UV Vis Diffuse Reflectance Spectra Research Articles

Innovative synthesis and practical application of graphitic carbon nitride/α-zirconium phosphate in visible light-activated Knoevenagel condensation

To advance the development of efficient photocatalysts activated by visible light for environmental applications. We employed a simple approach to synthesize g-C3N4/α-ZrP composite in different mass ratios, followed by comprehensive characterization through several techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM/EDS), and UV–Visible diffuse reflectance spectra (DRS). Furthermore, the g-C3N4/α-ZrP with mass ratio 6:1 was demonstrated high performance catalytic activity in Knoevenagel condensation (Yield 88 %–96 %) in a short reaction time (5–20 min) under visible light irradiation. The use of g-C3N4/α-ZrP has transformed the traditional synthesis of carbon–carbon double bonds, offering improved reaction rates and reduced by-products. These next-generation photocatalysts also exhibit remarkable properties that facilitate the activation of substrates under milder conditions, opening up new possibilities for green and sustainable synthesis. This advancement contributes to the development of environmentally friendly and efficient synthetic methodologies.

Enhanced removal of phenolic pollutants over MnO2 initiated by peracetic acid: In situ generation of a heterogeneous Mn(III)-hydroperoxo complex

Widely distributed manganese oxides are among the strongest oxidants in nature and effectively enhance the water decontamination by peracetic acid (PAA) activation. However, the precise mechanism requires further investigation. In this work, the intrinsic mechanism of PAA activation by MnO2 was systematically studied. Through in situ diffuse-reflectance UV–vis spectra and resonance Raman spectra, the active species was identified as a non-radical heterogenous Mn(III)-hydroperoxo complex. During the process, PAA drastically converted Mn(IV) in MnO2 into homogeneous Mn(II), which subsequently generated the active Mn(III) species in the aid of PAA on the surface of MnO2. By interacting with pollutants, the peroxide bond in Mn(III)-hydroperoxo broke, accompanied by the regeneration of Mn(IV). Eight phenolic compounds having para-substituent of –CH3, −H, −Cl, –COCH3, –CHO, –COOH, –COOCH3, and –NO2 were selected for degradation. Due to the electrophilic character of Mn(III)-hydroperoxo, the removal rates were 100 %, 100 %, 98.8 %, 69.8 %, 49.6 %, 30.2 %, 28.1 %, and 3.0 % respectively at the 45 min of experiment. The MnO2/PAA system was also readily coupled with a filtration membrane for continuous treatment of phenol in nearly 100 % removal efficiency. This study not only offered an efficient non-radical PAA activation protocol for water decontamination, but also elucidated the catalytic mechanism and redox cycle of MnO2 in PAA solution in the selective oxidation process.

“Investigating impact of Ni-Cd substitution on structural magnetic and optical properties of nanosize Al ferrites”

Ferrites are among the most extensively studied materials, specifically due to their amazing and diverse characteristics. Therefore, we synthesized NixCd1-xAlyFe2-yO4 (NCAF) ferrites using a microwave auto-combustion process, with x varying from 0.0 to 1.0 and y set at 0.1. We conducted a meticulous characterization of their structural, surface morphological, magnetic, molecular vibrational and optical properties. X-ray diffraction confirms the lattice parameter and a single-phase spinel structure. Rietveld refined XRD patterns identified the Fd-3m space group cubic spinel phase. HR-TEM examination shows pseudo-spherical particles with an average size of 40–45 nm. Surface topography exhibits tiny, spherical microstructures. The lognormal histogram showed an average particle size of 56.6 nm–124.8 nm, decreasing with nickel concentration. At a nickel concentration (x) of 0.6, saturation magnetization (Ms) increases and then decreases at 1.0. FTIR confirms no organic phase and spinel development. Absorption measurements determined the band gap energy, which Tauc plot revealed to be 2.5870–2.1657 eV. We used the Kubelka-Munk function to find the band gap energy in the UV–Vis diffuse reflectance spectra (DRS), which was between 2.0027 and 1.6817 eV.

Vibrational, optical, electronic and electrocatalytic properties of SrCuSi4O10 ceramic

This research reports the synthesis of powdered SrCuSi4O10 ceramic powder, obtained through a solid-state chemical reaction methodology. The sample was characterized using X-ray powder diffraction (XRPD), Raman and Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), reflectance (R), electron paramagnetic resonance spectrum (EPR), lattice dynamic calculations, electronic and electrocatalytic properties analyses. The X-ray analysis showed that crystalline structure of SrCuSi4O10 compound belongs to a tetragonal system with the P4/ncc space group, containing four formulas per unit cell (Z = 4). The SEM micrographs present a morphology of layered microplates with some irregularity in size and shapes. UV–vis diffuse reflectance spectra show three intense reflection regions. Regarding the vibrational properties, the theoretical calculation was performed using a rigid ion model in order to assign the experimental Raman and IR modes. Additionally, electronic properties calculations were carried out using Density Functional Theory (DFT). Finally, the hydrogen evolution reaction (HER) performance of the SrCuSi4O10 electrocatalyst was evaluated.

Photodegradation of Polyethersulfone (PES), Polyvinylidene Fluoride (PVDF) and Polymethyl Methacrylate (PMMA) Microplastics via a Metal Organic Framework Namely ZIF-8/ZnO/C

The aim of this study was to photodegrade the Polyethersulfone (PES), Polyvinylidene fluoride (PVDF) and Polymethyl methacrylate (PMMA) microplastics using Zeolitic imidazolate framework-8/Zinc oxide/Carbon (ZIF-8/ZnO/C) nanocomposite generated under laboratory conditions. The produced nanocomposite was analysed using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photo Spectroscopy (XPS), Scanning Electron Microscope (SEM), Diffuse reflectance UV-vis spectra (DRS) and Electron Spin Resonance (ESR) analyses. The maximum PES, PVDF and PPMA photodegradation yields were 99%, 98%, and 96%, respectively, at 1 mg/l ZIF-8/ZnO/C nanocomposites (NCs) concentration, 1000 mg/l microplastics concentration, at pH = 10.0, at a temperature and photodegradation time of 40°C and 20 min, under oxic conditions at a sunlight intensity of 80 W/m<sup>2</sup> and a photon yield of 16. The XRD analysis showed the generation of ZIF-8/ZnO/C, while the FTIR analysis indicated the ZnO, C, and ZIF-8.

Synergistic photocatalytic degradation of TC-HCl by MIL-53(Fe)/CoWO4 composite and PMS under visible light

A series of novel MIL-53(Fe)/CoWO4 composites were synthesized by combining MIL-53(Fe) and CoWO4 nanoparticles via solvothermal method. The structural characterizations showed that CoWO4 nanoparticles were uniformly distributed on the surface of hexagonal bipyramid MIL-53(Fe). Combining XPS and Mott-Schottky plots, a Z-scheme heterojunction was formed between MIL-53(Fe) and CoWO4, resulting in a significant improvement in the electron-hole pair separation efficiency. UV–vis diffused reflectance spectra indicated that the optical arrange of MIL-53(Fe)/CoWO4 composites were expanded to visible light. The photocatalytic degradation experiments under visible light irradiation showed that MIL/CWO-60 synergistically with PMS degraded 90.5 % of TC-HCl within 50 min. The XRD spectra of used and unused composites were identical, indicating good stability in four consecutive cycles. Electron paramagnetic resonance (EPR) and free radicals trapping experiment revealed that active species included O2−, SO4−, h+, OH and 1O2, and mechanism of the synergistic degradation of TC-HCl by MIL-53(Fe)/CoWO4 composites and PMS was proposed.

Compositing of rGO to TiO2 by Low-Temperature Treatment and Their Photocatalytic Properties

Reduced graphene oxide (rGO)/TiO2 nanocomposites were prepared by low-temperature and low-pressure heat treatment. The structure and photocatalysis performance of the composites were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and UV-visible diffuse reflectance spectrum (UV-Vis DRS). The photocatalytic degradation performance of methyl orange (MO) by composites with different raw material ratios was studied under simulated solar-irradiation conditions. Results indicated that graphene oxide (GO) was reduced to graphene during heat treatment and bonded well with TiO2. Compared with TiO2, GO addition greatly improved its photocatalytic efficiency. Under simulated sunlight irradiation, the samples exhibited good photocatalysis performance. Within 50[Formula: see text]min, MO can be rapidly degraded by TiO2/40% rGO composite.

Ag QDs modified BiOCl/UiO-66-NH2 Z-scheme heterojunction for accelerated visible light-driven photocatalytic degradation of ciprofloxacin

Ag quantum dots (QDs) anchored on the surface of BiOCl/UiO-66-NH2 Z-scheme heterojunctions were synthesized and characterized by various techniques such as X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), electrochemical impedance spectroscopy (EIS), and photoluminescence (PL). The effects of Ag QDs loading, pH values and co-existing anions on the photocatalytic performance were comprehensively analyzed. The results concluded that the Ag QDs modified catalysts exhibited excellent photocatalytic performance for the degradation of ciprofloxacin (CIP), especially, the catalyst with 5 % Ag QDs loading (referred to as ABU-5) achieved a degradation efficiency of 72 % within 120 min and the apparent reaction rate constant was 0.00538 min−1. The outstanding performance of the ABU-5 catalyst is attributed to the introduction of Ag QDs as electron transfer bridges, improving visible light absorption and enhancing charge transfer between BiOCl and UiO-66-NH2. Free radical trapping experiments and leaching tests were carried out to determine the contribution rates of reactive species to the degradation efficiency and the concentration of Ag+ in solution after the reaction. The possible degradation pathways of CIP by ABU-5 were investigated by gas chromatography-mass spectrometry (GC-MS).

Down-conversion luminescence and thermometric properties of novel orange-red Bi2Mo3O12:Pr3+ phosphors

Bi2Mo3O12: Pr3+ phosphors have been successfully synthesized through a one-step solid-state reaction method. The effects of Pr3+ concentration on lattice constants and optical properties were also studied. XRD patterns showed well-crystallized monoclinic structures for the prepared Bi2Mo3O12 and Bi2Mo3O12: Pr3+ samples. The UV-visible diffuse reflectance spectra indicated strong absorption in the ultraviolet region. Excitation spectra demonstrated that the Bi2Mo3O12: Pr3+ could be efficiently excited under UV light in the 250-430 nm range and blue light at 450 nm. By varying the excitation wavelength, the emission color could be tuned from orange-red to red region. The strongest emission peak is located at around 597 nm, which is attributed to the 1D2→3H4 transition of Pr3+. An optical thermometer based on fluorescence intensity ratio (FIR) shows a high sensitivity of Sr=2.02% K-1, indicating the developed materials have potential applications in the optical temperature sensing field.

Extended Interfacial Charge Transference in CoFe2O4/WO3 Nanocomposites for the Photocatalytic Degradation of Tetracycline Antibiotics.

The large-scale utilization of antibiotics has opened a separate chapter of pollution with the generation of reactive drug-resistant bacteria. To deal with this, in this work, different mass ratios of CoFe2O4/WO3 nanocomposites were prepared following an in situ growth method using the precursors of WO3 and CoFe2O4. The structure, morphology, and optical properties of the nanocomposite photocatalysts were scrutinized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectra (UV-Vis DRS), photoluminescence spectrum (PL), etc. The experimental data signified that the loading of CoFe2O4 obviously changed the optical properties of WO3. The photocatalytic performance of CoFe2O4/WO3 composites was investigated by considering tetracycline as a potential pollutant. The outcome of the analyzed data exposed that the CoFe2O4/WO3 composite with a mass ratio of 5% had the best degradation performance for tetracycline eradication under the solar light, and a degradation efficiency of 77% was achieved in 20 min. The monitored degradation efficiency of the optimized photocatalyst was 45% higher compared with the degradation efficiency of 32% for pure WO3. Capturing experiments and tests revealed that hydroxyl radical (·OH) and hole (h+) were the primary eradicators of the target pollutant. This study demonstrates that a proper mass of CoFe2O4 can significantly push WO3 for enhanced eradication of waterborne pollutants.

Synthesis of corn straw based carbon doped Nb2O5 as photocatalysts for Rhodamine B degradation under visible light illumination

Developing efficient visible light photocatalytic materials has always been a challenge for researchers. We have successfully prepared a series of corn straw based carbon doped Nb2O5 with excellent photocatalytic performance under visible light. A series of characterizations were carried out on the synthesized materials, including power X-Ray diffraction (XRD), scan electron microscopy (SEM), nitrogen adsorption, UV–vis diffuse reflectance spectra, X-ray photoelectron spectroscopy (XPS). The photocatalytic performance of the synthesized samples was investigated under visible light irradiation using Rhodamine B as the degradation target. Under visible light irradiation for 30 min, C/Nb2O5 can decompose Rhodamine B by 97.1 %, and the photocatalytic performance remains unchanged after 5 cycles. In the article, the contributions of three active substances involved in the photodegradation of Rhodamine B were studied through scavenger study, and the mechanism of C/Nb2O5 photodegradation of Rhodamine B was analyzed. This research is of great significance for the application of biomass materials and the improvement of environmental quality, and also provides new ideas for designing and synthesizing new composite functional materials.

Enhancement Study of the Photoactivity of TiO2 Photocatalysts during the Increase of the WO3 Ratio in the Presence of Ag Metal

Nanocomposites (NCs) consisting of 4%Ag/x%WO3/TiO2, with varied concentrations (x = 1, 3, 5, 7 wt.%) of WO3, were successfully synthesized using the sol-gel process to examine their photocatalytic performance. The synthesized 4%Ag/x%WO3/TiO2 nanopowder was characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL), and Brunauer–Emmett–Teller (BET) surface area analysis to elucidate its physicochemical properties. The photocatalytic evaluation revealed that the Ag/1%WO3/TiO2 nanocomposite exhibits 98% photoreduction efficiency for Cr(VI) after 2 h under visible light due to the impact of the plasmonic effect of Ag atoms. In addition, the Ag/4%WO3/TiO2 shows about 95% photooxidation efficiency for methylene blue (MB) dye after 4 h.

Construction of Pillared-Layer Metal-Organic Frameworks as an All-Visible-Light Switchable Photocatalyst for Aqueous Cr(VI) Reduction.

Recently, two-dimensional metal-organic frameworks that are photoactive have shown great potential for efficiently converting solar energy into chemical energy. In this work, we successfully synthesized and designed two M2-MOFs ([Cu(L1)((CH3)2NH)]n (Cu-MOF) and [Zn(L1)(CH3)2NH)]n (Zn-MOF), H2L1 = 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid). Structural analysis suggests that the five-coordinated M(II) ion is surrounded by four oxygen ions from two ligands and one nitrogen atom from one dimethylamine molecule. The ligand spacer acts as a bridge between two SBUs and forms a 2D layer with rhomboid windows. These moieties are arranged in a staggered ABAB pattern, which likely aids in exfoliation. The UV-vis diffuse reflectance spectra (DRS) test shows that when the metal center in the MOF framework is replaced with Cu(II) ions, the light absorption range covers 200-1100 nm, which is much larger than the light absorption range of Zn-MOF. Moreover, the photoelectric current, electrochemical impedance spectra (EIS), and Mott-Schottky tests all indicate that Cu-MOF has better photoelectric properties. When applied to the photocatalytic reduction of Cr(VI), Cu-MOF and Zn-MOF can completely reduce Cr(VI) within 100 min under 450 nm LED light irradiation. Under sunlight irradiation, Cu-MOF can completely reduce Cr(VI) within 40 min, achieving the removal of Cr(VI) ions, which is much faster than the rate of Cr(VI) removal by Zn-MOF.

Heptanuclear Cadmium Borovanadate Containing a Sandwich-Type Anionic Partial Structure {B20V12} as a Heterogeneous Photocatalyst for the Reduction of CO2 into CH4.

The novel heptanuclear cadmium borovanadate [Cd(en)3]{[Cd(H2O)(en)]6[B20V12O60(OH)2]}·8H2O (en = ethylenediamine) has been prepared under hydrothermal condition. It exhibits a 2D layered architecture that is built up from the [Cd(H2O)(en)]2+ coordination cations and new sandwich-type borovanadate anions [B20V12O60(OH)2]14- constructed by BO3, BO4, BO3(OH), and VO5 units. It features the first heptanuclear cadmium borovanadate containing the single valence of V4+ cations and unique B/V ratio (B/V = 20/12). Its thermal, magnetic, XPS, and optical properties have been systematically studied. The Eg (2.60 eV), EVB (1.69 eV), and ECB (-0.91 eV) were well determined by the UV-vis diffuse reflectance spectrum, UPS curve, and the formula ECB = EVB - Eg, respectively. The photocatalytic experiments revealed that the borovanadate could be selected as an effective and stable heterogeneous catalyst for the reduction of CO2 to CH4 by means of visible light (the amount for CH4 gas could reach 50.57 μmol·g-1·h-1 when the reaction time was 3 h). The recycling experiment and photocatalytic mechanism were also well investigated and established in detail.

Tuning oxygen vacancies via photoinduced defect engineering in plasma pre-treated TiO2 for efficient solar-light-driven oxidation of trace methane

Photocatalysis employing cost-effective commercial titanium dioxide offers an ideal solution for eliminating trace methane emissions from livestock and poultry farming. However, significant challenges such as the rapid recombination of photogenerated carriers, a limited light absorption spectrum, and weak adsorption capabilities considerably hinder the effectiveness of titanium dioxide in the photocatalytic treatment of trace methane. This study proposes a novel approach to activate plasma pre-treated N-doped commercial anatase TiO2 into dual-defect TiO2 (N-doped TiO2-x) featuring stable and controllable oxygen vacancies (OV) through photoinduced defect engineering. Characterizations of the photocatalyst confirm the successful creation of surface defects, further evaluated through solar-light-driven CH4 (ppm level) removal investigations. The yield of this N-doped TiO2-x in converting CH4 is 4.84 μmol h−1, 44 times greater than that of unmodified TiO2, significantly outperforming previous studies. UV–Vis diffuse reflection spectra, and photoluminescence indicate that the modified commercial anatase TiO2 possesses a narrower band gap, efficient photogenerated carrier separation, and enhanced charge transfer. Furthermore, density functional theory (DFT) calculations demonstrate that the synergistic effects of oxygen vacancies and N doping enhance the adsorption and activation of both O2 and CH4 in the rate-determining step of the reaction. This innovative strategy holds considerable promise for modifying various materials for more efficient photocatalytic applications.

Synthesis, characterization, wastewater treatment & plant growth application of ZnFe2O4/Bi2O3 nanocomposite

Vital for the prospective and sustainable environment, Bi2O3, ZnFe2O4 and ZnFe2O4/Bi2O3 (BZF) nanocomposite was synthesized in the present study by utilizing conventional combustion technique by green approach fueling with Aloe vera extract. The crystallite size calculated using Debye-Scherrer formula from X-Ray Diffraction (XRD) spectrum of BZF nanocomposite is ∼27 nm validated by XRD spectrum. Band gap of the nanocomposite is estimated using UV-Vis Diffuse Reflectance Spectra (DRS) analysis and was found to be 2.73 eV. The findings of the investigations have been validated by applications in photocatalytic degradation of acid green dye. The usage of Bi2O3, ZnFe2O4 and BZF nanocomposite as a catalyst for the degradation of acid green (AG) dye being subjected to visible light at ambient temperature results in improved photocatalytic response for Bi2O3, ZnFe2O4 and BZF nanocomposite was 88 %, 93 % and 97 % for 120 min respectively. Notably, the environmental impact of the entire technique has been examined in terms of the development of green gram plants displaying effective plant growth using the treated dye wastewater.

Photocatalytic activity of TiO2-Carbon nanocomposite films against Culex pipiens mosquito larvae under sunlight irradiation

Recent research has focused on developing eco-friendly nanomaterials to combat mosquito infestations. This study demonstrates the enhancement of titanium dioxide (TiO2) nanoparticles through the addition of carbon nanoparticles (C-NPs), significantly boosting their photocatalytic efficiency. This enhancement allows TiO2 to purify water and act as an effective pesticide. Formulated TiO2-carbon (TiO2–C) nanocomposite films showed increased photocatalytic activity against third-instar larvae of Culex pipiens under natural sunlight. The addition of C-NPs improved sunlight absorption and reduced electron-hole recombination rates compared to pristine TiO2 (P–TiO2), making it more effective for mosquito control. The superior performance of the TiO2–C nanocomposite was confirmed through X-ray Photoelectron Spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), and Photoluminescence emission (PL). These analyses confirmed successful carbon incorporation, expanding the absorption spectrum and enhancing optical properties. The UV–vis DRS spectra showed a decrease in the bandgap energy (Eg) of P–TiO2 from 3.2 eV to 3.1 eV, improving its photocatalytic effectiveness under natural sunlight. Bioactivity tests, including catalase activity, reduced glutathione (GSH) colorimetric assay, and superoxide dismutase (SOD) assay, along with microscopic and histological examinations of treated larvae, indicated that the TiO2–C nanocomposite effectively reduces the mosquito population and causes significant physiological damage and abnormalities in larval structures and midgut cells. These findings highlight the enhanced photocatalytic capabilities of the TiO2–C nanocomposite, making it a novel and effective solution for mosquito control with significant public health and environmental benefits.

N-doped nano-casted carbon monolith for Pb (II) removal and photocatalytic degradation of thiamethoxam from aqueous solution.

Single rock-like N-doped carbon monolith (ND-PFCM) was successfully constructed via nanocasting method. Phenol formaldehyde resin was taken as carbon source and nitrogen was incorporated in monoliths through NaNH2 activation. The synthesized monoliths were used for the removal of Pb (II) from aqueous solution. Various characterization techniques, namely Brunauer-Emmett-Teller (BET), Raman spectroscopy, UV-visible diffuse reflectance spectra (DRS) UV-DRS, zeta potential, scanning electron microscopy (SEM), TEM (transmission electron microscopy), TGA (thermogravimetric analysis), and XPS (X-ray photoelectron spectroscopy), were utilized to characterize synthesized monolithic samples. The different parameters such as pH, adsorbent dosage, and time were enquired on the removal efficiency of monoliths toward Pb(II). ND-PFCM exhibited the highest adsorption capacity of 330.03mgg-1 in 180min at pH 6. This is attributed to the fact that the better texture properties and presence of nitrogen functional groups enhance the uptake of Pb (II) ions on the monolith surface. In the kinetic studies, pseudo-second-order model fitted best with the experimental data. Furthermore, the removal of thiamethoxam (TM) from aqueous solution was done by using different weight ratios of ND-PFCM under the visible light. The maximum removal efficiency of 97.35% with rate constant of 0.02085min-1was obtained in 160min. Moreover, monoliths exhibited good reusability for five consecutive cycles. The findings suggest that the synthesized monoliths exhibit characteristics suitable and eco-friendly for sustainable use in water treatment applications.

Anodized commercial galvanized grids decorated with Ag nanospheres and Cu worm-like nanorods for photoelectrochemical water splitting

The current work introduces novel and low-cost AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes for the photoelectrochemical (PEC) water-splitting reaction. The photoanodes were fabricated by anodizing commercial galvanized grids(A@CGGs) in the sodium carbonate solution followed by deposition of Ag or Cu through a simple electroless substitution. Surface studies showed that AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes have a unique morphology including Ag nanospheres (AgNSs) and Cu worm-like nanorods (CuNRs) with huge surface area. The UV-VIS diffuse reflectance spectra (DRS) of AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes displayed the lower band gap energies of 2.4 eV, and 2.83 eV respectively, which compared to 3.91 eV for the A@CGGs, showing excellent photoanodic behavior for AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes. Investigations of photoelectrochemical water-splitting under visible light irradiation showed that the production amount of H2 from AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes was about 18570 and 6895 μmol h−1 cm−2 respectively. Moreover, AgNSs-A@CGGs showed 15.27 and 5.0 times higher photoconversion efficiency than CGGs and A@CGGs respectively. In this study, the introduced photoanode grids are expected to be used as cheap and industrial photoanodes for PEC water-splitting and hydrogen gas production.

Polarized Raman, infrared and dielectric spectra of lead-free K0.5Na0.5NbO3 piezoelectric system: insights from ab-initio theoretical and experimental studies

The K0.5Na0.5NbO3 (KNN) system has emerged as one of the most promising lead-free piezoelectric over the years. In this work, we perform a comprehensive investigation of electronic structure, lattice dynamics and dielectric properties of room temperature phase of KNN by combining ab-initio DFT based theoretical analysis and experimental characterization. We assign the symmetry labels to KNN vibrational modes and obtain ab-initio polarized Raman spectra, Infrared reflectivity, Born-effective charge tensors, oscillator strengths etc. The KNN ceramic samples are prepared using conventional solid-state method and Raman and UV–Vis diffuse reflectance spectra are obtained. The computed Raman spectrum is found to agree well with the experimental spectrum. In particular, the results suggest that the mode in range ∼840–870 cm−1 reported in the experimental studies is longitudinal optical with A1 symmetry. The Raman mode intensities are calculated for different light polarization set-ups that suggests the observation of different symmetry modes in different polarization set-ups. The electronic structure of KNN is investigated and optical absorption spectrum is obtained. Further, the performances of DFT semi-local, meta-GGA and hybrid exchange-correlations functionals, in the estimation of KNN band gaps are investigated. The KNN bandgap computed using GGA-1/2 and HSE06 hybrid functional schemes are found to be in excellent agreement with the experimental value. The COHP, electron localization function and Bader charge analysis is also performed to deduce the nature of chemical bonding in the KNN. Overall, our study provides several bench-mark important results on KNN that have not been reported so far.