Eco-friendly Fabrication of CeO2 Nanoparticles with Solanum nigrum: A Study on Cytotoxicity and Photocatalysis with plant growth studies

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The nanoparticles were characterized by XRD, FE-SEM, EDX, UV-Vis and XPS methods. The XRD pattern exhibits the cubic structure. The FESEM/PSA pictures have shown the agglomerated morphology of CeO 2 -NPs. The chemical bonding nature of CeO 2 nanoparticles was examined using the XPS technique, which showed that Ce, O, and Ag make up the majority of the sample. Spin-orbit doublets and a well-separated spin-orbit splitting are visible in the high-resolution Ce 3D spectra. Lattice and surface adsorbed oxygen ions are associated with the three primary binding energies. The C 1S peak indicates the presence of organic carbon. The UV-Vis spectra for the nanoparticles exhibit a prominent adsorption band at the wavenumber region of 417 nm. Moreover, the photocatalytic efficiency of CeO 2 -NPs has been examined by carrying out the degradation of RB dye under UVA light showing the degradation percentage of 78%, which are linked to contaminants found in sewage water. The MTT assay results have indicated that the cytotoxicity of CeO 2 -NPs on HeLa cell lines is not concentration-dependent. Additionally, the cytotoxicity analysis shows a significant toxicity for the higher concentration of 200 µg/mL for the cancer cells against the nanoparticles. The study found significant differences in the effects of CeO 2 NPs on seed weights, root and shoot lengths, and both. Plants treated with a 10 ⁻4 M dose had longer shoots and roots, while those treated with 5a had significantly larger seeds. Photocatalyst CeO2 Nanoparticles HeLa cell Plant growth Solanum nigrum Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Cerium is an abundant rare-earth element that is frequently present in the Earth's crust in the form of uncombined metal or oxide salts. Cerium oxide nanoparticles (CeO₂ NPs) have attracted considerable interest in the field of nanotechnology because of their wide range of uses [ 1 – 3 ]. Cerium oxide is a semiconductor that has a large energy band gap of 3.19 eV and can absorb wavelengths between 330–370 nm. It is known for its exceptional chemical and thermal stability, high conductivity, capacity to store oxygen, absorb UV radiation, and catalytic activity. CeO₂ NPs possess exceptional characteristics that render them extremely effective photocatalysts, which are crucial for environmental and energy-related functions. Additionally, they are widely utilized in UV light absorption, glass polishing, biosensors, sunscreens, and numerous biomedical applications [ 4 – 12 ]. The conventional manufacturing methods for cerium oxide nanoparticles have historically depended on techniques such as hydrothermal, solvothermal, co-precipitation, sol-gel, and microwave approaches [ 13 – 20 ]. These techniques may produce high-quality nanoparticles, but they generally suffer from significant limitations, like the use of toxic chemical reducing agents, high-temperature, pressure requirements, high energy consumption, and environmental pollution concerns [ 21 ]. These approaches have shown effectiveness in creating nanoparticles, but they frequently require the use of strong chemicals and energy-intensive procedures, which raises environmental issues and results in the production of toxic byproducts. Recently, there has been an increasing focus on implementing green synthesis methods to tackle these difficulties. Green synthesis approaches employ natural sources such as plant extracts, bacteria, fungi, and algae, utilizing their biochemical capabilities to generate nanoparticles in a more sustainable manner [ 22 – 32 ]. Plant extracts have emerged as highly promising options among the many green synthesis processes. Plant extracts contain a diverse range of phytochemicals, such as tannins, flavonoids, and terpenoids, that serve as reducing and stabilizing agents in the process of synthesizing nanoparticles. The bioactive substances have a significant impact on the nucleation, growth, and shape of the nanoparticles, resulting in the creation of precise and stable nanostructures. In addition, green synthesis techniques have the benefit of being environmentally friendly, as they remove the use of harmful chemicals and reduce energy consumption. This makes them very appealing for a wide range of industrial applications in nanotechnology [ 33 – 35 ]. However, several limitations remain in green synthesis investigations, such as poor control over particle agglomeration, batch-to-batch variability, and limited exploration of multifunctional properties like combined photocatalytic and biological effects. In this study, we utilized S. nigrum extract as a stabilizing agent during the synthesis of CeO 2 -NPs. S. nigrum is a prominent botanical specimen that is extensively cultivated in S. nigrum. S. nigrum is a potent medicinal plant that plays a crucial part in cancer treatment due to the therapeutic properties found in the extract derived from its leaves. S. nigrum has been utilized in traditional medicine and has been reported to possess cytotoxic effects on cancer cell lines [ 36 ]. Because of its abundance of phytochemicals, including flavonoids, polyphenols, alkaloids, and tannins, which function as natural reducing and capping agents during nanoparticle synthesis, Solanum nigrum was utilised as the stabilising agent. In addition to aiding in the reduction of cerium ions, these biomolecules also adsorb onto the surface of nanoparticles, preventing agglomeration and improving stability. The wide range of functional groups and antioxidants for the extracts promotes controlled nucleation and smaller crystallite formation, which enhances the surface reactivity and photocatalytic efficiency synthesized CeO₂ nanoparticles. The unregulated release of chemicals into water and air in recent decades has caused considerable environmental issues, which have been worsened by the increase in energy shortages and pollution. Organic pollutants such as methylene blue, rhodamine, and reactive blue are extremely harmful to aquatic life and human health due to their non-biodegradable nature and high toxicity. Their existence in water bodies adds to worldwide water pollution, affecting the well-being of ecosystems and the purity of water. Photocatalytic degradation is a viable alternative for water treatment, with advantages over traditional methods in addressing organic dye pollution and protecting the environment and human well-being [ 37 – 40 ]. There has been significant interest in utilizing semiconductor materials for photocatalysis in the fields of water purification and water splitting [ 41 , 42 ]. In this context, CeO 2 emerges as a promising n-type semiconductor with a band gap of approximately 3.2 eV, making it a viable material for decolorizing organic dyes found in industrial wastewaters. In this study, we employed an eco-friendly synthesis, structural characterization, utilizing S. nigrum plant aqueous extract to fabricate CeO 2 nanoparticles (NPs). The nanocomposite was extensively characterized using techniques such as X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Photoluminescence (PL), and UV-vis diffuse reflectance spectroscopy (UV-DRS). Subsequently, the synthesized CeO 2 NPs were evaluated for their efficacy in photodegrading aqueous Reactive Blue (RB) dye under light irradiation, demonstrating significantly enhanced degradation rates. Additionally, the nanocomposite's anticancer activity was assessed using HeLa cell lines, providing valuable insights into its potential biomedical applications. 2. Experimental section 2.1. Preparation of S. nigrum plant extract The S. nigrum leaves, sourced from the S. nigrum plant, were thoroughly washed two to three times using distilled water to eliminate debris and additional residues. Which undergo air drying. After air-drying for 2 days, 5 g of the finely ground leaf powder were boiled in distilled water at 80 ºC for 30 mins. Subsequently, the acquired extract was passed through Whatman No. 1 filter paper and stored for future investigations. 2.2. Preparation CeO 2 -NPs using of S. nigrum plant extract The synthesis of CeO 2 NPs using of S. nigrum plant extract was carried out by sol-gel approach. Ce(NO 3 ) 3 .6H2O was used as the cerium precursor, S. nigrum plant extract and DI water were employed as the stabilizing agent and solvent respectively. Subsequently, the synthesis was initiated by dissolving 3 g of cerium nitrate hexahydrate into 50 mL of DI water. The resulting mixture was then agitated at room temperature for a duration of 30 min. Thereafter, the solution was gradually introduced in small drops to a volume of m = 30mL of S. nigrum plant extract. The amalgamated mixture was continuously agitated at a temperature of 80°C for a duration of 16 h. Upon continual stirring, a white precipitate underwent a colour change and transformed into gel with a lemon hue. The gel was allowed to dried for a duration of 4 h at a temperature of 100°C. Ultimately, the dehydrated gel underwent calcination at temperatures of 400, 500, and 600°C for a duration of 2 h each, resulting in the formation of yellow-hued CeO 2 -NPs. 2.3. Characterization techniques The X-ray diffraction (XRD) pattern of the samples that were manufactured was analyzed using a PANalytical instrument equipped with a copper K-alpha radiation source. The surface characteristics, micro/nanostructures, and elemental composition of the sample were analyzed using a FE-SEM (Quanta FEG-250 instrument), HR-TEM (JEOL-2100 + tool), and the EDS linked to the FE-SEM instrument. The absorption spectra in the UV–vis DRS range were obtained using an Analytik Jena Specord-200 model. We assessed the cytotoxic impact of CeO 2 -NPs on the PC12 cancer cell line using the MTT assay. 2.4. Photocatalytic degradation test The effectiveness of degrading reactive blue (RB) using cerium oxide nanoparticles was examined through light irradiation. To conduct the test, 50 mg of the photocatalyst was dispersed in 100ml of dye solution and it was agitated for 30 min and kept in a dark room to achieve desired equilibrium of adsorption and desorption. It was then irradiated to light and the photocatalytic efficiency was monitored at every 30 min of time interval. The degradation efficiency was observed using UV-Vis spectroscopy. Furthermore, the stability test was performed by repeating the experiments over four cycles. 2.5 Cytotoxicity The assessment of anticancer activity was conducted using cell lines derived from human cervical carcinoma (HeLa) cell line, obtained from the National Centre for Cell, Pune, India. Briefly, Cells were maintained in DMEM supplemented with 2 mM l-glutamine and balanced salt solution (BSS) adjusted to contain 1.5 g/L Na2CO3, 0.1 mM nonessential amino acids, 1 mM sodium pyruvate, 2 mM glutamine, 1.5 g/L glucose, 10 mM HEPES (4-(2-hydroxyethyl)-1-piperazine ethane sulfonic acid) and 10% fetal bovine serum (GIBCO, USA). Penicillin and streptomycin (100 IU/100µg) were adjusted to 1 mL/L. The cells were maintained at 37 ºC with 5% CO 2 in a humidified CO 2 incubator. The cytotoxicity of the HeLa cell line was analysed through MTT assay. HeLa cell line with the concentrations of 1 ×10 5 were allowed to grow on the previously sterilized MEM and DMEM media. To this, the sample concentration of 100 and 200 µg/mL loaded in the 96 well plate and maintained in the humidified atmosphere. An inverted microscope was applied to investigate the modification in morphologies after the incubation of 48 h at 37°C. After that, to the above solution 80 µg/mL of MTT was added and then the solution was raised for 4 h and develop formazan crystals. The formazan crystals were liquified through substituting the solution with dimethyl sulphoxide (DMSO) and the cytotoxicity was measured using the optical intensity (OD) values at the wavelength of 570 nm. 3. Results and discussion 3.1. X-Ray diffraction analysis The X-ray diffraction (XRD) technique offers a comprehensive analysis of the crystallite structure of materials, providing vital insights into their composition and phase. The X-ray diffraction (XRD) patterns shown in Fig. 1 for cerium oxide nanoparticles (CeO 2 -NPs) generated from S. nigrum plant exhibit clear peaks that correspond to certain crystallographic planes. The major diffraction peaks appear at approximately the 2θ values at 28.6°, 33.1°, 47.5°, 56.3°, 59.1°, 69.4°, 76.7°, and 79.1° represents the peaks indexed to the (111), (200), (220), (311), (222), (400), (331), and (420) for the corresponding crystallographic planes, respectively. The indices mentioned are specific to the face-centered cubic structure commonly found in CeO 2 -NPs. This is a well-established fact supported by the reference code 34–0394 from the Joint Committee on Powder Diffraction Standards (JCPDS) [ 43 ]. The detection of these peaks signifies the existence of crystalline phases in the produced CeO 2 -NPs. The average crystallite size of the synthesized CeO₂ nanoparticles was calculated to be 11.4 nm employing the Debye–Scherrer formula. In addition, the presence of a small diffraction peak indicates that the material has a very pure crystalline structure, providing further confirmation of its composition and crystallinity. This thorough examination of XRD data not only offers useful understanding of the structural characteristics of the synthesized CeO 2 -NPs but also acts as a critical confirmation of their excellence and appropriateness for diverse applications like photocatalysis and anticancer activity. 3.2. FE- SEM and EDX analysis The surface morphology of the CeO 2 nanoparticles was meticulously examined through FE-SEM and EDX analysis, as illustrated in Fig. 2 (a–c). The images obtained through FE-SEM elucidate the distinctive agglomerated spherical shape of the CeO 2 nanoparticles, which were synthesized utilizing S. nigrum plant extract. Furthermore, the Energy Dispersive X-ray (EDX) spectrum corroborated the elemental composition of the sample, confirming the presence of atomic Ce and O with no other detectable atoms. This attests to the high purity of the synthesized CeO 2 nanoparticles. Moreover, the EDX analysis highlighted prominent peaks corresponding to Ce and O elements at an energy level of 20 keV. This clear and distinct EDX spectrum serves as compelling evidence of the successful synthesis process of CeO 2 nanoparticles. Together, these findings from FE-SEM and EDX analyses provide comprehensive insights into both the morphology and elemental composition of the synthesized CeO 2 nanoparticles, validating their quality and purity for potential applications. 3.3 UV-Vis DRS analysis The UV-Vis DRS study was conducted to investigate the absorption and optical characteristics of the nanomaterial. Figure 3 displays the UV-Vis spectra and energy band gap of CeO 2 nanoparticles (NPs) of 300°C and 600°C. The optical absorption spectra exhibit maxima at wavelengths of 374, and 417 nm under these circumstances. The absorption peaks are most likely caused by the transfer of charge from O 2p orbitals to Ce 4f orbitals [ 44 , 45 ]. The band gap energy value of the CeO 2 NPs produced using sol gel method was found by fitting the absorption of direct transition using the following equation: αhʋ=A(hʋ-E g ) n (1) The variable α represents the coefficient of optical absorption. The energy of a photon is represented by the symbol (hʋ), where h is Planck's constant and ʋis the frequency of the photon. The direct band gap is denoted by the symbol 𝐸 g . The values for the indirect and direct band gaps are n = 2 and n = 1/2, respectively, and A is a constant value [ 46 ]. The band gap energy of CeO 2 at 300°C, and 600°C was determined to be 2.73 eV using the above formulaic calculation. The reduction in the band gap value can be attributed to quantum events that take place in nanoparticles at the nanoscale [ 47 ]. The band gap plot of CeO 2 NPs showed a blue shift, confirming the effective synthesis of the nanoparticles. A significant observation is that in direct semiconductors, decreasing the particle size distribution results in an elevation of the band gap energy. The reduction in nanoparticle aggregation can be ascribed to the remarkable capacity of cerium ions, obtained from S. nigrum plant extract, to function as stabilizing agents [ 48 ]. 3.4. Photoluminescence Studies Figure 4 illustrates the photoluminescence spectra of CeO 2 nanoparticles synthesized at temperatures of 300°C, and 600°C. The photoluminescence (PL) spectra unveil a notable emission band at 405 nm, which appears more pronounced compared to other nanoparticles synthesized under similar conditions. This enhanced PL emission intensity suggests a reduction in the recombination rate of photogenerated electron-hole (e-/h+) pairs in the nanocomposites. The decrease in PL emission intensity can be attributed to the active role of CeO 2 NPs as electron collectors on the nanoparticle surfaces [ 49 ]. This active involvement of CeO 2 nanoparticles effectively enhances the efficiency of separating photogenerated carriers, thereby reducing recombination rates. Consequently, this mechanism facilitates the utilization of visible light, offering significant advantages in bolstering the performance of photocatalytic degradation processes. In summary, the findings underscore the potential of CeO 2 nanoparticles to greatly improve the efficiency of separating photogenerated carriers, leading to a reduction in recombination rates. This enhancement in visible light utilization holds immense promise for enhancing the efficacy of photocatalytic degradation processes. 3.5. XPS technique The XPS technique is used to analyze the chemical bonding nature of CeO 2 nanoparticles. With corresponding binding energies of 880–920 eV (Ce 3d) and ~ 530 eV (O 1s), the survey spectrum in Fig. 5 a shows that the sample is primarily constituted of Ce, O, and Ag. The high-resolution Ce 3d spectra, which include the spin-orbit doublets Ce 3d 5/2 (~ 882 eV) and Ce 3d 3/2 (917 eV), are shown in Fig. 5 b. The predominant Ce 4+ and Ce 3+ oxidation states of CeO 2 are appropriately attributed to these binding energies. About 18.6 eV is the well-separated spin–orbit splitting in the Ce 3d region. Furthermore, the satellite peaks (v1, ν2, µ1, and µ2) are evident in Fig. 5 b together with the Ce 3d 5/2 and Ce 3d 3/2 peaks, which are associated with the energy-gain (shake-down) process. The three main binding energies, 527.8 eV (OIII), ~ 530 eV (OII), and ~ 532.5 eV (OI), are linked to the lattice oxygen ions (Olat) and surface adsorbed oxygen ions (Oads), according to the deconvoluted O1s (Fig. 5 d) spectra. Furthermore, the presence of organic carbon in the nanoparticles is indicated by the C 1S peak (Fig. 5 (c)), which corresponds to the binding energies of ~ 281.5 eV (C–C), ~ 285.1 eV (C–O), and ~ 288.9 eV (C = O). 3.6 Photocatalytic Analysis Figure 5 illustrates the photo-degradation activity of CeO 2 NPs photocatalysts utilizing CB aqueous dyes under light irradiation. The RB solution's absorption spectra were monitored periodically at intervals of 30, 60, 90, 120, and 150 min to study the rate of change in the absorption peak intensity, which indicates the degradation. The peak at 400 nm shows that 78% of the dye has been broken down after 150 min. This is because the CeO 2 -NPs synthesized from S. nigrum plant work so well as catalysts. Equation 2 can be used to study the kinetics of photo-catalytic degradation. -ln C/C0 = kt → (2) In this equation, 'k' represents the rate constant, 'C' represents the concentration at time 't', and 'C0' represents the concentration at time 't = 0'. The relationship between the natural logarithm of the concentration ratio C/C0 and the duration of irradiation exhibited linear patterns for CeO 2 NPs showed in Fig. 7 a & b. The results indicate that the degradation of RB by CeO 2 NPs exhibits a reaction rate that approximates a first-order reaction kinetics. 3.7. Photocatalytic mechanism The mechanism of the photocatalytic response of CeO 2 -NPs synthesised from S. nigrum plant is described below. When CeO 2 nanoparticles (CeO 2 -NPs) are exposed to sunlight, electrons in the valence band absorb energy and are excited to move to the conduction band. This transition creates vacancies, known as holes, in the valence band. As a result, electron-hole pairs are generated. These pairs are then transported to the surface of the nanoparticles. At the surface, hydroxyl radicals (OH) are formed from water molecules present in the pores of the material. Simultaneously, the excited electrons reduce oxygen molecules to form superoxide radicals (O 2−) . The interaction between these reactive species—hydroxyl radicals and superoxide radicals—plays a pivotal role in the degradation of dye molecules present in the solution. The conduction band facilitates the movement of electrons, while the valence band accommodates the holes created during the excitation process. This separation and subsequent movement of charges are crucial for the photocatalytic activity, enabling the breakdown of dye molecules. The detailed photocatalytic reaction mechanism is illustrated below. CeO 2 + hv → CeO 2 (e¯+h + ) (3) CeO 2 (h + ) + OH¯ →OH• (4) CeO 2 (e+) + O 2 → O 2• ¯ (5) O 2• ¯+H + → HO 2• (6) CeO 2 (e¯) + H + +HO 2• → OH • +OH¯ (7) O 2• ¯+HO 2• +OH • or (h+) + RB dye degradation product (8) The degradation of MO dye is mainly caused by the size, shape, and surface charge characteristics of the produced CeO 2 nanoparticles (CeO 2 -NPs). Photon-induced chemical reactions take place on the catalyst's surface during photocatalytic activity [ 50 ]. Photon-generated electron-hole pairs enhance redox reactions on the catalyst's surface, resulting in the production of superoxide ions and hydroxyl free radicals [ 51 ]. The radicals produced have strong photocatalytic properties, efficiently breaking down harmful compounds present in wastewater. This suggests that the CeO 2 -NPs produced by biosynthesis effectively break down the dye when exposed to sunlight. The increased photocatalytic activity of the synthesized CeO₂ nanoparticles is mainly because of their improved surface activity, and increased oxygen vacancy concentration resulting from the use of Solanum nigrum extract during synthesis. Additionally, the Ce⁴⁺/Ce³⁺ redox pair promotes the formation of oxygen vacancies, which improves charge separation by reducing electron–hole recombination. This leads to a higher generation of reactive oxygen species (•OH and O₂•⁻), which are responsible for the effective degradation of dye molecules under light irradiation. Therefore, the efficiency is achieved through the combined effects of optimized nanoparticle size, surface stabilization, and enhanced charge carrier dynamics. 3.8. Anticancer activity 3.8.1. MTT Assay CeO 2 -NPs-600°C has been chosen for MTT experiments because it has the superior optical characteristics as shown in Fig. 8 . The inhibitory concentration (IC 50 ) value was evaluated using an MTT assay. Cultured cells (1×10 5 ) were seeded in a 96-well plate and incubated for 48 h at 37°C at 5% CO 2 incubator. After 48 h, monolayer was washed with medium and 100 µL of different test concentrations of samples were added on to the monolayer and the cells were further incubated at the same conditions. The cultured medium was removed, and 100 µL of the MTT solution was added to each well and incubated at 37°C for 4 h. After removal of the supernatant, 100 µL of DMSO was added to each of the wells and incubated for 10 min to solubilize the formazan crystals. The optical density was measured at 590 nm. The IC 50 value is a critical parameter that represents the half-maximal inhibitory concentration, indicating the concentration at which 50% of cell growth or viability is inhibited [52]. In the context of this study, the IC 50 value for CeO 2 NPs was determined to be 143.323. This value signifies that at a concentration of 143.323 µg/mL, CeO 2 NPs induce a 50% inhibition of cell growth in HeLa cell lines. Moreover, the comparison made between the IC 50 value of CeO 2 NPs and that of the standard drug, cisplatin, suggests that CeO 2 NPs exhibit comparable or even higher cytotoxic efficiency against HeLa cell lines. Therefore, the finding that CeO 2 NPs demonstrate comparable cytotoxicity to cisplatin indicates their potential as a promising alternative or adjunct therapy for cancer treatment. Table 1 represents the comparative analysis of the photocatalysis and cytotoxicity of the CeO 2 NPs. Table 1 Comparative discussion of the CeO 2 nanoparticles with the previous report Reference Synthesis route Photocatalysis Performance Cytotoxicity Shetty et al., 2025 Green synthesis Dye photodegradation (reported) High activity; stability emphasized — Mim et al., 2024 Green plant-mediated Methylene Blue; UV 56.8% in 150 min — Kalaycıoğlu et al., 2023 CeO₂/GO/PAM composite MB under visible light High, rapid MB removal; reusable — Dunna et al., 2023 Chemical synthesis - - HeLa cell line, significant dose-dependent cytotoxicity Abedi-Tameh et al., 2024 Green synthesis using plant extract - - MCF-7 cell line shows the IC₅₀ at 175 µg/mL 3.9. Plant growth studies The effect of CeO 2 NPs on the growth and development of mung bean plant growth, as depicted in Fig. 9 , reveals that all tested concentrations of CeO 2 , ranging from 10⁻ 2 to 10⁻ 4 M in aqueous solutions, markedly enhance the growth and development of roots, shoots, and seed systems in mung bean plants when compared to the control plant (Fig. 9 ). The CeO 2 NPs exhibited variable effects on root and shoot lengths as well as seed weights, demonstrating significant differences across treatments. The maximum shoot length of 27.0 cm was observed in plants treated with a 10⁻ 4 M concentration, whereas the shortest shoot length of 21.0 cm was recorded in the control plants. Similarly, the longest root length, measuring 15.0 cm, was noted in plants treated with the 10⁻ 2 M concentration, while the shortest root length of 10.0 cm occurred in plants treated with control plants. Seed weights were notably higher in the CeO 2 -treated plants, with the heaviest seeds (0.7012 g) found in plants treated with the 10⁻ 4 M concentration, compared to the lowest seed weight of 0.2351 g in the control plants. The plant growth analysis further demonstrated that the CeO₂ nanoparticles endorsed seed germination, root elongation, and biomass accumulation at low concentrations, however, growth inhibition was observed at higher nanoparticle doses, suggesting that excessive reactive oxygen species generation can induce oxidative stress and physiological imbalance. Table 2 Effects on root and shoot lengths and seed weights with respect to the CeO 2 NPs S. no Parameters Control Molar concentration (CeO 2 NPs) 10 − 2 10 − 4 1 Shoot length (cm) 20.10 ± 0.97 22.17 ± 0.88 26.22 ± 1.08 2 Root length (cm) 09.90 ± 1.02 14.06 ± 0.97 12.25 ± 1.09 3 Seed weight (g) 0.224 ± 0.009 0.513 ± 0.008 0.691 ± 0.009 4. Conclusion In this work, a green sol–gel method was successfully used to create CeO₂ nanoparticles from S. nigrum leaf extract, providing an eco-friendly substitute for chemically assisted synthesis. The formation of phase-pure, crystalline CeO₂ with bio-functional surface groups derived from the plant extract was validated by the structural and surface analyses. Under light irradiation, the produced nanoparticles showed strong photocatalytic activity towards Reactive Blue dye, which is explained by enhanced surface-active sites, oxygen vacancy formation, and charge separation. A moderate inhibitory effect on HeLa cancer cells was found in the cytotoxicity evaluation, suggesting that CeO₂ nanoparticles could be used as an additional anticancer agent while still having acceptable biocompatibility at lower concentrations. Additionally, the plant growth assay demonstrated that CeO₂ nanoparticles have a dose-dependent effect, preventing growth at higher amounts while promoting germination of seeds and seedling growth at lower concentrations. Overall, the findings indicate that, through careful oversight of concentration and exposure levels, green-synthesized CeO₂ nanoparticles have promising multifunctional applications in agriculture, biomedical fields, and environmental remediation. Optimisation of nanoparticle dosage, assessing long-term biological interactions, and investigating useful application systems should be the primary objectives of future research. Declarations Funding : Not Abblicable Conflict of Intrest : Not Abblicable Ethical approval : Not Abblicable Informed Consent : Not Abblicable Author Contribution Dr. A. Malarvizhi: Conceptualization, Methodology, Investigation Supervision; Writing-Original Draft and Formal analysis. Dr. P. 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Suresh, Indian Physics, 92 (2018) 1601–1612. L. Tolosa, M.T. Donato, Gomez-Lechon, M.J. (2015). General Cytotoxicity Assessment by Means of the MTT Assay. In: Vinken, M., Rogiers, V. (eds) Protocols in In Vitro Hepatocyte Research. Methods in Molecular Biology, vol 1250. Humana Press, New York, NY. https://doi.org/10.1007/978-1-4939-2074-7-26. Additional Declarations No competing interests reported. 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. 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nanoparticles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/3870ef0918799f932017a090.png"},{"id":100373743,"identity":"9917a3e9-66b1-4f4f-b47d-06ffe31247ba","added_by":"auto","created_at":"2026-01-16 08:18:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":244641,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSEM images and the EDX spectrum of CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e NPs prepared through \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eS. nigrum \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003eplant extract\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/07f9f80fcb64e90d7888dd82.png"},{"id":100333303,"identity":"ef71b9fd-6327-4ce1-b21d-2623d6cc35e2","added_by":"auto","created_at":"2026-01-15 18:44:12","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":108890,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUV-Vis DRS spectra of CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/550995f55571bacfe79dc65d.png"},{"id":100373582,"identity":"a4ee66ab-d7a6-4ccf-85cf-4ab03137bccc","added_by":"auto","created_at":"2026-01-16 08:15:04","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":62011,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotoluminescence spectra of CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanoparticles synthesized at temperatures of 300 °C, and 600°C\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/dc23b4ca7fe5ccb8a3949497.png"},{"id":100333306,"identity":"fbb791bd-32ba-4d58-9dea-71ca668ea4a0","added_by":"auto","created_at":"2026-01-15 18:44:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":105022,"visible":true,"origin":"","legend":"\u003cp\u003eXPS survey full survey a) high-resolution spectra of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles, b) Ce 3d, c) C 1s and d) O 1s\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/0948908c64561ea60d7937b5.png"},{"id":100379367,"identity":"7c348817-917e-404e-abfc-5f26d35e0f7d","added_by":"auto","created_at":"2026-01-16 09:07:34","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":242427,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhoto-degradation activity of CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eNPs photocatalysts utilizing RB aqueous dyes under light irradiation\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/714200167299cd89051a07c6.png"},{"id":100333311,"identity":"5fe67993-58be-43de-9515-bb6764a8a56f","added_by":"auto","created_at":"2026-01-15 18:44:12","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":80678,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea \u0026amp; b concentration ratio C/C\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and the duration of irradiation for CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e NPs\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/499b20894bea83ba6261500d.png"},{"id":100373297,"identity":"7735c062-3c9c-4304-8f58-e2bdcf9860cb","added_by":"auto","created_at":"2026-01-16 08:14:01","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":694204,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ecytotoxicity image for blank and CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanoparticles a) 100 µg/mL and b) 200 µg/mL for HeLa cells\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/81c595558eee3fd0622279a4.png"},{"id":100372759,"identity":"1044e591-89bd-42a3-8152-5d1aefb9f423","added_by":"auto","created_at":"2026-01-16 08:13:09","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":35435,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePlant growth studies of CeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanoparticle\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/b55871f521da5493b91322a3.png"},{"id":101397979,"identity":"0593cd45-7621-43d7-9557-8de3d3c81f2e","added_by":"auto","created_at":"2026-01-29 09:38:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2602834,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8342477/v1/82b4d9c4-7736-497f-a01d-b228e92aafb2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Eco-friendly Fabrication of CeO2 Nanoparticles with Solanum nigrum: A Study on Cytotoxicity and Photocatalysis with plant growth studies","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCerium is an abundant rare-earth element that is frequently present in the Earth's crust in the form of uncombined metal or oxide salts. Cerium oxide nanoparticles (CeO₂ NPs) have attracted considerable interest in the field of nanotechnology because of their wide range of uses [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Cerium oxide is a semiconductor that has a large energy band gap of 3.19 eV and can absorb wavelengths between 330\u0026ndash;370 nm. It is known for its exceptional chemical and thermal stability, high conductivity, capacity to store oxygen, absorb UV radiation, and catalytic activity. CeO₂ NPs possess exceptional characteristics that render them extremely effective photocatalysts, which are crucial for environmental and energy-related functions. Additionally, they are widely utilized in UV light absorption, glass polishing, biosensors, sunscreens, and numerous biomedical applications [\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8 CR9 CR10 CR11\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe conventional manufacturing methods for cerium oxide nanoparticles have historically depended on techniques such as hydrothermal, solvothermal, co-precipitation, sol-gel, and microwave approaches [\u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17 CR18 CR19\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. These techniques may produce high-quality nanoparticles, but they generally suffer from significant limitations, like the use of toxic chemical reducing agents, high-temperature, pressure requirements, high energy consumption, and environmental pollution concerns [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. These approaches have shown effectiveness in creating nanoparticles, but they frequently require the use of strong chemicals and energy-intensive procedures, which raises environmental issues and results in the production of toxic byproducts. Recently, there has been an increasing focus on implementing green synthesis methods to tackle these difficulties. Green synthesis approaches employ natural sources such as plant extracts, bacteria, fungi, and algae, utilizing their biochemical capabilities to generate nanoparticles in a more sustainable manner [\u003cspan additionalcitationids=\"CR23 CR24 CR25 CR26 CR27 CR28 CR29 CR30 CR31\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Plant extracts have emerged as highly promising options among the many green synthesis processes. Plant extracts contain a diverse range of phytochemicals, such as tannins, flavonoids, and terpenoids, that serve as reducing and stabilizing agents in the process of synthesizing nanoparticles. The bioactive substances have a significant impact on the nucleation, growth, and shape of the nanoparticles, resulting in the creation of precise and stable nanostructures. In addition, green synthesis techniques have the benefit of being environmentally friendly, as they remove the use of harmful chemicals and reduce energy consumption. This makes them very appealing for a wide range of industrial applications in nanotechnology [\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. However, several limitations remain in green synthesis investigations, such as poor control over particle agglomeration, batch-to-batch variability, and limited exploration of multifunctional properties like combined photocatalytic and biological effects.\u003c/p\u003e \u003cp\u003eIn this study, we utilized \u003cem\u003eS. nigrum\u003c/em\u003e extract as a stabilizing agent during the synthesis of CeO\u003csub\u003e2\u003c/sub\u003e-NPs. \u003cem\u003eS. nigrum\u003c/em\u003e is a prominent botanical specimen that is extensively cultivated in \u003cem\u003eS. nigrum. S. nigrum\u003c/em\u003e is a potent medicinal plant that plays a crucial part in cancer treatment due to the therapeutic properties found in the extract derived from its leaves. \u003cem\u003eS. nigrum\u003c/em\u003e has been utilized in traditional medicine and has been reported to possess cytotoxic effects on cancer cell lines [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Because of its abundance of phytochemicals, including flavonoids, polyphenols, alkaloids, and tannins, which function as natural reducing and capping agents during nanoparticle synthesis, Solanum nigrum was utilised as the stabilising agent. In addition to aiding in the reduction of cerium ions, these biomolecules also adsorb onto the surface of nanoparticles, preventing agglomeration and improving stability. The wide range of functional groups and antioxidants for the extracts promotes controlled nucleation and smaller crystallite formation, which enhances the surface reactivity and photocatalytic efficiency synthesized CeO₂ nanoparticles.\u003c/p\u003e \u003cp\u003eThe unregulated release of chemicals into water and air in recent decades has caused considerable environmental issues, which have been worsened by the increase in energy shortages and pollution. Organic pollutants such as methylene blue, rhodamine, and reactive blue are extremely harmful to aquatic life and human health due to their non-biodegradable nature and high toxicity. Their existence in water bodies adds to worldwide water pollution, affecting the well-being of ecosystems and the purity of water. Photocatalytic degradation is a viable alternative for water treatment, with advantages over traditional methods in addressing organic dye pollution and protecting the environment and human well-being [\u003cspan additionalcitationids=\"CR38 CR39\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. There has been significant interest in utilizing semiconductor materials for photocatalysis in the fields of water purification and water splitting [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this context, CeO\u003csub\u003e2\u003c/sub\u003e emerges as a promising n-type semiconductor with a band gap of approximately 3.2 eV, making it a viable material for decolorizing organic dyes found in industrial wastewaters. In this study, we employed an eco-friendly synthesis, structural characterization, utilizing \u003cem\u003eS. nigrum\u003c/em\u003e plant aqueous extract to fabricate CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles (NPs). The nanocomposite was extensively characterized using techniques such as X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Photoluminescence (PL), and UV-vis diffuse reflectance spectroscopy (UV-DRS). Subsequently, the synthesized CeO\u003csub\u003e2\u003c/sub\u003e NPs were evaluated for their efficacy in photodegrading aqueous Reactive Blue (RB) dye under light irradiation, demonstrating significantly enhanced degradation rates. Additionally, the nanocomposite's anticancer activity was assessed using HeLa cell lines, providing valuable insights into its potential biomedical applications.\u003c/p\u003e"},{"header":"2. Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Preparation of \u003cem\u003eS. nigrum\u003c/em\u003e plant extract\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003eS. nigrum\u003c/em\u003e leaves, sourced from the \u003cem\u003eS. nigrum\u003c/em\u003e plant, were thoroughly washed two to three times using distilled water to eliminate debris and additional residues. Which undergo air drying. After air-drying for 2 days, 5 g of the finely ground leaf powder were boiled in distilled water at 80 \u0026ordm;C for 30 mins. Subsequently, the acquired extract was passed through Whatman No. 1 filter paper and stored for future investigations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Preparation CeO\u003csub\u003e2\u003c/sub\u003e-NPs using of \u003cem\u003eS. nigrum\u003c/em\u003e plant extract\u003c/h2\u003e \u003cp\u003eThe synthesis of CeO\u003csub\u003e2\u003c/sub\u003e NPs using of \u003cem\u003eS. nigrum\u003c/em\u003e plant extract was carried out by sol-gel approach. Ce(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e.6H2O was used as the cerium precursor, \u003cem\u003eS. nigrum\u003c/em\u003e plant extract and DI water were employed as the stabilizing agent and solvent respectively. Subsequently, the synthesis was initiated by dissolving 3 g of cerium nitrate hexahydrate into 50 mL of DI water. The resulting mixture was then agitated at room temperature for a duration of 30 min. Thereafter, the solution was gradually introduced in small drops to a volume of m\u0026thinsp;=\u0026thinsp;30mL of \u003cem\u003eS. nigrum\u003c/em\u003e plant extract. The amalgamated mixture was continuously agitated at a temperature of 80\u0026deg;C for a duration of 16 h. Upon continual stirring, a white precipitate underwent a colour change and transformed into gel with a lemon hue. The gel was allowed to dried for a duration of 4 h at a temperature of 100\u0026deg;C. Ultimately, the dehydrated gel underwent calcination at temperatures of 400, 500, and 600\u0026deg;C for a duration of 2 h each, resulting in the formation of yellow-hued CeO\u003csub\u003e2\u003c/sub\u003e -NPs.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Characterization techniques\u003c/h2\u003e \u003cp\u003eThe X-ray diffraction (XRD) pattern of the samples that were manufactured was analyzed using a PANalytical instrument equipped with a copper K-alpha radiation source. The surface characteristics, micro/nanostructures, and elemental composition of the sample were analyzed using a FE-SEM (Quanta FEG-250 instrument), HR-TEM (JEOL-2100\u0026thinsp;+\u0026thinsp;tool), and the EDS linked to the FE-SEM instrument. The absorption spectra in the UV\u0026ndash;vis DRS range were obtained using an Analytik Jena Specord-200 model. We assessed the cytotoxic impact of CeO\u003csub\u003e2\u003c/sub\u003e-NPs on the PC12 cancer cell line using the MTT assay.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Photocatalytic degradation test\u003c/h2\u003e \u003cp\u003eThe effectiveness of degrading reactive blue (RB) using cerium oxide nanoparticles was examined through light irradiation. To conduct the test, 50 mg of the photocatalyst was dispersed in 100ml of dye solution and it was agitated for 30 min and kept in a dark room to achieve desired equilibrium of adsorption and desorption. It was then irradiated to light and the photocatalytic efficiency was monitored at every 30 min of time interval. The degradation efficiency was observed using UV-Vis spectroscopy. Furthermore, the stability test was performed by repeating the experiments over four cycles.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Cytotoxicity\u003c/h2\u003e \u003cp\u003eThe assessment of anticancer activity was conducted using cell lines derived from human cervical carcinoma (HeLa) cell line, obtained from the National Centre for Cell, Pune, India. Briefly, Cells were maintained in DMEM supplemented with 2 mM l-glutamine and balanced salt solution (BSS) adjusted to contain 1.5 g/L Na2CO3, 0.1 mM nonessential amino acids, 1 mM sodium pyruvate, 2 mM glutamine, 1.5 g/L glucose, 10 mM HEPES (4-(2-hydroxyethyl)-1-piperazine ethane sulfonic acid) and 10% fetal bovine serum (GIBCO, USA). Penicillin and streptomycin (100 IU/100\u0026micro;g) were adjusted to 1 mL/L. The cells were maintained at 37 \u0026ordm;C with 5% CO\u003csub\u003e2\u003c/sub\u003e in a humidified CO\u003csub\u003e2\u003c/sub\u003e incubator. The cytotoxicity of the HeLa cell line was analysed through MTT assay. HeLa cell line with the concentrations of 1 \u0026times;10\u003csup\u003e5\u003c/sup\u003e were allowed to grow on the previously sterilized MEM and DMEM media. To this, the sample concentration of 100 and 200 \u0026micro;g/mL loaded in the 96 well plate and maintained in the humidified atmosphere. An inverted microscope was applied to investigate the modification in morphologies after the incubation of 48 h at 37\u0026deg;C. After that, to the above solution 80 \u0026micro;g/mL of MTT was added and then the solution was raised for 4 h and develop formazan crystals. The formazan crystals were liquified through substituting the solution with dimethyl sulphoxide (DMSO) and the cytotoxicity was measured using the optical intensity (OD) values at the wavelength of 570 nm.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. X-Ray diffraction analysis\u003c/h2\u003e \u003cp\u003eThe X-ray diffraction (XRD) technique offers a comprehensive analysis of the crystallite structure of materials, providing vital insights into their composition and phase. The X-ray diffraction (XRD) patterns shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e for cerium oxide nanoparticles (CeO\u003csub\u003e2\u003c/sub\u003e-NPs) generated from \u003cem\u003eS. nigrum\u003c/em\u003e plant exhibit clear peaks that correspond to certain crystallographic planes. The major diffraction peaks appear at approximately the 2θ values at 28.6\u0026deg;, 33.1\u0026deg;, 47.5\u0026deg;, 56.3\u0026deg;, 59.1\u0026deg;, 69.4\u0026deg;, 76.7\u0026deg;, and 79.1\u0026deg; represents the peaks indexed to the (111), (200), (220), (311), (222), (400), (331), and (420) for the corresponding crystallographic planes, respectively. The indices mentioned are specific to the face-centered cubic structure commonly found in CeO\u003csub\u003e2\u003c/sub\u003e-NPs. This is a well-established fact supported by the reference code 34\u0026ndash;0394 from the Joint Committee on Powder Diffraction Standards (JCPDS) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. The detection of these peaks signifies the existence of crystalline phases in the produced CeO\u003csub\u003e2\u003c/sub\u003e-NPs. The average crystallite size of the synthesized CeO₂ nanoparticles was calculated to be 11.4 nm employing the Debye\u0026ndash;Scherrer formula. In addition, the presence of a small diffraction peak indicates that the material has a very pure crystalline structure, providing further confirmation of its composition and crystallinity. This thorough examination of XRD data not only offers useful understanding of the structural characteristics of the synthesized CeO\u003csub\u003e2\u003c/sub\u003e-NPs but also acts as a critical confirmation of their excellence and appropriateness for diverse applications like photocatalysis and anticancer activity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. FE- SEM and EDX analysis\u003c/h2\u003e \u003cp\u003eThe surface morphology of the CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles was meticulously examined through FE-SEM and EDX analysis, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a\u0026ndash;c). The images obtained through FE-SEM elucidate the distinctive agglomerated spherical shape of the CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles, which were synthesized utilizing \u003cem\u003eS. nigrum\u003c/em\u003e plant extract. Furthermore, the Energy Dispersive X-ray (EDX) spectrum corroborated the elemental composition of the sample, confirming the presence of atomic Ce and O with no other detectable atoms. This attests to the high purity of the synthesized CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles. Moreover, the EDX analysis highlighted prominent peaks corresponding to Ce and O elements at an energy level of 20 keV. This clear and distinct EDX spectrum serves as compelling evidence of the successful synthesis process of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles. Together, these findings from FE-SEM and EDX analyses provide comprehensive insights into both the morphology and elemental composition of the synthesized CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles, validating their quality and purity for potential applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 UV-Vis DRS analysis\u003c/h2\u003e \u003cp\u003eThe UV-Vis DRS study was conducted to investigate the absorption and optical characteristics of the nanomaterial. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e displays the UV-Vis spectra and energy band gap of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles (NPs) of 300\u0026deg;C and 600\u0026deg;C. The optical absorption spectra exhibit maxima at wavelengths of 374, and 417 nm under these circumstances. The absorption peaks are most likely caused by the transfer of charge from O 2p orbitals to Ce 4f orbitals [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The band gap energy value of the CeO\u003csub\u003e2\u003c/sub\u003e NPs produced using sol gel method was found by fitting the absorption of direct transition using the following equation:\u003c/p\u003e \u003cp\u003eαhʋ=A(hʋ-E\u003csub\u003eg\u003c/sub\u003e)\u003csup\u003en\u003c/sup\u003e (1)\u003c/p\u003e \u003cp\u003eThe variable α represents the coefficient of optical absorption. The energy of a photon is represented by the symbol (hʋ), where h is Planck's constant and ʋis the frequency of the photon. The direct band gap is denoted by the symbol \u0026#119864;\u003csub\u003eg\u003c/sub\u003e. The values for the indirect and direct band gaps are n\u0026thinsp;=\u0026thinsp;2 and n\u0026thinsp;=\u0026thinsp;1/2, respectively, and A is a constant value [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. The band gap energy of CeO\u003csub\u003e2\u003c/sub\u003e at 300\u0026deg;C, and 600\u0026deg;C was determined to be 2.73 eV using the above formulaic calculation. The reduction in the band gap value can be attributed to quantum events that take place in nanoparticles at the nanoscale [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. The band gap plot of CeO\u003csub\u003e2\u003c/sub\u003e NPs showed a blue shift, confirming the effective synthesis of the nanoparticles. A significant observation is that in direct semiconductors, decreasing the particle size distribution results in an elevation of the band gap energy. The reduction in nanoparticle aggregation can be ascribed to the remarkable capacity of cerium ions, obtained from \u003cem\u003eS. nigrum\u003c/em\u003e plant extract, to function as stabilizing agents [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Photoluminescence Studies\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the photoluminescence spectra of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles synthesized at temperatures of 300\u0026deg;C, and 600\u0026deg;C. The photoluminescence (PL) spectra unveil a notable emission band at 405 nm, which appears more pronounced compared to other nanoparticles synthesized under similar conditions. This enhanced PL emission intensity suggests a reduction in the recombination rate of photogenerated electron-hole (e-/h+) pairs in the nanocomposites. The decrease in PL emission intensity can be attributed to the active role of CeO\u003csub\u003e2\u003c/sub\u003e NPs as electron collectors on the nanoparticle surfaces [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. This active involvement of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles effectively enhances the efficiency of separating photogenerated carriers, thereby reducing recombination rates. Consequently, this mechanism facilitates the utilization of visible light, offering significant advantages in bolstering the performance of photocatalytic degradation processes. In summary, the findings underscore the potential of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles to greatly improve the efficiency of separating photogenerated carriers, leading to a reduction in recombination rates. This enhancement in visible light utilization holds immense promise for enhancing the efficacy of photocatalytic degradation processes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.5. XPS technique\u003c/h2\u003e \u003cp\u003eThe XPS technique is used to analyze the chemical bonding nature of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles. With corresponding binding energies of 880\u0026ndash;920 eV (Ce 3d) and ~\u0026thinsp;530 eV (O 1s), the survey spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows that the sample is primarily constituted of Ce, O, and Ag. The high-resolution Ce 3d spectra, which include the spin-orbit doublets Ce 3d\u003csub\u003e5/2\u003c/sub\u003e (~\u0026thinsp;882 eV) and Ce 3d\u003csub\u003e3/2\u003c/sub\u003e (917 eV), are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. The predominant Ce\u003csup\u003e4+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e oxidation states of CeO\u003csub\u003e2\u003c/sub\u003e are appropriately attributed to these binding energies. About 18.6 eV is the well-separated spin\u0026ndash;orbit splitting in the Ce 3d region. Furthermore, the satellite peaks (v1, ν2, \u0026micro;1, and \u0026micro;2) are evident in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb together with the Ce 3d\u003csub\u003e5/2\u003c/sub\u003e and Ce 3d\u003csub\u003e3/2\u003c/sub\u003e peaks, which are associated with the energy-gain (shake-down) process. The three main binding energies, 527.8 eV (OIII), ~\u0026thinsp;530 eV (OII), and ~\u0026thinsp;532.5 eV (OI), are linked to the lattice oxygen ions (Olat) and surface adsorbed oxygen ions (Oads), according to the deconvoluted O1s (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed) spectra. Furthermore, the presence of organic carbon in the nanoparticles is indicated by the C 1S peak (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c)), which corresponds to the binding energies of ~\u0026thinsp;281.5 eV (C\u0026ndash;C), ~\u0026thinsp;285.1 eV (C\u0026ndash;O), and ~\u0026thinsp;288.9 eV (C\u0026thinsp;=\u0026thinsp;O).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Photocatalytic Analysis\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e illustrates the photo-degradation activity of CeO\u003csub\u003e2\u003c/sub\u003e NPs photocatalysts utilizing CB aqueous dyes under light irradiation. The RB solution's absorption spectra were monitored periodically at intervals of 30, 60, 90, 120, and 150 min to study the rate of change in the absorption peak intensity, which indicates the degradation. The peak at 400 nm shows that 78% of the dye has been broken down after 150 min. This is because the CeO\u003csub\u003e2\u003c/sub\u003e -NPs synthesized from \u003cem\u003eS. nigrum\u003c/em\u003e plant work so well as catalysts.\u003c/p\u003e \u003cp\u003eEquation 2 can be used to study the kinetics of photo-catalytic degradation.\u003c/p\u003e \u003cp\u003e-ln C/C0\u0026thinsp;=\u0026thinsp;kt \u0026rarr; (2)\u003c/p\u003e \u003cp\u003eIn this equation, 'k' represents the rate constant, 'C' represents the concentration at time 't', and 'C0' represents the concentration at time 't\u0026thinsp;=\u0026thinsp;0'. The relationship between the natural logarithm of the concentration ratio C/C0 and the duration of irradiation exhibited linear patterns for CeO\u003csub\u003e2\u003c/sub\u003e NPs showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea \u0026amp; b. The results indicate that the degradation of RB by CeO\u003csub\u003e2\u003c/sub\u003e NPs exhibits a reaction rate that approximates a first-order reaction kinetics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.7. Photocatalytic mechanism\u003c/h2\u003e \u003cp\u003eThe mechanism of the photocatalytic response of CeO\u003csub\u003e2\u003c/sub\u003e-NPs synthesised from \u003cem\u003eS. nigrum\u003c/em\u003e plant is described below. When CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles (CeO\u003csub\u003e2\u003c/sub\u003e-NPs) are exposed to sunlight, electrons in the valence band absorb energy and are excited to move to the conduction band. This transition creates vacancies, known as holes, in the valence band. As a result, electron-hole pairs are generated. These pairs are then transported to the surface of the nanoparticles. At the surface, hydroxyl radicals (OH) are formed from water molecules present in the pores of the material. Simultaneously, the excited electrons reduce oxygen molecules to form superoxide radicals (O\u003csup\u003e2\u0026minus;)\u003c/sup\u003e. The interaction between these reactive species\u0026mdash;hydroxyl radicals and superoxide radicals\u0026mdash;plays a pivotal role in the degradation of dye molecules present in the solution. The conduction band facilitates the movement of electrons, while the valence band accommodates the holes created during the excitation process. This separation and subsequent movement of charges are crucial for the photocatalytic activity, enabling the breakdown of dye molecules. The detailed photocatalytic reaction mechanism is illustrated below.\u003c/p\u003e \u003cp\u003eCeO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;hv \u0026rarr; CeO\u003csub\u003e2\u003c/sub\u003e (e\u0026macr;+h\u003csup\u003e+\u003c/sup\u003e) (3)\u003c/p\u003e \u003cp\u003eCeO\u003csub\u003e2\u003c/sub\u003e (h\u003csup\u003e+\u003c/sup\u003e)\u0026thinsp;+\u0026thinsp;OH\u0026macr; \u0026rarr;OH\u0026bull; (4)\u003c/p\u003e \u003cp\u003eCeO\u003csub\u003e2\u003c/sub\u003e (e+)\u0026thinsp;+\u0026thinsp;O\u003csub\u003e2\u003c/sub\u003e\u0026rarr; O\u003csub\u003e2\u0026bull;\u003c/sub\u003e\u0026macr; (5)\u003c/p\u003e \u003cp\u003eO\u003csub\u003e2\u0026bull;\u003c/sub\u003e\u0026macr;+H\u003csup\u003e+\u003c/sup\u003e \u0026rarr; HO\u003csub\u003e2\u0026bull;\u003c/sub\u003e (6)\u003c/p\u003e \u003cp\u003eCeO\u003csub\u003e2\u003c/sub\u003e (e\u0026macr;)\u0026thinsp;+\u0026thinsp;H\u003csup\u003e+\u003c/sup\u003e +HO\u003csub\u003e2\u0026bull;\u003c/sub\u003e\u0026rarr; OH\u003csub\u003e\u0026bull;\u003c/sub\u003e+OH\u0026macr; (7)\u003c/p\u003e \u003cp\u003eO\u003csub\u003e2\u0026bull;\u003c/sub\u003e\u0026macr;+HO\u003csub\u003e2\u0026bull;\u003c/sub\u003e+OH\u003csub\u003e\u0026bull;\u003c/sub\u003e or (h+)\u0026thinsp;+\u0026thinsp;RB dye degradation product (8)\u003c/p\u003e \u003cp\u003eThe degradation of MO dye is mainly caused by the size, shape, and surface charge characteristics of the produced CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles (CeO\u003csub\u003e2\u003c/sub\u003e-NPs). Photon-induced chemical reactions take place on the catalyst's surface during photocatalytic activity [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Photon-generated electron-hole pairs enhance redox reactions on the catalyst's surface, resulting in the production of superoxide ions and hydroxyl free radicals [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. The radicals produced have strong photocatalytic properties, efficiently breaking down harmful compounds present in wastewater. This suggests that the CeO\u003csub\u003e2\u003c/sub\u003e-NPs produced by biosynthesis effectively break down the dye when exposed to sunlight. The increased photocatalytic activity of the synthesized CeO₂ nanoparticles is mainly because of their improved surface activity, and increased oxygen vacancy concentration resulting from the use of \u003cem\u003eSolanum nigrum\u003c/em\u003e extract during synthesis. Additionally, the Ce⁴⁺/Ce\u0026sup3;⁺ redox pair promotes the formation of oxygen vacancies, which improves charge separation by reducing electron\u0026ndash;hole recombination. This leads to a higher generation of reactive oxygen species (\u0026bull;OH and O₂\u0026bull;⁻), which are responsible for the effective degradation of dye molecules under light irradiation. Therefore, the efficiency is achieved through the combined effects of optimized nanoparticle size, surface stabilization, and enhanced charge carrier dynamics.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.8. Anticancer activity\u003c/h2\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.8.1. MTT Assay\u003c/h2\u003e \u003cp\u003eCeO\u003csub\u003e2\u003c/sub\u003e-NPs-600\u0026deg;C has been chosen for MTT experiments because it has the superior optical characteristics as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The inhibitory concentration (IC\u003csub\u003e50\u003c/sub\u003e) value was evaluated using an MTT assay. Cultured cells (1\u0026times;10\u003csup\u003e5\u003c/sup\u003e) were seeded in a 96-well plate and incubated for 48 h at 37\u0026deg;C at 5% CO\u003csub\u003e2\u003c/sub\u003e incubator. After 48 h, monolayer was washed with medium and 100 \u0026micro;L of different test concentrations of samples were added on to the monolayer and the cells were further incubated at the same conditions. The cultured medium was removed, and 100 \u0026micro;L of the MTT solution was added to each well and incubated at 37\u0026deg;C for 4 h. After removal of the supernatant, 100 \u0026micro;L of DMSO was added to each of the wells and incubated for 10 min to solubilize the formazan crystals. The optical density was measured at 590 nm. The IC\u003csub\u003e50\u003c/sub\u003e value is a critical parameter that represents the half-maximal inhibitory concentration, indicating the concentration at which 50% of cell growth or viability is inhibited [52]. In the context of this study, the IC\u003csub\u003e50\u003c/sub\u003e value for CeO\u003csub\u003e2\u003c/sub\u003e NPs was determined to be 143.323. This value signifies that at a concentration of 143.323 \u0026micro;g/mL, CeO\u003csub\u003e2\u003c/sub\u003e NPs induce a 50% inhibition of cell growth in HeLa cell lines. Moreover, the comparison made between the IC\u003csub\u003e50\u003c/sub\u003e value of CeO\u003csub\u003e2\u003c/sub\u003e NPs and that of the standard drug, cisplatin, suggests that CeO\u003csub\u003e2\u003c/sub\u003e NPs exhibit comparable or even higher cytotoxic efficiency against HeLa cell lines. Therefore, the finding that CeO\u003csub\u003e2\u003c/sub\u003e NPs demonstrate comparable cytotoxicity to cisplatin indicates their potential as a promising alternative or adjunct therapy for cancer treatment. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e represents the comparative analysis of the photocatalysis and cytotoxicity of the CeO\u003csub\u003e2\u003c/sub\u003e NPs.\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\u003eComparative discussion of the CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles with the previous report\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSynthesis route\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePhotocatalysis\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePerformance\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCytotoxicity\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShetty et al., 2025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGreen synthesis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDye photodegradation (reported)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHigh activity; stability emphasized\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMim et al., 2024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGreen plant-mediated\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMethylene Blue; UV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.8% in 150 min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKalaycıoğlu et al., 2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCeO₂/GO/PAM composite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMB under visible light\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHigh, rapid MB removal; reusable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDunna et al., 2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChemical synthesis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHeLa cell line, significant dose-dependent cytotoxicity\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbedi-Tameh et al., 2024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eGreen\u003c/b\u003e synthesis using plant extract\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMCF-7 cell line shows the IC₅₀ at 175 \u0026micro;g/mL\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 \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.9. Plant growth studies\u003c/h2\u003e \u003cp\u003eThe effect of CeO\u003csub\u003e2\u003c/sub\u003e NPs on the growth and development of mung bean plant growth, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, reveals that all tested concentrations of CeO\u003csub\u003e2\u003c/sub\u003e, ranging from 10⁻\u003csup\u003e2\u003c/sup\u003e to 10⁻\u003csup\u003e4\u003c/sup\u003e M in aqueous solutions, markedly enhance the growth and development of roots, shoots, and seed systems in mung bean plants when compared to the control plant (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe CeO\u003csub\u003e2\u003c/sub\u003e NPs exhibited variable effects on root and shoot lengths as well as seed weights, demonstrating significant differences across treatments. The maximum shoot length of 27.0 cm was observed in plants treated with a 10⁻\u003csup\u003e4\u003c/sup\u003e M concentration, whereas the shortest shoot length of 21.0 cm was recorded in the control plants. Similarly, the longest root length, measuring 15.0 cm, was noted in plants treated with the 10⁻\u003csup\u003e2\u003c/sup\u003e M concentration, while the shortest root length of 10.0 cm occurred in plants treated with control plants. Seed weights were notably higher in the CeO\u003csub\u003e2\u003c/sub\u003e-treated plants, with the heaviest seeds (0.7012 g) found in plants treated with the 10⁻\u003csup\u003e4\u003c/sup\u003e M concentration, compared to the lowest seed weight of 0.2351 g in the control plants. The plant growth analysis further demonstrated that the CeO₂ nanoparticles endorsed seed germination, root elongation, and biomass accumulation at low concentrations, however, growth inhibition was observed at higher nanoparticle doses, suggesting that excessive reactive oxygen species generation can induce oxidative stress and physiological imbalance.\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\u003eEffects on root and shoot lengths and seed weights with respect to the CeO\u003csub\u003e2\u003c/sub\u003e NPs\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=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eS. no\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMolar concentration (CeO\u003csub\u003e2\u003c/sub\u003e NPs)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;4\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\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShoot length (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e20.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e22.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e26.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRoot length (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e09.90\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e14.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e12.25\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSeed weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.224\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.513\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.691\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009\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 \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this work, a green sol\u0026ndash;gel method was successfully used to create CeO₂ nanoparticles from S. nigrum leaf extract, providing an eco-friendly substitute for chemically assisted synthesis. The formation of phase-pure, crystalline CeO₂ with bio-functional surface groups derived from the plant extract was validated by the structural and surface analyses. Under light irradiation, the produced nanoparticles showed strong photocatalytic activity towards Reactive Blue dye, which is explained by enhanced surface-active sites, oxygen vacancy formation, and charge separation. A moderate inhibitory effect on HeLa cancer cells was found in the cytotoxicity evaluation, suggesting that CeO₂ nanoparticles could be used as an additional anticancer agent while still having acceptable biocompatibility at lower concentrations. Additionally, the plant growth assay demonstrated that CeO₂ nanoparticles have a dose-dependent effect, preventing growth at higher amounts while promoting germination of seeds and seedling growth at lower concentrations. Overall, the findings indicate that, through careful oversight of concentration and exposure levels, green-synthesized CeO₂ nanoparticles have promising multifunctional applications in agriculture, biomedical fields, and environmental remediation. Optimisation of nanoparticle dosage, assessing long-term biological interactions, and investigating useful application systems should be the primary objectives of future research.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding :\u0026nbsp;\u003c/strong\u003eNot Abblicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Intrest :\u003c/strong\u003e Not Abblicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval :\u003c/strong\u003e Not Abblicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent :\u003c/strong\u003e Not Abblicable\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDr. A. Malarvizhi: Conceptualization, Methodology, Investigation Supervision; Writing-Original Draft and Formal analysis. Dr. P. Ananthi: Validation, Resources, Formal analysis, Methodology. Dr. M. Karthik: Resources, Formal analysis, and Editing. Dr. P. Karthikeyan: Validation, Visualization, Reviewing and editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eC. M. Strieder, D L P Macuvele, C. Soares, et. al., J Mater Res Tech, 30, 2024, 6376-6388.\u003c/li\u003e\n\u003cli\u003eT. Surendra, S.M. Roopan, Journal of Photochemistry and Photobiology B: Biology, 161 (2016) 122-128.\u003c/li\u003e\n\u003cli\u003eM. Keerthana, T. Pushpa Malini, R. Sangavi, J. P. Arockia Selvi, M. Arthanareeswari, \u003cem\u003eChemistrySelect\u003c/em\u003e 2022, \u003cem\u003e7\u003c/em\u003e, e202103610.\u003c/li\u003e\n\u003cli\u003eL. Wasef, AMK. Nassar, YS. El-Sayed, D. Samak, A. Noreldin, Elshony N, Sci Rep, (2021) 11:1-15.\u003c/li\u003e\n\u003cli\u003eL. Lu, G. Dai, L. Yan, L. Wang, L. Wang, Z. Wang, Optical Material (Amst), (2020) 101:109724.\u003c/li\u003e\n\u003cli\u003eJ. Calvache-Munoz, FA. Prado, Rodrı guez-Paez JE. 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Rabindran Jermy, Open Nano, (2023) 100169. \u003c/li\u003e\n\u003cli\u003eA. Muthuvel, M. Jothibas, C. Manoharan, S. J. Jayakumar, Research Chemical Intermediate Mar. (2020). Doi:10.1007/s11164-020-04115-\u003c/li\u003e\n\u003cli\u003eV. Ramasamy, V. Mohana, G. Suresh, Indian Physics, 92 (2018) 1601\u0026ndash;1612.\u003c/li\u003e\n\u003cli\u003eL. Tolosa, M.T. Donato, Gomez-Lechon, M.J. (2015). General Cytotoxicity Assessment by Means of the MTT Assay. In: Vinken, M., Rogiers, V. (eds) Protocols in In Vitro Hepatocyte Research. Methods in Molecular Biology, vol 1250. Humana Press, New York, NY. https://doi.org/10.1007/978-1-4939-2074-7-26.\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":"Photocatalyst, CeO2 Nanoparticles, HeLa cell, Plant growth, Solanum nigrum","lastPublishedDoi":"10.21203/rs.3.rs-8342477/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8342477/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe synthesis of cerium oxide nanoparticles (CeO\u003csub\u003e2\u003c/sub\u003e-NPs) has been carried out using a sol-gel method, in which \u003cem\u003eSolanum nigrum\u003c/em\u003e (\u003cem\u003eS. nigrum)\u003c/em\u003e extract was used as the stabilizing agent. The nanoparticles were characterized by XRD, FE-SEM, EDX, UV-Vis and XPS methods. The XRD pattern exhibits the cubic structure. The FESEM/PSA pictures have shown the agglomerated morphology of CeO\u003csub\u003e2\u003c/sub\u003e-NPs. The chemical bonding nature of CeO\u003csub\u003e2\u003c/sub\u003e nanoparticles was examined using the XPS technique, which showed that Ce, O, and Ag make up the majority of the sample. Spin-orbit doublets and a well-separated spin-orbit splitting are visible in the high-resolution Ce 3D spectra. Lattice and surface adsorbed oxygen ions are associated with the three primary binding energies. The C 1S peak indicates the presence of organic carbon. The UV-Vis spectra for the nanoparticles exhibit a prominent adsorption band at the wavenumber region of 417 nm. Moreover, the photocatalytic efficiency of CeO\u003csub\u003e2\u003c/sub\u003e-NPs has been examined by carrying out the degradation of RB dye under UVA light showing the degradation percentage of 78%, which are linked to contaminants found in sewage water. The MTT assay results have indicated that the cytotoxicity of CeO\u003csub\u003e2\u003c/sub\u003e-NPs on HeLa cell lines is not concentration-dependent. Additionally, the cytotoxicity analysis shows a significant toxicity for the higher concentration of 200 \u0026micro;g/mL for the cancer cells against the nanoparticles. The study found significant differences in the effects of CeO\u003csub\u003e2\u003c/sub\u003e NPs on seed weights, root and shoot lengths, and both. Plants treated with a 10\u003csup\u003e⁻4\u003c/sup\u003e M dose had longer shoots and roots, while those treated with 5a had significantly larger seeds.\u003c/p\u003e","manuscriptTitle":"Eco-friendly Fabrication of CeO2 Nanoparticles with Solanum nigrum: A Study on Cytotoxicity and Photocatalysis with plant growth studies","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-15 18:44:07","doi":"10.21203/rs.3.rs-8342477/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":"3d59351f-fcfb-47fd-8573-28d70d22286b","owner":[],"postedDate":"January 15th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-28T08:09:56+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-15 18:44:07","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8342477","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8342477","identity":"rs-8342477","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}