Photocatalytic Degradation of Tetracycline Hydrochloride via a CdS-TiO₂ Heterostructure Composite under Visible Light Irradiation

A photocatalytic active CdS-TiO₂ heterostructure composite was prepared by hydrothermal method and its morphology and properties were characterized. Results indicate that the CdS nanoparticles deposited on the surface of a TiO₂ nanoparticles, which was in anatase phase. The particle scale of both of the components reached approximately 15 nm. In comparison to pure TiO₂ (410 nm), the light absorption edge of the heterostructure composite was 550 nm, which could extend the light response from UV to the visible region. Under visible light irradiation, the degradation efficiency of tetracycline hydrochloride by the CdS-TiO₂ composite achieved 87.06%, significantly enhancing photocatalytic activity than the as-prepared pure TiO₂ and commercial TiO₂ (Degussa P25). This character is attributed to the synergetic effect of these two components in the absorption of visible light.

Green synthesis of mesoporous flower-like TiO2/graphite nanosheets (TGNS) prepared by high-pressure homogenization (HPH)

TiO₂ particles uniformly spread on graphite nanosheets (GNS) by utilizing the broken edges brought by high-pressure homogenization.

Steering Surface Reaction at Specific Sites with Self-Assembly Strategy

To discern the catalytic activity of different active sites, a self-assembly strategy is applied to confine the involved species that are "attached" to specific surface sites. The employed probe reaction system is the Ullmann coupling of 4-bromobiphenyl, C₆H₅C₆H₄Br, on an atomically flat Ag(111) surface, which is explored by combined scanning tunneling microscopy, synchrotron X-ray photoelectron spectroscopy, and density functional theory calculations. The catalytic cycle involves the detachment of the Br atom from the initial reactant to form an organometallic intermediate, C₆H₅C₆H₄AgC₆H₄C₆H₅, which subsequently self-assembles with its central Ag atom residing either on 2-fold bridge or 3-fold hollow sites at full coverage. The hollow site turns out to be catalytically more active than the bridge one, allowing us to achieve site-steered reaction control from the intermediate to the final coupling product, p-quaterphenyl, at 390 and 410 K, respectively.

Ag-AgBr/TiO2/RGO nanocomposite: Synthesis, characterization, photocatalytic activity and aggregation evaluation

Ag-AgBr/TiO₂ supported on reduced graphene oxide (Ag-AgBr/TiO₂/RGO) with different mass ratios of grapheme oxide (GO) to TiO₂ were synthesized via a facile solvothermal-photo reduction method. Compared to the single-, two- and three-component nanocomposites, the four-component nanocomposite, Ag-AgBr/TiO₂/RGO-1 with mass ratio of GO to TiO₂ at 1%, exhibited a much higher photocatalytic activity for the degradation of penicillin G (PG) under white light-emitting diode (LED-W) irradiation. The PG degradation efficiency increased with the increase of mass ratio of GO to TiO₂ from 0.2% to 1%, then it decreased with the increase of mass ratio of GO to TiO₂ from 1% to 5%. The zeta potentials of RGO-nanocomposites became more negative with the presence of humic acid (HA) due to the negatively charged HA adsorption, resulting in the shift of points of zero charge to lower values of pH. The aggregations of nanocomposites were more significant due to the bridging effect of HA. Furthermore, the aggregated particle sizes were larger for RGO-nanocomposites compared to other nanoparticles, due to the bindings of the carboxylic and phenolic functional groups in HA with the oxygen-containing functional groups in the RGO-nanocomposites. The microfiltration (MF) membrane was effective for the nanocomposites separation. In the continuous flow through submerged membrane photoreactor (sMPR) system, backwashing operation could efficiently reduce membrane fouling and recover TiO₂, and thus indirectly facilitate the PG removal.

A novel P/Ag/Ag2O/Ag3PO4/TiO2 composite film for water purification and antibacterial application under solar light irradiation

TiO₂-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films with 3 coating layers, synthesized at 400°C for 2h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite film reached 99.9% after 60min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO₂ film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 10⁷CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films were photo-generated holes and O₂^- radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films.

Monodisperse Ag–AgBr nanocrystals anchored on one-dimensional TiO2 nanotubes with efficient plasmon-assisted photocatalytic performance

A novel ternary Ag–AgBr/TiO₂ plasmonic nanotube heterojunction photocatalyst was fabricated, showing a very high-performance for decomposition of organic pollutants.

Heteroarchitectured Ag–Bi2O3–ZnO as a bifunctional nanomaterial

Ag–Bi₂O₃–ZnO, fabricated by photodeposition–hydrothermal method, shows a morphology of intercrossed sheets and peanut shell structure. High methanol oxidation current of Ag–Bi₂O₃–ZnO reveals its potential as an anode catalyst in methanol fuel cells.

Magnetically Separable Fe3O 4/AgBr Hybrid Materials: Highly Efficient Photocatalytic Activity and Good Stability

Magnetically separable Fe3O4/AgBr hybrid materials with highly efficient photocatalytic activity were prepared by the precipitation method. All of them exhibited much higher photocatalytic activity than the pure AgBr in photodegradation of methyl orange (MO) under visible light irradiation. When the loading amount of Fe3O4 was 0.5 %, the hybrid materials displayed the highest photocatalytic activity, and the degradation yield of MO reached 85 % within 12 min. Silver halide often suffers serious photo-corrosion, while the stability of the Fe3O4/AgBr hybrid materials improved apparently than the pure AgBr. Furthermore, depositing Fe3O4 onto the surface of AgBr could facilitate the electron transfer and thereby leading to the elevated photocatalytic activity. The morphology, phase structure, and optical properties of the composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible diffuse reflectance spectra (UV-vis DRS), and photoluminescence (PL) techniques.

Multichannel-improved charge-carrier dynamics in well-designed hetero-nanostructural plasmonic photocatalysts toward highly efficient solar-to-fuels conversion

The charge-carrier dynamics process in well-designed hetero-nanostructural plasmonic photocatalysts is greatly improved through a multichannel sensitization effect, which therefore results in a significant enhancement of the efficiencies of solar-to-fuels conversion.

Advanced nanoarchitectures of silver/silver compound composites for photochemical reactions

Silver/silver compound (SSC) composites have received much attention as a type of potential materials in photochemical reactions due to their high efficiency, facile syntheses and availability of raw materials. This article reviews the state-of-the-art progress on the advanced nanoarchitectures of SSC composites. We begin with a survey on the general synthetic strategies for SSC composites, and then step into relatively detailed methods for size and morphology tunable two-component and more delicate multi-component SSC nanostructures. In addition, the electronic structure-related mechanisms of such materials and the recent studies on their stability are summarized. This review also highlights some perspectives on challenges related to the SSC composites and the possible research in the future.

Plasmonic Z-scheme α/β-Bi2O3–Ag–AgCl photocatalyst with enhanced visible-light photocatalytic performance

The plasmonic Z-scheme α/β-Bi₂O₃–Ag–AgCl photocatalysts were successfully synthesized and their photocatalytic performance for the degradation of Rhodamine B and acid orange 7 dyes were systematically investigated.

Biomimetic synthesis of TiO₂-SiO₂-Ag nanocomposites with enhanced visible-light photocatalytic activity

Ternary TiO2-SiO2-Ag nanocomposites with enhanced visible-light photocatalytic activity have been synthesized through a facile biomimetic approach by utilizing lysozyme as both inducing agent of TiO2 and reducing agent of Ag(+). TiO2 nanoparticles (∼280 nm) are at first fabricated by the inducing of lysozyme. Afterward, SiO2 layers are formed as "pancakes" stuck out of TiO2 nanoparticles through a sol-gel process. Finally, Ag nanocrystals (∼24.5 nm) are deposited onto the surface of TiO2-SiO2 composites via the reduction of lysozyme, forming TiO2-SiO2-Ag nanocomposites. The resultant nanocomposites display a high photocatalytic activity for the degradation of Rhodamine B under the visible-light irradiation, which can be attributed to the synergistic effect of enhanced photon absorption from the surface plasma resonance of Ag nanocrystals and the elevated adsorption capacity for Rhodamine B from the high specific surface area of SiO2. This study may provide some inspiration for the rational design and the facile synthesis of composite catalysts with a high and tunable catalytic property through a green, efficient pathway.

Hierarchically plasmonic photocatalysts of Ag/AgCl nanocrystals coupled with single-crystalline WO₃ nanoplates

The hierarchical photocatalysts of Ag/AgCl@plate-WO₃ have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO₃ nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO₃ suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO₃ composites, which were then photoreduced to form Ag/AgCl@WO₃ nanostructures in situ. WO₃ nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO₃ photocatalysts, and the effects of the WO₃ contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N₂ adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO₃ nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO₃ photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO₃ and TiO₂ (P25). The contents and morphologies of the WO₃ substrates in the Ag/AgCl@plate-WO₃ photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.

Role of hydroxyl radicals and mechanism of Escherichia coli inactivation on Ag/AgBr/TiO2 nanotube array electrode under visible light irradiation

A ternary Ag/AgBr/TiO(2) nanotube array electrode with enhanced visible-light activity was synthesized by a two-step approach including electrochemical process of anodization and an in situ photoassisted deposition strategy. The dramatically enhanced photoelectrocatalytic activity of the composite electrode was evaluated via the inactivation of Escherichia coli under visible light irradiation (λ>420 nm), whose performance of complete sterilization was much superior to other reference photocatalysts. PL, ESR, and radicals trapping studies revealed hydroxyl radicals were involved as the main active oxygen species in the photoelectrocatalytic reaction. The process of the damage of the cell wall and the cell membrane was directly observed by ESEM, TEM, and FTIR, as well as further confirmed by determination of potassium ion leakage from the killed bacteria. The present results pointed to oxidative attack from the exterior to the interior of the Escherichia coli by OH(•), O(2)(•-), holes and Br(0), causing the cell to die as the primary mechanism of photoelectrocatalytic inactivation.