X-ray Photoelectron Spectroscopy Studies Research Articles

Effect of Co2+ doping on structural, optical and photocatalytic properties of La2CuO4 perovskite

In this article, structural, optical and photocatalytic properties of a series of Co2+ doped La2CuO4 perovskites, synthesized via sol–gel auto-combustion method, have been investigated for the first time. Structural and Fourier-transform infrared (FTIR) studies revealed pure orthorhombic phase formation with smaller crystallite sizes at higher Co2+ concentrations. Elemental composition was confirmed by energy-dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS) studies indicated the possible oxidation states of the constituent elements. The optical energy band gaps were estimated to be 1.31–1.04 eV, indicating the semiconducting nature and proper bandgap tuning with increased Co2+ content of the prepared perovskites. The highest photocatalytic methylene blue dye degradation efficiency, about 90%, was achieved for the 15% Co2+ doped La2CuO4 perovskite, indicating its potential use as a photocatalyst for environmental remediation.

Facile in-situ synthesis of solid mediator based CdS-rGO-WO3 Z-scheme photocatalytic system for efficient photocatalytic hydrogen generation

Reduced graphene oxide (rGO) solid state mediator based Z scheme photocatalyst CdS-rGO-WO3 heterojunction comprising of nano-rods of CdS and nanoplates of WO3 was fabricated in-situ by a facile hydrothermal process, characterized and tested for solar hydrogen generation. The systematically designed heterojunction created separated oxidative and reductive sites for photo generated electron hole pairs with enhanced redox ability, improving the charge separation and photo-stability, mitigating the problem of photo-corrosion of CdS. This was evident from an enhanced photocatalytic activity of 11.69 mmolg−1h−1 which was almost 2.3 times than pristine CdS (4.9 mmolg−1h−1), in presence of simulated solar light. Due to the high electron mobility property of graphene sheet, rapid transport of electrons was possible at the interface between CdS and WO3. The charge transfer via Z scheme mechanistic pathway was verified by X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) and photocurrent measurement studies. This research study will provide a newer insight in engineering nano-hetero-structures for enhanced photocatalytic hydrogen evolution, in an attempt to make the process commercially viable.

Highly porous NiO microstructure for NO2 detection

Nickel oxide (NiO) thin films were deposited on to the glass substrates via chemical bath deposition (CBD) method at various deposition times of 5, 6, 7 and 8 h. The X-ray diffraction (XRD) study showed the cubic crystal structure of NiO. The field emission scanning electron microscopy (FE-SEM) images exhibit the porous structured morphology composed of randomly oriented nanosheets. The atomic force microscopy (AFM) analysis reveals the maximum surface roughness of 107.9 nm for NiO film deposited at 7 h. The X-ray photoelectron spectroscopy (XPS) study reveals the presence of Ni2+ and Ni3+ chemical states. The transmission electron microscopy (TEM) images reveal an average size of 5 nm for NiO nanocrystalline particles. The nitrogen dioxide (NO2) gas sensing performance was tested at various working temperatures and gas concentrations. The sensing tests showed 45.6 % response to 100 ppm NO2 at 200 °C with Tresponse = 13 s and Trecovery = 146 s.

Highly porous hierarchical NiO coated ZnO p-n heterostructure for NO2 detection

In the present work, NiO coated ZnO films have been deposited at various deposition times such as 1, 2, 4 and 8 h using chemical bath deposition (CBD) method. X-ray diffraction (XRD) study showed the presence of both hexagonal ZnO and cubic NiO crystal structures. The field emission scanning electron microscopy (FE-SEM) images reveal the porous hierarchical microflower-like morphology. The atomic force microscopy (AFM) micrographs exhibit a maximum surface roughness of 174 nm. Brunauer Emmett-Teller (BET) shows the higher surface area of 31.41 m2/g. X-ray photoelectron spectroscopy (XPS) study showed the presence of Zn-2p3/2 and Zn-2p1/2 for Zn2+ oxidation state in ZnO whereas Ni-2p3/2 and Ni-2p1/2 for Ni2+ oxidation state in NiO. The NiO coated ZnO film shows the response of 76.5 % to 100 ppm NO2 at working temperature of 150 °C with Tresponse = 12 s and Trecovery = 140 s. Finally, NO2 sensing mechanism is proposed.

Aerobic bacteria-supported biohybrid palladium catalysts for efficient cross-coupling reactions

Palladium-based catalysts are of key importance in organic synthesis due to their versatility and tolerance for a wide range of functional groups. However, their use challenged by increasing sustainability issues and complex preparation methods. Consequently, the development of new heterogeneous catalysts with enhanced sustainability is of significant interest. Typically, the synthesis of carbon supports for palladium is associated with high energy consumption or the generation of substantial chemical waste, prompting extensive research into the creation of sustainable biological supports. In this study, the potential use of aerobic bacterial cells as a support for palladium nanoparticles was explored, using Paracoccus yeei VKM B-3302 as a model organism. Electron microscopy, powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of palladium particles on the cell surface as well as inside microorganisms following deposition from a solution. Control experiments established that bacterial cells do not interact with either the reactants or the products of selected cross-coupling processes. Furthermore, bacteria do not affect the analysis of reaction mixtures by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC–MS). At the same time, palladium/Paracoccus yeei demonstrated efficient catalysis of the Mizoroki-Heck and Suzuki-Miyaura reactions, yielding results comparable to commercial palladium on carbon (Pd/C) catalysts. Employing a fresh start procedure and catalyst separation method, the catalyst was successfully recycled and reused across five cycles, maintaining good catalytic activity. In a broader aspect, bacteria-supported biohybrid palladium catalysts can represent a new type of catalysts worth to explore in a number of processes, where sustainability issues are concerned.

Effect of local chemical disordering on magnetic properties in high entropy manganite of variable hole concentration

A series of high entropy manganite perovskites (La0.2Pr0.2Nd0.2Bi0·2Ba0.2)MnO3, (La1/6Pr1/6Gd1/6Bi1/6Sr1/6Ba1/6)MnO3, (La0.2Nd0.2Gd0.2Sr0·2Ba0.2)MnO3 and (La1/6Pr1/6Nd1/6Ca1/6Sr1/6Ba1/6)MnO3 with variable hole concentration at fixed A-site ionic radius (<rA> = 1.253 Å) have prepared by sol-gel technique. Single phase samples were characterized by the powder X-ray diffraction (PXRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX) analysis and elemental mapping which confirm the phase purity of the samples, surface morphology, elemental ratio and chemical homogeneity. X-ray photoelectron spectroscopic (XPS) studies reveal the increase of Mn4+ ions systematically with the substitution of hole concentration at A-site. Magnetization study in this high entropy sample with variable hole concentration at fixed <rA> = 1.253 Å exhibits several contrasting behaviour compare to the conventional hole doped samples. In these high entropy manganites the variation in critical temperature (TC) does not follow expected trend neither with the hole concentration nor to the cationic size disorder parameter, σ2. Though the <rA> is fixed, there is a slight increase in tolerance factor (f) due to hole variation in B-site. Interestingly, TC variation with f shows similar trend to the hole concentration, which is expected to be increased linearly. The effect of f on TC is rather weaker in comparison to σ2. The large drop in TC for high entropy system with respect to the conventional manganite is related to the local structural distortion which severely hampers the Mn3+—O—Mn4+ double exchange interaction. The competing magnetic interactions lead to magnetic phase separation as well as Griffith like phase. Spin pinning is noticed for the samples containing six elements in A-site which is independent on hole concentration. Possible spin clustering is also realized above ferromagnetic TC. Careful analysis of the magnetization data suggests that observed anomaly in magnetic behaviour can be ascribed to the local chemical disordering apart from the size disorder parameter. The possible role on magnetic properties of the number of elements occupying in a crystallographic site is emphasized.

Elucidating the Role of Copper-Induced Mixed Phases on the Electrochemical Performance of Mn-Based Thin-Film Electrodes.

Manganese oxide is a fascinating material for use as a thin-film electrode in supercapacitors. Herein, the consequences of copper incorporation on spray pyrolyzed manganese oxide thin films and their electrochemical performance were investigated. The Cu-incorporated manganese oxide thin films were deposited by spray pyrolysis, and their structural and electrochemical properties were thoroughly evaluated. The formation of the spinel Mn3O4 phase with effective Cu incorporation was confirmed by X-ray diffraction investigation. Through Raman studies, it was noticed that mixed phases of manganese oxide tend to form after Cu incorporation, and this result was also reflected in X-ray photoelectron spectroscopic studies. The surface morphology and roughness were also altered by the addition of copper. However, electrochemical measurements implied a reduction in the specific capacitance upon copper inclusion. The cyclic voltammetry test indicated a specific capacitance of 132 F/g for Mn3O4 electrodes, but a substantial drop for copper-incorporated samples due to the mixed manganese phase. The decremental tendency was further supported by galvanostatic charge-discharge studies and electrochemical impedance spectroscopic measurements. These results provide valuable insights into the effects of copper addition in manganese oxide thin-film-based electrodes for energy storage applications.

Salvia officinalis-Hydroxyapatite Nanocomposites with Antibacterial Properties.

In the present study, sage-coated zinc-doped hydroxyapatite was incorporated into a dextran matrix (7ZnHAp-SD), and its physico-chemical and antimicrobial activities were investigated. A 7ZnHAp-SD nanocomposite suspension was obtained using the co-precipitation method. The stability of the nanocomposite suspension was evaluated using ultrasound measurements. The stability parameter calculated relative to double-distilled water as a reference fluid highlights the very good stability of the 7ZnHAp-SD suspension. X-ray diffraction (XRD) experiments were performed to evaluate the characteristic diffraction peak of the hydroxyapatite phase. Valuable information regarding the morphology and chemical composition of 7ZnHAp-SD was obtained via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) studies. Fourier-transform infrared spectroscopy (FTIR) measurements were performed on the 7ZnHAp-SD suspensions in order to evaluate the functional groups present in the sample. Preliminary studies on the antimicrobial activity of 7ZnHAp-SD suspensions against the standard strains of Staphylococcus aureus 25923 ATCC, Enterococcus faecalis 29212 ATCC, Escherichia coli 25922 ATCC, and Pseudomonas aeruginosa 27853 ATCC were conducted. More than that, preliminary studies on the biocompatibility of 7ZnHAp-SD were conducted using human cervical adenocarcinoma (HeLa) cells, and their results emphasized that the 7ZnHAp-SD sample did not exhibit a toxic effect and did not induce any noticeable changes in the morphological characteristics of HeLa cells. These preliminary results showed that these nanoparticles could be possible candidates for biomedical/antimicrobial applications.

Enhancing Aqueous Chlorate Reduction Using Vanadium Redox Cycles and pH Control.

Chlorate (ClO3-) is a toxic oxyanion pollutant from industrial wastes, agricultural applications, drinking water disinfection, and wastewater treatment. Catalytic reduction of ClO3- using palladium (Pd) nanoparticle catalysts exhibited sluggish kinetics. This work demonstrates an 18-fold activity enhancement by integrating earth-abundant vanadium (V) into the common Pd/C catalyst. X-ray photoelectron spectroscopy and electrochemical studies indicated that VV and VIV precursors are reduced to VIII in the aqueous phase (rather than immobilized on the carbon support) by Pd-activated H2. The VIII/IV redox cycle is the predominant mechanism for the ClO3- reduction. Further reduction of chlorine intermediates to Cl- could proceed via VIII/IV and VIV/V redox cycles or direct reduction by Pd/C. To capture the potentially toxic V metal from the treated solution, we adjusted the pH from 3 to 8 after the reaction, which completely immobilized VIII onto Pd/C for catalyst recycling. The enhanced performance of reductive catalysis using a Group 5 metal adds to the diversity of transition metals (e.g., Cr, Mo, Re, Fe, and Ru in Groups 6-8) for water pollutant treatment via various unique mechanisms.

XPS study of NiO thin films obtained by chemical vapor deposition

Nickel oxide (NiO) thin films are of great importance for a variety of technological applications, especially in (photo)electrocatalysis for clean energy production and pollutant degradation. In this field, various research efforts are devoted to the preparation of thin films with controllable chemicophysical properties. In the framework of our research activities, we have recently fabricated NiO thin films by means of chemical vapor deposition (CVD) using a series of closely related Ni(II) β-diketonate-diamine molecular precursors. In the present work, the attention is focused on the x-ray photoelectron spectroscopy (XPS) analysis of a representative NiO film grown at 400 °C in an O2 + H2O reaction atmosphere. Besides the wide scan spectrum, high resolution spectra for C 1s, O 1s, and, in particular, Ni 2p are reported and discussed in detail.

Electrocatalytic Enhancement of CO Methanation at the Metal–Electrolyte Interface Studied Using In Situ X-ray Photoelectron Spectroscopy

For the direct reduction of CO2 and H2O in solid oxide electrolysis cells (SOECs) with cermet electrodes toward methane, a fundamental understanding of the role of elemental carbon as a key intermediate within the reaction pathway is of eminent interest. The present synchrotron-based in situ near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) study shows that alloying of Ni/yttria-stabilized-zirconia (YSZ) cermet electrodes with Cu can be used to control the electrochemical accumulation of interfacial carbon and to optimize its reactivity toward CO2. In the presence of syngas, sufficiently high cathodic potentials induce excess methane on the studied Ni/yttria-stabilized-zirconia (YSZ)-, NiCu/YSZ- and Pt/gadolinium-doped-ceria (GDC) cermet systems. The hydrogenation of carbon, resulting from CO activation at the triple-phase boundary of Pt/GDC, is most efficient.

Pt nanoparticles supported LaCoO3 as highly efficient catalysts for photo-thermal catalytic CO2 methanation

Photo-thermal catalytic CO2 hydrogenation to value-added products is considered a viable strategy for CO2 conversion, whereas the unsatisfactory selectivity and conversion efficiency hinder its practical applications. Herein, Pt nanoparticles supported on LaCoO3 with different loadings were prepared for photo-thermal catalytic CO2 hydrogenation. Transmission Electron Microscope (TEM) images revealed that the Pt nanoparticles (about 2∼4 nm) were evenly dispersed on the surface of rhomboid-phased LaCoO3 supports. X-ray photoelectron spectroscopy (XPS) studies showed that in the composited catalysts, electron transfer from LaCoO3 to Pt occurred, suggesting a strong interaction between Pt and LaCoO3. In result, 0.6 Pt/LaCoO3 showed a remarkable CH4 production rate of 119.8 mmol gcat−1 h−1 with 87% selectivity at 250°C under visible light irradiation. Additionally, the in situ diffuse reflectance infrared Fourier transformations spectroscopy (DRIFTS) indicated that formate is the main intermediate species in the photo-thermal catalytic CO2 hydrogenation process and illumination could promote the conversion of intermediate species without changing the reaction pathway, thus increasing the yield of CH4. Given that the catalyst preparation approaches could be easily scaled up and the conversion efficiency of CO2 is satisfactory, it is confident that this research will offer valuable guidance for the future industrialization of CO2 conversion.

Understanding the Buoy Effect of Surface-Enriched Pt Complexes in Ionic Liquids: A combined ARXPS and Pendant Drop Study.

Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C4C1Im][PF6] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our angle-resolved X-ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5%mol down to 1%mol and present complementary surface tension pendant drop (PD) measurements under ultra clean vacuum conditions. This combination allows for connec-ting the microscopic information on the IL/gas interface from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1%mol. It also displays a strong temperature dependence, which was not observed for 5%mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy-complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of ionic catalyst solutions contact areas with a surrounding reactant/product phase, such as in SILP catalysis.

Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption

Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 °C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH.

Novel NASICON-Type Na-V-Mn-Ni-Containing Cathodes for High-Rate and Long-Life SIBs.

Partial substitution of V by other transition metals in Na3 V2 (PO4 )3 (NVP) can improve the electrochemical performance of NVP as a cathode for sodium-ion batteries (SIBs). Herein, phosphate Na-V-Mn-Ni-containing composites based on NASICON (Natrium Super Ionic Conductor)-type structure have been fabricated by sol-gel method. The synchrotron-based X-ray study, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) studies show that manganese/nickel combinations successfully substitute the vanadium in its site within certain limits. Among the received samples, composite based on Na3.83 V1.17 Mn0.58 Ni0.25 (PO4 )3 (VMN-0.5, 108.1 mAh g-1 at 0.2 C) shows the highest electrochemical ability. The cyclic voltammetry, galvanostatic intermittent titration technique, in situ XRD, ex situ XPS, and bond valence site energy calculations exhibit the kinetic properties and the sodium storage mechanism of VMN-0.5. Moreover, VMN-0.5 electrode also exhibits excellent electrochemical performance in quasi-solid-state sodium metal batteries with PVDF-HFP quasi-solid electrolyte membranes. The presented work analyzes the advantages of VMN-0.5 and the nature of the substituted metal in relation to the electrochemical properties of the NASICON-type structure, which will facilitate further commercialization of SIBs.

Influence of K+ substitution on germanium doped strontium silicate (Sr3-3xK3xSi3-3yGe3yO9-δ; 0 ≤ x ≤ 0.20, y=0.1) for application as solid electrolyte

The different alkali metal substitution strategies of the strontium meta-silicate based ion conductors have been enormously cross-examined to synthesize cost-effective novel electrolyte for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). In the present investigation, crystal structure, phase formation, microstructure, total conductivity and stability of the Potassium and Germanium incorporated Sr3Si3O9 based system, Sr3-3xK3xSi3-3yGe3yO9-δ (0 ≤ x ≤ 0.20, y = 0.1), is examined for their application as solid electrolyte for electrochemical devices such as ITSOFCs. These samples have been made via solid state reaction route. X-ray Rietveld refinement method was used for the structural investigation. Raman and FT-IR spectroscopy were performed to examine the phase formation and absorption of light by the bonds of vibrating molecules to provide molecular characteristics and vibrational modes of the molecules. The X-ray Photoelectron Spectroscopy study was used to validate the characteristic valence states of the constituting elements. Thermo-gravimetric analysis was performed to inspect the thermal stability and weight changes in the compounds during heating process. In the SEM and EDS mapping, an amorphous phase of K2Si2O5 can be visualized which seems to segregate along grain boundaries and this amorphous complexion augmented with K+ dopant concentration. AC Electrical impedance spectroscopy studies suggest that the ionic conduction in Sr3-3xK3xSi3-3yGe3yO9-δ could be from the oxide ions along with mobility of K+ ions of the glassy phase. In this study, we also tried to get the optimal doping condition with compositions to minimize numerous concern of the system.

Enhanced Chalcopyrite-Galena separation through Galena-Assisted ferric ion reduction in Fenton reaction

Developing an efficient and eco-friendly approach for the separation of chalcopyrite and galena is crucial for maximizing the resource utilization. This study explores the use of galena-assisted Fenton reaction as a method for depressing galena flotation. Various analytical techniques, including micro-flotation tests, contact angle (CA) measurements, Fourier Transform Infrared Spectroscopy (FT-IR) analysis, Scanning Electron Microscope (SEM) observation, X-ray Photoelectron Spectroscopy (XPS) studies, Raman Spectra determinations, electrochemical analysis, and UV–visible spectrophotometer (UV–vis) surveying, were employed to investigate the effectiveness of this approach. The results of the flotation tests reveal that the cooperation of ferric ions and hydrogen peroxide can strongly and selectively depress galena. The CA and FT-IR analyses demonstrate the significant decrease of hydrophobicity and collector adsorption of the galena surface by the synergistic effect of ferric ions and hydrogen peroxide. Further analysis using SEM, XPS, Raman spectra and electrochemical analysis show that galena can reduce ferric ions to ferrous ions, creating a Fenton reaction system upon the addition of hydrogen peroxide. The galena surface is intensely oxidized by the generated hydroxyl radicals, leading to the production of a compact layer of PbSO4. These findings provide a promising solution for the efficient and environmentally responsible separation of chalcopyrite and galena.

A novel K-ion KVPO4F0.5O0.5/graphite full cell: Correlation between XPS SEI studies and electrochemical testing results

Like li- and Na-ion batteries, electrolyte reactivity (i.e., salt and solvent decomposition) is important in the electrochemical performance of K-ion batteries (KIBs). Indeed, X-ray photoelectron spectroscopy (XPS) analysis of a solid electrolyte interphase (SEI) in KIBs is still based on K-ion half-cells. This may lead to incorrect interpretations of the results considering the contamination of the studied electrode SEI due to the high K metal reactivity. Therefore, this study aims to provide a reliable XPS study without potassium metal, investigating the impact of various parameters, including open-circuit voltage (OCV) temperature, upper cut-off voltage (UCV), depth of discharge (DOD), and vanadium dissolution, on the electrochemical performance of KVPO4F0.5O0.5/graphite full cells. This work highlights the importance of SEI preformation, which is more pronounced at higher OCV temperatures. At specific UCV and DOD, the cell provides the best trade-off between the organic and inorganic passivation layer, leading to good electrochemical performance. The study also demonstrates that vanadium dissolution is a potential mechanism affecting capacity fading in K-ion batteries. Finally, understanding these SEI growth mechanisms should help researchers get reliable XPS analysis of the SEI in KIBs and move forward with the practical passivation layer characterizations.

X-ray photoelectron spectroscopy and tunable photoluminescence study of gold nanoparticles embedded in PVA films.

This article reports the systematic photoluminescence study of the various contents of gold nanocomposites in polyvinyl alcohol (PVA) films. The variations in the gold content in PVA film were 0.2, 0.5, 1.0, and 1.5wt%. All the samples were excited at two selected wavelengths; those are at 400 nm and 532 nm. On exciting the gold-PVA nanocomposite films at 400 nm the photoluminescence was observed in the region of 430-500 nm in comparison to pure PVA films that show an emission at 400 nm. However, on exciting the gold-PVA nanocomposites at 532 nm, the emission was observed at 560-650 nm with a long tail till 700 nm that is unlike the pure PVA films that do not show any emission peak in this region. This suggests that emission between 430 and 500 nm regions is due to the coordination of PVA with gold nanoparticles because PVA has an emission at 400 nm. However, the emission peak between 560 and 650 nm is entirely due to the gold nanocomposite particle. The peak also shows a smaller red-shift that is usually with the increasing nanoparticles size with the increasing content in the PVA films. The formation of gold nanoparticles was justified by X-ray diffraction (XRD) analysis which is further supported by X-ray photoelectron spectroscopy (XPS) analysis.

Rapid elimination of thiamethoxam insecticide under visible light using novel Au nanoparticles/CdSe/WO3 ternary nanocomposite

In this study, we have created a unique ternary photocatalyst using WO3 nanostructures in conjunction with CdSe and gold nanoparticles (Au NPs), which exhibits remarkable efficacy in purifying contaminated water under visible light. The Au, CdSe, and WO3 assembled ternary photocatalyst was synthesized through ultrasonication followed by a photoreduction process. The X-ray diffraction (XRD) analysis confirmed the presence of monoclinic WO3, hexagonal CdSe, and Au NPs in the ternary photocatalyst. Structural analysis and elemental composition were further substantiated through X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) studies. Transmission electron microscopy (TEM) examinations revealed irregularly shaped Au NPs (5–15 nm), CdSe, and WO3 particles. Diffuse reflectance studies demonstrated a reduction in the band gap energy of the Au@CdSe/WO3 nanostructures. The Au@CdSe/WO3 ternary photocatalyst exhibited remarkable efficiency in the photocatalytic degradation of thiamethoxam (TXM) insecticide and methylene blue (MB) dye under visible light. It achieved an impressive 94.13 % removal efficiency for TXM in just 40 min, which was ∼2.04 more efficient than undoped WO3. Additionally, the Au@CdSe/WO3 nanostructures successfully decolorized MB dye under visible light within 14 min. This exceptional photocatalytic performance can be attributed to the increased surface area, enhanced light absorption capacity, and improved photo-induced carrier transfer with efficient separation behavior, as evidenced by photoluminescence and photocurrent transient analyses.