Synthesis of nanostructured silver/silver halides on titanate surfaces and their visible-light photocatalytic performance

Boosted photocatalytic effect of binary AgI/Ag2WO4 nanocatalyst: characterization and kinetics study towards ceftriaxone photodegradation

In modern chemistry, great interest has been paid to introducing outstanding photocatalysts for degrading organic pollutants. Herein, a highly efficient binary AgI/Ag₂WO₄ photocatalyst was prepared from AgI and Ag₂WO₄ nanoparticles (NPs) and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared (FT-IR) techniques. In the Scherrer model, the average crystallite sizes of 34.9, 42.0, and 24.1 nm were estimated for the AgI, Ag₂WO₄, and the binary catalyst, while the values were 91, 13, and 85 nm by the Williamson-Hall model. FTIR confirmed the presence of W-O-W, O-W-O, Ag-I, and O-Ag-O bonds in the coupled material. DRS results showed absorption edge wavelengths of 451, 462, and 495 nm (corresponding to the band gap values of 2.75, 2.68, and 2.51 eV) for Ag₂WO₄, AgI, and AgI/Ag₂WO₄ catalyst, respectively. Synergistic photocatalytic activity of the coupled system was achieved towards ceftriaxone (CTX) in an aqueous solution (about 33% 10 ppm CTX solution was degraded without any optimization in the initial conditions of catal dose 0.3 g/L (Ag₂WO₄:AgI with mole ratio 1:2 and 30 min abrasion time), and irrad. time 45 min, C_CTX). This boosted effect depended on the AgI:Ag₂WO₄ mole ratio and grinding time for the mechanical preparation of the binary catalyst (optimums: mole ratio of 4:1 and time 30 min). The photodegradation kinetics obeyed the Hinshelwood model with the apparent first-order rate constant (k) of 0.013 min^-1 (t_1/2 = 53.30 min). Performing the COD on the photodegraded CTX solutions got a Hinshelwood plot with a slope of 0.019 min^-1 (t_1/2 = 36.5 min).

Surface modification of BiOBr/TiO2 by reduced AgBr for solar-driven PAHs degradation: Mechanism insight and application assessment

A novel solar active AgBr/BiOBr/TiO₂ catalyst was synthesized by a facile coprecipitation method for solar-driven water remediation. The synthesized material composed of flower-like TiO₂ nanoparticles loaded on BiOBr nanosheets and with homogeneous surface distributed Ag/AgBr nanoparticles. The internal electric field between BiOBr/TiO₂ heterojunction greatly facilitated the charge carrier migration; the introduction of narrow band gap semiconductors (AgBr and BiOBr) promoted the visible light adsorption; and the Ag/AgBr nanoparticles acted as photosensitizer to further improve the light utilization. The new material showed 7.6- and 4.0-times activity of pure TiO₂ and BiOBr under solar light, and the contribution of reactive species on anthracene degradation followed the order of h⁺ >O₂^•-> •OH. The degradation mechanism and pathway were proposed based on intermediates analysis and DFT calculation. The QSAR analysis revealed that the environmental risks of contaminants were greatly reduced during the photocatalysis process but some intermediates were still toxic. The high photocatalytic activity, stability and adaptability all indicated that this new material owns great application potential for cost-effective photocatalytic remediation of persistent organic contaminants under solar light.

In situ construction of a direct Z-scheme AgBr/α-Ag2WO4 heterojunction with promoted spatial charge migration and photocatalytic performance

A hierarchical AgBr/α-Ag₂WO₄ Z-scheme heterojunction was facially constructed for greatly improved photocatalytic activity towards pollutant elimination due to promoted spatial separation of carriers with high redox capacity.

Ultra-Uniform and Very Thin Ag Nanowires Synthesized via the Synergy of Cl-, Br- and Fe3+ for Transparent Conductive Films

The properties and applications of Ag nanowires (AgNWs) are closely related to their morphology and composition. Therefore, controlling the growth process of AgNWs is of great significance for technological applications and fundamental research. Here, silver nanowires (AgNWs) were synthesized via a typical polyol method with the synergistic effect of Cl⁻, Br⁻, and Fe³⁺ mediated agents. The synergistic impact of these mediated agents was investigated intensively, revealing that trace Fe³⁺ ions provided selective etching and hindered the strong etching effect from Cl⁻ and Br⁻ ions. Controlling this synergy allowed the obtainment of highly uniform AgNWs with sub-30 nm diameter and an aspect ratio of over 3000. Transparent conductive films (TCFs) based on these AgNWs without any post-treatment showed a very low sheet resistance of 4.7 Ω sq⁻¹, a low haze of 1.08% at a high optical transmittance of 95.2% (at 550 nm), and a high figure of merit (FOM) of 1210. TCFs exhibited a robust electrical performance with almost unchanged resistance after 2500 bending cycles. These excellent high-performance characteristics demonstrate the enormous potential of our AgNWs in the field of flexible and transparent materials.

Preparation of the plasmonic Ag/AgBr/ZnO film substrate for reusable SERS detection: Implication to the Z-scheme photocatalytic mechanism

In this work, a novel Ag/AgBr/ZnO SERS substrate was prepared by calcinating spin-coated zinc acetate on glass slides in the presence of ethanolamine (EA), followed by the process of impregnating-precipitation-photoreduction treatment. The SERS performances of Ag/AgBr/ZnO substrates were evaluated using aqueous crystal violet (CV) and Rhodamine 6G (R6G) as target analytes. The effects of initial immersion precursor concentration and irradiation time on the SERS performance were systematically studied. The as-prepared SERS substrate exhibited good chemical detection sensitivity, reproducibility and reusability. The optimal Ag/AgBr/ZnO (10 mM-30 min) substrates were capable of detecting 10^-12 M CV and 10^-11 M R6G aqueous solutions. The quantitative detection by the SERS substrate was investigated by constructing a linear corresponding calibration plot. The Ag/AgBr/ZnO SERS substrate was regenerated by a simple visible light driven photocatalytic process. A plausible Z-scheme visible light photocatalytic mechanism seems to account for the Ag-ZnO-AgBr system. This SERS substrate can be separated from the reaction easily, and the results indicated that the film was reusable for eight times without significantly losing the SERS efficiency, each time accompanied by a simple photo-driven regeneration. This study reveals that the Ag/AgBr/ZnO film on glass is practically applicable as an ultra-highly sensitive SERS substrate that can be readily regenerated.

Pt/POMs/TiO2 composite nanofibers with an enhanced visible-light photocatalytic performance for environmental remediation

Pt/PMo₁₂/TiO₂ composite nanofibers have been prepared and exhibit a highly efficient visible-light photocatalytic performance for removing methyl orange, tetracycline, Bisphenol A and Cr(vi).

Controllable synthesis of coloured Ag0/AgCl with spectral analysis for photocatalysis

Broad spectrum absorption of semiconductor photocatalysts is an essential requirement to achieve the best values of solar energy utilization. Here, through precise surface state adjustment, coaxial tri-cubic Ag0/AgCl materials with distinct apparent colours (blue and fuchsia) were successfully fabricated. The reasons for the different colour generation of the Ag0/AgCl materials were investigated by performing corresponding spectrum analysis. It was revealed that Ag0/AgCl-blue and Ag0/AgCl-fuchsia crystals could efficiently boost the photon energy harvesting, spanning from the UV to near-infrared spectral region (250-800 nm), and achieved 2.6 and 5.4 times the wastewater degradation efficiency of AgCl-white. Simultaneously, these two fresh coloured candidates were demonstrated to have preferable photocatalytic CO2 photoreduction capability, with yields of ∼3.6 (Ag0/AgCl-fuchsia) and 2.6 (Ag0/AgCl-blue) times that of AgCl-white. It is expected that this work will provide a beneficial perspective for understanding the solar absorption feature at both the major structure modulation and particular surface state regulation level.

Synergistic effects of plasmon induced Ag@Ag3VO4/ZnCr LDH ternary heterostructures towards visible light responsive O2 evolution and phenol oxidation reactions

The SPR effect of monodisperse Ag nanoparticles in Ag@Ag₃VO₄/ZnCr LDH heterostructures exhibits high photocatalytic activity towards evolution of O₂ and oxidation of phenol.

Ag/AgxH3-xPMo12O40 Nanowires with Enhanced Visible-Light-Driven Photocatalytic Performance

Photocatalysis, a promising technology platform to address the environmental problems, has been attracting considerable attention. In this paper, Ag/Ag_xH_3-xPMo₁₂O₄₀ (simplified as Ag/AgHPMo₁₂) nanowires have been synthesized by a facile solid reaction route and in situ photodeposited method. The results of SEM and TEM indicate that the diameters of AgHPMo₁₂ nanowires are about 45 ± 10 nm, and Ag nanoparticles with diameters in the range of 5-15 nm are uniformly anchored on the surface of AgHPMo₁₂ nanowires. The Ag content in the Ag/AgHPMo₁₂ composite was manipulated by the light irradiation time (Ag/AgHPMo₁₂-x; x stands for the irradiation time; x = 2, 4, 6, 8 h, respectively). With increasing irradiation time, the light absorption of as-synthesized samples in the visible region was gradually enhanced. The Ag/AgHPMo₁₂-4 exhibits the best photocatalytic performance for the degradation of methyl orange and reduction of Cr₂O₇^2- under visible-light (λ > 420 nm) irradiation. The study of the photocatalytic mechanism reveals that both Ag and AgHPMo₁₂ can be excited by visible light. The photoinduced electrons were transferred from AgHPMo₁₂ to metallic Ag, and combined with the Ag plasmonic holes. The Ag plasmonic electrons were trapped by O₂ to form ·O₂^-, or directly reduced Cr₂O₇^2- to Cr³⁺. Meanwhile, the ·O₂^- species and the photogenerated holes of AgHPMo₁₂ were used to oxidize MO or i-PrOH; thus, they showed highly efficient and recyclable photocatalytic performance for removing the organic and inorganic pollutants.

In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting

An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ ≥ 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion.

Cube-like Ag/AgCl fabricated via a photoirradiation method and its substantially boosted plasmonic photocatalytic reactivity by an oxidation–chloridization treatment

Cube-like Ag/AgCl species are produced by a photoirradiation method, where substantially boosted plasmonic photocatalytic reactivity has been realized via an oxidation–chloridization treatment.

Titanate nanowire/NiO nanoflake core/shell heterostructured nanonanocomposite catalyst for methylene blue photodegradation

A core/shell heterostructured nanonanocomposite catalyst based on NiO nanoflakes and titanate nanowires (TNWs) was fabricated.

The role of reduction extent of graphene oxide in the photocatalytic performance of Ag/AgX (X = Cl, Br)/rGO composites and the pseudo-second-order kinetics reaction nature of the Ag/AgBr system

The role of reduction extent of GO in a graphene-based photocatalyst has been studied using Ag/AgX (X = Cl, Br)/rGO composites as a model. The pseudo-second-order kinetics reaction nature of the Ag/AgBr system was also observed.

Convenient recycling of 3D AgX/graphene aerogels (X = Br, Cl) for efficient photocatalytic degradation of water pollutants

3D AgX/graphene aerogel (GA) composites (X = Br, Cl) are synthesized. Not only is the photocatalytic performance increased in comparison with pristine AgX, but also the photocatalytic cycling process is facilitated just using tweezers Thus, the comprehensive performance of the AgX/GA composites provides robust support for future industrial applications of the photocatalyst.

Visible-light-driven Ag/AgCl plasmonic photocatalysts via a surfactant-assisted protocol: enhanced catalytic performance by morphology evolution from near-spherical to 1D structures

Fibrous Ag/AgCl structures with boosted photocatalytic performances have been fabricatedviaa one-pot surfactant-assisted morphology evolution from near-spherical to 1D architectures.

Titanate and titania nanostructured materials for environmental and energy applications: a review

The state-of-the-art development of fabrication strategies of multi-dimensional titanate and titania nanostructures is reviewed first. This is followed by an overview of their potential applications in environmental, energy, and biomedical sectors.

Evolution of AgX nanowires into Ag derivative nano/microtubes for highly efficient visible-light photocatalysts

Our study proposes a novel strategy for the synthesis of Ag derivatives (AgX@Ag (X = Cl and Br) or Ag nano/microtubes) using the controlled chemical reduction or electron-beam irradiation of AgX nanowires (NWs), which are formed from the controlled dewetting of a AgX thin film on colloidal particles. The size of the AgX@Ag and Ag nano/microtubes can be controlled using the AgCl NWs as templates and varying the concentration of NaX. By controlling the concentration of NaBr, heterojunction-structured AgCl/AgBr NWs (H-AgCl/AgBr NWs) can be produced from the AgCl NWs due to a partial ion-exchange reaction (low concentration), and the AgBr NWs produced after a complete ion-exchange reaction between Cl- and Br- are further grown into micrometer-sized AgBr wires (high concentration). The resulting AgX NWs can be transformed into corresponding AgX@Ag or Ag nano/microtubes via a controlled chemical or physical method. The AgX derivatives (AgX@Ag nanotubes (NTs) and AgX NWs) are tested as visible-light-induced photocatalysts for decomposition of methyl orange. The AgX@Ag NTs exhibit the best photocatalytic activities due to the advantages of the core@shell structure, allowing multiple reflections of visible light within the interior cavity, providing a well-defined and clean Ag/AgX interface, and preventing direct adsorption of pollutants on AgX because of the shell structure. These advantages allow AgX@Ag NTs to maintain high catalytic performance even after multiple uses. The approach can also be used as a direct method for preparing Ag nano/microtubes with a tailored size and as a new method for incorporating a AgX NW core into a Ag nano/microtube shell. Our approach is useful for synthesizing various types of one-dimensional heterostructured NWs or metal NTs with controlled structures and properties.