Synthesis of one-dimensional TiO2/V2O5 branched heterostructures and their visible light photocatalytic activity towards Rhodamine B

Controlled synthesis of MWCNTs/V2O5 nanocomposite by hydrothermal approach for adsorption and photodegradation processes

The current paper outlines the synthesis of pristine multi-wall carbon nanotubes (PMWCNTs)/Vanadium pentoxide V2O5 and functionalized multi-wall carbon nanotubes (FMWCNTs)/V2O5 nanocomposite for photocatalytic applications. The FMWCNTs were obtained by the oxidizing agents (H2SO4 and HNO3) to introduce the oxygenated functional groups. The samples were synthesized by hydrothermal approach and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity of multi-wall carbon nanotubes (MWCNTs), FMWCNTs/V2O5, and PMWCNTs/V2O5 nanocomposites was assessed via methylene blue (MB) degradation from water under visible light. The results demonstrated that the removal efficiency of MB by PMWCNTs, FMWCNTs/V2O5, and PMWCNTs/V2O5 could reach 90.4, 98.9, and 94.9%, respectively. It was noticed that MB adsorption and photodegradation tend to follow pseudo-second-order kinetics. The mechanism of MB photodegradation by FMWCNTs/V2O5 nanoparticles was explained. MWCNTs/V2O5 nanocomposites will allow further applications to remove other dyes and contaminants from wastewater.

Vanadium Oxide: Phase Diagrams, Structures, Synthesis, and Applications

Vanadium oxides with multioxidation states and various crystalline structures offer unique electrical, optical, optoelectronic and magnetic properties, which could be manipulated for various applications. For the past 30 years, significant efforts have been made to study the fundamental science and explore the potential for vanadium oxide materials in ion batteries, water splitting, smart windows, supercapacitors, sensors, and so on. This review focuses on the most recent progress in synthesis methods and applications of some thermodynamically stable and metastable vanadium oxides, including but not limited to V₂O₃, V₃O₅, VO₂, V₃O₇, V₂O₅, V₂O₂, V₆O₁₃, and V₄O₉. We begin with a tutorial on the phase diagram of the V-O system. The second part is a detailed review covering the crystal structure, the synthesis protocols, and the applications of each vanadium oxide, especially in batteries, catalysts, smart windows, and supercapacitors. We conclude with a brief perspective on how material and device improvements can address current deficiencies. This comprehensive review could accelerate the development of novel vanadium oxide structures in related applications.

Effect of the Deposition of Vanadium-Oxide on the Photocatalytic Activity of TiO2 Nanotubes and Its Photodiode Performance Interfaced with CH3NH3PbI3 Single Crystal

In this study, we report the influence of vanadium oxide (VO), as a photosensitive component, on the photoactivity of TiO2 nanotubes (TNTs). A series of TNTs of varying tube diameter were synthesized by the anodization of titanium foils at different voltages, while vanadium oxide was deposited on TNTs by wet chemical deposition. An improvement in the optical properties of nanotubes was observed after the deposition of vanadium oxide. An improvement in the optical properties (redshift in UV-Vis spectra) of TNTs and TNT/VO was noted. The photocatalytic activity was improved with increasing tube diameter, while it was weakened after the deposition of VO. Furthermore, photoactivity was investigated in photodiodes based on TNTs or TNT/VO and single crystals of CH3NH3PbI3. The photoelectric measurement revealed that different TNT diameters did not influence the I-V characteristic of the photodiodes, while the deposition of VO improved the photocurrent for smaller TNTs.

Effect of Biogenic Silica Behavior in the Incorporation of Mesoporous Anatase TiO2 for Excellent Photocatalytic Mineralization of Sodium Diclofenac

TiO2/SiO2 composites were synthesized via a simple sol gel method by surface reduction of Ti4+ ions to Ti3+ using titanium isopropoxide as a TiO2 precursor and rice husks (RHA) as a SiO2 source. The silica content and calcination temperature of the materials were evaluated. Thermal, crystallographic and physicochemical aspects suggest that biogenic silica (SiO2) can improve the thermal stability of the anatase phase of TiO2, when the SiO2 content reaches 20%. The N2 adsorption-desorption isotherms showed that the SiO2-modified samples have uniform pore diameters and a large specific surface area. The XPS analysis showed the surface reduction of Ti4+ ions to Ti3+ within the TiO2 network via oxygen vacancies after SiO2 introduction, which is beneficial for the photocatalytic reaction. Photocatalytic degradation of sodium diclofenac (SDFC) shows that TiO2/SiO2 composites have better activity compared to commercial P25. Mesoporous TiO2 composite modified with 20 wt% SiO2 showed better photocatalytic mineralization than P25 (83.7% after 2 h instead of 57.3% for P25). The excellent photocatalytic mineralization of the photocatalysts can be attributed to the high anatase crystallinity exhibited by XRD analysis, high specific surface area, surface hydroxyl groups, and the creation of oxygen vacancy, as well as the presence of Ti3+ ions.

Improved visible-light-driven photocatalytic removal of Bisphenol A using V2O5/WO3 decorated over Zeolite: Degradation mechanism and toxicity

WO₃/Zeolite/V₂O₅ (TZV) composite synthesized through co-precipitation was used for the degradation of Bisphenol-A (BpA). XRD and Raman spectra were employed to ascertain the crystallinity of the composite. The pristine nature of the compound without any free particles over the zeolite surface was established through FESEM, thus, substantiating the composite character of the material. The enhancement in activity after doping with WO₃ was ascertained by DRS-UV. Photocatalytic degradation studies clearly established the superiority of TZV 10 over bare V₂O₅. Complete BpA degradation (100%) was attained at 50 min of incubation with 0.75 g/L TZV-10 in acidic medium (pH 3) for an initial BpA concentration of 100 mg/L. HPLC-MS/MS analysis was used to decipher the degradation pathway. The catalyst was stable even after 9 cycles. Phytotoxicity studies and lake water treatment results proved the environmental efficiency of the synthesized material.

Atomic Layer Deposition of Metal Oxides and Chalcogenides for High Performance Transistors

Atomic layer deposition (ALD) is a deposition technique well-suited to produce high-quality thin film materials at the nanoscale for applications in transistors. This review comprehensively describes the latest developments in ALD of metal oxides (MOs) and chalcogenides with tunable bandgaps, compositions, and nanostructures for the fabrication of high-performance field-effect transistors. By ALD various n-type and p-type MOs, including binary and multinary semiconductors, can be deposited and applied as channel materials, transparent electrodes, or electrode interlayers for improving charge-transport and switching properties of transistors. On the other hand, MO insulators by ALD are applied as dielectrics or protecting/encapsulating layers for enhancing device performance and stability. Metal chalcogenide semiconductors and their heterostructures made by ALD have shown great promise as novel building blocks to fabricate single channel or heterojunction materials in transistors. By correlating the device performance to the structural and chemical properties of the ALD materials, clear structure-property relations can be proposed, which can help to design better-performing transistors. Finally, a brief concluding remark on these ALD materials and devices is presented, with insights into upcoming opportunities and challenges for future electronics and integrated applications.

Honeycomb-like V2O5 Based Films: Synthesis, Structural, Thermal, and Optical Properties for Environmental Applications

In the present study, new composite films consisting of hierarchical nanobelt V2O5 and polymer mixture were prepared via a simple casting method. The incorporation of 30 wt.% of V2O5 into the polymer matrix yielded a honeycomb like structure with abundant micro-voids (5.5 μm), higher roughness average by 45.8%, and a higher root mean square roughness by 52%, which are beneficial for the enhancement of active surface area for dye adsorption. Furthermore, optical property studies have shown that the incorporation of V2O5 has made the nanocomposite film a suitable UV–visible light-sensitive material, and thus the application of films can be expanded towards photocatalytic degradation of various toxic pollutants such as nitrophenol, Cr(VI), antibiotects, and so on. Finally, the composite film exhibited enhanced thermostability in comparison to unmodified film, as confirmed by TGA and DSC analysis. The optimal film showed 96.3% removal efficiency and 27.02 mg/g adsorption capacity. The dye sorption performance of V2O5 based films is studied at various times, dosages, and initial dye concentrations. The experimental data more closely fit the Langmuir isotherm model (R2 = 0.997) than the Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, demonstrating a monolayer adsorption mechanism. The MB adsorption process on V2O5 film was controlled by the chemical adsorption step, which was evidenced by the good-fitting of kinetic adsorption results to the pseudo second order model (R2 = 0.991). The obtained results indicated that the V2O5 based films in this work are hopeful candidates for environmental applications.

Photoelectrochemical detection of microRNAs based on target-triggered self-assembly of energy band position-matched CdS QDs and C3N4 nanosheets

An ultrasensitive photochemical biosensor based on the target miRNA-triggered catalytic hairpin assembly (CHA) reaction between Au nanoparticles (AuNPs)/C₃N₄ nanosheets and CdS quantum dots (QDs) was developed for the determination of miRNAs. Firstly, AuNPs/C₃N₄ nanosheets were immobilized onto a working glassy carbon electrode. Then, the hairpin probe 1 (H1) was loaded through Au-S bonding. Afterward, the unbound sites were blocked with 6-mercaptohexanol to avoid nonspecific adsorption. In the presence of the target miRNA, the CHA reaction between the H1 and hairpin probe 2-CdS QDs (H2-CdS QDs) could be triggered. As a result, the AuNPs/C₃N₄ nanosheet and CdS QDs were linked by the double helix structure H1-H2. Unlike the other CHA reactions, H2 used in this work is longer than H1 so that the AuNPs/C₃N₄ nanosheets could touch the CdS QDs. Given the matched energy band positions between the C₃N₄ nanosheet and CdS QDs, a strong photocurrent could be obtained after the CHA reaction was triggered by the target miRNA. In addition, p-type C₃N₄ nanosheets and n-type CdS QDs presented reduction photocurrents and oxidation photocurrents, respectively. Therefore, the photocurrents were vectors in this design that can eliminate the interference of nonspecific adsorption and avoid the generation of false-positive signals. Under the optimal conditions, the limit of detection was 92 aM. The constructed photoelectrochemical biosensor showed good reproducibility and selectivity in the analysis of serum samples, which indicates its great prospects in disease diagnostics and bioanalysis.

Porous V2O5/TiO2 Nanoheterostructure Films with Enhanced Visible-Light Photocatalytic Performance Prepared by the Sparking Method

Porous V2O5/TiO2 nanoheterostructure films with different atomic ratios of Ti/V (4:1, 2:1, 1:1, and 1:2) were synthesized by a sparking method for the first time. The sparking method, which is a simple and cost-effective process, can synthesize highly porous and composite films in one step. Field-emission scanning electron microscope (FE-SEM) images revealed the porosity morphology of all prepared samples. V2O5/TiO2 nanoheterostructure films were confirmed by Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The secondary particle size and band gap of the samples were highly correlated to the V2O5 proportion, resulting in enhanced visible-light absorbance. V2O5/TiO2 nanoheterostructure films at an atomic ratio of 1:1 showed the highest photocatalytic performance, which improved the degradation rate up to 24% compared to pure TiO2 film. It is believed that the formed nanoheterostructure and greater portion of V4+ ions are reflected by this ratio.

CdS Quantum-Dots-Decorated V2O5 Nanosheets as Chemically Etchable Active Materials for Sensitive Photoelectrochemical Immunoassay of Carcinoembryonic Antigen

We report here CdS quantum-dots (QDs)-decorated V₂O₅ nanosheets as high-performance and chemically etchable photoelectric active materials for constructing a photoelectrochemical (PEC) immunoassay platform. CdS QDs-decorated V₂O₅ nanosheets as new photoelectric materials can show superior photocurrent to V₂O₅ nanosheets and CdS QDs under visible-light irradiation because of the promoted photogenerated electron-hole separation and the increased visible-light absorption. V₂O₅ nanosheets can be etched by ascorbic acid (AA) because of the reduction of V₂O₅ to V⁴⁺, and the photocurrent of CdS/V₂O₅-nanocomposite-modified indium tin oxide electrode decreases significantly after being etched by AA. Inspired by this phenomenon, a PEC immunoassay platform is constructed for carcinoembryonic antigen (CEA) detection by using CdS/V₂O₅ nanocomposite as the photoelectric material and AA-encapsulated liposome immunonanocapsules as labels. The linear detection range for detecting CEA is from 0.5 pg mL^-1 to 1 ng mL^-1, with a limit of detection of 0.1 pg mL^-1. The proposed method also shows good selectivity, excellent reproducibility, and satisfactory recovery in detection of CEA in human serum samples. We believe that this work will lay the foundation for the future development of V₂O₅-based materials for PEC analysis, and also provide a reasonable design and implementation for the development of PEC immunoassay.

Fabrication of spent FCC catalyst composites by loaded V2O5 and TiO2 and their comparative photocatalytic activities

The spent fluid catalytic cracking catalyst (FCC) has been loaded with different content of V₂O₅ and TiO₂ through a modified-impregnation method. X-ray Diffraction (XRD), ultraviolet-visible spectrophotometry (UV-Vis), Scanning Electron Microscope (SEM), and Fourier Transform Infrared spectroscopy (FT-IR) are used to characterize the structure and morphology of these samples. Their photocatalytic activity was evaluated by degradation of methylene blue (MB) solution under 300 W Xenon lamp irradiation. The interplanar spacing of the zeolite Y (111) plane is affected by the amount of the loaded V₂O₅ on spent FCC catalyst. The (111) plane of spent FCC catalyst loaded with V₂O₅ and TiO₂ sample is 1.404 nm, which is higher than that of the zeolite Y (1.395 nm). The amount of adsorption of MB and the photocatalytic activity for the degradation increased with increasing the interplanar spacing of the (111) plane of sample. We fabricated of spent FCC catalyst composites by loaded V₂O₅ and TiO₂, which effectively solved the spent FCC catalyst disposal problem. The efficiency of the developed sample provides a potentially economical way of degrading MB.

Titanium-based nanocomposite materials for arsenic removal from water: A review

Arsenic is highly carcinogenic element and less concentration of this chemical element makes natural water unsafe for human consumption. Versatile techniques including adsorption method have been established to remove the arsenic from water. However, adsorption is found to be one of effective method for the remediation of arsenic from contaminated water. Different types of natural adsorbents i.e. clays, waste materials, carbon based material have been studied widely for the adsorption of arsenic. Recently, nanotechnology is considered to be one of the best technology for waste water treatment. Therefore researchers have synthesized several types of nanoadsorbents and investigated them for the removal of various pollutants including arsenic from water. Now days, attention is paid on development of nanocomposite materials which are proven as competent arsenic adsorbent candidate as compared to other adsorbents due to dominant structural and surface features. Various metal/metal oxide based nanocomposites have been developed and studied for arsenic removal from aqueous media. It has been reported that TiO₂ based nanocomposite exhibit stong affinity for both inorganic form of arsenic. Therefore, in this review numerous metal or metal oxide based titania nanocomposites i.e. TiO₂-αFe₂O₃, NHITO, Ce-Ti oxide, Zr-TiO_2, RGO-MFT etc. have been discussed in details for the water treatment containing arsenic. This review also presents an overview of low cost adsorbents, titania based nanoadsorbent and hybrid titania nanostructures for the removal of arsenic. In this review paper the particle size, surface area and adsorption efficiency of these titania based materials at different pH are also been presented in tabulated form. It provides the opportunity to choose best titania based nanocomposites for the treatment of arsenic polluted water.

Synthesis of oxy-sulfide based nanocomposite catalyst for visible light-driven reduction of Cr(VI)

The oxy-sulfide based V₂O₅@(In,Ga)₂(O,S)₃ nanocomposite catalyst, at different weight percentages of V₂O₅, was successfully synthesized via a simplistic procedural route for the detoxification of hazardous Cr(VI). The two pure catalysts were intimately allied and used for visible light-driven reduction of hazardous Cr(VI). The nanocomposite catalysts were characterized to observe the effects of V₂O₅ on crystal phase, morphology, light absorption, catalytic activity, and electrical properties. Compared to all, 40% V₂O₅ loaded nanocomposite catalyst, designated as VOS-2, exhibited the best-reducing capability. It completely reduced toxic Cr(VI) at 2 min under visible light illumination. From the kinetics, it was found that the rate constant of the nanocomposite catalyst was improved by a factor of 3.6 compared to the host nanoflower catalyst. The plausible mechanism of charge transfer process across the interfacial region indicates the diminished recombination probability of photogenerated charge carriers. Therefore, the nanocomposite catalyst is promising for enhanced reduction of Cr(VI) in the Cr-based industrial activities, which is significantly relevant for environmental remediation.

V2O5/TiO2 and V2O5/TiO2–SO42− catalysts for the total oxidation of chlorobenzene: one-step sol–gel preparation vs. two-step impregnation

This paper examines the effect of the preparation method of sulfated and unsulfated V₂O₅/TiO₂ catalysts on chlorobenzene total oxidation.

Synthesis and trimethylamine sensing properties of spherical V2O5 hierarchical structures

Spherical V₂O₅ hierarchical structures assembled from nanosheets exhibit rapid response/recovery speeds to TMA gas.

TiO₂-Based Nanoheterostructures for Promoting Gas Sensitivity Performance: Designs, Developments, and Prospects

Gas sensors based on titanium dioxide (TiO₂) have attracted much public attention during the past decades due to their excellent potential for applications in environmental pollution remediation, transportation industries, personal safety, biology, and medicine. Numerous efforts have therefore been devoted to improving the sensing performance of TiO₂. In those effects, the construct of nanoheterostructures is a promising tactic in gas sensing modification, which shows superior sensing performance to that of the single component-based sensors. In this review, we briefly summarize and highlight the development of TiO₂-based heterostructure gas sensing materials with diverse models, including semiconductor/semiconductor nanoheterostructures, noble metal/semiconductor nanoheterostructures, carbon-group-materials/semiconductor nano- heterostructures, and organic/inorganic nanoheterostructures, which have been investigated for effective enhancement of gas sensing properties through the increase of sensitivity, selectivity, and stability, decrease of optimal work temperature and response/recovery time, and minimization of detectable levels.

Advances in Photocatalytic CO₂ Reduction with Water: A Review

In recent years, the increasing level of CO₂ in the atmosphere has not only contributed to global warming but has also triggered considerable interest in photocatalytic reduction of CO₂. The reduction of CO₂ with H₂O using sunlight is an innovative way to solve the current growing environmental challenges. This paper reviews the basic principles of photocatalysis and photocatalytic CO₂ reduction, discusses the measures of the photocatalytic efficiency and summarizes current advances in the exploration of this technology using different types of semiconductor photocatalysts, such as TiO₂ and modified TiO₂, layered-perovskite Ag/ALa₄Ti₄O₁₅ (A = Ca, Ba, Sr), ferroelectric LiNbO₃, and plasmonic photocatalysts. Visible light harvesting, novel plasmonic photocatalysts offer potential solutions for some of the main drawbacks in this reduction process. Effective plasmonic photocatalysts that have shown reduction activities towards CO₂ with H₂O are highlighted here. Although this technology is still at an embryonic stage, further studies with standard theoretical and comprehensive format are suggested to develop photocatalysts with high production rates and selectivity. Based on the collected results, the immense prospects and opportunities that exist in this technique are also reviewed here.

Growth, Structure, and Photocatalytic Properties of Hierarchical V₂O₅-TiO₂ Nanotube Arrays Obtained from the One-step Anodic Oxidation of Ti-V Alloys

V₂O₅-TiO₂ mixed oxide nanotube (NT) layers were successfully prepared via the one-step anodization of Ti-V alloys. The obtained samples were characterized by scanning electron microscopy (SEM), UV-Vis absorption, photoluminescence spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), and micro-Raman spectroscopy. The effect of the applied voltage (30-50 V), vanadium content (5-15 wt %) in the alloy, and water content (2-10 vol %) in an ethylene glycol-based electrolyte was studied systematically to determine their influence on the morphology, and for the first-time, on the photocatalytic properties of these nanomaterials. The morphology of the samples varied from sponge-like to highly-organized nanotubular structures. The vanadium content in the alloy was found to have the highest influence on the morphology and the sample with the lowest vanadium content (5 wt %) exhibited the best auto-alignment and self-organization (length = 1 μm, diameter = 86 nm and wall thickness = 11 nm). Additionally, a probable growth mechanism of V₂O₅-TiO₂ nanotubes (NTs) over the Ti-V alloys was presented. Toluene, in the gas phase, was effectively removed through photodegradation under visible light (LEDs, λmax = 465 nm) in the presence of the modified TiO₂ nanostructures. The highest degradation value was 35% after 60 min of irradiation. V₂O₅ species were ascribed as the main structures responsible for the generation of photoactive e- and h⁺ under Vis light and a possible excitation mechanism was proposed.

Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species

SnO₂ nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO₂ nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO₂ nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO₂ cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V₂O₅-like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10^-7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO₂ materials reported until now.

A novel ethanol gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures

Much greater surface-to-volume ratio of hierarchical nanostructures renders them attract considerable interest as prototypical gas sensors. In this work, a novel resistive gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures is fabricated by a facile one-step synthetic process and the ethanol sensing performance of this device is characterized systematically, which shows faster response/recovery behavior, better selectivity, and higher sensitivity of about 9 times as compared to the pure TiO2 nanofibers. The enhanced sensitivity of the TiO2/Ag0.35V2O5 branched nanoheterostructures should be attributed to the extraordinary branched hierarchical structures and TiO2/Ag0.35V2O5 heterojunctions, which can eventually result in an obvious change of resistance upon ethanol exposure. This study not only indicates the gas sensing mechanism for performance enhancement of branched nanoheterostructures, but also proposes a rational approach to design nanostructure based chemical sensors with desirable performance.

Mapping polaronic states and lithiation gradients in individual V2O5 nanowires

The rapid insertion and extraction of Li ions from a cathode material is imperative for the functioning of a Li-ion battery. In many cathode materials such as LiCoO2, lithiation proceeds through solid-solution formation, whereas in other materials such as LiFePO4 lithiation/delithiation is accompanied by a phase transition between Li-rich and Li-poor phases. We demonstrate using scanning transmission X-ray microscopy (STXM) that in individual nanowires of layered V2O5, lithiation gradients observed on Li-ion intercalation arise from electron localization and local structural polarization. Electrons localized on the V2O5 framework couple to local structural distortions, giving rise to small polarons that serves as a bottleneck for further Li-ion insertion. The stabilization of this polaron impedes equilibration of charge density across the nanowire and gives rise to distinctive domains. The enhancement in charge/discharge rates for this material on nanostructuring can be attributed to circumventing challenges with charge transport from polaron formation.

Synthesis of V2O5@TiO2 core–shell hybrid composites for sunlight degradation of methylene blue

We have demonstrated a simple but efficient synthesis route to obtain V₂O₅@TiO₂ core–shell nanostructures under mild conditions (≤100 °C in water).

Rod-in-tube nanostructure of MgFe2O4: electrospinning synthesis and photocatalytic activities of tetracycline

The special structure of MgFe₂O₄ has better photocatalytic performance and better stability.

Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts

V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.

Nanostructuring of a GNS-V2O5–TiO2 core–shell photocatalyst for water remediation applications under sun-light irradiation

The GNS-V₂O₅–TiO₂ composite, as a new class of nanoarchitecture, has been successfully fabricated by a facile hydrothermal process followed by a sol–gel technique.

Synthesis of Au-decorated V2O5@ZnO heteronanostructures and enhanced plasmonic photocatalytic activity

A ternary plasmonic photocatalyst consisting of Au-decorated V2O5@ZnO heteronanorods was successfully fabricated by an innovative four-step process: thermal evaporation of ZnO powders, CVD of intermediate on ZnO, solution deposition of Au NPs, and final thermal oxidization. SEM, TEM, EDX, XPS, and XRD analyses revealed that the interior cores and exterior shells of the as-prepared heteronanorods were single-crystal wurtzite-type ZnO and polycrystalline orthorhombic V2O5, respectively, with a large quantity of Au NPs inlaid in the V2O5 shell. The optical properties of the ternary photocatalyst were investigated in detail and compared with those of bare ZnO and V2O5@ZnO. UV-vis absorption spectra of ZnO, V2O5@ZnO, and Au-decorated V2O5@ZnO showed gradually enhanced absorption in the visible region. In addition, gradually decreased emission intensity was also observed in the photoluminescence (PL) spectra, revealing enhanced charge separation efficiency. Because of these excellent qualities, the photocatalytic behavior of the ternary photocatalyst was studied in the photodegradation of methylene blue under UV-vis irradiation, which showed an enhanced photodegradation rate nearly 7 times higher than that of bare ZnO and nearly 3 times higher than that of V2O5@ZnO, mainly owing to the enlarged light absorption region, the effective electron-hole separation at the V2O5-ZnO and V2O5-Au interfaces, and strong localization of plasmonic near-field effects.

Ag2O/TiO2/V2O5 one-dimensional nanoheterostructures for superior solar light photocatalytic activity

Titanium dioxide has attracted considerable interest as a prototypical semiconductor photocatalyst. However, because of the relative large bandgap energy, further application of TiO2 photocatalyst is limited by its inefficient solar energy conversion. Various attempts have been made to broaden the light absorption window of the TiO2, such as growth of TiO2-based heterostructures. Herein, a novel three-component system, Ag2O/TiO2/V2O5 one-dimensional nanoheterostructures with enhanced solar light absorption, is prepared by depositing Ag2O nanoparticles onto the surface of TiO2/V2O5 nanofibers through a two-step synthetic process. This three-component system exhibits excellent solar-driven photocatalytic activity, far exceeding those of the single- and two-component systems, as a result of extended solar light absorption and efficient electron-hole separation. Furthermore, the photocatalytic performance of Ag2O/TiO2/V2O5 one-dimensional nanoheterostructures is very stable for recycling use.

BiFeO3/TiO2 nanotube arrays composite electrode: construction, characterization, and enhanced photoelectrochemical properties

This work aims at the exploration of nanostructured ferroelectric-material-modified semiconductor electrodes for enhanced photo-induced activity. A well-aligned BiFeO3/TiO2-nanotubes (NTs) array with visible-light activity was successfully synthesized on a titanium sheet by combining anodization and an ultrasonic-immersion method followed by annealing. The structural and optical properties of the TiO2-NTs and the composite BiFeO3/TiO2-NTs were comparatively characterized. The composite BiFeO3/TiO2-NTs grown on a Ti sheet and used as an electrode exhibited a stronger absorption in the visible region and a much higher photoconversion efficiency than the pure TiO2-NTs/Ti electrode. Electrochemical impedance investigation attested to a significant improvement of the interfacial electron-transfer kinetics with enhanced separation of electron-hole pairs. The as-prepared composite electrode showed a high efficiency for photoelectrocatalytic degradation towards rhodamine B under visible-light irradiation (λ > 400 nm). The enhanced photoelectrocatalytic activity of the composite electrode could be attributed to the synergistic effect between the lowered electron-hole recombination rate by the applied bias and the wider spectral response promoted by the BiFeO3 component.

Synthesis of tunable ZnS–CuS microspheres and visible-light photoactivity for rhodamine B

The heterostructure of obtained ZnS–CuS can timely transfer and separate photogenerated electrons and holes, which enhances their photocatalytic abilities.

Catalytic oxidation of acetone over CuCeOx nanofibers prepared by an electrospinning method

A series of CuCeO_x nanofiber catalysts with excellent performance toward acetone oxidation were prepared by an electrospinning method.

Review on modified N–TiO2 for green energy applications under UV/visible light: selected results and reaction mechanisms

Modifications of the activity, band structure, morphology, optical and electronic properties of N–TiO₂ for energy and environmental applications.

Visible light driven type II heterostructures and their enhanced photocatalysis properties: a review

Considerable efforts have been devoted to enhancing the photocatalytic activity and solar energy utilization of photocatalysts. The fabrication of type II heterostructures plays an important role in photocatalysts modification and has been extensively studied. In this review, we briefly trace the application of type II heterostructured semiconductors in the area of environmental remediation and water splitting, summarize major fabrication methods, describe some of the progress and resulting achievements, and discuss the future prospects. The scope of this review covers a variety of type II heterostructures, focusing particularly on TiO2 and ZnO based visible light driven type II 0D and 1D heterostructured photocatalysts. Some other low dimensional nanomaterials which have shown high-performance photocatalysis are also presented. We expect this review to provide a guideline for readers to gain a clear picture of fabrication and application of type II heterostructures.