Water purification using a BiVO4/graphene oxide multifunctional hydrogel based on interfacial adsorption-enrichment and photocatalytic antibacterial activity

Photocatalytic degradation by visible light-driven generation of reactive oxygen species shows great promise for purification of environmental water. However, such degradation is limited by the low separation efficiency of photogenerated carriers and the poor adsorption capacity of the photocatalyst itself. To solve these problems, we successfully constructed and prepared a composite hydrogel (BV-GH) combining a three-dimensional network structure composed of graphene oxide and BiVO₄ to achieve the synergistic effects of adsorption enrichment and photocatalytic degradation. The results show that the amount of methylene blue and methyl orange adsorbed by BV-GH is 258.78 mg g^?1 and 217.16 mg g^?1, respectively, which is much higher than that obtained for pure BiVO₄. Due to the synergistic effect of adsorption enrichment and photocatalytic degradation, the degradation rate of the dye by BV-GH reaches 94.18% in 60 min, which is 6.98 times higher than that obtained for pure BiVO₄. Electron spin-resonance (ESR) experiments confirm that the main factor affecting the dye degradation by BV-GH is the ability to produce more ·OH and ·O₂^?, which is an important reason for the excellent antibacterial performance of BV-GH against E. coli. This work can provide further inspiration for photocatalytic technology in water purification.     

Evaluation of biosynthesized nickel oxide nanoparticles from Clerodendrum phlomidis: A promising photocatalyst for methylene blue and acid blue dyes degradation

In the present investigation, nickel oxide nanoparticles (NiO) were biosynthesized utilizing an extract of Clerodendrum phlomidis leaves. Their size, phase study, and shape were investigated using a variety of research methods. In addition, we assessed the photocatalytic effects of NiO nanoparticles on the degradation of methylene blue (MB) and acid blue (AB) dyes. Throughout the research process, we found that these nanoparticles had extraordinary potential for photocatalysis when exposed to UV light. This is a 100% environmentally friendly method that makes no use of any harmful or poisonous solvents. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and ultraviolet–visible spectroscopy (UV–Vis) were used to analyze the biosynthesized NiO nanoparticles. The catalytic activity of the newly synthesized nanoparticles was evaluated by seeing how well they degraded dyes called methylene (MB) and acid blue (AB). Following the first-order reaction, kinetics was the photocatalytic effectiveness against the methylene blue (MB) and acid blue (AB) dyes, both of which exhibited a maximum degradation efficiency of 92% and 63%. Because of this, the biosynthesized NiO nanoparticles synthesized utilizing the extract of Clerodendrum phlomidis leaves have the potential to be used in photocatalytic applications.     

Enhancement in the photocatalytic and optoelectronic properties of erbium oxide by adding zinc oxide and molybdenum

Rare earth metals like erbium oxide (Er₂O₃) show outstanding photocatalytic properties. However, its high recombination rate and low surface area limit its performance. Therefore, various metal oxide composites with Er₂O₃ have been reported to improve their photocatalytic and optoelectronic properties. In this study, a composite of Er₂O₃ and zinc oxide (ZnO) was synthesized using the sol-gel combustion method to enhance its surface area. Moreover, molybdenum (Mo) was loaded on the matrix to suppress the charge recombination. The detailed characterizations were conducted by employing X-ray Diffraction (XRD), Raman Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET) analysis, Photoluminescence (PL) spectroscopy and UV–Vis spectroscopy. BET analysis revealed the enhancement in surface area by adding ZnO and Mo (from S_BET = 29.07 m²/g to S_BET = 45.71 m²/g). Additionally, the loading of Mo enhanced the immobilization of carriers that facilitate the photooxidation process and suppressed the electron-holes recombination (from 800 counts to 100 counts) as confirmed by the PL spectroscopy. Photocatalytic studies were comparatively analyzed by degradation of textile dye named methylene blue (MB). The efficiency of Er₂O₃ improved by up to 80% by adding the ZnO and Mo. The composite of Er₂O₃ with ZnO and loading of Mo, not only improved the photocatalytic properties but also improved the electrical properties of the Er₂O₃ (σ = 4.4 × 10⁻⁴ Sm⁻¹ to σ = 5.1 × 10⁻⁴ Sm⁻¹) as confirmed by the Hall Effect. Due to enhancement in properties, the proposed material can be rendered as one of the most suitable candidates for optoelectronic applications.     

Synthesis of hollow spherical WO3 powder by spray solution combustion and its photocatalytic properties

Hollow spherical WO₃ powder was prepared from mixed solution of ammonium metatungstate, glycine and ammonium nitrate by spray solution combustion synthesis (SSCS) method. The effects of fuel ratio, temperature, precursor solution concentration on the structure and morphology of as-prepared powder, and the SSCS mechanism have been discussed in detail. When precursor solution concentration is 0.10 mol/L, in which the fuel ratio is 2, and reaction temperature set to be 800 °C, the spherical WO₃ powder with smooth surface and a median diameter of 24.02 μm can be obtained, which consists of particles with a diameter of about 30 nm, and the specific surface area is 13.5 m²/g. Moreover, the as-synthesized WO₃ powder is applied to degrade RhB solution in visible light to evaluate its catalytic performance by PLS-SXE300/300UV. Only 10 mg powder can degrade 70.1% RhB solution within 2 h.     

Hydrogen treatment-improved uniform deposition of Ag nanoparticles on ZnO nanorod arrays and their visible-light photocatalytic and surface-enhanced Raman scattering properties

ZnO nanorod arrays were synthesized by chemical bath deposition. After heat treatment in hydrogen or air, Ag nanoparticles were deposited on ZnO nanorod arrays by photo-reduction method. The size of Ag nanoparticles as well as the surface morphology, structure, composition, and optical property of ZnO nanorod arrays before and after the deposition of Ag nanoparticles were characterized by SEM, XRD, EDS, and UV/VIS/NIR spectrophotometer. As compared to the samples with heat treatment in air or without heat treatment, the ZnO nanorod arrays after heat treatment in hydrogen allowed Ag nanoparticles to be deposited more uniformly, densely, and numerously. Also, they exhibited higher efficiency for the visible light-driven photocatalytic degradation of Rhodamine 6G (R6G) dye. The effects of the amount of Ag nanoparticles, initial dye concentration, and temperature on the photocatalytic degradation efficiency were investigated. Furthermore, they also exhibited better surface-enhanced Raman scattering property for the detection of R6G dyes.     

Photocatalytic activity of TiO2 nanotube layers coated with Ag and Pt

Abstract

Abstract

Thin films of anatase TiO₂ nanotube arrays (TiO₂ NTs) were prepared in this study. Pt and Ag were coated on the TiO₂ NTs films, which intend to increase the photocatalytic activity under ultraviolet-visible (UV-vis) irradiation. The phase and structure of the films were investigated by X-ray diffraction and scanning electron microscopy. Photocatalytic activity was tested by UV-vis absorption spectroscopy and showed that UV-vis light absorption of the films was remarkably improved by coated Ag and Pt by 72% and 183% respectively. The photocatalytic activities of the films towards degraded methyl orange and HCHO were compared and were all found to follow the sequence Pt/TiO₂ NTs>Ag/TiO₂ NTs>TiO₂ NTs. It was also found that the kinetics of HCHO photocatalytic degradation by the films fits the first order reaction model better and has higher efficiency than that of the methyl orange photocatalytic degradation by the same films.     

抗菌薄膜的最新研究进展

介绍了抗菌薄膜的抗菌机理。综述了抗菌薄膜的种类和最新研究进展。提出了抗菌薄膜研究的发展趋势,即无机抗菌薄膜以纳米复合型抗菌薄膜为主要的发展趋势;天然抗菌薄膜以壳聚糖抗菌薄膜为主要的发展方向;高分子抗菌薄膜以含吡啶基团的聚合物抗菌薄膜为拓展方向;光催化型无机抗菌薄膜以纳米TiO2复合抗菌薄膜为主要的拓展趋势。     

Effect of TiO2 thin film thickness and specific surface area by low-pressure metal–organic chemical vapor deposition on photocatalytic activities

TiO₂ photocatalyst films having an anatase crystal structure with different thickness were prepared by the low-pressure metal–organic chemical vapor deposition (LPMOCVD) to examine the effect of growth conditions on photocatalytic activity. Film thickness was linearly proportional to the deposition time. Structure of the film was strongly dependent on the deposition time. In early stage of deposition, fine particles deposit on the substrate. As increasing the deposition time, crystal orientation is gradually selected following the Kolmogorov model and c-axis oriented columnar crystals become dominant. The photocatalytic activity strongly depends on the film deposition time (or film thickness) in nonlinear way. The optimum thickness of TiO₂ catalyst film grown by LPMOCVD may locate between 3 and 5 μm.     

Bi12TiO20 synthesized directly from bismuth (III) nitrate pentahydrate and titanium glycolate and its activity

Pure phase of sillenite structure, Bi₁₂TiO₂₀, was directly synthesized using stoichiometric bismuth (III) nitrate pentahydrate and titanium glycolate by co-precipitation. The influence of pH on the structure of Bi₁₂TiO₂₀ was studied in the pH range of 3–10. The sillenite structure was characterized using XRD and FTIR. The photo-degradation reaction of 4-nitrophenol (4-NP) was used to study photocatalytic activity of Bi₁₂TiO₂₀ as a function of the preparation pH. The rate of decomposition was followed by UV-vis and TOC. The beginning concentration of 4-NP, 44 ppm, decreased to less than 1 ppm within 30 min for all prepared catalysts. It was found that the decomposition rate constant of Bi₁₂TiO₂₀ is six times higher than those of either TiO₂ or Bi₂O₃ under the same conditions.     

Photocatalytic degradation kinetics of di- and tri-substituted phenolic compounds in aqueous solution by TiO2/UV

In this study, photocatalytic degradation of 2,4,6-trimethylphenol (TMP), 2,4,6-trichlorophenol (TCP), 2,4,6-tribromophenol (TBP), 2,4-dimethylphenol (DMP), 2,4-dichlorophenol (DCP) and 2,4-dibromophenol (DBP) has been studied by TiO₂/UV. Although degraded phenolic compound concentration increased by increasing initial concentration photocatalytic decomposition rates of di- and tri-substituted phenols at 0.1–0.5 mM initial concentrations decreased when the initial concentration increased. The fastest degradation observed for TCP and the slowest for TMP. Photodegradation kinetics of the compounds has been explained in terms of Langmuir–Hinshelwood kinetics model. Degradation rate constants have been observed to be extremely depended on electronegativity of the substituents on phenolic ring. Degradation rate constant and adsorption equilibrium constant of TCP were calculated as k 0.0083 mM min⁻¹ and K 9.03 mM⁻¹. For TBP and TMP the values of k and K were obtained as 0.0040 mM min⁻¹, 19.20 mM⁻¹, and 0.0017 mM min⁻¹, 51.68 mM⁻¹, respectively. Degradation rate constant of DBP was similar as DCP (0.0029 mM min⁻¹ for DBP and 0.0031 mM min⁻¹ for DCP) whereas adsorption equilibrium constants differed (48.40 mM⁻¹ for DBP and 30.52 mM⁻¹ for DCP). K and k of DMP found as 83.68 mM⁻¹ and 0.0019 mM min⁻¹, respectively. The adsorption equilibrium constants in the dark were ranged between 1.11 and 3.28 mM⁻¹ which are lower than those obtained in kinetics. Adsorption constants have inversely proportion with degradation rate constants for all phenolic compounds studied.