Facile one-step synthesis of TiO2/Ag/SnO2 ternary heterostructures with enhanced visible light photocatalytic activity

Harnessing the synergistic potential of TiO2-CuSe composites for enhanced photocatalytic and antibacterial activities

With growing environmental concerns, the removal of toxic industrial dyes from wastewater has become a critical global issue. In this study, TiO2-CuSe composites were synthesized using a cost-effective and simple chemical method to determine the optimal concentration of CuSe for the efficient degradation of methylene blue (MB) under visible light. The TiO2 samples exhibited a mix of rutile and anatase phases, while CuSe formed in a hexagonal phase. Both TiO2 and CuSe were observed to have agglomerated particles with indistinct boundaries. The optical bandgap shifted towards the visible region from 3.25 eV (pure TiO2) to 2.91 eV with increasing the amount of CuSe in the composites. The photocatalytic activity of TiO2, CuSe, and TiO2-CuSe composites was evaluated by monitoring MB degradation, with the composites outperforming the individual components under visible light. Notably, the TiO2-20% CuSe composite (AK-4) demonstrated superior efficiency, removing 98% of MB in just 70 minutes. The photocatalysts also exhibited enhanced antibacterial properties, effectively reducing E. coli colonies from 1.71 × 1012 CFU mL-1 (pure TiO2) to 1 × 1010 CFU mL-1 for the AK-4 composite. This study suggests that visible light-activated TiO2-CuSe composites could be effective for both water purification and bacterial infection control.

A Novel Recyclable Magnetic Nano-Catalyst for Fenton-Photodegradation of Methyl Orange and Imidazole Derivatives Catalytic Synthesis

A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe3O4) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe3O4) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe3O4) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91-97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis.

Design, spectral characterization, quantum chemical investigation, biological activity of nano-sized transition metal complexes of tridentate 3-mercapto-4H-1,2,4-triazol-4-yl-aminomethylphenol Schiff base ligand

A tridentate Schiff base ligand, H2MTIP, was produced by condensing salicylaldehyde with 4-amino-4H-1,2,4-triazole-3-thiol. The ligand was then used to create nanosized complexes of Pt(II), Ni(II), Cu(II), and Pd(II). The complexes have the composition [Pt/Ni/Cu/or Pd(MTIP)(H2O)], this conclusion is supported by molar conductance, magnetic moments, elemental analyses, spectral analyses. In DFT analysis, the 6-31+ g(d,p) basis set was used to fully optimize the energy with respect to the shapes of Schiff base ligand and metal complexes. Pt(II), Ni(II), Cu(II), and Pd(II) complexes have been assigned square-planar geometries. At the same time, the intense diffraction peaks in X-ray diffractograms show their crystalline features with particle sizes in the nanoscale range. The binding interaction of calf thymus DNA with these metal complexes and their insulin-like activity was examined in vitro by inhibiting α-amylase. The study investigated the in-vitro activity of several complexes and identified Pt(II) complex as the one with the highest activity. The researchers then tested this complex for in-vivo antidiabetic activity in induced diabetic rats using the STZ model, and it significantly lowered blood glucose levels. The antioxidant activity and toxicity level of Pt(II) complex were also excellent, suggesting that it could be a good candidate for further research as a possible diabetes drug.Communicated by Ramaswamy H. Sarma.

Effects of Lanthanum Substitution and Annealing on Structural, Morphologic, and Photocatalytic Properties of Nickel Ferrite

Nanoparticles of NiLaxFe2-xO4 ferrite spinel incorporated in a SiO2 matrix were synthesized via a sol-gel method, followed by annealing at 200, 500, and 800 °C. The resulting materials were characterized via XRD, AFM, and BET techniques and evaluated for photocatalytic activity. The XRD diffractograms validate the formation of a single-phase cubic spinel structure at all temperatures, without any evidence of secondary peaks. The size of crystallites exhibited a decrease from 37 to 26 nm with the substitution of Fe3+ with La3+ ions. The lattice parameters and crystallite sizes were found to increase with the rise in La3+ content and annealing temperature. Isotherms were employed to calculate the rate constants for the decomposition of malonate precursors to ferrites and the activation energy for each ferrite. All nanocomposites have pores within the mesoporous range, with a narrow dispersion of pore sizes. The impact of La content on sonophotocatalytic activity was evaluated by studying Rhodamine B degradation under visible light irradiation. The results indicate that the introduction of La enhances nanocomposite performance. The prepared Ni-La ferrites may have potential application for water decontamination.

Electrospun silk nanofiber loaded with Ag-doped TiO2 with high-reactive facet as multifunctional air filter

Particulate matter (PM) and volatile organic compounds (VOCs) are air pollution that can cause high risk to public health. To protect individuals from air pollution exposure, fibrous filters have been widely employed. In this work, we develop silk nanofibers, which are loaded with Ag-doped TiO2 nanoparticles with exposed (001) (assigned as Ag-TiO2-silk), via electrospinning method and utilized them as multifunctional air filters that can efficiently reduce PM2.5, organic pollutants and microbials. The results showed that Ag-TiO2-silk with a loading of 1 wt% (1%Ag-TiO2-silk) exhibited the best performance among various different Ag-doped samples, as it performed the best as an air filter, which had the highest PM2.5 removal efficiency of 99.04 ± 1.70% with low pressure drop of 34.3 Pa, and also exhibited the highest photodegradation efficiency of formaldehyde. In addition, the Ag-TiO2-silk demonstrated antibacterial activity. These properties make silk composite nanofibers attractive for multifunctional and environmentally-friendly air filter application.

Effect of Ag modification on TiO2 and melem/g-C3N4 composite on photocatalytic performances

Here, the comparison of two different semiconductor materials is demonstrated, TiO₂ and melem/g-C₃N₄ composites-modified with balls of approximately 5 nm Ag nanoparticles (NPs) as photocatalysts for the degradation of the model dye acid orange 7 (AO7). The melem molecule synthesized here is one of a series of organic compounds consisting of triazine ring compounds with a structure similar to that of melam and melamine. The photodegradation process of AO7 was carried out to examine all powder materials as a potential photocatalyst. Additionally, two different lamps of wavelengths 368 nm (UV light) and 420 nm (VIS light) were applied to compare the photodegradation tests. A new synthesis route for the acquisition of Ag NPs (Ag content 0.5, 1.0 and 2.5 wt%), based on a wet and low temperature method without the use of reducing reagents was proposed. The best photocatalytic performances under UV and VIS light were obtained for both, TiO₂ and melem/g-C₃N₄ materials (new synthesis route) modified with a very low Ag content-0.5 wt%. The photodegradation activities using UV lamp (3 h, 368 nm irradiation) for samples with 0.5 wt% of Ag: TiO₂ and melem/g-C₃N₄, in excess of 95 and 94%, respectively, were achieved. The highest photoactive materials melem/g-C₃N₄ with 0.5 and 1 wt% Ag revealed 98% of activity under the VIS lamp after 3 h long irradiation. Our work demonstrates a novel, environmentally acceptable, and cost-effective chemical strategy for preparation of photocatalysts suitable for degradation of organic contaminants in wastewater treatment.

Microwave Synthesis of Visible-Light-Activated g-C3N4/TiO2 Photocatalysts

The preparation of visible-light-driven photocatalysts has become highly appealing for environmental remediation through simple, fast and green chemical methods. The current study reports the synthesis and characterization of graphitic carbon nitride/titanium dioxide (g-C₃N₄/TiO₂) heterostructures through a fast (1 h) and simple microwave-assisted approach. Different g-C₃N₄ amounts mixed with TiO₂ (15, 30 and 45 wt. %) were investigated for the photocatalytic degradation of a recalcitrant azo dye (methyl orange (MO)) under solar simulating light. X-ray diffraction (XRD) revealed the anatase TiO₂ phase for the pure material and all heterostructures produced. Scanning electron microscopy (SEM) showed that by increasing the amount of g-C₃N₄ in the synthesis, large TiO₂ aggregates composed of irregularly shaped particles were disintegrated and resulted in smaller ones, composing a film that covered the g-C₃N₄ nanosheets. Scanning transmission electron microscopy (STEM) analyses confirmed the existence of an effective interface between a g-C₃N₄ nanosheet and a TiO₂ nanocrystal. X-ray photoelectron spectroscopy (XPS) evidenced no chemical alterations to both g-C₃N₄ and TiO₂ at the heterostructure. The visible-light absorption shift was indicated by the red shift in the absorption onset through the ultraviolet-visible (UV-VIS) absorption spectra. The 30 wt. % of g-C₃N₄/TiO₂ heterostructure showed the best photocatalytic performance, with a MO dye degradation of 85% in 4 h, corresponding to an enhanced efficiency of almost 2 and 10 times greater than that of pure TiO₂ and g-C₃N₄ nanosheets, respectively. Superoxide radical species were found to be the most active radical species in the MO photodegradation process. The creation of a type-II heterostructure is highly suggested due to the negligible participation of hydroxyl radical species in the photodegradation process. The superior photocatalytic activity was attributed to the synergy of g-C₃N₄ and TiO₂ materials.

TiO2/AgO composites by one step photo reduction technique as electron transport layers (ETL) for dye-sensitized solar cells

Dye-sensitized solar cell's electron transport layer is responsible for transporting photo-generated electrons to the outer circuit. Utilizing localized surface plasmon resonance (SPR), light absorption could be enhanced to a greater degree, which can drive dye molecules to excited state more effectively than far-field light. In this work, TiO₂ nanoparticles were prepared by solvothermal method, and Ag nanoparticles were decorated over TiO₂ surface through photodeposition method. XRD data of the TiO₂ sample exhibits anatase phase and in the Ag nanoparticle decorated TiO₂ sample, peaks corresponding to (111) planes of Ag was observed. UV-Vis absorption analysis of the TiO₂ and Ag decorated TiO₂ samples showed absorption in the UV region for the TiO_2, and the SPR effect was detected for the Ag deposited TiO₂ samples. Ag nanoparticles decorated over TiO₂ was observed to be spherical in shape through the images from transmission electron microscope. Presence of both Ag and AgO in the prepared sample was revealed through the data from X-ray photoelectron spectroscopy. The prepared material was used as photoanodes in the construction of the DSSCs, and their performance was evaluated.

Grapefruit Extract-Mediated Fabrication of Photosensitive Aluminum Oxide Nanoparticle and Their Antioxidant and Anti-Inflammatory Potential

Aluminum oxide nanoparticles (Al₂O₃ NPs) were synthesized using a simple, eco-friendly green synthesis approach in an alkaline medium from the extract of grapefruit peel waste. The pre-synthesized, nano-crystalline Al₂O₃ NPs were characterized by using spectroscopic (UV-vis, FTIR, XRD, and EDX) and microscopic (SEM and TEM) techniques. The formed Al₂O₃ NPs exhibited a pronounced absorption peak at 278 nm in the UV-vis spectrum. The average particle size of the as-prepared Al₂O₃ NPs was evaluated to be 57.34 nm, and the atomic percentages of O and Al were found to be 54.58 and 45.54, respectively. The fabricated Al₂O₃ NPs were evaluated for antioxidant, anti-inflammatory, and immunomodulatory properties. The Al₂O₃ NPs showed strong antioxidant potential towards all the four tested assays. The anti-inflammatory and immunomodulatory potential of Al₂O₃ NPs was investigated by measuring the production of nitric oxide and superoxide anion (O₂^•-), as well as proinflammatory cytokines tumour necrosis factor (TNF-α, IL-6) and inhibition of nuclear factor kappa B (NF- κB). The results revealed that Al₂O₃ NPs inhibited the production of O₂^•- (99.4%) at 100 μg mL^-1 concentrations and intracellular NO^•- (55%), proinflammatory cytokines IL-6 (83.3%), and TNF-α (87.9%) at 50 μg mL^-1 concentrations, respectively. Additionally, the Al₂O₃ NPs inhibited 41.8% of nuclear factor kappa B at 20 μg mL^-1 concentrations. Overall, the outcomes of current research studies indicated that Al₂O₃ NPs possess anti-inflammatory and immunomodulatory properties and could be used to treat chronic and acute anti-inflammatory conditions.

Ag Decoration and SnO2 Coupling Modified Anatase/Rutile Mixed Crystal TiO2 Composite Photocatalyst for Enhancement of Photocatalytic Degradation towards Tetracycline Hydrochloride

The anatase/rutile mixed crystal TiO2 was prepared and modified with Ag decoration and SnO2 coupling to construct a Ag@SnO2/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO2 coupling on the structure and photocatalytic properties of TiO2 were studied. Ag decoration and SnO2 coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO2/TiO2 exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO2 increased from 63.3% to 83.1% with Ag@SnO2/TiO2.

Effect of magnetic field on improvement of photocatalytic performance of V2O5/TiO2 nanoheterostructure films prepared by sparking method

Our porous V2O5/TiO2 nanoheterostructure films (with a Ti/V atomic ratio of 1:1) were fabricated via a single-step sparking method using a strong magnetic field (0.5 T) without annealing requirement for the first time. We found that the magnetic flux arrangement has effect on film crystallization, unique morphology, large specific surface area, and surprisingly controllable phase structure of the films. An amorphous TV film was transformed to the TiO2 (anatase/rutile) phase (for TVN) and V2O5-VO2 mixed-phase (for TVH) without destroying the mesopores from an annealing process. Moreover, the TVH sample able to improve the degradation rate up to 270% compared with pre-annealed TV films and up to 30% with post-annealed (400 °C) TVA films. In this paper, the influence of magnetic flux arrangement on structural, morphological, optical, and photocatalytic properties of prepared sample have been investigated and reported.

Core/Shell Ag/SnO2 Nanowires for Visible Light Photocatalysis

This study presents core/shell Ag/SnO2 nanowires (Ag/SnO2NWs) as a new photocatalyst for the rapid degradation of organic compounds by the light from the visible range. AgNWs after coating with a SnO2 shell change optical properties and, due to red shift of the absorbance maxima of the longitudinal and transverse surface plasmon resonance (SPR), modes can be excited by the light from the visible light region. Rhodamine B and malachite green were respectively selected as a model organic dye and toxic one that are present in the environment to study the photodegradation process with a novel one-dimensional metal/semiconductor Ag/SnO2NWs photocatalyst. The degradation was investigated by studying time-dependent UV/Vis absorption of the dye solution, which showed a fast degradation process due to the presence of Ag/SnO2NWs photocatalyst. The rhodamine B and malachite green degraded after 90 and 40 min, respectively, under irradiation at the wavelength of 450 nm. The efficient photocatalytic process is attributed to two phenomenon surface plasmon resonance effects of AgNWs, which allowed light absorption from the visible range, and charge separations on the Ag core and SnO2 shell interface of the nanowires which prevents recombination of photogenerated electron-hole pairs. The presented properties of Ag/SnO2NWs can be used for designing efficient and fast photodegradation systems to remove organic pollutants under solar light without applying any external sources of irradiation.

Carbon Dot-Doped Titanium Dioxide Sheets for the Efficient Photocatalytic Performance of Refractory Pollutants

Broad solar light harvesting and fast photoinduced electron-hole migration are two critical factors for the catalytic capacity of photocatalytic system. In this study, novel visible light-driven carbon dot-TiO₂ nanosheet (CD-TN) photocatalysts are successfully prepared by loading CDs on the surface of TNs through the hydrothermal method. The microstructure, chemical components, and optical properties of the prepared samples are characterized via X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy analysis. Congo red (CR), rhodamine B (RhB), and tetracycline (TC) are selected as pollutants to assess the catalytic performance of CD-TNs. As expected, the removal efficiencies of CD-TNs for CR, RhB, and TC are 94.6% (120 min), 97.2% (150 min), and 96.1% (60 min), respectively, obviously higher than that of pure TNs. The enhanced degradation efficiency of CD-TNs is predominantly ascribed to the merits of CDs (excellent up-conversion property and electron transfer property). Moreover, according to the several degradation cycles, CD-TNs possess the excellent stability, having removed 93.3% of CR after 120 min irradiation.

Highly Porous SnO2/TiO2 Heterojunction Thin-Film Photocatalyst Using Gas-Flow Thermal Evaporation and Atomic Layer Deposition

Highly porous heterojunction films of SnO2/TiO2 were prepared using gas-flow thermal evaporation followed by atomic layer deposition (ALD). Highly porous SnO2 was fabricated by introducing an inert gas, Ar, during thermal evaporation. To build heterogeneous structures, the TiO2 layers were conformally deposited on porous SnO2 with a range of 10 to 100 cycles by means of ALD. The photocatalytic properties for different TiO2 thicknesses on the porous SnO2 were compared using the degradation of methylene blue (MB) under UV irradiation. The comparisons showed that the SnO2/TiO2-50 heterostructures had the highest photocatalytic efficiency. It removed 99% of the MB concentration, and the decomposition rate constant (K) was 0.013 min−1, which was approximately ten times that of the porous SnO2. On the other hand, SnO2/TiO2-100 exhibited a lower photocatalytic efficiency despite having a TiO2 layer thicker than SnO2/TiO2-50. After 100 cycles of TiO2 ALD deposition, the structure was transferred from the heterojunction to the core–sell structure covered with TiO2 on the porous SnO2, which was confirmed by TEM analysis. Since the electrons photogenerated by light irradiation were separated into SnO2 and produced reactive oxygen, O2−, the heterojunction structure, in which SnO2 was exposed to the surface, contributed to the high performance of the photocatalyst.

Straightforward Synthesis of Mn3O4/ZnO/Eu2O3-Based Ternary Heterostructure Nano-Photocatalyst and Its Application for the Photodegradation of Methyl Orange and Methylene Blue Dyes

Zinc oxide-ternary heterostructure Mn₃O₄/ZnO/Eu₂O₃ nanocomposites were successfully prepared via waste curd as fuel by a facile one-pot combustion procedure. The fabricated heterostructures were characterized utilizing XRD, UV-Visible, FT-IR, FE-SEM, HRTEM and EDX analysis. The photocatalytic degradation efficacy of the synthesized ternary nanocomposite was evaluated utilizing model organic pollutants of methylene blue (MB) and methyl orange (MO) in water as examples of cationic dyes and anionic dyes, respectively, under natural solar irradiation. The effect of various experimental factors, viz. the effect of a light source, catalyst dosage, irradiation time, pH of dye solution and dye concentration on the photodegradation activity, was systematically studied. The ternary Mn₃O₄/ZnO/Eu₂O₃ photocatalyst exhibited excellent MB and MO degradation activity of 98% and 96%, respectively, at 150 min under natural sunlight irradiation. Experiments further conclude that the fabricated nanocomposite exhibits pH-dependent photocatalytic efficacy, and for best results, concentrations of dye and catalysts have to be maintained in a specific range. The prepared photocatalysts are exemplary and could be employed for wastewater handling and several ecological applications.

Fabrication of Electrochemical Biosensor Based on Titanium Dioxide Nanotubes and Silver Nanoparticles for Heat Shock Protein 70 Detection

This paper presents the fabrication methodology of an electrochemical biosensor for the detection of heat shock protein 70 (HSP70) as a potential tumor marker with high diagnostic sensitivity. The sensor substrate was a composite based on titanium dioxide nanotubes (TNTs) and silver nanoparticles (AgNPs) produced directly on TNTs by electrodeposition, to which anti-HSP70 antibodies were attached by covalent functionalization. This manuscript contains a detailed description of the production, modification, and the complete characteristics of the material used as a biosensor platform. As-formed TNTs, annealed TNTs, and the final sensor platform—AgNPs/TNTs, were tested using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction analysis (XRD). In addition, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) of these substrates were used to assess the influence of TNTs modification on their electrochemical characteristics. The EIS technique was used to monitor the functionalization steps of the AgNPs/TNTs electrode and the interaction between anti-HSP70 and HSP70. The produced composite was characterized by high purity, and electrical conductivity improved more than twice compared to unmodified TNTs. The linear detection range of HSP70 of the developed biosensor was in the concentration range from 0.1 to 100 ng/mL.

Facile Fabrication of a ZnO/Eu2O3/NiO-Based Ternary Heterostructure Nanophotocatalyst and Its Application for the Degradation of Methylene Blue

The ZnO-based ternary heterostructure ZnO/Eu2O3/NiO nanoparticles are synthesized using waste curd as fuel by a simple one-pot combustion method. The as-synthesized heterostructure is characterized by using various spectroscopic and microscopic techniques including X-ray diffraction, UV-vis, FTIR, SEM, and TEM analyses. The photocatalytic activity of the ternary nanocomposite was tested for the photodegradation of methylene blue (MB) under solar light irradiation. The results have revealed that the ternary ZnO/Eu2O3/NiO photocatalyst exhibits excellent performance toward the photocatalytic degradation of the studied dye. Optimization studies revealed that the synthesized heterostructure exhibited a pH-dependent photocatalytic activity, and better results are obtained for specific concentrations of dye and catalysts. Among the different light sources employed during the study, the catalyst was found to possess the best degradation efficiency in visible light.

Atomic Level Interface Control of SnO2-TiO2 Nanohybrids for the Photocatalytic Activity Enhancement

This review article highlights atom-level control of the heterojunction and homojunction in SnO2-TiO2 nanohybrids, and the effects on the photocatalytic property. Firstly, a comprehensive description about the origin for the SnO2-TiO2 coupling effect on the photocatalytic activity in the conventional SnO2-TiO2 system without heteroepitaxial junction is provided. Recently, a bundle of thin SnO2 nanorods was hetero-epitaxially grown from rutile TiO2 seed nanocrystals (SnO2-NR#TiO2, # denotes heteroepitaxial junction). Secondly, the heterojunction effects of the SnO2-NR#TiO2 system on the photocatalytic activity are dealt with. A novel nanoscale band engineering through the atom-level control of the heterojunction between SnO2 and TiO2 is presented for the photocatalytic activity enhancement. Thirdly, the homojunction effects of the SnO2 nanorods on the photocatalytic activity of the SnO2-NR#TiO2 system and some other homojunction systems are discussed. Finally, we summarize the conclusions with the possible future subjects and prospects.

Highly efficient solar photocatalytic degradation of a textile dye by TiO2/graphene quantum dots nanocomposite

Herein, two sunlight responsive photocatalysts including TiO₂ nanoparticles (NPs) and TiO₂/graphene quantum dots (GQDs) nanocomposite for degrading a textile dye, Reactive Black 5 (RB5), were prepared. The results showed that 100% of 50 ppm RB5 could be degraded by TiO₂ NPs and TiO₂/GQDs within 60 and 30 min sunlight irradiation, respectively. Hence, much better photocatalytic activity in degradation of RB5 was achieved by TiO₂/GQDs under sunlight irradiation compared with pure TiO₂ NPs due to its lower band gap (2.13 eV) and electron/hole recombination rate. The photocatalytic degradation mechanism of RB5 by TiO₂ NPs was elucidated by adding some scavengers to the solution. The main reactive species contributing to RB5 degradation were surface hydroxyl radicals. The first-order solar degradation rate constant of RB5 for TiO₂/GQDs is greater than that of TiO₂ NPs under sunlight illumination.

A radially controlled ZnS interlayer on ultra-long ZnO-Gd2S3 core-shell nanorod arrays for promoting the visible photocatalytic degradation of antibiotics

Nanorod (NR) arrays offer commendable visible-light-driven photocatalytic performances. Herein, we describe the construction of a ternary ZnO-ZnS-Gd₂S₃ nanostructural array in which a sulfidation process is used to decorate a Gd₂S₃ shell layer with a ZnS interface over vapor-phase-grown vertically-aligned ZnO. With control over the shell-wall thickness, the shell layer of ∼25 nm wall thickness on the ultra-long ZnO NR arrays exhibited a higher catalytic efficiency close to 3.3, 2.0, 1.2, and 1.8 times those of the bare ZnO, the ZnO-ZnS, the Gd₂S₃-decorated (∼10 nm) and Gd₂S₃ shell-layered (∼40 nm) ZnO-ZnS core-shell structures, respectively. The core-shell geometry and the shell-wall thickness with maximized contact interface afforded increased light absorption in the visible region and effectively retarded the recombination rate of the photoinduced charge carriers by confining electrons and holes separately, thus providing advantages in terms of the degradation of the pharmaceutical residue tetracycline and the industrial pollutant 4-nitrophenol in wastewater.

Nanoengineered Advanced Materials for Enabling Hydrogen Economy: Functionalized Graphene-Incorporated Cupric Oxide Catalyst for Efficient Solar Hydrogen Production

Cupric oxide (CuO) is a promising candidate as a photocathode for visible-light-driven photo-electrochemical (PEC) water splitting. However, the stability of the CuO photocathode against photo-corrosion is crucial for developing CuO-based PEC cells. This study demonstrates a stable and efficient photocathode through the introduction of graphene into CuO film (CuO:G). The CuO:G composite electrodes are prepared using graphene-incorporated CuO sol-gel solution via spin-coating techniques. The graphene is modified with two different types of functional groups, such as amine (-NH2) and carboxylic acid (-COOH). The -COOH-functionalized graphene incorporation into CuO photocathode exhibits better stability and also improves the photocurrent generation compare to control CuO electrode. In addition, -COOH-functionalized graphene reduces the conversion of CuO phase into cuprous oxide (Cu2O) during photo-electrochemical reaction due to effective charge transfer and leads to a more stable photocathode. The reduction of CuO to Cu2O phase is significantly lesser in CuO:G-COOH as compared to CuO and CuO:G-NH2 photocathodes. The photocatalytic degradation of methylene blue (MB) by CuO, CuO:G-NH2 and CuO:G-COOH is also investigated. By integrating CuO:G-COOH photocathode with a sol-gel-deposited TiO2 protecting layer and Au-Pd nanostructure, stable and efficient photocathode are developed for solar hydrogen generation.

Enhanced photocatalytic and electrochemical performance of TiO2-Fe2O3 nanocomposite: Its applications in dye decolorization and as supercapacitors

This work reveals a green combustion route for the synthesis of TiO₂, Fe₂O₃ and TiO₂-Fe₂O₃ nanocomposites as photocatalysts for decolorization of Titan Yellow (TY) and Methyl Orange (MO) dyes at room temperature in aqueous solution concentration of 20 ppm under UV-light irradiation. We observed that the TiO₂-Fe₂O₃ nanocomposite shows superior photocatalytic activity for TY dye compared to pure TiO₂ and Fe₂O₃. Rate constant (k) values of TiO₂, Fe₂O₃ and TiO₂–Fe₂O₃ for TY and MO are 0.0194, 0.0159, 0.04396 and 0.00931, 0.00772 0.0119 kmin⁻¹ respectively. The surface area and pore volume of TiO₂-Fe₂O₃ nanocomposite were found to be 71.56 m²/g and 0.076 cm³/g, respectively as revealed by BET studies. From the Barrett–Joyner–Halenda (BJH) plot, the mean pore diameter of TiO₂-Fe₂O₃ nanoparticles was found to be 2.43 nm. Further, the TiO₂-Fe₂O₃ nanocomposite showed good electrochemical behavior as an electrode material for supercapacitors when compared to pure TiO₂ and Fe₂O₃ nanoparticles resulted in stable electrochemical performance with nearly 100% coulombic efficiency at a scan rate of 10 mV/s for 1000 cycles. Interestingly, the novelty of this work is that the designed supercapacitors showed stable electrochemical performance even at 1000^th cycle, which might be useful for rechargeable supercapacitor applications. The electrochemical properties of the nanocomposites were compared by the data obtained by cyclic voltammograms, charge-discharge tests and electrochemical impedance spectroscopic studies. These results demonstrated that the TiO₂-Fe₂O₃ nanocomposite showed stable performance compared to TiO₂ and Fe₂O₃ nanoparticles at current density of 5 Ag⁻¹.

Facile in-situ growth of Ag/TiO2 nanoparticles on polydopamine modified bamboo with excellent mildew-proofing

Bamboo with the outstanding properties, such as good mechanical strength, fast growth rate and low growth cost, is considered as one of utilitarian structural nature materials. But bamboo is easy to get mildewed resulting in disfiguration and fungi corrosion. In this work, a facile method was developed to improve the mildew-proofing capability of bamboo. Mussel-inspired polydopamine (PDA) with biomimetic adhesion function and highly active functional groups was employed to immobilize highly-dispersed Ag and TiO₂ nanoparticles on the surface of bamboo via an in-situ growth method. Integrating the uniform PDA coating, photocatalytic function of TiO₂ nanoparticles and bactericidal role of Ag nanoparticles, the mildew-proofing capability of bamboo is enhanced significantly. The results show a non-covalent interaction is more likely to account for the binding mechanism of PDA to bamboo. And the prepared bamboo samples show good photocatalytic performance and have excellent resistance leachability. Meanwhile, the mildew-proofing property of prepared bamboo sample was greatly improved.

Evaluating the photocatalytic efficiency of the BiVO4/rGO photocatalyst

The present study reported the preparation of BiVO4 by co-precipitation method. The as-prepared BiVO4 photocatalyst were deposited on rGO sheets to form BiVO4/rGO via the hydrothermal method. The crystalline structure, morphological, optical properties, and surface properties of the synthesized pure BiVO4 compared to BiVO4/rGO composite were studied using X-ray diffraction (XRD), scanning electronmicroscopy (SEM), photoluminescence (PL) spectrophotoscopy, UV-vis spectrophotometer with an integrating sphere, and N2 adsorption-desorption isotherm based on BET theory. The photocatalytic activity of the prepared samples were evaluated by the degradation of MB dye in aqueous medium under visible light irradiation. The result showed that the BiVO4/rGO composite exhibited greater photocatalytic efficiency compared to pure BiVO4 with the photocatalytic degradation efficiency remains stable up to fifth cycle. The improved activity of the BiVO4/rGO composite might be attributed to the high surface area available to adsorb more MB molecules, and efficient charge separation of BiVO4 through π electron on the rGO structure. According to experimental results, the possible photocatalytic mechanism of the BiVO4/rGO composite were determined and the active species hydroxyl radical were reported. Based on photocatalytic activity inhibition in the presence of both h+ (VB) and O2•- (CB) scavengers over the BiVO4 photocatalyst, it can be proposed that the hydroxyl radical generated during the photocatalytic degradation mechanism is mainly responsible by the main active species of h+ and O2•- at VB and CB positions, respectively.

Synthesis, characterization and photocatalytic activity of Zn2+, Mn2+ and Co2+ doped SnO2 nanoparticles

Nanomaterials with many improved properties have been used in versatile applications. Herein we have synthesized SnO2 NPs doped with transition metal ions such as Zn2+, Mn2+ and Co2+ through a facile and inexpensive hydrothermal approach. The synthesized nanomaterials were characterized by XRD, FT-IR, SEM and UV-Vis analysis. The optical properties of the NPs were characterized by using UV–vis and photoluminescence spectroscopy (PLS). Their photocatalytic performances were investigated by degrading methylene blue (MB) dye with UV irradiation. Transition metal doping to SnO2 NPs improved the photocatalytic activity to degradation of methylene blue dye due to tuning of band gap energy i.e. lowering of band gap energy compared to undoped SnO2 NPs. The results suggest that the synthesized NPs could be used efficiently for remediation/degradation of environmentally hazardous dyes from waste water or environmental cleanup.

Pt nanoparticles decorated heterostructured g-C3N4/Bi2MoO6 microplates with highly enhanced photocatalytic activities under visible light

Exploring an efficient and photostable heterostructured photocatalyst is a pivotal scientific topic for worldwide energy and environmental concerns. Herein, we reported that Pt decorated g-C₃N₄/Bi₂MoO₆ heterostructured composites with enhanced photocatalytic performance under visible light were simply synthesized by one-step hydrothermal method for methylene blue (MB) dye degradation. Results revealed that the synthetic Pt decorated g-C₃N₄/Bi₂MoO₆ composites with Bi₂MoO₆ contents of 20 wt.% (Pt@CN/20%BMO) presented the highest photocatalytic activity, exhibiting 7 and 18 times higher reactivity than the pure g-C₃N₄ and Bi₂MoO₆, respectively. Structural analyses showed that Bi₂MoO₆ microplates were anchored on the wrinkled flower-like g-C₃N₄ matrix with Pt decoration, leading to a large expansion of specific surface area from 10.79 m²/g for pure Bi₂MoO₆ to 46.09 m²/g for Pt@CN/20%BMO. In addition, the Pt@CN/20%BMO composites exhibited an improved absorption ability in the visible light region, presenting a promoted photocatalytic MB degradation. Quenching experiments were also conducted to provide solid evidences for the production of hydroxyl radicals (^•OH), electrons (e⁻), holes (h⁺) and superoxide radicals (^•O²⁻) during dye degradation. The findings in this critical work provide insights into the synthesis of heterostructured photocatalysts with the optimization of band gaps, light response and photocatalytic performance in wastewater remediation.