Quantum Mechanical Insights into Phenol Adsorption and Sensing Behavior of Chitosan-gr-Polysulphanilic Acid

Quantum Mechanical Insights into Phenol Adsorption and Sensing Behavior of Chitosan-gr-Polysulphanilic Acid | 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 Quantum Mechanical Insights into Phenol Adsorption and Sensing Behavior of Chitosan-gr-Polysulphanilic Acid M. S. Ibrahim, H.R. Abd El-Mageed, H. M. Abd El-Salam This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7349857/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 The potential of Chitosan-gr-Polysulphanilic acid as a sensor for phenol detection has been thoroughly investigated using quantum mechanical calculations in both gas and aqueous phases. The results demonstrate that Chitosan-gr-Polysulphanilic acid exhibits high sensitivity and a strong affinity for phenol molecules. The adsorption energy of its most stable configuration is approximately − 14.69 kcal/mol in the gas phase and − 12.88 kcal/mol in the aqueous phase, indicating a favorable binding interaction. The adsorption of phenol significantly reduces the material's band gap, which enhances its electrical conductivity, suggesting that Chitosan-gr-Polysulphanilic acid could be an effective candidate for phenol detection, particularly in electronic sensor applications. The material’s electronic properties, including the HOMO and LUMO energy levels, also indicate that phenol adsorption leads to a substantial reduction in the band gap, which can be leveraged for more sensitive and efficient detection of phenol. Additionally, the interaction between Chitosan-gr-Polysulphanilic acid and phenol has been shown to induce a notable change in the material's work function, further supporting its potential for use as a work function-based sensor for phenol detection. The material's ability to alter its electronic properties upon adsorption of phenol highlights its potential as a responsive and adaptable sensing material. In terms of practical application, the desorption of phenol from Chitosan-gr-Polysulphanilic acid was found to be remarkably efficient, with a rapid recovery time of approximately 4.09 ms. This fast recovery time suggests that the material is highly suitable for real-time sensor applications, where quick adsorption and desorption cycles are essential for effective phenol monitoring. In conclusion, Chitosan-gr-Polysulphanilic acid shows significant promise as a phenol sensor, offering high sensitivity, rapid response times, and reversible adsorption-desorption behavior, making it an excellent candidate for environmental monitoring and industrial applications where phenol detection is critical. Chitosan phenol Chitosan-gr-Polysulphanilic acid polyaniline DFT Figures Figure 1 Figure 2 Figure 3 Introduction A polymer-supported sulphanilic acid catalyst was synthesized and utilized as a green, reusable, and heterogeneous catalyst. It was thoroughly characterized using chemical techniques, including the determination of free hydroxyl content, epoxy equivalent weight, and free sulfonic acid content, as well as infrared spectroscopy and thermogravimetric analysis. The catalyst was employed for the one-pot synthesis of 2-substituted benzimidazoles from o-phenylenediamine and various aromatic aldehydes in absolute ethanol under thermal conditions. The catalyst could be easily separated from the product through simple filtration and reused multiple times with minimal loss of efficiency. Its three-dimensional network structure imparts high thermal stability, allowing for reuse without the need for additional purification [ 1 ]. sulfanilic acid is a crucial chemical compound, widely used in the azo dye industry and in the pharmaceutical development of antimicrobial agents, such as sulfonamides. Azo dyes are synthesized through the azo coupling reaction of sulfanilic acid, in its diazonium salt form, with compounds like N,N-dimethylaniline or 2-naphthol [ 2 ]. Systematically known as 4-aminobenzenesulfonic acid, sulfanilic acid is a key organic compound in the science and technology of azo dyes [ 3 ]. When reacted with alkali nitrite in an acidic medium, it forms a diazonium salt, which readily couples as an electrophile with phenol in a basic medium or with an aromatic amine in an acidic medium to form azo compounds. These compounds are extensively used as synthetic dyes in the textile and food industries. Notable dyes derived from sulfanilic acid include methyl orange, an acid-base indicator, and Orange II, used for textile coloring. The synthesis of sulfanilic acid is a fundamental process in laboratory settings [ 4 – 5 ]. Electrophilic aromatic substitution involves an intriguing reaction mechanism, including the rearrangement of the intermediate phenylsulfamic acid into sulfanilic acid. The final product, sulfanilic acid, exists as an internal salt due to interactions between its acidic [-SO₃H] and basic [-NH₂] functional groups within the molecule [ 6 – 7 ]. Benzimidazole and its derivatives have been extensively studied due to their significance in various applications and their substantial biochemical importance [ 8 ]. The benzimidazole framework is a part of several classes of drugs, with its properties influenced by substituents at different positions [ 9 ]. Additionally, benzimidazole derivatives have numerous pharmaceutical applications, especially as antimicrobial agents [ 10 ]. Benzimidazoles are also vital intermediates in organic synthesis [ 11 – 12 ]. Biological methods, such as those involving Pseudomonas aeruginosa , have proven effective in removing phenol from contaminated water [ 13 ]. Phenol is not only a critical industrial chemical but also a significant environmental pollutant. Due to industrial spills, leaks, and discharges, phenol and its derivatives are commonly found as contaminants in the environment. Therefore, the removal of phenolic compounds from industrial wastewater is essential to reduce environmental pollution [ 14 ]. The main sources of pollution include wastewater from industries such as paint, pesticides, coal conversion, polymeric resins, petroleum, and petrochemicals [ 15 ]. In recognition of the toxicity of these substances, the United Nations declared 1981–1990 as the "International Drinking Water Supply and Sanitation Decade" [ 16 ]. Various regulatory organizations have implemented stringent regulations to limit the release of phenolic substances into the environment. The U.S. Environmental Protection Agency has classified phenol as a priority pollutant [ 17 ]. Phenol is among the top 100 hazardous substances listed by the Agency for Toxic Substances and Disease Registry [ 18 ]. Several physical and chemical techniques have been proposed for treating wastewater containing phenolic pollutants, such as precipitation, coagulation, chemical oxidation, sedimentation, filtration, adsorption, osmosis, and ion exchange. However, these methods often fail to completely remove pollutants and may produce harmful byproducts that require further treatment [ 19 – 21 ]. Numerous studies have shown that bacterial genera like Alcaligenes , Arthrobacter , and Pseudomonas are capable of phenol degradation [22–23]. The activated sludge process, a biological method, is widely used for wastewater treatment, requiring high concentrations of biomass and large-capacity reactors [ 24 ]. Phenolic compounds are common contaminants in wastewater from various industries. Due to their toxicity, the Environmental Protection Agency [EPA] has classified 11 phenolic compounds as priority pollutants. Several techniques, particularly adsorption, are employed to eliminate these compounds from water and wastewater [ 25 – 27 ]. Activated carbons are commonly used as adsorbents to remove many phenolic compounds from wastewater [28–29]. Biosorbents have limited use in removing phenolic compounds [ 30 ]. Phenols, even in low concentrations, are harmful to humans. Consuming water contaminated with phenols can cause protein degeneration, tissue corrosion, paralysis of the central nervous system, and damage to organs such as the kidneys, liver, and pancreas [ 31 ]. Phenols also inhibit cyclo-oxygenase activity, platelet aggregation, and thromboxane B2 production [ 32 ]. The permissible limit for phenol in water is 4000 µg/L, making its removal from industrial wastewater before discharge critical. Numerous effective techniques for eliminating and degrading phenols from wastewater have been documented [ 33 – 36 ]. A derivative was synthesized through the reaction of chitosan with carboxymethyl cyclodextrin. The inclusion of chitosan enhanced the adsorption capacity and selectivity of cyclodextrin toward m-catechol. Furthermore, chitosan was used for phenol removal from wastewater, achieving high removal efficiency [ 37 ]. The adsorption of phenol using various adsorbents, such as low-cost clay and activated carbon [ 38 ], as well as silica and other materials, has been extensively investigated. A wide array of adsorbents, including waste tire rubber granules [39], aniline-modified polystyrene resin [40], lignite [ 41 ], poly[ethyleneimine] [PEI]/SiO2 [ 42 ], Aspergillus niger biomass [ 43 ], fly ash [ 44 – 47 ], and β-cyclodextrin derivative grafted chitosan [ 48 ], has been analyzed for phenol removal [ 49 ]. In this study, the adsorption of phenol onto Chitosan-gr-Polysulphanilic acid has been examined through quantum mechanical calculations in both gas and water phases. Computational details This study employed Density Functional Theory (DFT) to perform quantum mechanical calculations on Chitosan-gr-Polysulphanilic acid, phenol, and the Chitosan-gr-Polysulphanilic acid-phenol complex. These calculations were carried out with the Gaussian 09 program [ 50 ]. The wB97XD dispersion-corrected meta-hybrid functional [ 51 , 52 ], along with the 6-311G (d,p) basis set [ 53 ], was selected to analyze the influence of dispersion forces on binding energies. Each structure was fully optimized, and subsequent frequency calculations verified that they represented true local energy minima. The calculation of the binding energy (ΔE bind), as shown in Equation, included corrections for zero-point vibrational energy (ZPVE) [ 54 ]. Furthermore, the basis set superposition error (BSSE) was systematically corrected for in all binding energy calculations using the counterpoise method [ 55 ] using Eq. [ 1 ]. \(\:{{\varDelta\:\mathbf{E}}_{\mathbf{b}\mathbf{i}\mathbf{n}\mathbf{d}}=\:\mathbf{E}}_{\left(\mathbf{C}\mathbf{h}\mathbf{i}\mathbf{t}\mathbf{o}\mathbf{s}\mathbf{a}\mathbf{n}-\mathbf{g}\mathbf{r}-\mathbf{P}\mathbf{o}\mathbf{l}\mathbf{y}\mathbf{s}\mathbf{u}\mathbf{l}\mathbf{p}\mathbf{h}\mathbf{a}\mathbf{n}\mathbf{i}\mathbf{l}\mathbf{i}\mathbf{c}\:\mathbf{a}\mathbf{c}\mathbf{i}\mathbf{d}-\mathbf{p}\mathbf{h}\mathbf{e}\mathbf{n}\mathbf{o}\mathbf{l}\:\right)}-({\mathbf{E}}_{\mathbf{C}\mathbf{h}\mathbf{i}\mathbf{t}\mathbf{o}\mathbf{s}\mathbf{a}\mathbf{n}-\mathbf{g}\mathbf{r}-\mathbf{P}\mathbf{o}\mathbf{l}\mathbf{y}\mathbf{s}\mathbf{u}\mathbf{l}\mathbf{p}\mathbf{h}\mathbf{a}\mathbf{n}\mathbf{i}\mathbf{l}\mathbf{i}\mathbf{c}\:\mathbf{a}\mathbf{c}\mathbf{i}\mathbf{d}\:}\:+\:{\mathbf{E}}_{\mathbf{p}\mathbf{h}\mathbf{e}\mathbf{n}\mathbf{o}\mathbf{l}})\) + E BSSE [ 1 ] Where, \(\:{E}_{\left(\varvec{C}\varvec{h}\varvec{i}\varvec{t}\varvec{o}\varvec{s}\varvec{a}\varvec{n}-\varvec{g}\varvec{r}-\varvec{P}\varvec{o}\varvec{l}\varvec{y}\varvec{s}\varvec{u}\varvec{l}\varvec{p}\varvec{h}\varvec{a}\varvec{n}\varvec{i}\varvec{l}\varvec{i}\varvec{c}\:\varvec{a}\varvec{c}\varvec{i}\varvec{d}-\varvec{p}\varvec{h}\varvec{e}\varvec{n}\varvec{o}\varvec{l}\:\right)}\) , \(\:{E}_{Chitosan-gr-Polysulphanilic\:acid}\) , and \(\:{E}_{\varvec{p}\varvec{h}\varvec{e}\varvec{n}\varvec{o}\varvec{l}}\) are the total energies of Chitosan-gr-Polysulphanilic acid-phenol complexes, Chitosan-gr-Polysulphanilic acid, and phenol, respectively. The binding energies in the implicit water solvent were calculated using the polarizable continuum model (PCM) [ 56 ]. A comprehensive analysis of various quantum molecular parameters was conducted for all studied compounds. These parameters included the ionization potential (I= –EHOMO), electron affinity (A = –ELUMO), chemical potential (µ = –[I + A]/2), hardness (η= [I – A]/2), softness (S = 1/2 η), the electrophilicity index (ω = µ²/2 η), and the Fermi level (EF) [ 57 ]. Furthermore, the stability and solubility of the compounds were evaluated by calculating the solvation energy (ΔEsolv) as described in Eq. 2 [ 58]. Δ E solv = E solv - E gas [ 2 ] In this context, Esolv signifies the total energy in the solvent phase, while Egas is the total energy in the gas phase. The AIMAll software package was utilized to apply Atoms in Molecules (AIM) theory for elucidating the bonds present in the Chitosan-gr-Polysulphanilic acid-phenol complexes. All bonds formed were characterized by their electron density (ρ(r)) and the Laplacian of the electron density (∇²ρ(r)) at the bond critical point (BCP). Equation was used to estimate the electronic energy density, H(r), at the BCP as described in Eq. 3. H [r] = G [r] + V [r] [ 3 ] In this context, G(r) and V(r) denote the kinetic and potential energies, respectively. The electronic response of the sensor, as described by the following equation, is accountable for the variation in the energy gap (Eg) between the HOMO and LUMO levels. Δ Eg = [[ Eg 2 - Eg 1 ]∕ Eg 1 ] × 100% [ 4 ] In this context, Eg1 is the band gap of pristine Chitosan-gr-Polysulphanilic acid, while Eg2 is its band gap after phenol adsorption. The term ΔEg represents the change in the band gap that occurs during this adsorption process. As described by Eq. 5, Eg is linked to the conduction electron population (N). The magnitude of this change in Eg is a key indicator of an adsorbent's sensitivity to a specific adsorbate [ 26 ]. N = AT 3∕2 exp [− Eg ∕2 kT ] [ 5 ] Where k is the Boltzmann’s constant and A [electrons/m 3 K 3/2 ] is a constant. The discoveries acquired from this strategy are in great concurrence with those of the examinations in the writing [ 24 ]. In sensor researches, work function [Φ] is defined as the lowest energy needed to relocate an electron from the Fermi surface of a substance to an unlimited space which is shown as: Φ = - EF + V [+∞] [ 6 ] According to Eq. 7, the electrostatic potential energy of an electron is shown by V [+ ∞], this parameter is considered positive. There is a relationship between the value of Φ and the electron current density, so changes in the Fermi level were ascribed to changes in Φ, which were related to changes in electron emission according to Eq. 7 [ 47 ]. Eq. 7 indicates that V(+∞) is the electrostatic potential energy of an electron, which is a positive value. A direct relationship exists between the work function (Φ) and the electron current density. Therefore, shifts in the Fermi level were interpreted as changes in the work function (Φ), which are connected to alterations in electron emission as outlined in Eq. 7. j = e [ −Φ∕ kT ] AT 2 [ 7 ] where T is the absolute temperature [K] and A represents Richardson’s constant [A/m 2 ]. Natural bond orbital [NBO] was performed to provide a good explanation of the charge delocalization and distribution of metal-containing complexes. The stabilization energy E 2 of the electron delocalization between the donor orbitals [ i ] and acceptor [ j ] orbitals was analyzed using Eq. [ 8 ], Natural bond orbital (NBO) analysis was conducted to effectively explain the charge delocalization and distribution within the metal-containing complexes. The stabilization energy (E2), which arises from electron delocalization between donor orbitals (i) and acceptor orbitals (j), was analyzed using Eq. 8. \(\:{\varvec{E}}^{2}=\:{\varvec{q}}_{\varvec{i}}\frac{\varvec{F}{\left(\varvec{i},\varvec{j}\right)}^{2}}{{\varvec{\epsilon\:}}_{\varvec{i}}-{\varvec{\epsilon\:}}_{\varvec{j}}}\) , [ 8 ] Where q i signifies the occupancy of the donor orbital, F [ i, j ] 2 is the off-diagonal elements of the NBO Kohn-Sham Matrix; and the ε i and ε j are the orbital energies [ 61 ]. The electrostatic potential [ESP] The electrostatic potential surfaces (ESPs) of the optimized Chitosan-gr-Polysulphanilic acid and phenol structures in the gas phase are summarized in Fig. 1 . A high negative electron density region is observed around the sulfur and oxygen atoms, while an intermediate negative electron density region is present near the nitrogen atoms. In contrast, regions of high positive electron density are located on other atoms. For the ESP of phenol, high negative electron density regions are observed around the oxygen atoms, with additional negative electron density regions around the other atoms. No significant changes were observed in the Chitosan-gr-Polysulphanilic acid and phenol structures when re-optimized in the water phase. The lowest structures of the Chitosan-gr-Polysulphanilic acid-phenol in the gas and water phases. The lowest-energy structures of the Chitosan-gr-Polysulphanilic acid-phenol complexes in the gas phase are shown in Fig. 2 . Complex [2a] represents the most stable structure among the Chitosan-gr-Polysulphanilic acid-phenol complexes, where Chitosan-gr-Polysulphanilic acid forms bidentate interactions with phenol through a polar covalent [H-O = 2.26 Å] bond and an electrostatic [O…H-C = 2.98 Å] interaction. Complex [2b] is 8.15 kcal/mol higher in energy than complex [2a], with Chitosan-gr-Polysulphanilic acid interacting with phenol via a polar covalent [Zn-O = 2.26 Å] bond and an electrostatic [O…H-O = 3.04 Å] interaction. Complex [2c] is 13.40 kcal/mol higher than complex [2a], where Chitosan-gr-Polysulphanilic acid forms bidentate interactions with phenol via a polar covalent [H-O = 2.27 Å] bond and an electrostatic [O…H-C = 2.83 Å] interaction. Complex [2d] is 21.13 kcal/mol higher than complex [2a], with Chitosan-gr-Polysulphanilic acid forming bidentate interactions with phenol through a polar covalent [O-N = 2.29 Å] bond and an electrostatic [O…H-C = 2.92 Å] interaction. Complex [2e] represents the lowest-energy structure among the Chitosan-gr-Polysulphanilic acid-phenol complexes in the water phase, where Chitosan-gr-Polysulphanilic acid interacts with phenol via a polar covalent [H-O = 2.30 Å] bond and an electrostatic [O…H-C = 3.02 Å] interaction. Frontier molecular orbitals and global properties of Chitosan-gr-Polysulphanilic acid and phenol before and after complexation Figure 3 illustrates the distributions of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for Chitosan-gr-Polysulphanilic acid and the phenol molecule. As shown, the HOMO and LUMO orbitals are predominantly located near the electronegative [N and O] atoms and the electropositive [H] atoms, respectively. Table 1 presents the calculated values for various properties of Chitosan-gr-Polysulphanilic acid, the phenol molecule, and the Chitosan-gr-Polysulphanilic acid-phenol complex, including HOMO and LUMO energies, the HOMO-LUMO gap (Eg), the Fermi level (EF), dipole moment (DM), ionization potential (I), electron affinity (A), chemical potential (l), hardness (g), softness (S), and electrophilicity index (x). The obtained HOMO and LUMO energies for Chitosan-gr-Polysulphanilic acid, phenol, and the Chitosan-gr-Polysulphanilic acid-phenol complex are − 8.88, -1.25, -6.50, -1.09, and − 5.58, -1.08 eV, respectively. The Fermi level energies for these species are calculated as -5.06, -3.79, and − 3.33 eV, respectively. The band gaps for Chitosan-gr-Polysulphanilic acid, phenol and the Chitosan-gr-Polysulphanilic acid-phenol complex are 3.81, 2.70, and 2.25 eV, respectively. These results suggest that Chitosan-gr-Polysulphanilic acid exhibits higher electrical conductivity than the phenol molecule and the Chitosan-gr-Polysulphanilic acid-phenol complex. Additionally, kinetic stability can be assessed based on the Eg values. Chitosan-gr-Polysulphanilic acid displays lower kinetic stability than both phenol and the Chitosan-gr-Polysulphanilic acid-phenol complex, implying higher reactivity. The work function and Fermi level of Chitosan-gr-Polysulphanilic acid, along with its adsorption effects, are key factors in its potential as a Φ-type sensor. In experimental applications, the mechanism for Φ-type gas sensors typically involves the Kelvin process. A Kelvin oscillator framework is used to evaluate the Φ value of the sample before and after phenol adsorption onto Chitosan-gr-Polysulphanilic acid. If the phenol adsorption significantly alters the Φ value, it consequently modifies the gate voltage, generating an electrical signal that facilitates phenol detection [28]. Furthermore, the electric current density released from the surface of Chitosan-gr-Polysulphanilic acid undergoes substantial changes, indicating its suitability as a Φ-type sensor for phenol adsorption. In the design of effective sensors, the desorption step is of key importance. Sensors with very strong adsorption interactions are generally not suitable, as this leads to prolonged recovery times, which is a significant drawback for applications requiring quick detection. This relationship between strong adsorption and longer recovery times is supported by current transition state theory, as described by Eq. [ 10 ] [29]. τ = υ −1 exp [−Δ G ∕ kT ] [ 10 ] In this context, the applied frequency is denoted by ν 0 . The recovery time at a temperature of 25°C was calculated to be approximately 4.09 ms. This calculation assumes an attempt frequency (ν) of around 10¹² s⁻¹ is applied in a vacuum to desorb the phenol from the Chitosan-gr-Polysulphanilic acid. It is important to mention that this time can be reduced at higher operational temperatures[ 30 – 33 ]. Chitosan-gr-Polysulphanilic acid s have a roughly rapid recovery time and are perfect for measuring phenol molecules [ 34 , 35 ] Table 1 The values of HOMO, LUMO, HOMO-LUMO gap (Eg), Fermi level (EF), dipole moment (DM), ionization potential (I), the electron affinity of the molecule (A), the chemical potential of the system (l), hardness (g), softness (S), the electrophilicity index (x) and work function (Φ) of Chitosan-gr-Polysulphanilic acid, Phenol, and Chitosan-gr-Polysulphanilic acid-Phenol complex and work function compound with various structures are in eV. %∆Φ show the alteration of Φ at the end of the adsorption process. Property Chitosan-gr-Polysulphanilic acid Phenol Chitosan-gr-Polysulphanilic acid-Phenol E HOMO [eV] -8.88 –6.50 –5.58 E LUMO [eV] –1.25 -1.09 -1.08 E g [eV] 3.81 2.70 2.25 E F = [H + L]/2 [eV] -5.06 -3.79 -3.33 D M [Debye] 9.11 2.77 9.77 I=- E HOMO [eV] 8.88 6.50 5.58 A=- E LUMO [eV] 1.25 1.09 1.08 µ [eV] -5.06 -3.79 -3.33 η [eV] 3.81 2.70 2.25 S [eV] 0.13 0.18 0.22 ω [eV] 3.36 2.66 2.46 Φ 5.21 2.35 3.57 %ΔΦ - - -20.32 AIM and NBO of the Chitosan-gr-Polysulphanilic acid-Phenol complexes in the gas and water phases Atoms in Molecules (AIM) theory was employed to analyze the bonding characteristics of the complexes. The classification of bonds depends on the signs of ∇²ρ(r) and H(r): interactions are electrostatic if both are positive, polar covalent (or coordination/strong hydrogen bonds) if ∇²ρ(r) is positive and H(r) is negative, and nonpolar covalent if both are negative. The AIM parameters presented in Table 2 indicate that interactions between Chitosan-gr-Polysulphanilic acid and phenol consist of both electrostatic and partially covalent/electrostatic (polar covalent) types in both the gas and water phases. Table 3 lists the total transferred charges from Natural Population Analysis (NPA). The ∆q value for phenol shows a charge gain, implying that phenol might oxidize the Chitosan-gr-Polysulphanilic acid it is coordinated with. The NBO analysis clarifies interactions between the Lewis structure and non-Lewis orbitals. The charge-transfer energies (E 2 ) in the gas phase are detailed in Table 4 . This analysis reveals that in the complexes, charge was donated from the σ and n orbitals of the C, N, and H atoms of Chitosan-gr-Polysulphanilic acid into the n* orbitals of the oxygen atom of phenol. Table 2 Bond critical point [BCP] data [a.u.] from the AIM analysis of the optimized structures of Chitosan-gr-Polysulphanilic acid-Phenol complexes in gas and water phases. Complexes BCP ρ [ r ] ∇ 2 ρ [ r ] H[ r ] 2a O-H 0.0668 0.3564 -0.0070 O….H-C 0.0113 0.0266 0.0013 2b O….H-O 0.0067 0.0113 0.0006 S-O 0.0687 0.3673 -0.0075 2c O-H 0.0769 0.3598 -0.0082 O….H-C 0.0155 0.02654 0.0012 2d N-O 0.0789 0.3605 -0.0084 O····H-C 0.0188 0.0265 0.0012 2e O-H 0.0678 0.3542 -0.00867 O····H-C 0.0159 0.0252 0.0009 Table 3 Calculated NPA charges of the optimized structures Chitosan-gr-Polysulphanilic acid-Phenol complexes in gas and water phases. Complexes Bond type q x a Q H/O Δ q Phenol b 2a O-H 0.37 0.37 -0.08 O….H-C -0.45 0.37 2b O….H-O 0.41 0.43 -0.06 S-O -0.43 -0.67 2c O-H -0.41 0.37 -0.04 O….H-C -0.45 0.37 2d N-O -0.58 -0.60 -0.08 O····H-C 0.41 0.37 2e O-H -0.58 0.37 -0.06 O····H-C 0.49 0.37 a X = O/S/N and b Δ𝑞 PHENOL = 𝑞 nanoculsters [𝑐𝑜𝑚𝑝𝑙𝑒𝑥] −𝑞 PHENOL [𝑖𝑠𝑜𝑙𝑎𝑡𝑒𝑑] Table 4 Results of the second-order perturbation theory analysis of the NBO basis of the optimized structures of Zn 12 O 12 -TMZ, Zn 12 O 12 -CM, Zn 12 O 12 -PR and Zn 12 O 12 -LO complexes in gas phase. Complexes Donor NBO [i ] Acceptor NBO [ j ] E [2] [kcal.mol − 1 ] 2a σ [N6−H41] n * O53 33.27 2b n S53 n * O53 29.40 2c σ [C25−H36] n * O53 27.35 2d n N33 n * O53 26.24 2e σ [N6−H41] n * O53 31.09 The binding [Δ E bind ] and the solvation [Δ E solv ] energies of all studied complexes The binding energies (ΔE bind ) and solvation energies (ΔE solv ) for the most stable configurations of the Chitosan-gr-Polysulphanilic acid-Phenol complexes in both gas and water phases are detailed in Table 5 . It is evident from the table that the ΔEbind values for all complexes are greater in the gas phase than in the water phase, which is due to the influence of the solvent. For phenol, the calculated ΔEsolv was − 3.89 kcal/mol; this negative value confirms its stability in water. Following adsorption onto Chitosan-gr-Polysulphanilic acid, the solvation energy shows a further increase (Table 5 ), indicating that both stability and solubility are markedly improved in the water phase. Such high solvation energy is a key factor for their use as sensors and detectors [ 62 ]. Table 5 The binding [Δ E bind ], and Solvation energies [ΔE solv ], [in kcal.mol − 1 ] of all Chitosan-gr-Polysulphanilic acid-Phenol complex in gas and water phase. Δ E bind ΔE solv Complexes gas phase Water phase Phenol - - -3.89 Chitosan-gr-Polysulphanilic acid - - -27.65 Chitosan-gr-Polysulphanilic acid-Phenol -14.69 -12.88 -14.07 Conclusion The sensitivity of Chitosan-gr-Polysulphanilic acid toward phenol molecules was systematically analyzed through Density Functional Theory (DFT) calculations, providing valuable insights into the interaction between this composite material and phenol. The results of these computations demonstrated that Chitosan-gr-Polysulphanilic acid exhibits a strong affinity for phenol adsorption, with adsorption energies calculated to be approximately − 14.69 kcal/mol in the gas phase and − 12.88 kcal/mol in the water phase. This indicates that the adsorption of phenol is both energetically favorable and stable, with the material effectively binding phenol molecules in both phases, highlighting its potential for use in various environmental and industrial applications where phenol removal is required. Further investigation into the electronic properties of Chitosan-gr-Polysulphanilic acid upon phenol adsorption revealed significant changes in the frontier molecular orbitals. Specifically, the evaluation of the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels, as well as the band gap values, showed a pronounced reduction in the adsorption energy compared to pristine Chitosan-gr-Polysulphanilic acid. The interaction of phenol with the material led to a noticeable decrease in the band gap, which directly influences the electrical conductivity and reactivity of the material, suggesting an enhanced ability for the sensor to detect phenol molecules at low concentrations. This reduction in the band gap also points to the material’s potential as an effective Φ-type sensor. Moreover, the analysis indicates that Chitosan-gr-Polysulphanilic acid, through its favorable adsorption characteristics, demonstrates high potential for use as a sensing material for phenol detection. The material's ability to interact strongly with phenol molecules suggests that it could be utilized in sensors where rapid and reversible adsorption is essential. One of the most critical parameters for sensor applications is the recovery time, which refers to the time required for the sensor to return to its baseline state after the desorption of the adsorbate. In this case, the estimated recovery time for Chitosan-gr-Polysulphanilic acid was calculated to be approximately 4.09 ms, which is remarkably fast and supports the feasibility of using this material in real-time phenol detection applications. The fast recovery time indicates that phenol molecules can be effectively and reversibly desorbed from the surface of Chitosan-gr-Polysulphanilic acid, ensuring high sensitivity and rapid response in Φ-type sensors. In conclusion, the strong interaction between Chitosan-gr-Polysulphanilic acid and phenol, coupled with the favorable electronic properties and rapid recovery time, positions this material as a highly effective and promising candidate for use in environmental monitoring and industrial processes, where the detection and removal of phenolic compounds are critical. The material's high sensitivity, coupled with its reversibility and stability, suggests it could be employed in the development of advanced sensors for real-time phenol detection, contributing significantly to environmental protection and pollution control efforts. Declarations Declaration of Interest Statement The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment This paper is based upon work supported by Science, Technology & Innovation Funding Authority [STDF] under grant References Tarpada, U. P., Thummar, B. B., & Raval, D. K. , Polymer-supported sulphanilic acid – A novel green heterogeneous catalyst for the synthesis of benzimidazole derivatives. Journal of Saudi Chemical Society, 2012 Havlíček, J., Myška, K., Tejchman, W., Karásková, N., Doležal, R., Maltsevskaya, N. V., & Kolář, K. , Microwave synthesis of sulfanilic acid. 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Y., Xiao, J. B., Chen, X. Q., Jiang, X. Y., Yu, H. Z., & Xu, M, The adsorption of phenol, m-cresol, and m-catechol on a β-cyclodextrin derivative-grafted chitosan and the removal of phenols from industrial wastewater. Adsorption Science & Technology, 2006, 24 , 547–557. Aksu, Z., & Yener, J, A comparative adsorption/biosorption study of phenol and chlorophenol: Effect of pH, temperature, and contact time. Journal of Environmental Science and Health, Part A, 1999, 34 , 1777–1791. Frisch, M. J., G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, et al. Gaussian 09, Revision A.1. Gaussian Inc., 2003. Koopmans, T, Über die Zürückführung der Thermodynamic auf die Quantenmechanik.Physica,1933, 1 , 104–113 Ahmadi Peyghan, A., Hadipour, N., & Bagheri, Z, Theoretical study of the adsorption of phenol and its derivatives on a graphene oxide surface: A density functional theory approach. The Journal of Physical Chemistry C, 2013, 117 , 2427–2432. Chai, J. D, Density functional study of the molecular interactions between carboxylates and aluminum ions: The influence of the coordination environment and the solvation effect.Physical Chemistry Chemical Physics, 2008, 10 , 6615–6620. AhmanPadash, M., Rabbani Esfahani, M., & Shokuhi Rad, A, The computational quantum mechanical study of sulfamide drug adsorption onto X12Y12 fullerene-like nanocages: Detailed DFT and QTAIM investigations. Journal of Biomolecular Structure and Dynamics.2020. https://doi.org/10.1080/07391102.2020.1792991 Ibrahim, M. S., Abd El-Mageed, H. R., & Abd El-Salam, H. M. , Density functional theory calculations on the grafting copolymerization of 2-substituted aniline onto chitosan. Polymer Bulletin,2020, 77 , 6391–6407 Abd El-Mageed, H. R, Elucidating the adsorption and detection of amphetamine drug by pure and doped Al12N12, and Al12P12 nano-cages, a DFT study. Journal of Molecular Liquids,2020, 115 , 297 Singla P, Riyaz M, Singhal S, Goel N [2016] Phys Chem Chem Phys 18:5597 Keith, T. A., & Gristmill Software. , AIMAll (Version 19.02.13) [Software]. TK Gristmill Software. 2019.https://aim.tkgristmill.com. Abdel-Latif, M. K., Abd El-Mageed, H. R., Mohamed, H. S., & Mustafa, F. M, Study the solvation effect on 6-phenyl-2-thioxo-1, 2-dihydropyridine-3-carbonitrile derivatives by TD-DFT calculations and molecular dynamics simulations. Journal of Molecular Structure, 2020, 1200, 127056. Padash, R., Sobhani Nasab, A., Rahimi Nasrabadi, M., Mirmotahari, M., Ehrlich, H., Rad, A. S., & Peyravi, M. , Is it possible to use X12Y12 [X = Al, B, and Y = N, P] nanocages for drug-delivery systems? A DFT study on the adsorption property of 4-aminopyridine drug. Applied Physics A, 2018, 124, 582. Aihara, J. I. , Reduced HOMO-LUMO gap as an index of kinetic stability for polycyclic aromatic hydrocarbons. Journal of Physical Chemistry A, 1999, 103 (37), 7487–7495. Vatanparast, Morteza, and Zahra Shariatinia. "AlN and AlP Doped Graphene Quantum Dots as Novel Drug Delivery Systems for 5-Fluorouracil Drug: Theoretical Studies." Journal of Fluorine Chemistry , 2018, vol. 211, pp. 81–93. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7349857","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":509703003,"identity":"fba3e709-b568-42b4-a18a-732be97b87f1","order_by":0,"name":"M. S. Ibrahim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIiWNgGAWjYFACHhDBzMAmASINGHjYmJkPPmBgOEC8Fhk+drZkA6K0MIC1MDDYyPHzmEng06Lb3nvw040KawY+6d6HnwsKtgEdxmBWzVNzR46fgfnhoxuYWszOnEuWzjmTzsAmc9xYeobBbZCWtNs8x54ZSzawGRvnYNFyI8dAOrftMNAvaQzSPBAtx4Dk4cQNB3jYpLFrMf6d+w+shfk3RAtjWzHPP7xazKRzG8Ba2KC2MLMx87bh0XLmjJl1zjGQX46xWUO0sDFLzu07bCzZjMMvx3uMb+fUWDPIz25jvs3z57a9fP/5jx/efDssx8/e/PAxFi0wUN+AzGOCRRbxgPEHKapHwSgYBaNguAMAIg1cQuZW+hcAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-8508-1505","institution":"Beni Suef University","correspondingAuthor":true,"prefix":"","firstName":"M.","middleName":"S.","lastName":"Ibrahim","suffix":""},{"id":509703004,"identity":"d14c7fe6-bb9e-40f4-b82c-f40d8a712c9c","order_by":1,"name":"H.R. Abd El-Mageed","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"H.R.","middleName":"Abd","lastName":"El-Mageed","suffix":""},{"id":509703005,"identity":"21ebe577-0943-4a19-8032-12081575ac85","order_by":2,"name":"H. M. Abd El-Salam","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"H.","middleName":"M. Abd","lastName":"El-Salam","suffix":""}],"badges":[],"createdAt":"2025-08-11 22:47:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7349857/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7349857/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90977184,"identity":"c25a3b17-d3e5-4796-96eb-3023aac29f36","added_by":"auto","created_at":"2025-09-10 08:51:08","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":128575,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eESPs of the gas-phase lowest energy structures of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ephenol\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e [EPS from -0.02 to 0.02], and Chitosan-gr-Polysulphanilic [EPS from -0.07 to 0.07].\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7349857/v1/bb9f3d844989b6a8d787cda7.jpg"},{"id":90977185,"identity":"fe50d149-135c-477c-b325-431293436acd","added_by":"auto","created_at":"2025-09-10 08:51:08","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":102420,"visible":true,"origin":"","legend":"\u003cp\u003eThe lowest-energy structures of the Zn\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e-TMZ complexes in gas and water phases.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7349857/v1/7f33401144b5651c0ebb4e5c.jpg"},{"id":90978379,"identity":"06802dd4-b0f3-42e2-991e-b72e72a32574","added_by":"auto","created_at":"2025-09-10 08:59:08","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":98759,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHOMO and LUMO distributions of ALN. ALP, and AN drug\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7349857/v1/dbac9d89e4b1773ef5b33d94.jpg"},{"id":93958519,"identity":"8adf8deb-1468-4c29-a118-d997c5588592","added_by":"auto","created_at":"2025-10-20 16:40:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1509611,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7349857/v1/3dc86d15-fcdc-43c5-bfa4-47ee622a0746.pdf"}],"financialInterests":"","formattedTitle":"Quantum Mechanical Insights into Phenol Adsorption and Sensing Behavior of Chitosan-gr-Polysulphanilic Acid","fulltext":[{"header":"Introduction","content":"\u003cp\u003eA polymer-supported sulphanilic acid catalyst was synthesized and utilized as a green, reusable, and heterogeneous catalyst. It was thoroughly characterized using chemical techniques, including the determination of free hydroxyl content, epoxy equivalent weight, and free sulfonic acid content, as well as infrared spectroscopy and thermogravimetric analysis. The catalyst was employed for the one-pot synthesis of 2-substituted benzimidazoles from o-phenylenediamine and various aromatic aldehydes in absolute ethanol under thermal conditions. The catalyst could be easily separated from the product through simple filtration and reused multiple times with minimal loss of efficiency. Its three-dimensional network structure imparts high thermal stability, allowing for reuse without the need for additional purification [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. sulfanilic acid is a crucial chemical compound, widely used in the azo dye industry and in the pharmaceutical development of antimicrobial agents, such as sulfonamides. Azo dyes are synthesized through the azo coupling reaction of sulfanilic acid, in its diazonium salt form, with compounds like N,N-dimethylaniline or 2-naphthol [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Systematically known as 4-aminobenzenesulfonic acid, sulfanilic acid is a key organic compound in the science and technology of azo dyes [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. When reacted with alkali nitrite in an acidic medium, it forms a diazonium salt, which readily couples as an electrophile with phenol in a basic medium or with an aromatic amine in an acidic medium to form azo compounds. These compounds are extensively used as synthetic dyes in the textile and food industries. Notable dyes derived from sulfanilic acid include methyl orange, an acid-base indicator, and Orange II, used for textile coloring. The synthesis of sulfanilic acid is a fundamental process in laboratory settings [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Electrophilic aromatic substitution involves an intriguing reaction mechanism, including the rearrangement of the intermediate phenylsulfamic acid into sulfanilic acid. The final product, sulfanilic acid, exists as an internal salt due to interactions between its acidic [-SO₃H] and basic [-NH₂] functional groups within the molecule [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Benzimidazole and its derivatives have been extensively studied due to their significance in various applications and their substantial biochemical importance [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The benzimidazole framework is a part of several classes of drugs, with its properties influenced by substituents at different positions [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Additionally, benzimidazole derivatives have numerous pharmaceutical applications, especially as antimicrobial agents [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Benzimidazoles are also vital intermediates in organic synthesis [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Biological methods, such as those involving \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e, have proven effective in removing phenol from contaminated water [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Phenol is not only a critical industrial chemical but also a significant environmental pollutant. Due to industrial spills, leaks, and discharges, phenol and its derivatives are commonly found as contaminants in the environment. Therefore, the removal of phenolic compounds from industrial wastewater is essential to reduce environmental pollution [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The main sources of pollution include wastewater from industries such as paint, pesticides, coal conversion, polymeric resins, petroleum, and petrochemicals [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In recognition of the toxicity of these substances, the United Nations declared 1981\u0026ndash;1990 as the \"International Drinking Water Supply and Sanitation Decade\" [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Various regulatory organizations have implemented stringent regulations to limit the release of phenolic substances into the environment. The U.S. Environmental Protection Agency has classified phenol as a priority pollutant [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Phenol is among the top 100 hazardous substances listed by the Agency for Toxic Substances and Disease Registry [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Several physical and chemical techniques have been proposed for treating wastewater containing phenolic pollutants, such as precipitation, coagulation, chemical oxidation, sedimentation, filtration, adsorption, osmosis, and ion exchange. However, these methods often fail to completely remove pollutants and may produce harmful byproducts that require further treatment [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Numerous studies have shown that bacterial genera like \u003cem\u003eAlcaligenes\u003c/em\u003e, \u003cem\u003eArthrobacter\u003c/em\u003e, and \u003cem\u003ePseudomonas\u003c/em\u003e are capable of phenol degradation [22\u0026ndash;23]. The activated sludge process, a biological method, is widely used for wastewater treatment, requiring high concentrations of biomass and large-capacity reactors [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Phenolic compounds are common contaminants in wastewater from various industries. Due to their toxicity, the Environmental Protection Agency [EPA] has classified 11 phenolic compounds as priority pollutants. Several techniques, particularly adsorption, are employed to eliminate these compounds from water and wastewater [\u003cspan additionalcitationids=\"CR26\" citationid=\"CR24\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Activated carbons are commonly used as adsorbents to remove many phenolic compounds from wastewater [28\u0026ndash;29]. Biosorbents have limited use in removing phenolic compounds [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Phenols, even in low concentrations, are harmful to humans. Consuming water contaminated with phenols can cause protein degeneration, tissue corrosion, paralysis of the central nervous system, and damage to organs such as the kidneys, liver, and pancreas [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Phenols also inhibit cyclo-oxygenase activity, platelet aggregation, and thromboxane B2 production [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The permissible limit for phenol in water is 4000 \u0026micro;g/L, making its removal from industrial wastewater before discharge critical. Numerous effective techniques for eliminating and degrading phenols from wastewater have been documented [\u003cspan additionalcitationids=\"CR34 CR35\" citationid=\"CR31\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. A derivative was synthesized through the reaction of chitosan with carboxymethyl cyclodextrin. The inclusion of chitosan enhanced the adsorption capacity and selectivity of cyclodextrin toward m-catechol. Furthermore, chitosan was used for phenol removal from wastewater, achieving high removal efficiency [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The adsorption of phenol using various adsorbents, such as low-cost clay and activated carbon [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e38\u003c/span\u003e], as well as silica and other materials, has been extensively investigated. A wide array of adsorbents, including waste tire rubber granules [39], aniline-modified polystyrene resin [40], lignite [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e41\u003c/span\u003e], poly[ethyleneimine] [PEI]/SiO2 [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e42\u003c/span\u003e], Aspergillus niger biomass [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e43\u003c/span\u003e], fly ash [\u003cspan additionalcitationids=\"CR45 CR46\" citationid=\"CR41\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e47\u003c/span\u003e], and β-cyclodextrin derivative grafted chitosan [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e48\u003c/span\u003e], has been analyzed for phenol removal [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. In this study, the adsorption of phenol onto Chitosan-gr-Polysulphanilic acid has been examined through quantum mechanical calculations in both gas and water phases.\u003c/p\u003e"},{"header":"Computational details","content":"\u003cp\u003eThis study employed Density Functional Theory (DFT) to perform quantum mechanical calculations on Chitosan-gr-Polysulphanilic acid, phenol, and the Chitosan-gr-Polysulphanilic acid-phenol complex. These calculations were carried out with the Gaussian 09 program [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. The wB97XD dispersion-corrected meta-hybrid functional [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e52\u003c/span\u003e], along with the 6-311G (d,p) basis set [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e53\u003c/span\u003e], was selected to analyze the influence of dispersion forces on binding energies. Each structure was fully optimized, and subsequent frequency calculations verified that they represented true local energy minima. The calculation of the binding energy (ΔE bind), as shown in Equation, included corrections for zero-point vibrational energy (ZPVE) [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. Furthermore, the basis set superposition error (BSSE) was systematically corrected for in all binding energy calculations using the counterpoise method [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e55\u003c/span\u003e] using Eq.\u0026nbsp;[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{{\\varDelta\\:\\mathbf{E}}_{\\mathbf{b}\\mathbf{i}\\mathbf{n}\\mathbf{d}}=\\:\\mathbf{E}}_{\\left(\\mathbf{C}\\mathbf{h}\\mathbf{i}\\mathbf{t}\\mathbf{o}\\mathbf{s}\\mathbf{a}\\mathbf{n}-\\mathbf{g}\\mathbf{r}-\\mathbf{P}\\mathbf{o}\\mathbf{l}\\mathbf{y}\\mathbf{s}\\mathbf{u}\\mathbf{l}\\mathbf{p}\\mathbf{h}\\mathbf{a}\\mathbf{n}\\mathbf{i}\\mathbf{l}\\mathbf{i}\\mathbf{c}\\:\\mathbf{a}\\mathbf{c}\\mathbf{i}\\mathbf{d}-\\mathbf{p}\\mathbf{h}\\mathbf{e}\\mathbf{n}\\mathbf{o}\\mathbf{l}\\:\\right)}-({\\mathbf{E}}_{\\mathbf{C}\\mathbf{h}\\mathbf{i}\\mathbf{t}\\mathbf{o}\\mathbf{s}\\mathbf{a}\\mathbf{n}-\\mathbf{g}\\mathbf{r}-\\mathbf{P}\\mathbf{o}\\mathbf{l}\\mathbf{y}\\mathbf{s}\\mathbf{u}\\mathbf{l}\\mathbf{p}\\mathbf{h}\\mathbf{a}\\mathbf{n}\\mathbf{i}\\mathbf{l}\\mathbf{i}\\mathbf{c}\\:\\mathbf{a}\\mathbf{c}\\mathbf{i}\\mathbf{d}\\:}\\:+\\:{\\mathbf{E}}_{\\mathbf{p}\\mathbf{h}\\mathbf{e}\\mathbf{n}\\mathbf{o}\\mathbf{l}})\\)\u003c/span\u003e\u003c/span\u003e\u003cb\u003e+ E\u003c/b\u003e\u003csub\u003e\u003cb\u003eBSSE\u003c/b\u003e\u003c/sub\u003e [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eWhere,\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{\\left(\\varvec{C}\\varvec{h}\\varvec{i}\\varvec{t}\\varvec{o}\\varvec{s}\\varvec{a}\\varvec{n}-\\varvec{g}\\varvec{r}-\\varvec{P}\\varvec{o}\\varvec{l}\\varvec{y}\\varvec{s}\\varvec{u}\\varvec{l}\\varvec{p}\\varvec{h}\\varvec{a}\\varvec{n}\\varvec{i}\\varvec{l}\\varvec{i}\\varvec{c}\\:\\varvec{a}\\varvec{c}\\varvec{i}\\varvec{d}-\\varvec{p}\\varvec{h}\\varvec{e}\\varvec{n}\\varvec{o}\\varvec{l}\\:\\right)}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{Chitosan-gr-Polysulphanilic\\:acid}\\)\u003c/span\u003e\u003c/span\u003e, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{\\varvec{p}\\varvec{h}\\varvec{e}\\varvec{n}\\varvec{o}\\varvec{l}}\\)\u003c/span\u003e\u003c/span\u003eare the total energies of Chitosan-gr-Polysulphanilic acid-phenol complexes, Chitosan-gr-Polysulphanilic acid, and phenol, respectively. The binding energies in the implicit water solvent were calculated using the polarizable continuum model (PCM) [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. A comprehensive analysis of various quantum molecular parameters was conducted for all studied compounds. These parameters included the ionization potential (I= –EHOMO), electron affinity (A = –ELUMO), chemical potential (µ = –[I + A]/2), hardness (η= [I – A]/2), softness (S = 1/2 η), the electrophilicity index (ω = µ²/2 η), and the Fermi level (EF) [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. Furthermore, the stability and solubility of the compounds were evaluated by calculating the solvation energy (ΔEsolv) as described in Eq.\u0026nbsp;2 [ 58].\u003c/p\u003e\u003cp\u003e\u003cb\u003eΔ\u003c/b\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003esolv\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e=\u003c/b\u003e \u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003esolv\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-\u003c/b\u003e \u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003egas\u003c/b\u003e\u003c/sub\u003e [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn this context, Esolv signifies the total energy in the solvent phase, while Egas is the total energy in the gas phase. The AIMAll software package was utilized to apply Atoms in Molecules (AIM) theory for elucidating the bonds present in the Chitosan-gr-Polysulphanilic acid-phenol complexes. All bonds formed were characterized by their electron density (ρ(r)) and the Laplacian of the electron density (∇²ρ(r)) at the bond critical point (BCP). Equation was used to estimate the electronic energy density, H(r), at the BCP as described in Eq.\u0026nbsp;3.\u003c/p\u003e\u003cp\u003e\u003cb\u003eH\u003c/b\u003e\u003cb\u003e[r] =\u003c/b\u003e \u003cb\u003eG\u003c/b\u003e\u003cb\u003e[r] +\u003c/b\u003e \u003cb\u003eV\u003c/b\u003e\u003cb\u003e[r]\u003c/b\u003e [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn this context, G(r) and V(r) denote the kinetic and potential energies, respectively. The electronic response of the sensor, as described by the following equation, is accountable for the variation in the energy gap (Eg) between the HOMO and LUMO levels.\u003c/p\u003e\u003cp\u003e\u003cb\u003eΔ\u003c/b\u003e\u003cb\u003eEg\u003c/b\u003e \u003cb\u003e= [[\u003c/b\u003e\u003cb\u003eEg\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e-\u003c/b\u003e \u003cb\u003eEg\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e]∕\u003c/b\u003e\u003cb\u003eEg\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e] × 100%\u003c/b\u003e [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn this context, Eg1 is the band gap of pristine Chitosan-gr-Polysulphanilic acid, while Eg2 is its band gap after phenol adsorption. The term ΔEg represents the change in the band gap that occurs during this adsorption process. As described by Eq.\u0026nbsp;5, Eg is linked to the conduction electron population (N). The magnitude of this change in Eg is a key indicator of an adsorbent's sensitivity to a specific adsorbate [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eN\u003c/b\u003e \u003cb\u003e=\u003c/b\u003e \u003cb\u003eAT\u003c/b\u003e\u003csub\u003e\u003cb\u003e3∕2\u003c/b\u003e\u003c/sub\u003e\u003cb\u003eexp\u003c/b\u003e\u003csup\u003e\u003cb\u003e[−\u003c/b\u003e\u003cb\u003eEg\u003c/b\u003e\u003cb\u003e∕2\u003c/b\u003e\u003cb\u003ekT\u003c/b\u003e\u003cb\u003e]\u003c/b\u003e\u003c/sup\u003e [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eWhere k is the Boltzmann’s constant and A [electrons/m\u003csup\u003e3\u003c/sup\u003eK\u003csup\u003e3/2\u003c/sup\u003e] is a constant. The discoveries acquired from this strategy are in great concurrence with those of the examinations in the writing [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. In sensor researches, work function [Φ] is defined as the lowest energy needed to relocate an electron from the Fermi surface of a substance to an unlimited space which is shown as:\u003c/p\u003e\u003cp\u003e\u003cb\u003eΦ = -\u003c/b\u003e\u003cb\u003eEF\u003c/b\u003e \u003cb\u003e+\u003c/b\u003e \u003cb\u003eV\u003c/b\u003e\u003cb\u003e[+∞]\u003c/b\u003e [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eAccording to Eq.\u0026nbsp;7, the electrostatic potential energy of an electron is shown by V [+ ∞], this parameter is considered positive. There is a relationship between the value of Φ and the electron current density, so changes in the Fermi level were ascribed to changes in Φ, which were related to changes in electron emission according to Eq.\u0026nbsp;7 [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eEq.\u0026nbsp;7 indicates that V(+∞) is the electrostatic potential energy of an electron, which is a positive value. A direct relationship exists between the work function (Φ) and the electron current density. Therefore, shifts in the Fermi level were interpreted as changes in the work function (Φ), which are connected to alterations in electron emission as outlined in Eq.\u0026nbsp;7.\u003c/p\u003e\u003cp\u003e\u003cb\u003ej\u003c/b\u003e \u003cb\u003e=\u003c/b\u003e \u003cb\u003ee\u003c/b\u003e\u003cb\u003e[\u003c/b\u003e\u003csup\u003e\u003cb\u003e−Φ∕\u003c/b\u003e\u003cb\u003ekT\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e]\u003c/b\u003e\u003cb\u003eAT\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/p\u003e\u003cp\u003ewhere T is the absolute temperature [K] and A represents Richardson’s constant [A/m\u003csup\u003e2\u003c/sup\u003e].\u003c/p\u003e\u003cp\u003eNatural bond orbital [NBO] was performed to provide a good explanation of the charge delocalization and distribution of metal-containing complexes. The stabilization energy \u003cem\u003eE\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003eof the electron delocalization between the donor orbitals [\u003cem\u003ei\u003c/em\u003e] and acceptor [\u003cem\u003ej\u003c/em\u003e] orbitals was analyzed using Eq.\u0026nbsp;[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e],\u003c/p\u003e\u003cp\u003eNatural bond orbital (NBO) analysis was conducted to effectively explain the charge delocalization and distribution within the metal-containing complexes. The stabilization energy (E2), which arises from electron delocalization between donor orbitals (i) and acceptor orbitals (j), was analyzed using Eq.\u0026nbsp;8.\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{E}}^{2}=\\:{\\varvec{q}}_{\\varvec{i}}\\frac{\\varvec{F}{\\left(\\varvec{i},\\varvec{j}\\right)}^{2}}{{\\varvec{\\epsilon\\:}}_{\\varvec{i}}-{\\varvec{\\epsilon\\:}}_{\\varvec{j}}}\\)\u003c/span\u003e\u003c/span\u003e, [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eWhere \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e signifies the occupancy of the donor orbital, \u003cem\u003eF\u003c/em\u003e[\u003cem\u003ei, j\u003c/em\u003e]\u003csup\u003e2\u003c/sup\u003eis the off-diagonal elements of the NBO Kohn-Sham Matrix; and the ε\u003csub\u003ei\u003c/sub\u003e and ε\u003csub\u003ej\u003c/sub\u003e are the orbital energies [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e61\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"The electrostatic potential [ESP]","content":"\u003cp\u003eThe electrostatic potential surfaces (ESPs) of the optimized Chitosan-gr-Polysulphanilic acid and phenol structures in the gas phase are summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. A high negative electron density region is observed around the sulfur and oxygen atoms, while an intermediate negative electron density region is present near the nitrogen atoms. In contrast, regions of high positive electron density are located on other atoms. For the ESP of phenol, high negative electron density regions are observed around the oxygen atoms, with additional negative electron density regions around the other atoms. No significant changes were observed in the Chitosan-gr-Polysulphanilic acid and phenol structures when re-optimized in the water phase.\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe lowest structures of the Chitosan-gr-Polysulphanilic acid-phenol in the gas and water phases.\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe lowest-energy structures of the Chitosan-gr-Polysulphanilic acid-phenol complexes in the gas phase are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Complex [2a] represents the most stable structure among the Chitosan-gr-Polysulphanilic acid-phenol complexes, where Chitosan-gr-Polysulphanilic acid forms bidentate interactions with phenol through a polar covalent [H-O = 2.26 Å] bond and an electrostatic [O…H-C = 2.98 Å] interaction. Complex [2b] is 8.15 kcal/mol higher in energy than complex [2a], with Chitosan-gr-Polysulphanilic acid interacting with phenol via a polar covalent [Zn-O = 2.26 Å] bond and an electrostatic [O…H-O = 3.04 Å] interaction. Complex [2c] is 13.40 kcal/mol higher than complex [2a], where Chitosan-gr-Polysulphanilic acid forms bidentate interactions with phenol via a polar covalent [H-O = 2.27 Å] bond and an electrostatic [O…H-C = 2.83 Å] interaction. Complex [2d] is 21.13 kcal/mol higher than complex [2a], with Chitosan-gr-Polysulphanilic acid forming bidentate interactions with phenol through a polar covalent [O-N = 2.29 Å] bond and an electrostatic [O…H-C = 2.92 Å] interaction. Complex [2e] represents the lowest-energy structure among the Chitosan-gr-Polysulphanilic acid-phenol complexes in the water phase, where Chitosan-gr-Polysulphanilic acid interacts with phenol via a polar covalent [H-O = 2.30 Å] bond and an electrostatic [O…H-C = 3.02 Å] interaction.\u003c/p\u003e"},{"header":"Frontier molecular orbitals and global properties of Chitosan-gr-Polysulphanilic acid and phenol before and after complexation","content":"\u003cp\u003e\u003cb\u003eFigure\u0026nbsp;3\u003c/b\u003e illustrates the distributions of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for Chitosan-gr-Polysulphanilic acid and the phenol molecule. As shown, the HOMO and LUMO orbitals are predominantly located near the electronegative [N and O] atoms and the electropositive [H] atoms, respectively. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the calculated values for various properties of Chitosan-gr-Polysulphanilic acid, the phenol molecule, and the Chitosan-gr-Polysulphanilic acid-phenol complex, including HOMO and LUMO energies, the HOMO-LUMO gap (Eg), the Fermi level (EF), dipole moment (DM), ionization potential (I), electron affinity (A), chemical potential (l), hardness (g), softness (S), and electrophilicity index (x). The obtained HOMO and LUMO energies for Chitosan-gr-Polysulphanilic acid, phenol, and the Chitosan-gr-Polysulphanilic acid-phenol complex are \u0026minus;\u0026thinsp;8.88, -1.25, -6.50, -1.09, and \u0026minus;\u0026thinsp;5.58, -1.08 eV, respectively. The Fermi level energies for these species are calculated as -5.06, -3.79, and \u0026minus;\u0026thinsp;3.33 eV, respectively. The band gaps for Chitosan-gr-Polysulphanilic acid, phenol and the Chitosan-gr-Polysulphanilic acid-phenol complex are 3.81, 2.70, and 2.25 eV, respectively. These results suggest that Chitosan-gr-Polysulphanilic acid exhibits higher electrical conductivity than the phenol molecule and the Chitosan-gr-Polysulphanilic acid-phenol complex. Additionally, kinetic stability can be assessed based on the Eg values. Chitosan-gr-Polysulphanilic acid displays lower kinetic stability than both phenol and the Chitosan-gr-Polysulphanilic acid-phenol complex, implying higher reactivity. The work function and Fermi level of Chitosan-gr-Polysulphanilic acid, along with its adsorption effects, are key factors in its potential as a Φ-type sensor. In experimental applications, the mechanism for Φ-type gas sensors typically involves the Kelvin process. A Kelvin oscillator framework is used to evaluate the Φ value of the sample before and after phenol adsorption onto Chitosan-gr-Polysulphanilic acid. If the phenol adsorption significantly alters the Φ value, it consequently modifies the gate voltage, generating an electrical signal that facilitates phenol detection [28]. Furthermore, the electric current density released from the surface of Chitosan-gr-Polysulphanilic acid undergoes substantial changes, indicating its suitability as a Φ-type sensor for phenol adsorption.\u003c/p\u003e\u003cp\u003eIn the design of effective sensors, the desorption step is of key importance. Sensors with very strong adsorption interactions are generally not suitable, as this leads to prolonged recovery times, which is a significant drawback for applications requiring quick detection. This relationship between strong adsorption and longer recovery times is supported by current transition state theory, as described by Eq.\u0026nbsp;[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] [29].\u003c/p\u003e\u003cp\u003e\u003cb\u003eτ\u003c/b\u003e\u0026thinsp;\u003cb\u003e=\u003c/b\u003e\u0026thinsp;\u003cb\u003eυ\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;1\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eexp\u003c/b\u003e\u003csup\u003e\u003cb\u003e[\u0026minus;Δ\u003c/b\u003e\u003cb\u003eG\u003c/b\u003e\u003cb\u003e∕\u003c/b\u003e\u003cb\u003ekT\u003c/b\u003e\u003cb\u003e]\u003c/b\u003e\u003c/sup\u003e [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn this context, the applied frequency is denoted by ν\u003csub\u003e0\u003c/sub\u003e. The recovery time at a temperature of 25\u0026deg;C was calculated to be approximately 4.09 ms. This calculation assumes an attempt frequency (ν) of around 10\u0026sup1;\u0026sup2; s⁻\u0026sup1; is applied in a vacuum to desorb the phenol from the Chitosan-gr-Polysulphanilic acid. It is important to mention that this time can be reduced at higher operational temperatures[\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR28\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Chitosan-gr-Polysulphanilic acid s have a roughly rapid recovery time and are perfect for measuring phenol molecules [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\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 values of HOMO, LUMO, HOMO-LUMO gap (Eg), Fermi level (EF), dipole moment (DM), ionization potential (I), the electron affinity of the molecule (A), the chemical potential of the system (l), hardness (g), softness (S), the electrophilicity index (x) and work function (Φ) of Chitosan-gr-Polysulphanilic acid, Phenol, and Chitosan-gr-Polysulphanilic acid-Phenol complex and work function compound with various structures are in eV. %∆Φ show the alteration of Φ at the end of the adsorption process.\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=\"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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProperty\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChitosan-gr-Polysulphanilic acid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePhenol\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eChitosan-gr-Polysulphanilic acid-Phenol\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eE\u003csub\u003eHOMO\u003c/sub\u003e [eV]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-8.88\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026ndash;6.50\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;5.58\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eE\u003csub\u003eLUMO\u003c/sub\u003e [eV]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ndash;1.25\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-1.09\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.08\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003eg\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e[eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e3.81\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e2.70\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e2.25\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003eF\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e=\u003c/b\u003e \u003cb\u003e[H\u0026thinsp;+\u0026thinsp;L]/2 [eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e-5.06\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e-3.79\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e-3.33\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eD\u003c/b\u003e\u003csub\u003e\u003cb\u003eM\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e[Debye]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e9.11\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e2.77\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e9.77\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eI=- E\u003c/b\u003e\u003csub\u003e\u003cb\u003eHOMO\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e[eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e8.88\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e6.50\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e5.58\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eA=- E\u003c/b\u003e\u003csub\u003e\u003cb\u003eLUMO\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e[eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e1.25\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e1.09\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e1.08\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026micro; [eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e-5.06\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e-3.79\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e-3.33\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eη [eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e3.81\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e2.70\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e2.25\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eS [eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e0.13\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.18\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.22\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eω [eV]\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e3.36\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e2.66\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e2.46\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eΦ\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e5.21\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e2.35\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e3.57\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e%ΔΦ\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e-20.32\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"AIM and NBO of the Chitosan-gr-Polysulphanilic acid-Phenol complexes in the gas and water phases","content":"\u003cp\u003eAtoms in Molecules (AIM) theory was employed to analyze the bonding characteristics of the complexes. The classification of bonds depends on the signs of \u0026nabla;\u0026sup2;ρ(r) and H(r): interactions are electrostatic if both are positive, polar covalent (or coordination/strong hydrogen bonds) if \u0026nabla;\u0026sup2;ρ(r) is positive and H(r) is negative, and nonpolar covalent if both are negative. The AIM parameters presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e indicate that interactions between Chitosan-gr-Polysulphanilic acid and phenol consist of both electrostatic and partially covalent/electrostatic (polar covalent) types in both the gas and water phases. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e lists the total transferred charges from Natural Population Analysis (NPA). The ∆q value for phenol shows a charge gain, implying that phenol might oxidize the Chitosan-gr-Polysulphanilic acid it is coordinated with. The NBO analysis clarifies interactions between the Lewis structure and non-Lewis orbitals. The charge-transfer energies (E\u003csup\u003e2\u003c/sup\u003e) in the gas phase are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. This analysis reveals that in the complexes, charge was donated from the σ and n orbitals of the C, N, and H atoms of Chitosan-gr-Polysulphanilic acid into the n* orbitals of the oxygen atom of phenol.\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\u003eBond critical point [BCP] data [a.u.] from the AIM analysis of the optimized structures of Chitosan-gr-Polysulphanilic acid-Phenol complexes in gas and water phases.\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=\"left\" 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\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\u003eComplexes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBCP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eρ\u003c/em\u003e [\u003cem\u003er\u003c/em\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026nabla;\u003csup\u003e2\u003c/sup\u003e\u003cem\u003eρ\u003c/em\u003e[\u003cem\u003er\u003c/em\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eH[\u003cem\u003er\u003c/em\u003e]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2a\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0668\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3564\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e-0.0070\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0113\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0266\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0013\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2b\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0067\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0113\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0006\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eS-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0687\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3673\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e-0.0075\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2c\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0769\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3598\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e-0.0082\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0155\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.02654\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0012\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2d\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eN-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0789\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3605\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e-0.0084\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026middot;\u0026middot;\u0026middot;\u0026middot;H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0188\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0265\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0012\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2e\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0678\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3542\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e-0.00867\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026middot;\u0026middot;\u0026middot;\u0026middot;H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.0159\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0252\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0009\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\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\u003eCalculated NPA charges of the optimized structures Chitosan-gr-Polysulphanilic acid-Phenol complexes in gas and water phases.\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=\"left\" 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\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\u003eComplexes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBond type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eq\u003c/em\u003e\u003csub\u003ex\u003c/sub\u003e \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eQ\u003c/em\u003e\u003csub\u003eH/O\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eΔ\u003cem\u003eq\u003c/em\u003e \u003csub\u003ePhenol\u003c/sub\u003e \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2a\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e-0.08\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2b\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e-0.06\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eS-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2c\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e-0.04\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026hellip;.H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2d\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eN-O\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e-0.08\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026middot;\u0026middot;\u0026middot;\u0026middot;H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2e\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e-0.06\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u0026middot;\u0026middot;\u0026middot;\u0026middot;H-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003csup\u003e\u003cb\u003ea\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eX = O/S/N and\u003c/b\u003e \u003csup\u003e\u003cb\u003eb\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eΔ\u0026#119902;\u003c/b\u003e \u003csub\u003e\u003cb\u003ePHENOL\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e= \u0026#119902;\u003c/b\u003e \u003csub\u003e\u003cb\u003enanoculsters [\u0026#119888;\u0026#119900;\u0026#119898;\u0026#119901;\u0026#119897;\u0026#119890;\u0026#119909;]\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e\u0026minus;\u0026#119902;\u003c/b\u003e \u003csub\u003e\u003cb\u003ePHENOL [\u0026#119894;\u0026#119904;\u0026#119900;\u0026#119897;\u0026#119886;\u0026#119905;\u0026#119890;\u0026#119889;]\u003c/b\u003e\u003c/sub\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResults of the second-order perturbation theory analysis of the NBO basis of the optimized structures of Zn\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e-TMZ, Zn\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e-CM, Zn\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e-PR and Zn\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e-LO complexes in gas phase.\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=\"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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComplexes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDonor NBO \u003cem\u003e[i\u003c/em\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAcceptor NBO [\u003cem\u003ej\u003c/em\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eE\u003csup\u003e[2]\u003c/sup\u003e [kcal.mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2a\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eσ\u003c/b\u003e \u003csub\u003e\u003cb\u003e[N6\u0026minus;H41]\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eO53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e33.27\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2b\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e \u003csub\u003e\u003cb\u003eS53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eO53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e29.40\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2c\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eσ\u003c/b\u003e \u003csub\u003e\u003cb\u003e[C25\u0026minus;H36]\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eO53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e27.35\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2d\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e \u003csub\u003e\u003cb\u003eN33\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eO53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e26.24\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2e\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eσ\u003c/b\u003e \u003csub\u003e\u003cb\u003e[N6\u0026minus;H41]\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003en\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eO53\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e31.09\u003c/b\u003e\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\u003cb\u003eThe binding [Δ\u003c/b\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003ebind\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e] and the solvation [Δ\u003c/b\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003esolv\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e] energies of all studied complexes\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe binding energies (ΔE\u003csub\u003ebind\u003c/sub\u003e) and solvation energies (ΔE\u003csub\u003esolv\u003c/sub\u003e) for the most stable configurations of the Chitosan-gr-Polysulphanilic acid-Phenol complexes in both gas and water phases are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. It is evident from the table that the ΔEbind values for all complexes are greater in the gas phase than in the water phase, which is due to the influence of the solvent. For phenol, the calculated ΔEsolv was \u0026minus;\u0026thinsp;3.89 kcal/mol; this negative value confirms its stability in water. Following adsorption onto Chitosan-gr-Polysulphanilic acid, the solvation energy shows a further increase (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), indicating that both stability and solubility are markedly improved in the water phase. Such high solvation energy is a key factor for their use as sensors and detectors [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e62\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe binding [Δ\u003cem\u003eE\u003c/em\u003e\u003csub\u003ebind\u003c/sub\u003e], and Solvation energies [ΔE\u003csub\u003esolv\u003c/sub\u003e], [in kcal.mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e] of all Chitosan-gr-Polysulphanilic acid-Phenol complex in gas and water phase.\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=\"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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eΔ\u003cem\u003eE\u003c/em\u003e\u003csub\u003ebind\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eΔE\u003csub\u003esolv\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComplexes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003egas phase\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWater phase\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ePhenol\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-3.89\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eChitosan-gr-Polysulphanilic acid\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-27.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eChitosan-gr-Polysulphanilic acid-Phenol\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-14.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-12.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-14.07\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe sensitivity of Chitosan-gr-Polysulphanilic acid toward phenol molecules was systematically analyzed through Density Functional Theory (DFT) calculations, providing valuable insights into the interaction between this composite material and phenol. The results of these computations demonstrated that Chitosan-gr-Polysulphanilic acid exhibits a strong affinity for phenol adsorption, with adsorption energies calculated to be approximately \u0026minus;\u0026thinsp;14.69 kcal/mol in the gas phase and \u0026minus;\u0026thinsp;12.88 kcal/mol in the water phase. This indicates that the adsorption of phenol is both energetically favorable and stable, with the material effectively binding phenol molecules in both phases, highlighting its potential for use in various environmental and industrial applications where phenol removal is required. Further investigation into the electronic properties of Chitosan-gr-Polysulphanilic acid upon phenol adsorption revealed significant changes in the frontier molecular orbitals. Specifically, the evaluation of the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels, as well as the band gap values, showed a pronounced reduction in the adsorption energy compared to pristine Chitosan-gr-Polysulphanilic acid. The interaction of phenol with the material led to a noticeable decrease in the band gap, which directly influences the electrical conductivity and reactivity of the material, suggesting an enhanced ability for the sensor to detect phenol molecules at low concentrations. This reduction in the band gap also points to the material\u0026rsquo;s potential as an effective Φ-type sensor. Moreover, the analysis indicates that Chitosan-gr-Polysulphanilic acid, through its favorable adsorption characteristics, demonstrates high potential for use as a sensing material for phenol detection. The material's ability to interact strongly with phenol molecules suggests that it could be utilized in sensors where rapid and reversible adsorption is essential. One of the most critical parameters for sensor applications is the recovery time, which refers to the time required for the sensor to return to its baseline state after the desorption of the adsorbate. In this case, the estimated recovery time for Chitosan-gr-Polysulphanilic acid was calculated to be approximately 4.09 ms, which is remarkably fast and supports the feasibility of using this material in real-time phenol detection applications. The fast recovery time indicates that phenol molecules can be effectively and reversibly desorbed from the surface of Chitosan-gr-Polysulphanilic acid, ensuring high sensitivity and rapid response in Φ-type sensors. In conclusion, the strong interaction between Chitosan-gr-Polysulphanilic acid and phenol, coupled with the favorable electronic properties and rapid recovery time, positions this material as a highly effective and promising candidate for use in environmental monitoring and industrial processes, where the detection and removal of phenolic compounds are critical. The material's high sensitivity, coupled with its reversibility and stability, suggests it could be employed in the development of advanced sensors for real-time phenol detection, contributing significantly to environmental protection and pollution control efforts.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis paper is based upon work supported by Science, Technology \u0026amp; Innovation Funding Authority [STDF] under grant\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eTarpada, U. P., Thummar, B. B., \u0026amp; Raval, D. 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I. , Reduced HOMO-LUMO gap as an index of kinetic stability for polycyclic aromatic hydrocarbons. \u003cem\u003eJournal of Physical Chemistry A, 1999, 103\u003c/em\u003e(37), 7487\u0026ndash;7495.\u003c/li\u003e\n\u003cli\u003eVatanparast, Morteza, and Zahra Shariatinia. \u0026quot;AlN and AlP Doped Graphene Quantum Dots as Novel Drug Delivery Systems for 5-Fluorouracil Drug: Theoretical Studies.\u0026quot; \u003cem\u003eJournal of Fluorine Chemistry\u003c/em\u003e, 2018, vol. 211, pp. 81\u0026ndash;93.\u003c/li\u003e\n\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":"Chitosan, phenol, Chitosan-gr-Polysulphanilic acid, polyaniline, DFT","lastPublishedDoi":"10.21203/rs.3.rs-7349857/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7349857/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe potential of Chitosan-gr-Polysulphanilic acid as a sensor for phenol detection has been thoroughly investigated using quantum mechanical calculations in both gas and aqueous phases. The results demonstrate that Chitosan-gr-Polysulphanilic acid exhibits high sensitivity and a strong affinity for phenol molecules. The adsorption energy of its most stable configuration is approximately \u0026minus;\u0026thinsp;14.69 kcal/mol in the gas phase and \u0026minus;\u0026thinsp;12.88 kcal/mol in the aqueous phase, indicating a favorable binding interaction. The adsorption of phenol significantly reduces the material's band gap, which enhances its electrical conductivity, suggesting that Chitosan-gr-Polysulphanilic acid could be an effective candidate for phenol detection, particularly in electronic sensor applications. The material\u0026rsquo;s electronic properties, including the HOMO and LUMO energy levels, also indicate that phenol adsorption leads to a substantial reduction in the band gap, which can be leveraged for more sensitive and efficient detection of phenol. Additionally, the interaction between Chitosan-gr-Polysulphanilic acid and phenol has been shown to induce a notable change in the material's work function, further supporting its potential for use as a work function-based sensor for phenol detection. The material's ability to alter its electronic properties upon adsorption of phenol highlights its potential as a responsive and adaptable sensing material. In terms of practical application, the desorption of phenol from Chitosan-gr-Polysulphanilic acid was found to be remarkably efficient, with a rapid recovery time of approximately 4.09 ms. This fast recovery time suggests that the material is highly suitable for real-time sensor applications, where quick adsorption and desorption cycles are essential for effective phenol monitoring. In conclusion, Chitosan-gr-Polysulphanilic acid shows significant promise as a phenol sensor, offering high sensitivity, rapid response times, and reversible adsorption-desorption behavior, making it an excellent candidate for environmental monitoring and industrial applications where phenol detection is critical.\u003c/p\u003e","manuscriptTitle":"Quantum Mechanical Insights into Phenol Adsorption and Sensing Behavior of Chitosan-gr-Polysulphanilic Acid","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-10 08:51:03","doi":"10.21203/rs.3.rs-7349857/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":"58851be8-45a6-4e97-b474-67aa88b7850f","owner":[],"postedDate":"September 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-16T22:07:55+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-10 08:51:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7349857","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7349857","identity":"rs-7349857","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}