Xue-Gang Zhang

Decolorization of an azo dye Orange G in microbial fuel cells using Fe(II)-EDTA catalyzed persulfate.

This study constructed a microbial fuel cell (MFC) using Fe(II)-EDTA catalyzed persulfate as the cathode solutions to decolorize Orange G (OG) and harvest electricity simultaneously. Chelated Fe(2+) could activate persulfate to generate sulfate free radicals (SO(4)(-)) which with high oxidation potential (E(0)=2.6 V) can degrade azo dyes. The influence of some important factors such as pH value of cathode solutions, dosages of K(2)S(2)O(8), Fe(2+) and EDTA were investigated in a two-chamber microbial fuel cell. Under an optimal condition, the maximum power density achieved 91.1 mW m(-2), the OG removal rate was 97.4% and the K(2)S(2)O(8) remaining rate was 47.3% after 12 h. The OG degradation by Fe(II)-EDTA catalyzed persulfate was found to follow the second-order kinetic model.

Facile synthesis of a visible light α-Fe2O3/BiOBr composite with high photocatalytic performance

Novel α-Fe2O3/BiOBr composites were synthesized by a simple in hydrolysis method for the first time, and were fully characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS). The α-Fe2O3/BiOBr composite showed much higher visible-light-driven (VLD) photocatalytic activity than pure α-Fe2O3 and BiOBr for rhodamine B (RhB) degradation. Specifically, the 10Fe/100Bi composite showed the highest photocatalytic activity for the degradation of dyes under visible light irradiation. The stability of the photocatalyst is found to be satisfying, which gives it potential in practical applications. The high photocatalytic activity could be attributed to the enhanced light absorption and the improved separation of photogenerated charge carriers, due to the formation of a p–n heterojunction between α-Fe2O3 and BiOBr.

High-efficiency visible-light AgI/Ag/Bi2MoO6 as a Z-scheme photocatalyst for environmental applications

A novel ternary composite AgI/Ag/Bi2MoO6 photocatalyst was successfully synthesized by a facile hydrothermal method combined with an ultrasonic-assisted precipitation-photoreduction technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence emission spectra (PL) analysis were employed to characterize the composition, phase structures, crystallinity, morphologies and optical properties of the obtained catalysts. The experimental results indicated that the AgI/Ag/Bi2MoO6 (15.0%) composite display higher visible light photoactivity for organic pollutants degradation compared with pure Bi2MoO6 and Ag/AgI nanocrystals. On the basis of band structure analysis and active species trapping experimental results, the excellent photocatalytic performance of the AgI/Ag/Bi2MoO6 photocatalysts can be ascribed to the efficient electron transfer and lower recombination of photogenerated electron–hole pairs through the Z-scheme system. And the Ag nanoparticles act as the charge transmission bridge in the process. The physicochemical features and high degradation efficiencies were maintained after five cycling experiment, indicating that the samples exhibited good durability and stability. It is expected that the novel AgI/Ag/Bi2MoO6 hybrid is a promising candidate material for the environmental applications.

A facile “turn-on” fluorescent method with high sensitivity for Hg2+ detection using magnetic Fe3O4 nanoparticles and hybridization chain reactions

In this manuscript, the authors molecularly engineered a hybridization chain reactions (HCRs) based probe on magnetic Fe3O4 nanoparticles for the sensitive detection of Hg(2+). The sensing system comprised three probes: capture probe H1, report probe H2, and report probe H3. The capture probe was modified on the surface of magnetic Fe3O4 nanoparticles. The report probes were labeled with fluorescein isothiocyanate (FITC). Without Hg(2+), the report probes were stable as molecular beacons in solution. In the presence of Hg(2+), the T-rich capture probes and report probes will hybridize into double-helical DNA domains with the aid of T-Hg(2+)-T coordination chemistry. Trigged by this reaction, more molecular beacons open and form a super tandem structure. Herein, the fluorescence signal was magnified by capturing more report probes. Separating the target and captured report probes from reaction solution was benefit to decrease the background signal and interference from other metal ions. The detection limit of this method was about 0.36nM, which is much lower than the regulations of World Health Organization and U.S. Environmental Protection Agency on Hg(2+) in drink water. This proposed sensing strategy also showed favorable selectivity over other common metal ions. In addition, it has good practicability in real water samples.

Synthesis of fern-like Ag/AgCl/CaTiO3 plasmonic photocatalysts and their enhanced visible-light photocatalytic properties

A novel visible-light-driven photocatalyst Ag/AgCl/CaTiO3 was successfully synthesized via a simple ultrasonic assisted precipitation–photoreduction process. The morphologies, phase structures as well as optical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectra and photoluminescence emission spectra (PL). The photocatalytic activity of Ag/AgCl/CaTiO3 was examined by the photodegradation of rhodamine B (RhB) under visible-light irradiation. Experimental results showed that the composites exhibited higher photocatalytic activity than pure CaTiO3 and Ag/AgCl. Among them, the Ag/AgCl-5/CaTiO3 composite exhibited the optimal photocatalytic activity. The enhanced photocatalytic activity of the Ag/AgCl/CaTiO3 photocatalyst was attributed predominantly to the synergetic effect between the Ag/AgCl nanoparticles and the fern-like CaTiO3 nanoparticles, which was superior for the separation of photogenerated electrons and holes. Based on the band structure analysis and trapping experimental results, a possible photocatalytic mechanism for Ag/AgCl/CaTiO3 was put forward.

Construction of highly efficient and stable ternary AgBr/Ag/PbBiO 2 Br Z-scheme photocatalyst under visible light irradiation: Performance and mechanism insight

In this work, the novel ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalysts were synthesized via a CTAB-assisted calcination process. The AgBr/Ag/PbBiO2Br composites were employed for the degradation of rhodamine B (RhB) and antibiotic bisphenol A (BPA) under visible light irradiation. Results showed that the obtained AgBr/Ag-3/PbBiO2Br displayed optimal photocatalytic performance, which could remove almost all RhB within 25 min and effectively decompose 82.3% of BPA in 120 min. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) were utilized for the purposes of fully grasping the behaviors of RhB molecules during the reaction process. Meanwhile, the effects of initial RhB concentration and co-existent electrolytes were investigated from the viewpoint of practical application. In addition, there was no obvious loss in degradation efficiency even after four cycles. The enhanced photocatalytic performances of AgBr/Ag/PbBiO2Br could be credited to the accelerated interfacial charge transfer process and the improved separation of the photogenerated electron-hole pairs. The existence of a small amount of metallic Ag played a significant role in preventing AgBr from being further photocorroded, resulting in the formation of a stable Z-scheme photocatalyst system. This study demonstrated that using metallic Ag as an electron mediator to construct Z-scheme photocatalytic system provided a feasible strategy in promoting the stability of Ag-based semiconductors.