UV Vis Diffuse Reflectance Spectroscopy Research Articles

Green synthesis and studies on citrus medica leaf extract-mediated Au–ZnO nanocomposites: A sustainable approach for efficient photocatalytic degradation of rhodamine B dye in aqueous media

Abstract Incorporating narrow band gap oxide semiconductors and metals into zinc oxide (ZnO) nanostructures broadens the range of light sensitivity to include visible wavelengths. In this study, the photocatalytic degradation of rhodamine B (RhB) dye was studied as a model for environmental pollution in aqueous media. This study describes the use of photodegradation catalysts, including gold (Au), ZnO, and Au–ZnO nanocomposites (prepared in ratios of 90:10 and 95:5) using the extract of Citrus medica leaves. X-ray diffraction (XRD) findings have shown that ZnO nanoparticles (NPs) have a hexagonal wurtzite structure. Field emission-scanning electron microscopy findings have depicted that ZnO NPs have diverse shapes, including spherical, quasi-spherical, hexagonal, and anisotropic, with some clumping. Au exhibits consistent spherical shapes and sizes with even distribution. Au–ZnO (90:10) shows quasi-spherical NPs with interconnected spherical Au, forming a porous and uneven surface. Au–ZnO (95:5) has spherical gold nanoparticles (Au NPs) dispersed on a textured ZnO surface, with some clustering and size variation as evident from the transmission electron microscopy, atomic force microscopy, and diffuse reflectance UV-visible spectroscopy analysis. The characterization results have demonstrated the uniform distribution of Au across the ZnO lattice. Additionally, the XRD patterns confirmed the hexagonal wurtzite structure of ZnO. Furthermore, energy-dispersive analysis of X-ray (EDX)-mapping verified the inclusion of zinc, oxygen, and Au in the hybrid Au–ZnO nanocomposites and their effective distribution. The topological analysis revealed a rough surface for the generated nanostructures. By comparing the results of various techniques, EDX analysis using atomic and weight ratios confirmed the presence of oxygen and Au in the nanocomposite. Additionally, the surface area analysis (BET) test has reported that the adsorption and desorption of nitrogen follow a Type III isotherm. The presence of an H3-type hysteresis loop further confirms the mesoporous nature of the composites, which reports the presence of wedge-shaped pores. The Au–ZnO (90:10) nanocomposite exhibits a higher surface roughness compared to other composites. In addition, this UV-visible diffuse reflectance spectroscopy has enumerated the band gaps of various nanomaterials using UV-visible spectroscopy. Moreover, the analysis has unveiled that combining ZnO with Au NPs (doping) improved the photocatalytic performance of ZnO. This improvement is attributed to the formation of additional energy levels within the ZnO band gap due to the presence of Au ions. Experimental investigation of the breakdown of RhB dye under visible light irradiation revealed superior photocatalytic activity for the Au–ZnO (90:10) nanocomposite compared to both Au–ZnO (95:5) and pure ZnO and Au counterparts. Multiple experiments confirmed the effective photodegradation and removal of RhB dye from the aqueous medium using the nanocatalyst under visible light irradiation. Under optimal conditions (1.0 g·L−1 photocatalyst, 10 ppm RhB, and pH 10), 99% photodegradation efficiency was reached within 50 min of irradiation. Investigation of reactive species revealed that the increased effectiveness of photodegradation in Au–ZnO (90:10) stems from the presence of photogenerated holes and hydroxyl radicals. The study also analyzed the reaction kinetics and order, and the reusability of the best photocatalyst Au–ZnO (90:10)) was confirmed through five consecutive cycles, demonstrating its sustained effectiveness in photodegradation. These findings highlight the potential of Au–ZnO (90:10) nanocomposite as a promising material for photocatalytic degradation of organic dyes.

Hydrothermal preparation, crystal structure, Hirshfeld surface analysis, photophysical properties and antifungal activity of a series of complexes assembled by 5-bromo-2-(carboxymethoxy)benzoic acid ligands

Five complexes [Co(BCBA)(H2O)3]n (1), [Co(BCBA)(4,4′-Bipy)2·(H2O)]n (2), [Cu(BCBA)(H2O)]n (3), [Zn(BCBA)(H2O)]n (4) and [Cd(BCBA)(2,2′-Bipy)(H2O)·(H2O)]n (5) (H2BCBA= 5‑bromo-2-(carboxymethoxy)benzoic acid, 4,4′-Bipy = 4,4′-bipyridine and 2,2′-Bipy = 2,2′-bipyridine) have been synthesized with H2BCBA ligand by solvothermal condition. All the complexes have been structurally characterized by infrared spectra (IR), elemental analyses and single-crystal X-ray diffraction analyses. Complex 1 is a zero-dimensional structure, and complexes 2–5 are one-dimensional chain structure. Furthermore, thermogravimetric analyses (TGA), Hirshfeld surface analysis, photo-luminescence properties, Solid-state UV–Vis diffuse reflectance spectroscopy and antifungal activity for complexes 1–5 were investigated. The reciprocal H···O/H/Br/C contacts dominate over 86 % of total Hirshfeld surface. Complexes 1–5 have certain inhibitory effects on 8 pathogenic fungi. Among them, complex 5 has the strongest antibacterial activity against Rhizoctonia solani AG1, Sphaeropsis sapinea and Colletotrichum fructicola, and the inhibitory rate reached 100 %.

Polyvinyl chloride coated paper postmodified by nucleophilic substitution with diphenylamine to enhance cation-π interactions with opioids in saliva samples

This article evaluates the potential of cellulose paper as a substrate for preparing a polyvinylchloride (PVC)-diphenylamine sorptive phase that can be used under the thin film microextraction (TFME) format. This phase was easily synthesized using the dip-coating technique to coat the filter paper with PVC, followed by the covalent bonding of diphenylamine. As a result, aromatics rings are available on paper surface to isolate the target analytes by a mixed-mode interaction at physiological pH. The resulting material was characterized by infrared spectroscopy, UV–Vis diffuse reflection spectroscopy, and scanning electron microscopy. As analytical problem, three opioids (methadone, codeine, and tramadol) were determined in saliva samples by direct infusion mass spectrometry. Different variables involved in the extraction procedure have been optimized (e.g. sample pH, extraction time, and sample dilution). The proposed method provides good linearity (R2 > 0.9817) and sensitivity (detection limits in the range from 1.5 µg L−1 to 15 µg L−1). The intra-day and inter-day precision, expressed as relative standard deviation, were better than 16.4 % and 18.5 % respectively. The accuracy, expressed as relative recovery, provides values in the interval from 82 % to 105 %. Finally, the proposed approach has been successfully applied to real saliva samples of patients under codeine and tramadol medical prescription.

Hierarchically, Low Band Gap Nanohybrid InVO4-CdS Heterojunction for Visible Light-Driven Toxic Organic Dye Degradations.

The synthesis of InVO4-CdS heterojunction photocatalysts has been achieved by a novel two-step approach, including a microwave-assisted technique, followed by a moderate hydrothermal method, marking the first successful instance of such a synthesis. X-ray diffraction, field-emission scanning electron microscopy, elemental color mapping, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, Raman analysis, photoluminescence, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller were employed to investigate the crystal structures, surface morphologies and particle sizes, chemical compositions, and optical characteristics of the as-synthesized materials. The research results indicated that the heterojunction InVO4-CdS, as synthesized, consisted of InVO4 microrods with an average size of around 15 nm and cadmium sulfide (CdS) microflowers with a diameter of 1.5 μm. Furthermore, all of the heterojunctions had favorable photoabsorption properties throughout the visible-light spectrum. The photocatalytic efficiency of the samples obtained was thoroughly assessed by the degradation of acid violet 7 (AV 7) under visible light irradiation with a wavelength greater than 420 nm. The photocatalytic efficiency for the decomposition of AV 7 was greatly enhanced in the InVO4-CdS (IVCS) heterojunctions when compared to prepared bare InVO4 and CdS. Additionally, it was observed that the composite material consisting of IVCS 3 wt % InVO4 combined with CdS exhibited the most significant enhancement in catalytic effectiveness for the photodegradation of AV 7 dye. Specifically, the catalytic performance of this composite material was found to be around 69.4 and 76.2 times greater than that of pure InVO4 and CdS, respectively. Furthermore, the experimental procedure including active species trapping provided evidence that h+ and •O2- radicals were the primary active species involved in the photocatalytic reaction process. Additionally, a potential explanation for the improved photocatalytic activity of the InVO4-CdS heterojunction was presented, taking into account the determination of band positions.

Electrocatalytic and photoelectrocatalytic investigation of Orange G degradation utilizing a novel BHP@Bi2O3 photoanode employing the CCD-RSM experimental design

In this study, we synthesized a bilayer film consisting of BaHPO4 (BHP) and Bi2O3 through the electrodeposition technique. The produced anode was subjected to characterization using cyclic voltammetry to clarify the deposition reactions. Subsequent to this, structural and morphological analyses were conducted utilizing X-ray diffraction alongside scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy. Additionally, UV–vis diffuse reflectance spectroscopy was employed to determine the bandgap energies of both semiconductors. Following an electrochemical characterization using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) measurements, the photoanode was employed for the electro-degradation of the anionic dye Orange G (OG), varying key degradation parameters such as current density, pollutant concentration, supporting electrolyte concentration, and pH using the CCD-RSM experimental design method. A degradation efficiency of 98% was achieved within a 20-minute timeframe. Photoelectrocatalytic tests under UV irradiation reduced the degradation time from 20 to 6 min, with a degradation rate of 99%. Additionally, under the same conditions, the BHP@Bi2O3 photoanode exhibited good stability, enduring up to 11 cycles of use.

Photocatalytic Degradation of Tartrazine and Naphthol Blue Black Binary Mixture with the TiO2 Nanosphere under Visible Light: Box-Behnken Experimental Design Optimization and Salt Effect

In this study, TiO2 nanospheres (TiO2-NS) were synthesized by the solvothermal method. Firstly, the synthesized nanomaterial was characterized by X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR), scanning electron microscopy (SEM) and UV-Vis Diffuse Reflectance Spectroscopy (DRS). To study the photocatalytic degradation of Tartrazine (TTZ) and Naphthol Blue Black (NBB) in a binary mixture, the influence of some key parameters such as pH, pollutant concentration and catalyst dose was taken into account under visible and UV light. The results show a 100% degradation efficiency for TTZ after 150 min of UV irradiation and 57% under visible irradiation at 180 min. The kinetic study showed a good pseudo-first-order fit to the Langmuir–Hinshelwood model. Furthermore, in order to get closer to the real conditions of textile wastewater, the influence of the presence of salt on TiO2-NS’s photocatalytic performance was explored by employing NaCl as an inorganic ion. The optimum conditions provided by the Response Surface Methodology (RSM) were low concentrations of TTZ (2 ppm) and NBB (2.33 ppm) and negligible salt (NaCl) interference. The percentage of photodegradation was high at low pollutant and NaCl concentrations. However, this yield became very low as NaCl concentrations increased. The photocatalytic treatment leads to 31% and 53% of mineralization yield after 1 and 3 h of visible light irradiation. The synthesis of TiO2-NS provides new insights that will help to develop an efficient photocatalysts for the remediation of contaminated water.

Degradation of Methyl Red (MR) dye via fabricated Y2O3–MgO/g-C3N4 nanostructures: Modification of band gap and photocatalysis under visible light

In this study, graphitic carbon nitride (g-C3N4) composites with metal oxide nanoparticles (Y2O3, MgO) and their combination (CN, YCN, MCN and YMCN) were synthesized by an ultrasonic technique and were then characterized by different tools such as UV–Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). From the XRD diffractograms of the YMCN ternary composite, the g-C3N4, cubic MgO and Y2O3 structural phases were identified. The morphology of the as prepared nanostructure from the SEM analysis revealed the dispersion of the metal oxides nanoparticles with the graphitic sheets and the presence of the corresponding elements were confirmed by the EDX and XPS data. The FT–IR bands confirmed the bonding of the metal oxides to the nitride host as indicated by the characteristic modes. A reduction of the band gap energies was confirmed by the UV–Vis to indicate its visible light possible photoactivity. Accordingly, its visible light driven photocatalytic performance was assessed for methyl red degradation. The degradation competence was highest for the ternary composite YMCN due to the coupling of the semiconductors which increases the absorption and the charge carriers’ separation as well. The kinetics of degradation was best described by pseudo-first-order, and the most active species were the holes and the hydroxyl radicals. Thus, the YMCN nanocomposite is a visible light-active photocatalyst which can be engaged in the degradation of organic pollutants.

Tailoring BiOBr Photocatalyst: In-situ Bi Doping for Enhanced Photocatalytic Removal of Sulfamethoxazole, SMX Antibiotic

There is a notable emphasis on the development of photocatalysts to degrade antibiotics, such as sulfamethoxazole (SMX), in aquatic environments due to their persistence and associated toxicological impacts. In this study, BiOBr photocatalysts were synthesized by incorporating in-situ Bi doping. Various Bi/BiOBr composites were produced through a hydrothermal method at varying temperatures and subsequently characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray fluorescence (XRF), and nitrogen adsorption-desorption isotherm. The characterization data revealed that the Bi-metal began to emerge at a hydrothermal temperature of 180 °C (BB180) in the BiOBr-based semiconductor and completed its conversion to Bi-metal at a hydrothermal temperature of 270 °C (BB270). This transformation leads to the generation of Bi3+ in conjunction with oxygen vacancies, acting as active electron traps and enhancing the separation efficiency of light-induced electron-hole pairs. This results in a narrow band gap of Bi/BiOBr photocatalyst, increasing its sensitivity towards visible light. BB180 exhibited the highest photocatalytic rate in the degradation of SMX with a removal efficiency of 74.35% within 4 hours of reaction under Xenon lamp irradiation and an apparent rate constant of 6.5 x 10-3 min-1, surpassing the commercial TiO2 Degussa P25. This finding opens up a new pathway for the development of a catalyst responsive to visible light, specifically designed for the detoxification of antibiotics in wastewater.

Zinc-modified barium stannate micro-rods: Investigating structural, morphological, and optical features

In the present study, we have synthesized pristine and Zn-doped (0.025, 0.05, 0.075, 0.10) barium stannate (BSO) micro-rods via the hydrothermal method. The prepared samples have been analyzed for their structural, optical, and morphological properties using X-ray diffraction technique (XRD), UV–Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDX). Our Rietveld refinement examination of the XRD data verifies that the samples are single-phase, with a cubic crystal structure. Additionally, the lattice parameters determined align closely with the existing literature. Furthermore, the FE-SEM analysis unveiled the presence of well-defined rod-shaped structures accompanied by particle agglomeration across the surface. Further, the EDX analysis confirmed the presence of key elements, providing crucial insights into the material's chemical makeup. Especially noteworthy was the UV-DRS analysis, demonstrating a direct correlation between increased Zn doping concentrations and a concurrent reduction in the band gap values. This adjustment aligns the material's band gap with those commonly found in key components utilized in DSSC and PSC cells, suggesting promising applications in these crucial technological domains.

Evaluation of Ce-MOFs as Photoanode Materials for the Water Oxidation Reaction: The Effect of Doping with [Ru(bpy)(dcbpy)(H2O)2]2+ Catalyst.

Artificial photosynthesis stands out as a highly effective method for harnessing sunlight to produce clean and renewable energy. The light-absorbing properties, chemical stability, and high redox activity of Ce-based metal-organic frameworks (MOFs) make them attractive materials for visible-light-driven water splitting. Currently, Ce-based MOFs remain a relatively underexplored system for photocatalytic water oxidation in acidic media. In this study, we synthesized a Ce-MOF with different linkers (1,4-benzenedicarboxylic acid, tetrafluoroterephthalic acid, 2-nitroterephthalic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, and 4,4'-biphenyldicarboxylic acid), which exhibit light-absorbing capability. Ce-based MOFs doped with [Ru(bpy)(dcbpy)(H2O)2]2+ (MOF-1 and MOF-2) water oxidation catalyst showed an enhanced photoelectrocatalytic current of ∼10-4 A·cm-2 at pH = 1, which is comparable with the [Ru(bpy)(dcbpy)(H2O)2]2+-doped MIL-126 Fe-based MOF. We also demonstrated the long-term durability of Ru-doped Ce-MOFs for photoelectrocatalytic water oxidation under acidic conditions. The as-synthesized MOFs were analyzed with powder X-ray diffraction (PXRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM), and electric conductivity measurements. This study contributes to the development of cost-effective materials for sustainable photocatalytic water splitting processes.

S-Schematic CuWO4/ZnO nanocomposite boosted photocatalytic degradation of organic dye pollutants

S-schematic CuWO4/ZnO nanocomposite photocatalyst was synthesized by an impregnation method. Synthesized CuWO4 and ZnO nanoparticles, and CuWO4/ZnO nanocomposites were thoroughly characterized. X-ray diffraction (XRD) analysis of the CuWO4/ZnO nanocomposite confirmed the respective triclinic and hexagonal wurtzite structures of CuWO4 and ZnO crystals. Raman and Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) revealed bond formations in CuWO4 and ZnO, and confirmed the synthesis of the CuWO4/ZnO nanocomposite. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed CuWO4 nanoparticles adhered to ZnO aggregates. Energy dispersive X-ray spectrometry (EDS) confirmed the distribution of CuWO4 on the ZnO aggregates. UV–Vis diffuse reflectance spectroscopy (DRS) showed optical bandgap energies of 2.36 eV for CuWO4 and 3.18 eV for ZnO nanoparticles. The photocatalytic performance of the CuWO4/ZnO nanocomposite was investigated through the degradation of the cationic dyes methylene blue (MB) and Rhodamine B (RhB) and the anionic dye methyl orange (MO). A 5.0%CuWO4/ZnO nanocomposite degraded 100% of MB within 120 min, 91.02% of RhB within 300 min, and 89.13% of MO within 300 min. The pseudo-first order kinetic rate constant fit well for the degradation of all the dyes on the CuWO4/ZnO nanocomposite. The CuWO4/ZnO nanocomposite could better degrade the cationic dyes than the anionic dye in an aqueous solution. The hole (h+), the hydroxyl radical (•OH), and the superoxide ion (•O2−) were the active species responsible for degrading MB, RhB and MO dyes. The proposed CuWO4/ZnO nanocomposite could be applied for environment friendly wastewater treatment.

Synthesis and characterization of Fe3O4 core nanoparticles coated with TiO2 and ZnO

The room temperature synthesis of the core-shell-shell (CSS) nanoparticles was demonstrated to be green, low-cost, and reproducible. The magnetic core of Fe3O4 nanoparticles was coated with TiO2 and ZnO in two steps. The obtained CSS nanoparticles were extensively characterized by XPS, TEM, XRD, DRS-UV–vis, N2 Physisorption, Electromagnetic, and Raman spectroscopy. XPS analysis revealed that the magnetic core was successfully functionalized with the citric acid. The ratio between the ferric cations (Fe3+) and ferrous (Fe2+) is typically reported to be around two due to the presence of FeO and Fe2O3 to balance the charge in the structure. Nevertheless, XPS results demonstrated that the ratio resulted in higher stability than that of the crystal nominal structure, suggesting that the surface of the CSS is slightly enriched with Fe3+ cations. TEM results indicated an average core diameter of approximately 9±1 nm for Fe3O4 (M-US); the first shell exhibited an average thickness of 3±1 nm, while the ZnO second shell thickness resulted in around 2±1 nm. X-ray diffraction analysis identified inverse spinel, hematite, anatase, and zincite phases in M-US, MT, and MTZ, respectively. Notably, the MTZ sample also contained hematite in addition to inverse spinel. Diffuse Reflectance UV-Vis Spectroscopy results demonstrated a reduction in the band gap as the shell coverage varied. N2 adsorption-desorption isotherms indicated an increase in the surface area as the core nanoparticles were coated with the subsequent shells. Additionally, the coated samples presented a mesoporous structure with a maximum surface area of 110 m2g−1 for the MT material. Raman spectroscopy confirmed the presence of vibrational modes related to TiO2 and ZnO. The core-shell-shell nanoparticles presented suitable electronic properties to potentially be applied in the photodegradation of harmful compounds and azo dyes.

Enhanced photocatalytic and antibacterial properties of silver–zirconia nanoparticles for environmental pollution treatment

Abstract Silver–zirconia nanoparticles (Ag–ZrO2 NPs) were synthesized via an in situ strategy at room temperature using NaBH4 as a reducing agent. The surface modification of ZrO2 nanoparticles with nano silver was confirmed through various characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), UV–vis Diffuse Reflectance Spectroscopy (UV–vis DRS), X-ray Diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The obtained results demonstrated that Ag nanoparticles, with a crystallite size of approximately 12 nm, were uniformly distributed on the surface of ZrO2 nanoparticles. The incorporation of Ag nanoparticles to the ZrO2 nanoparticles led to increasing the light absorption ability and reducing the band gap of Ag–ZrO2 nanoparticles, thereby enhancing their photocatalytic performance under infrared lamp exposure. When 1 g/L of Ag–ZrO2 nanoparticles was employed to methylene blue (MB) solution, the degradation of MB reached 90 % after 5 h of exposure. Additionally, the Ag–ZrO2 nanoparticles exhibited a high antibacterial activity against two bacterial strains, E. coli and S. aureus. These findings highlight the potential of Ag–ZrO2 nanoparticles as effective materials for environmental pollution treatment through advanced oxidation processes.

Study on Crystal Structure, Surface Area, and Energy Gap Behaviors of Nanotitania Polymorphs Prepared Using Monoethanolamine

Polymorphous nanotitania samples were prepared from titanium butoxide (TTB) as a precursor using sol-gel processing in ethanol as a solvent, without and with monoethanolamine (MEA). The experiments used 5.25 mL TTB and MEA with varied volumes of 0.5, 1.0, 1.5, and 2.0 mL. The sample without MEA was specified as sample A, and the samples produced using MEA were specified as samples B, C, D, and E, respectively. All samples were calcined at 500 °C for 4 h and then collected data by X-ray Diffraction (XRD), the Brunauer-Emmett-Teller (BET) method used to analyze Surface Area Analyzer (SAA), Transmission Electron Microscopy (TEM), Raman Spectroscopy, and UV-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS). The results of XRD characterization indicate that samples A and B form anatase phase, while samples C and D are composed of anatase, brookite, and rutile phases, and sample E is consisted of anatase and brookite phases with weight percentages of (94.53 ± 1.72) % and (5.47 ± 0.36) %, respectively. The presence of the three phases of titania is also confirmed by Raman spectroscopy analysis, which showed anatase peaks at 146, 197, 398, and 513 cm-1, brookite peaks at 245 and 402 cm-1, and rutile peaks at 319, 436, and 612 cm-1. According to XRD, the samples have the particle size in the range of 14-19 nm. A representative sample (sample C) was also characterized using TEM, revealing a particle size of 16.0 ± 0.3 nm. This representative sample revealed the largest surface area of 172.2 m2/g, as seen by BET, and the lowest energy gap of 3.03 eV.

Constructing stable type-II NaLiTi3O7/La2S3 heterojunctions for efficient photocatalytic charge separation and hydrogen production

Designing titanium-based oxides with efficient photogenerated carrier separation is an essential approach to enhance their photocatalytic hydrogen production performance. ALiTi3O7 possesses excellent stability, corrosion resistance, and non-toxicity. More importantly, its stoichiometry can be changed along with the variations in A-site elements and Li content, leading to tunable redox potentials of the conduction band minimum (CBM) and valence band maximum (VBM). Exploring the possible application of such materials in the field of photocatalysis is crucial for developing novel and efficient titanium-based photocatalysts. As a member of the family, NaLiTi3O7 (NLT) has a large bandgap, limiting its application as visible light photocatalyst. To address this issue, non-toxic La2S3 (LS) narrow-bandgap semiconductor was incorporated to form a heterojunction. The characterization techniques have revealed the structural and interfacial characteristics of the NLT-LS heterojunction, while the Infrared, Raman, UV–Vis diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and work-function tests elucidated the influence of the interface interaction on charge carrier separation mechanism. The test results further demonstrated that the formation of a type II heterojunction facilitated the transfer of photogenerated electrons from the conduction band of LS to the conduction band of NLT under light radiation. Simultaneously, the induced holes were confined to the valence band of LS. This charge transfer characteristic significantly improved the separation efficiency of the photogenerated carriers in the heterojunction, ultimately resulting in a photocatalytic hydrogen production rate of 102.4 μmol h−1 g−1 for the NLT-LS2 sample, which is ∼8 times higher than that of pure NLT and almost no decay after four cycles.

Efficient photocatalytic degradation of tetracycline hydrochloride by Cu2O/BiVO4 p-n heterostructure

Star-like BiVO4 and Cu2O nanocubes were prepared by hydrothermal method and chemical reduction, respectively, and Cu2O/BiVO4 p-n heterojunction with different mass ratios of Cu2O to BiVO4 (3:1, 1:1, 1:3) were synthesized via facile physical mixing. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflection spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance of the Cu2O/BiVO4 composites was evaluated by degradation of tetracycline hydrochloride (TC) under simulated solar illumination. Owing to the fast charge transfer between n-type BiVO4 and p-type Cu2O, Cu2O/BiVO4 composites exhibited superior photocatalytic activity. When the mass ratio of Cu2O to BiVO4 was 1:3, the highest degradation efficiency of TC reached 78.9% within 24 min.

Construction of AgCl/Bi2WO6 heterojunction for effective removal of RhB dye

Flower-like Bi2WO6 microspheres were prepared by a facile hydrothermal method, and AgCl/Bi2WO6 heterojunction was successfully synthesized by in-situ precipitation method. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (DRS). The effect of AgCl loading in AgCl/Bi2WO6 composites on the degradation of Rhodamine B (RhB) was also investigated. When the mass ratio of AgCl to Bi2WO6 was 4:1, AgCl/Bi2WO6 composites exhibited the highest photocatalytic degradation efficiency of 87.9% within 30 min, which could be attributed to the construction of heterojunction structure that effectively promoted the separation of photogenerated electron-hole pairs.

Understanding the mechanism of propane dehydrogenation over coordinatively unsaturated Co-O acid-base pairs and the inhibition effect of trace oxygen

High temperature and a reducing atmosphere are characteristic of propane dehydrogenation (PDH) reaction. Under such condition, the real surface structure of catalysts often differs from that in the ambient environment, particularly for CoOx species with multiple valence states and coordination. Here, a combination of in situ/operando Raman spectroscopy, in situ UV–Vis diffuse reflectance spectroscopy (DRS), and density functional theory (DFT) calculations reveal that coordinatively unsaturated Co-O (Cocu-O) acid-base pairs via lattice oxygen consumption are the PDH active sites of CoOx/Al2O3 catalysts. This highly dispersed Cocu-O species exhibit a C3H6 formation rate and C3H6 selectivity as high as 2 mmol‧gcat−1‧min−1 and 95 %, respectively, which is comparable to most state-of-the-art CoOx-based catalysts. However, industrial C3H8 raw gases typically contain 10–1000 ppm oxygen gas, and the complete eliminating oxygen increases costs. PDH catalytic performance of CoOx/Al2O3 catalysts is sensitive to the extremely low concentration of oxygen gas and is significantly inhibited by it. The fundamental reason is that the concentration of Cocu active sites is determined by the competitive reaction between the filling of trace oxygen on oxygen vacancies and lattice oxygen consumption. The reaction rate of the former is significantly higher than that of the latter. The higher reducibility of CoOx species leads to relatively weaken inhibition of trace oxygen for PDH activity. The oxygen content in the propane feed gas is a non-negligible factor in the development of new Co-based PDH catalysts, especially for their industrial applications.

A novel composite (BiVO4/TiS2) presenting an excellent Z-scheme photocatalytic degradation for Rhodamine B dye under the visible light irradiation

Dye pollutant in the water is the most challenging problem in the textile industries. Novel composites photo-catalysts (BiVO4/TiS2@3%, BiVO4/TiS2@6%, and BiVO4/TiS2@9%) have been prepared to solve this problem. These composites proved promising materials as they have high photocatalytic performance and excellent electro-conductivity properties. Novel BiVO4/TiS2@3%, BiVO4/TiS2@6%, and BiVO4/TiS2@9% composites nanomaterials characterized by Photoluminescence Spectroscopy, UV–visible Diffuse Reflectance Spectroscopy (DRS), Raman Spectroscopy, Energy dispersive X-ray Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction Techniques. BiVO4/TiS2@6% shows superior photocatalytic activity and removed RhB molecules (97%) in a very short time of 70 min when irradiated underneath visible light. Compared to pure BiVO4 and TiS2, the average photocatalytic efficiency of composite materials (BiVO4/TiS2@3%, BiVO4/TiS2@6%, and BiVO4/TiS2@9%) was high. Photo generated carrier's transmission becomes smooth due to the very small resistance of BiVO4/TiS2@3%, BiVO4/TiS2@6%, and BiVO4/TiS2@9%. The photoluminescence spectrum (PL) shows that photo-generated carriers of BiVO4/TiS2@6% have the highest separation efficiency. Focusing on a capturing experiment for the degradation of RhB, a good photocatalytic process was presented. It was unexpected to see how quickly the rate of degradation of a new BiVO4/TiS2@6% composite photocatalytic material could still be up to 90% after six cycles. Finally, proposed an excellent photo-catalyst BiVO4/TiS2@6% for wastewater treatment on an industrial scale.

Synthesis and Characterization of Iron-Doped TiO2 Nanotubes (Fe/TiNTs) with Photocatalytic Activity

One of the most significant global challenges for humans is environmental pollution. The technology to control this problem is the utilization of semiconductors as photocatalysts. In the current study, iron-doped titania nanotubes (Fe/TiNTs) with increased photocatalytic effect were synthesized via a modified hydrothermal method. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy (TEM), gas adsorption, electron spin resonance (ESR) and UV–Vis diffuse reflectance spectroscopy (DRS). TEM results indicated that Fe/TiNTs have a tubular and uniform structure with an average outer diameter of 23–48 nm and length of 10–15 µm. ESR and DRS revealed that Fe3+ ions were successfully introduced into the TiNT structure by replacing Ti4+ ions. An enhanced light absorption in the range of 400–600 nm additionally indicated successful doping. The band gap was narrowed as iron wt% was increased. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) in the presence of Fe/TiNTs and TiTNs by monitoring the degradation of MO under UV light irradiation. An acceleration on the hydration of Portland cement was observed in the presence of 2.0 wt% Fe/TiNTs. Fe/TiNTs can be used as a nanomaterial in cement-based building materials to provide self-cleaning properties to the surface of concrete even in indoor environments.