the changes in the dielectric function and absorption coefficient. Notably, at an energy of 1.69 eV, the reflectivity of the Ga-doped Si adsorption system approaches 0, indicating that the majority of light is transmitted or absorbed, thereby enhancing the excitation efficiency of photoelectrons. This phenomenon provides a theoretical foundation for transparent materials, the design of optical devices, anti-reflective coatings, surface engineering, and nano-optics. Furthermore, the spectral changes caused by doping demonstrate that all the doping adsorption curves have shifted to the right, which may indicate that the introduction of dopant elements (such as C, N, O, and Si) causes a blue shift in the characteristic spectrum of the GaS adsorption Hg system. This blue shift may be related to the electronic structure characteristics (e.g., ionic radius, electronegativity) of the dopant elements, which affect the electronic structure of GaS and further regulate its ability to adsorb Hg. For example, the redshift and band gap change introduced by Si doping may be related to Si's small ionic radius and high electronegativity. These properties may have promoted changes in the electronic cloud, which affected the material's band gap structure and optical absorption characteristics. The reflectivity of the GaS adsorption system doped with N at the Ga site is generally lower than that of the intrinsic system. This finding may indicate that the GaS adsorption system doped with N at the Ga site has more substantial light absorption capacity, especially in the low-to-medium energy region. This is due to the effect of N doping on the band gap of the material and the optimization of its electronic structure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e13\u003c/span\u003e, the energy loss function of each system is exhibited. In the low-energy region, the Si-doped Hg adsorption system at the Ga site manifests a higher energy loss function, thereby indicating that the electronic structure of this system is more unstable or 'relaxed' under low-energy electron excitation. Conversely, the adsorption system doped with non-metallic elements such as C, N, and O at the S site demonstrates a substantially diminished energy loss function in the low-energy region, signifying that doping enhances the stability of the electronic structure of the system. Further analysis indicates that the adsorption system doped with N at the Ga site exhibits optimal electronic stability in the low-energy region. In contrast, the adsorption system doped with Si at the Ga site demonstrates the poorest stability within this region. In the high-energy region, the difference in the energy loss function of each doping system is minimal, suggesting that the influence of different doping elements on the electronic structure of the GaS adsorption system in this region is negligible. In the broader context of the entire spectral range, the energy loss function values of the S-site doped O and Ga-site doped N systems are predominantly low, signifying that these two types of doping exert a substantial influence on the electronic structure of the GaS adsorption system and contribute to enhancing the overall stability of the system. In summary, S-site doping with O and Ga-site doping with N effectively enhance the system's stability in the low-energy region and maintain a lower energy loss function in the high-energy region. These improvements make these two doping types an important means of optimizing the electronic structure and optical properties of the GaS adsorption system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study employs first-principles calculations to comprehensively investigate the impact of non-metallic doping on the optical properties of single-layer GaS materials, focusing on regulating photoelectric performance during mercury adsorption. The results demonstrate that various doping elements significantly influence the electronic structure and optical response of GaS materials (e.g., C, N, O, and Si). The introduction of local defect states and new electronic states, a consequence of doping, has significantly changed the dielectric function, absorbance, and reflectivity of GaS, particularly within the low-energy and high-energy regions. The optical absorption characteristics have undergone substantial alterations, with the adsorption system of Ga-doped Si exhibiting a pronounced polarisation response and light absorption capacity in the low-energy region. The narrowing of the band gap has been evidenced to enhance the absorption of low-energy light. Moreover, the impact of doping on the energy loss function indicates that the S-site doped O and Ga-site doped N systems enhance the electronic structure's stability and optimize the material's overall photoelectric properties. Through these doping methods, the photoelectric response of GaS materials has been considerably enhanced, providing a theoretical foundation for utilizing novel optoelectronic devices, solar cells, and gas sensors.\u003c/p\u003e \u003cp\u003eThe findings of this study offer novel concepts for the regulation of performance in GaS-based optoelectronic materials. Furthermore, they establish a foundation for research on utilizing non-metallic doping in two-dimensional materials. Subsequent studies can extend this research by investigating the impact of diverse doping systems on additional physical properties of GaS materials. These properties include their stability and durability in complex environments and the interactions between dopant elements and the external environment.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthor contributionZilian Tian: Investigation, Methodology, Validation, Visualization, Writing - original draft, Writing - review \u0026amp; editing. Lu Yang: Software, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision. Xiaotong Yang: Writing - review \u0026amp; editing. Hang Yang: Writing - review \u0026amp; editing. Yao Dong: Writing - review \u0026amp; editing. Wei Zhao: Writing - review \u0026amp; editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eQi, C., Xu, X., Chen, Q., Liu, H., Min, X., Fourie, A., Chai, L.: Ab initio calculation of the adsorption of As, Cd, Cr, and Hg heavy metal atoms onto the illite (001) surface: Implications for soil pollution and reclamation. Environ. Pollut. \u003cb\u003e312\u003c/b\u003e, 120072 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTang, H., Duan, Y., Zhu, C., Cai, T., Li, C., Cai, L.: Theoretical evaluation on selective adsorption characteristics of alkali metal-based sorbents for gaseous oxidized mercury. Chemosphere. \u003cb\u003e184\u003c/b\u003e, 711\u0026ndash;719 (2017)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXia, M., Chen, Z., Li, Y., Li, C., Ahmad, N.M., Cheema, W.A., Zhu, S.: Removal of Hg (II) in aqueous solutions through physical and chemical adsorption principles. 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Mater. \u003cb\u003e7\u003c/b\u003e, 978\u0026ndash;983 (2008)\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"GaS material, non-metallic doping, electronic structure, optical properties, Hg adsorption","lastPublishedDoi":"10.21203/rs.3.rs-6183020/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6183020/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study systematically explores the optical properties of non-metallic doped single-layer GaS materials and their performance in mercury adsorption. Using first-principles calculations, the effects of different doping elements (including C, N, O, Si.) on the optical properties of GaS were investigated, with a focus on the regulatory effects of doping on the material's dielectric function, absorbance, reflectivity, and energy loss function. The results demonstrate that the doping elements induce substantial changes in the electronic structure and optical response of GaS. Notably, the Ga-doped Si system displays pronounced polarization response and light absorption capability in the low-energy region, resulting in a shift towards longer wavelengths in its absorption spectrum. The reflectivity of different doping systems in the low-energy and high-energy regions also exhibits divergent trends. Doping with elements such as Si and C shifts the absorption peak to lower energies, narrows the band gap, and enhances the material's absorption of low-energy light. In addition, energy loss function analysis elucidates the contribution of doped elements to the stability of the electronic structure in the low-energy region. The Ga-site doped N and S-site doped O systems demonstrate exceptional electronic stability. In conclusion, the findings of this study demonstrate that doping regulates the optical and electronic properties of GaS materials, thus providing novel optimisation strategies for applications such as optoelectronic devices, solar cells, and sensors. Through in-depth analysis of this study, we provide a theoretical basis for designing efficient optoelectronic materials and lay the foundation for applied research in related fields.\u003c/p\u003e","manuscriptTitle":"Effect of non-metallic doping on the electronic structure of GaS monolayers and mercury adsorption performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-12 06:40:38","doi":"10.21203/rs.3.rs-6183020/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"44bad20a-1534-4cf6-84a2-5fcbc1599a02","owner":[],"postedDate":"March 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-22T13:53:35+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-12 06:40:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6183020","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6183020","identity":"rs-6183020","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}