Diffuse Reflectance Spectroscopy Studies Research Articles

Beta-cyclodextrin supported Bi2Fe4O9-based n-p/n hetero-homojunction: A leach proof S-scheme photocatalyst for mitigation of micropollutants

The work proffers a novel Bi2Fe4O9 based n-p/n hetero-homojunction that offers excellent photocatalytic activity towards mitigation of three potential pharmaceutical and agrochemical pollutants. Nanoparticles of Prunus Amygdalus Dulcis shell derived carboxyl functionalized reduced graphene oxide (rGO) were encrusted over the surface of hydrothermally fabricated Bi2Fe4O9 nanoplates. Further, hydroxyl functionalization of fabricated composites was performed using beta-cyclodextrin (β-CD) and the fabricated materials were utilized for oxidative degradation of doxorubicin, levofloxacin drugs and malathion pesticide. The proffered modification not only enhanced the catalytic activity but also protected the surface of Bi2Fe4O9, which resulted 89.06 % and 86.84 % suppression in leaching of Fe and Bi ions as that of pristine bismuth ferrite (BF) was achieved with this beneficial modification. Practical viability of fabricated hetero-homojunction was testified via treating real pharmaceutical wastewater at lower concentration. Mott-Schottky (MS), Diffuse reflectance spectroscopy (DRS) and Kelvin Probe Force Microscopy (KPFM) studies were employed to investigate the band structure and charge transfer mechanism of fabricated n-p/n hetero-homojunction.

Facile Biogenic synthesis of Europium doped lanthanum silicate nanoparticles as novel supercapacitor electrodes for efficient energy storage applications

In this work, we demonstrated for the first time, use of Europium doped lanthanum silicate nanoparticles (LS NPs) as electrodes for supercapacitor applications. Europium (Eu3+) doped (5 mol%) LS NPs were synthesized by green solution combustion method using Mexican mint leaf extracts. Various analytical techniques such as High-Resolution Transmission Electron Microscopy (HRTEM), Selected Area Diffraction (SAED), Powder X-ray Diffraction (PXRD), Fourier Transform Infra-Red Spectroscopy (FTIR) and Diffuse Reflectance Spectroscopy (DRS) techniques were used to confirm the morphological and structural characteristics of the synthesized nanoparticles. The HRTEM and SAED patterns confirms the formation of NPs having agglomerated structure with a particle size less than 50 nm. The PXRD patterns reveals crystalline cubic structure for the NPs. Further, the FT-IR spectra reveal the successful doping of Europium in Lanthanum Silicate NPs. The DRS (Diffuse Reflectance Spectroscopy) studies confirm the reduced band gap for Europium (Eu3+) doped (5 mol%) LS NPs. Cyclic voltametric and electrochemical impedance spectroscopy experiments were performed in an alkaline medium to compare the electrochemical activity of Eu3+ doped LS NPs with that of their undoped counterpart. The Eu3+ doped (5 %) LS NPs electrodes attained a specific capacitance of 373.3 Fg-1 at a current density of 0.5 Ag-1 in comparison to pure LS NPs which is about 267 Fg-1. The long-term stability of the Eu3+ doped (5 %) LS NPs electrodes show excellent stability up to 4000 cycles of operation in comparison pure LS NPs electrodes. Doping of Eu3+ had a favourable effect on the conductivity and electrochemical activity of LS NPs. Due to favourable green combustion synthesis, superior electrochemical performance, these Eu3+ doped LS NPs could be potential materials for new generation supercapacitors in energy storage applications.

Synthesis and erudite insight into the structural, luminescence and thermal sensing characteristics of Sm3+ incorporated [formula omitted]-BaB2O4 novel phosphors

In this paper, we have presented the comprehensive characterization of red-light-emitting novel β-BaB2O4:xSm3+ (x = 0.5, 0.75, 1, 1.5, and 2 mol%) phosphor samples synthesized by making use of solid-state reaction method. The XRD patterns verified the successful synthesis and in-depth analyses were carried out to explore the structural, luminescence, and thermal properties. Notably, the introduction of Sm3+ through doping did not result in any substantial alterations in the crystal structure. Photoluminescence (PL) emission spectra exhibited 4 distinct peaks for 401 nm excitation. Out of these 4 peaks, the prominent peak was present at 601 nm, attributed to the magnetic dipole-allowed transition 4G5/2 → 6H7/2. The colorimetric analysis revealed the correlated color temperature (CCT) to be around 1700 K, accompanied by 99.9 % colour purity. The optimal doping concentration, before luminescence quenching, was identified as 1 mol%, with multipole-multipole interactions identified as the predominant quenching mechanism. Diffuse reflectance spectroscopy (DRS) studies on β-BaB2O4:1%Sm3+ confirmed characteristic peaks corresponding to Sm3+ transitions, revealing an ionic bonding nature between Sm3+ and the host. Also, the direct optical band gap was determined to be 5.62 eV. Furthermore, the optimized phosphor demonstrated exceptional temperature-dependent photoluminescent (TDPL) properties, exhibiting a negligible (∼5 %) decrease in emission intensity for prominent peaks even at 440 K. Overall, the phosphors displayed high activation energy, significant thermal stability, and thermal sensing properties, making them promising candidates for various optoelectronic applications.

“Perovskite SrTiO3 for photo catalytic and optoelectronic applications”

In this work, we report the synthesis of SrTiO3(STO) nanoparticles by solid-state method for photocatalytic applications. The samples were calcinated at different temperatures to obtain a single phase. The prepared samples were studied using various analytical techniques such as XRD, DRS, SEM/EDAX, and FTIR. XRD analysis before and after high-temperature calcination indicates eliminating impurities from the sample. FTIR spectroscopy also correlates with the formation of pure SrTiO3. SEM analysis shows the formation of cube-like nanostructures and a bandgap of 3.2 eV was observed from Diffuse Reflectance Spectroscopy studies. The photocatalytic activity of SrTiO3 towards methylene blue was studied for various catalyst concentrations. The SrTiO3 catalyst attained a degradation efficiency reaching up to 83 % in 120 min. IV measurements of the SrTiO3 thin films reveal the potential optoelectronic applications.

Enhanced Photo/Electrocatalytic Hydrogen Evolution by Hydrothermally Derived Cu-Doped TiO2 Solid Solution Nanostructures.

Highly efficient nanocatalysts with a high specific surface area were successfully synthesized by a cost-effective and environmentally friendly hydrothermal method. Structural and elemental purity, size, morphology, specific surface area, and band gap of pristine and 1 to 5% Cu-doped TiO2 nanoparticles were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), energy dispersive X-ray analysis (EDAX), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography-high resolution mass spectrometry (LC-HRMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible diffused reflectance spectroscopy (UV-DRS) studies. The XPS and EPR findings indicated the successful integration of Cu ions into the TiO2 lattice. UV-DRS and BET surface area investigations revealed that with an increase in dopant concentration, Cu-doped TiO2 NPs show a decrease in band gap (3.19-3.08 eV) and an increase in specific surface area (169.9-188.2 m2/g). Among all compositions, 2.5% Cu-doped TiO2 has shown significant H2 evolution with an apparent quantum yield of 17.67%. Furthermore, the electrochemical water-splitting study shows that 5% Cu-doped TiO2 NPs have superiority over pristine TiO2 for H2 evolution reaction. It was thus revealed that the band gap tuning with the desired dopant concentration led to enhanced photo/electrocatalytic sustainable energy applications.

Single-step synthesis of 1D/3D- BiYO3/BiOI direct Z-scheme heterostructure for the remediation of wastewater

In this work, a visible-light responsive BiYO3/BiOI nanocomposite photocatalyst with various amounts (1, 2, 3 wt %) of BiYO3 was synthesized by a solvothermal process. Furthermore, the prepared nanocomposite was investigated by various spectroscopic analysis, like X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV-DRS), photoelectrochemical and photoluminescence (PL) studies. The structural morphology study explored BiYO3 1D-nanorods are anchored on the surface of 3D-marigold flower-like structure of BiOI. Among different ratio of BiYO3 loaded over the samples, the optimized BYBI-2 nanocomposite seem to reveal much higher (83%) photocatalytic efficiency than the pure BiOI and BiYO3. In addition, the recycling tests too indicated that the optimized BYBI-2 nanocomposite is more robust, stable and reusable material for photocatalytic performances. The obtained rate constant value on the photodegradation of BYBI-2 nanocomposite is 0.02758 min−1 and has about 3.5 and 6.5 times larger than the pure BiOI (0.00808 min−1) and BiYO3 (0.00424 min−1) proportionately. The augmented photocatalytic activity of catalyst could be owed to the high visible-light absorption capability and the efficient separation of the charges. The radical trapping experiments too corroborated the vital role of h+ and •OH in the photocatalytic degradation of methylene blue (MB). According to the findings, a conceivable ZFTIR-scheme degradation mechanism of BiYO3/BiOI composite for detoxifying MB under 60 min of visible light irradiation has been presented. Thus, we considered that the as-synthesized material could be distinguished photocatalytic material for wastewater treatment.

Chemical Synthesis of ZnO:Er Nanorods for Photocatalytic H2 Evolution

The growth of one-dimensional (1D) ZnO systems has been attaining ample engrossment because of their unique photocatalytic and optoelectronic properties. In this context, we synthesized the high-quality ZnO and ZnO:Er nanorods through an inexpensive and facile solvothermal route. Morphological studies revealed that the fabricated samples correspond to nanorods. Erbium ion substitution into the host ZnO matrix was affirmed via XRD and Raman analyses. XPS analysis proposed that Er ion substitution in the Zn (II) site occurred with trivalent Er ions. The trivial diminishing of the optical band gap with the incorporation of Er into the host matrix was assessed by diffuse reflectance spectroscopy (DRS) studies. The photoluminescence spectra of both fabricated NRs display two nodes at ultraviolet and red luminescence. The fluorescence efficiency of the ZnO NRs diminished after Er doping. The ZnO and ZnO:Er NRs were measured for H2 evolution by water splitting beneath the UV light illumination. The ZnO:Er illustrated the efficient H2 evolution ability (21311 μmol h−1 g−1) in 5 h, which is higher than that of ZnO. To analyze the attained engrossing H2 outcomes, electrochemical studies were also employed. Fortunately, this is the first-ever endeavor in H2 production of the ZnO:Er NRs.

Efficient One‐pot Zeolite Synthesis Protocol from the Metastable *BEA to MTW Topology and Its Impact on the Methanol‐to‐Hydrocarbons Process

AbstractThe inter‐zeolite conversion is a method to convert one meta‐stable zeolite to a thermodynamically stable zeolite. Despite the enormous interest, this method is yet to be popularized or standardized in the zeolite community. Intending to provide more insights into hydrothermal conversions from one zeolite to another, this work developed a novel one‐pot and flexible synthetic protocol to efficiently obtain the meta‐stable *BEA topology and its derived MTW topology by varying the hydrothermal crystallization time. This inter‐zeolite conversion process led to changes in the zeolite framework and modified physicochemical properties during the process. Such a transformation was feasible by forming hierarchical zeolite phases sharing a similar “mtw”‐based common building units, possibly driving such conversion. The structure‐reactivity relationship of four different zeolite materials, synthesized from this one‐pot inter‐zeolite conversion method, was established concerning their performance in the methanol‐to‐hydrocarbon (MTH) process, which has been well supported by operando UV‐vis diffuse reflectance spectroscopic study coupled with online mass spectrometry and solid‐state NMR spectroscopy. As a result, the pathway to synthesize various target zeolites from an identical initial synthesis gel with desired physicochemical properties has been scrutinized.

Study of energy gaps and their temperature-dependent modulation in LaCrO3: A theoretical and experimental approach

In the present study, the origin of three energy gaps of lanthanum chromium oxide, one arises due to the charge-transfer gap between O-2p and Cr-3d and two arises from the d–d transitions, is analyzed in detail using the diffuse reflectance spectroscopy technique. The spin allowed transitions, such as 4T1(P)→4A2, 4T1(F)→4A2, and 4T2→4A2, and the spin and parity forbidden 2E →4A2 transitions are depicted using a Tanabe–Sugano (T–S) diagram and an absorption spectrum. The high crystal field strength of 3.27 obtained from the T–S diagram provides high directional emission and makes the system suitable for near infrared lasing applications. Moreover, the investigations into the variation of a charge-transfer gap with temperature will provide insights into the modification of numerous optical properties toward development of optoelectronic devices. Using this temperature-dependent diffuse reflectance spectroscopy studies, we have obtained the important optical parameters, such as Urbach energy (Eu) and Urbach focus. Furthermore, first-principles calculations are carried out in order to validate the experimental findings on LaCrO3. The experimental results are in consonance with the charge-transfer gap obtained from the theoretical calculations. Furthermore, the bandgap variation with temperature is fitted using Varshni's relation, and the Debye temperature is calculated.

Revealing electronic structure of nanostructured cobalt titanate via a combination of optical and electrochemical approaches toward water splitting and CO2 reduction

AbstractBackgroundThe shortage of clean energy has become a serious problem due to the rapid development of societies and the increasing consumption of fossil fuels. Metal oxide semiconductor nanomaterials have been studied as photo‐/electrocatalysts for water splitting in terms of clean energy generation. Applications of semiconductors depend on their electronic structures. Therefore, elucidating the electronic diagram is essential for determining the specific applications of novel semiconductors.ResultsHerein, we demonstrate using a combination of UV–visible diffuse reflectance spectroscopy (DRS) and Mott–Schottky analysis via electrochemical impedance spectroscopy for sketching the electronic diagram of nanostructured cobalt titanate (CoTiO3) prepared by the sol–gel method. UV–visible DRS studies reveal a band gap of 2.5 and 2.1 eV for direct and indirect transitions of prepared nanostructured materials, respectively. Mott–Schottky analysis shows a 0.8 V versus Ag/AgCl value for the flat band potential for CoTiO3. We further show the application of this diagram toward the interpretation of the electrochemical behavior of nanostructured CoTiO3 for electrochemical water splitting reactions and the electrochemical CO2 reduction reaction (eCO2RR).ConclusionThe presented electrochemical and photoelectrochemical studies demonstrate nanostructured CoTiO3 as an effective catalyst for electrochemical water oxidation and the eCO2RR. Moreover, our results provide valuable information for further investigation of water splitting and photovoltaic energy conversion. © 2023 Society of Chemical Industry (SCI).

Physico- and Electrochemical Properties of First-Row Transition-Metal-Substituted Sandwich Polyoxometalates.

The physico- and electrochemical behaviors of a series of [WZn3(H2O)2(ZnW9O34)2]12- (Zn-WZn3) and its first-row transition-metal-substituted analogues [WZn(TM)2(H2O)2(ZnW9O34)2]12- (Zn-WZn(TM)2; TM = MnII, CoII, FeIII, NiII and CuII) are reported. Various spectroscopic studies, including Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, electrospray ionization (ESI)-mass spectrometry, and Raman spectroscopy, show similar spectral patterns in all sandwich polyoxometalates (POMs) because of their isostructural geometry and constancy of the overall negative charge (-12). However, the electronic properties highly depend on the transition metals at the "sandwich core" and correlate well with the density functional theory (DFT) study. Further, depending on the substituted TM atoms, there is a decrease in the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) band-gap energy in these transition-metal-substituted POM (TMSP) complexes wrt Zn-WZn3, as confirmed by diffuse reflectance spectroscopy and DFT study. Cyclic voltammetry reveals that the electrochemistry of these sandwich POMs (Zn-WZn3 and TMSPs) is highly dependent on the pH of the solution. Moreover, the dioxygen binding/activation studies of these polyoxometalates show that Zn-WZn3 and Zn-WZnFe2 have better efficiency toward dioxygen binding, as confirmed by FTIR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA), which is also reflected in their catalytic activity toward imine synthesis.

Metal-Free Highly Stable and Crystalline Covalent Organic Nanosheet for Visible-Light-Driven Selective Solar Fuel Production in Aqueous Medium

Conversion of CO2 into solar fuels via artificial photosynthesis is one of the most promising and sustainable approaches to mitigate global warming and worldwide energy shortage. Covalent organic frameworks (COFs) exhibit well-defined arrangements of building blocks, tunable porosity, and high thermal and chemical stability in harsh conditions. The tunable band gaps of COFs by suitably introducing chromophoric light-harvesting units make them a unique class of metal-free heterogeneous photocatalysts for the successful conversion of CO2 to solar fuel. In this work, we report a simple, efficient, and low-cost 2D COF (TTA-Tz) composed of 1,3,5-tris-(4-aminophenyl)triazine (TTA) and 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)dibenzaldehyde (Tz) for photocatalytic CO2 reduction. The 2D-layered COF is exfoliated into ultrathin covalent organic nanosheets (CONs), which shows visible-light-driven photoreduction of CO2 to CO (yield = 2.8 mmol g–1, rate = 82 μmol h–1 g–1, and selectivity >99%) in aqueous medium without an external sacrificial electron donor. Interestingly, for a mixed solvent system, the CO evolution rate (163 μmol g–1 h–1) is found double than the aqueous medium case with 99% selectivity. By introducing both BNAH and TEA as sacrificial electron donors, the significant amount of CH4 (499 μmol g–1) is produced and the rate of CO evolution (310 μmol g–1 h–1) is further enhanced. The mechanistic insight of CO2 reduction is studied by DFT-based theoretical calculation, which is further supported by in situ diffuse reflectance spectroscopy study.

Defects Tune the Strong Metal-Support Interactions in Copper Supported on Defected Titanium Dioxide Catalysts for CO2 Reduction.

A highly active and stable Cu-based catalyst for CO2 to CO conversion was demonstrated by creating a strong metal-support interaction (SMSI) between Cu active sites and the TiO2-coated dendritic fibrous nano-silica (DFNS/TiO2) support. The DFNS/TiO2-Cu10 catalyst showed excellent catalytic performance with a CO productivity of 5350 mmol g-1 h-1 (i.e., 53,506 mmol gCu-1 h-1), surpassing that of almost all copper-based thermal catalysts, with 99.8% selectivity toward CO. Even after 200 h of reaction, the catalyst remained active. Moderate initial agglomeration and high dispersion of nanoparticles (NPs) due to SMSI made the catalysts stable. Electron energy loss spectroscopy confirmed the strong interactions between copper NPs and the TiO2 surface, supported by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The H2-temperature programmed reduction (TPR) study showed α, β, and γ H2-TPR signals, further confirming the presence of SMSI between Cu and TiO2. In situ Raman and UV-vis diffuse reflectance spectroscopy studies provided insights into the role of oxygen vacancies and Ti3+ centers, which were produced by hydrogen, then consumed by CO2, and then again regenerated by hydrogen. These continuous defect generation-regeneration processes during the progress of the reaction allowed long-term high catalytic activity and stability. The in situ studies and oxygen storage complete capacity indicated the key role of oxygen vacancies during catalysis. The in situ time-resolved Fourier transform infrared study provided an understanding of the formation of various reaction intermediates and their conversion to products with reaction time. Based on these observations, we have proposed a CO2 reduction mechanism, which follows a redox pathway assisted by hydrogen.

Enhanced Photodegradation of Rhodamine B Using Visible-Light Sensitive N-TiO2/rGO Composite

Rhodamine B (RhB) is extensively used for dyeing purposes, and cannot be completely removed using traditional water treatment technologies. Here, we report for the first time the photodegradation of RhB using nitrogen-doped titanium dioxide (N-TiO2) on reduced graphene oxide (rGO) composite (N-TiO2/rGO). The work primarily highlights the synergistic effect of the incorporation of N-TiO2 and rGO and its kinetic study for the photodegradation of RhB. The N-TiO2/rGO composite was synthesized by dispersing titanium(IV) isopropoxide and urea, followed by annealing treatment via the hydrothermal method with rGO. Scanning electron microscopy (SEM) images illustrated that N-TiO2 particles with an irregular round shape and white color were dispersed onto the rGO surface. X-Ray diffraction (XRD) patterns revealed that N-TiO2/rGO composite showed an anatase phase of TiO2 with a diffraction peak of 2θ = 25.622°. The gas sorption analysis (GSA) showed that N-TiO2/rGO had surface area, pore volume, and pore size of 53.393 m2/g, 0.096 cc/g, and 3.588 nm, respectively. The thermogravimetric-differential thermal analysis (TG-DTA) showed an anatase phase of TiO2 that appeared at a temperature of 200–500 °C, with a weight loss of 2.50%. According to the ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) study, TiO2, N-TiO2, and N-TiO2/rGO had band gap energies of 3.25, 2.95, and 2.86 eV, respectively. The highest photodegradation of RhB was obtained at the optimum condition in pH 2 with a photocatalyst mass of 20 mg and an irradiation time of 90 min. The photocatalytic activity of N-TiO2/rGO using visible light showed a higher percentage of photodegradation at 78.29%, compared to 44.08% under UV light. The kinetic study of the photodegradation of RhB using N-TiO2/rGO followed the pseudo-second-order model.

Structural, morphological and photoluminescence properties of Eu3+ doped Cd2Sr(PO4)2 nanopowder

Eu3+ doped cadmium strontium phosphate (Cd2Sr(PO4)2CSP) Nanopowder was synthesized by a simple and well known solid-state reaction method (SSR). The prepared nanopowder was characterized by various analytical techniques such as powder X-ray diffraction (P-XRD), scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) studies analysis along with photometric. Based on the results of XRD, the typical crystallite size of the as-prepared nanopowder is found to be 20 nm. The morphological study reveals that the sample has uneven distribution of nano-flakes like structure. The existence of vibrational bands of phosphate ions in the sample were identified by FT-IR spectroscopy. The DRS studies reveal that the sample has wide optical direct bandgap value of 5.4 eV. The Photoluminescence studies showed that the CSP nanopowder sample doped with Eu3+ ions exhibit six distinct emission bands which are ascribed to electronic transitions arose from 5D0 – 7FJ(J=0,1,2,3,4,5) corresponding to wavelengths 538 nm 588 nm, 612 nm, 651 nm, 698 nm and 724 nm respectively. In the present work it was found that the electronic transition from 5D0 → 7F2 at 612 nm (ED) is more intense than the transition from 5D0 → 7F1 at 588 nm (MD) resulting in Eu3+ ions asymmetry nature around the host site. The Photometric parameters like CIE chromatic coordinates, Color Correlated Temperature (CCT), Color Rendering Index(CRI), and Color purity(CP) reveals that the Eu3+ doped CSP nanopowder ions has potential application in the field of solid state lighting.

Large-scale production of ZnO nanoparticles by high energy ball milling

We present a structural, microstructural, and optical study on ZnO nanoparticles produced in large quantities (600 kg) by high energy ball milling. Dynamic light scattering analysis indicated a decrease in the particle size from 416.60 to 33.27 nm for the sample without and with the maximum energy of milling performed, respectively. X-ray diffraction results revealed a single phase corresponding to a hexagonal crystal structure as well as a broadening of the diffraction peaks in association with the decreasing crystal size. Diffuse reflectance spectroscopy study revealed a decrease in the reflectance due to the particle size reduction, and a contraction of the band gap energy from 3.244 to 3.112 eV. A correlation was found between crystal size and band gap. Brunauer-Emmett-Teller analysis revealed that the surface area increased almost threefold (from 4.4000 to 12.0031 m2 g-1) with increasing milling energy. Additionally, scanning electron microscopy observations showed an increased homogeneity in the particle size distribution with increasing milling energy.

A Z-scheme BiYO3/g-C3N4 heterojunction photocatalyst for the degradation of organic pollutants under visible light irradiation.

Photocatalysis is one of the fascinating fields for the wastewater treatment. In this regard, the present study deals with an effective visible light active BiYO3/g-C3N4 heterojunction nanocomposite photocatalyst with various ratios of BiYO3 and g-C3N4 (1:3, 1:1 and 3:1), synthesised by a wet chemical approach. The as-synthesised nanocomposite photocatalysts were investigated via different physicochemical approaches like Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electrons microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and photoelectrochemical studies to characterise the crystal structure, morphology, optical absorption characteristics and photoelectrochemical properties. The photocatalytic degradation ability of the prepared photocatalytic samples was also analysed through the degradation of RhB in the presence of visible light irradiation. Of all the synthesised photocatalysts, the optimised CB-1 composite showed a significant photocatalytic efficiency (88.7%), with excellent stability and recyclability after three cycles. O2•- and •OH radicals were found to act a major role in the RhB degradation using optimised CB-1 composite, and it possessed ~ 1 times greater photocurrent intensity than the pristine g-C3N4 and BiYO3. In the present work, a direct Z-scheme heterojunction BiYO3/g-C3N4 with a considerably improved photocatalytic performance is reported.

Expansion/shrinkage history of the Paratethys Sea during the Eocene: New insights from eolian Red Clay records in the Altyn Mountains, northern China

Uplift of the Tibetan Plateau, expansion/shrinkage of the Paratethys Sea, and global climate are three major forcings for central-east Asian climatic and environmental variations during the Cenozoic. However, knowledge of expansion/shrinkage history of the Paratethys Sea is much less well known in comparison with the other two forcings. Here, we present a first multiple-parameter environmental magnetic and diffuse reflectance spectroscopy study of the Eocene eolian Red Clay deposits (∼51–40 Ma) in the Xorkol Basin of the northeastern Tibetan Plateau, which is near the easternmost maximum boundary of the Eocene Paratethys Sea. The first detailed Eocene expansion/shrinkage history of the Paratethys Sea was reconstructed based on the hematite content of the Eocene Red Clay, which shows remarkable consistency with the previous low-resolution Paratethys Sea paleowater depth record in the southwestern Tarim Basin. These results demonstrate that the Paratethys Sea experienced a three-stage (shrinkage-expansion-shrinkage) evolution between ∼51 and 40 Ma, with boundaries at ∼46.2 and 42 Ma. Superimposed on this framework, the Paratethys Sea experienced four times of rapid shrinkages at the expansion phase (shows 400-kyr cycles) during ∼44–42 Ma modulated by eccentricity forcings. These new results are of great significance to evaluate respective role of Tibetan uplift, global climate, and Paratethys Sea area variations in Asian climate and environmental change over the Eocene.

Influence of Zr doping on Ag3PO4 for photocatalytic degradation of dyes and Cr(VI) reduction under visible light irradiation

In this study, pristine silver phosphate (Ag3PO4), 1, 3, and 5 at% Zr-doped Ag3PO4 have been synthesized using the precipitation method. In order to characterize the synthesized materials, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), UV–Visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL) was used. The tetrapod particles displayed by the pristine Ag3PO4 change into irregular particles upon the incorporation of Zr as shown in SEM images. The XRD patterns showed that pristine Ag3PO4 and all the Zr-doped Ag3PO4 exhibited body-centered cubic structure and were successfully prepared with no impurities. Similar FTIR spectra of all the synthesized materials showed the presence of the P–O and Zr–O groups. DRS studies showed that increasing Zr doping was found to reduce the band gap energy of Ag3PO4, except for 1 at% Zr doping. The photocatalytic ability of the synthesized materials was investigated through photodegradation of methylene blue (MB) and methyl orange (MO) as well as photoreduction of Cr(VI) under visible light illumination. Among the synthesized materials, 1 at% Zr-doped Ag3PO4 showed outstanding photocatalytic performance for both dye degradation and Cr(VI) reduction.

Multi-functional attributes of rare earth double doped SrBi2Nb2O9 ferroelectric system

The ferroelectric perovskite SrBi2Nb2O9 (SBN) material with a low concentration of double doping at the Bi-site of SBN was studied to understand its influence and usefulness in integrated optoelectronic, soft magnetic memory devices and wear-resistant tribomaterials. The aim of the present study is double doping of SBN with a set of rare earth elements Pr3+/Dy3+ (SBPDN), Pr3+/Gd3+ (SBPGN), Pr3+/Sm3+ (SBPSN), and Pr3+/Y3+ (SBPYN) at the Bi-site of SBN to establish the multifunctional ceramic nature pertaining to diverse applications. XRD with Rietveld refinement analysis acknowledged a single-phase orthorhombic structure with an increase in lattice parameters and unsystematic changes in crystallite size. SEM study indicated that the samples possessed non-uniformly distributed needle-shaped grains. The purity of the material and the detection of functional groups were received from the EDS and FTIR spectroscopy. Structural modifications in SBN have been determined based on a diffuse reflectance spectroscopy (DRS) study and therefore the band gap values decrease from 2.98 eV (SBN) to 2.70 eV (double doping) because of the growth of distortion in the structure and pronounced increase in the density of localized states. Photoluminescence (PL) study on double doped SBN material with an excitation wavelength of 320 nm has yielded a novel red emission at 609 nm, that may be useful for white LEDs. The ferromagnetic signature in the studied materials was confirmed from the room temperature VSM study. Noticed mild wear and a low coefficient of friction in the studied materials of SBPDN and SBPSN compared to other studied ceramic samples from mechanical studies. The simultaneous manifestation of optical, magnetic, and mechanical properties by double-doped SBN ceramics keeps the materials as multi-functional candidates for optoelectronic devices, soft magnetic memory devices, and wear-resistant tribomaterials.