Photodegradation of microcystin-LR using visible light-activated C/N-co-modified mesoporous TiO 2 photocatalyst

Microcystin-LR (MC-LR), a potent hepatotoxin produced by the cyanobacteria, is of increasing concern worldwide because of severe and persistent impacts on humans and animals by inhalation and consumption of contaminated waters and food. In this work, MC-LR was removed completely from aqueous solution using visible-light-active C/N-co-modified mesoporous anatase/brookite TiO 2 photocatalyst. The co-modified TiO 2 nanoparticles were synthesized by a one-pot hydrothermal process, and then calcined at different temperatures (300, 400, and 500 °C). All the obtained TiO 2 powders were analyzed by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), specific surface area (SSA) measurements, ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) analysis. It was found that all samples contained mixed-phase TiO 2 (anatase and brookite), and the content of brookite decreased with an increase in calcination temperature, as well as the specific surface area and the content of non-metal elements. The effects of initial pH value, the TiO 2 content, and MC-LR concentration on the photocatalytic activity were also studied. It was found that the photocatalytic activity of the obtained TiO 2 photocatalysts declined with increasing temperature. The complete degradation (100%) of MC-LR (10 mg L -1 ) was observed within 3 h, using as-synthesized co-modified TiO 2 (0.4 g L -1 ) at pH 4 under visible light. Based on the obtained results, the mechanism of MC-LR degradation has been proposed. © 2019 by the authors

Development of sulfur-doped graphitic carbon nitride for hydrogen evolution under visible-light irradiation

Developing eco-friendly strategies to produce green fuel has attracted continuous and extensive attention. In this study, a novel gas-templating method was developed to prepare 2D porous S-doped g-C(3)N(4) photocatalyst through simultaneous pyrolysis of urea (main g-C(3)N(4) precursor) and ammonium sulfate (sulfur source and structure promoter). Different content of ammonium sulfate was examined to find the optimal synthesis conditions and to investigate the property-governed activity. The physicochemical properties of the obtained photocatalysts were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), specific surface area (BET) measurement, ultraviolet-visible light diffuse reflectance spectroscopy (UV/vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and reversed double-beam photo-acoustic spectroscopy (RDB-PAS). The as-prepared S-doped g-C(3)N(4) photocatalysts were applied for photocatalytic H(2) evolution under vis irradiation. The condition-dependent activity was probed to achieve the best photocatalytic performance. It was demonstrated that ammonium sulfate played a crucial role to achieve concurrently 2D morphology, controlled nanostructure, and S-doping of g-C(3)N(4) in a one-pot process. The 2D nanoporous S-doped g-C(3)N(4) of crumpled lamellar-like structure with large specific surface area (73.8 m(2) g(−1)) and improved electron−hole separation showed a remarkable H(2) generation rate, which was almost one order in magnitude higher than that of pristine g-C(3)N(4). It has been found that though all properties are crucial for the overall photocatalytic performance, efficient doping is probably a key factor for high photocatalytic activity. Moreover, the photocatalysts exhibit significant stability during recycling. Accordingly, a significant potential of S-doped g-C(3)N(4) has been revealed for practical use under natural solar radiation

A comparative study of microcystin-LR degradation by UV-a, solar and visible light irradiation using bare and C/N/S-modified titania

In an endeavor to tackle environmental problems, the photodegradation of microcystin- LR (MC-LR), one of the most common and toxic cyanotoxins, produced by the cyanobacteria blooms, was examined using nanostructured TiO2 photocatalysts (anatase, brookite, anatase- brookite, and C/N/S co-modified anatase-brookite) under UV-A, solar and visible light irradiation. The tailoring of TiO2 properties to hinder the electron-hole recombination and improve MC-LR adsorption on TiO2 surface was achieved by altering the preparation pH value. The highest photocatalytic efficiency was 97% and 99% with degradation rate of 0.002 mmol L-1 min-1 and 0.0007 mmol L-1 min-1 under UV and solar irradiation, respectively, using a bare TiO2 photocatalyst prepared at pH 10 with anatase to brookite ratio of ca. 1:2.5. However, the bare TiO2 samples were hardly active under visible light irradiation (<25%) due to a large band gap. Upon UV, solar and vis irradiation, the complete MC-LR degradation (100%) was obtained in the presence of C/N/S comodified TiO2 with a degradation rate constant of 0.26 min-1, 0.11 min-1 and 0.04 min-1, respectively. It was proposed that the remarkable activity of co-modified TiO2 might originate from its mixedphase composition, mesoporous structure, and non-metal co-modification

A Comparative Study of Microcystin-LR Degradation by UV-A, Solar and Visible Light Irradiation Using Bare and C/N/S-Modified Titania

In an endeavor to tackle environmental problems, the photodegradation of microcystin-LR (MC-LR), one of the most common and toxic cyanotoxins, produced by the cyanobacteria blooms, was examined using nanostructured TiO2 photocatalysts (anatase, brookite, anatase&ndash;brookite, and C/N/S co-modified anatase&ndash;brookite) under UV-A, solar and visible light irradiation. The tailoring of TiO2 properties to hinder the electron&ndash;hole recombination and improve MC-LR adsorption on TiO2 surface was achieved by altering the preparation pH value. The highest photocatalytic efficiency was 97% and 99% with degradation rate of 0.002 mmol L&minus;1 min&minus;1 and 0.0007 mmol L&minus;1 min&minus;1 under UV and solar irradiation, respectively, using a bare TiO2 photocatalyst prepared at pH 10 with anatase to brookite ratio of ca. 1:2.5. However, the bare TiO2 samples were hardly active under visible light irradiation (&lt;25%) due to a large band gap. Upon UV, solar and vis irradiation, the complete MC-LR degradation (100%) was obtained in the presence of C/N/S co-modified TiO2 with a degradation rate constant of 0.26 min&minus;1, 0.11 min&minus;1 and 0.04 min&minus;1, respectively. It was proposed that the remarkable activity of co-modified TiO2 might originate from its mixed-phase composition, mesoporous structure, and non-metal co-modification

Bi2WO6-based Z-scheme photocatalysts : Principles, mechanisms and photocatalytic applications

The development of novel photocatalysts for efficient utilization of solar energy is highly essential for the most critical humanitarian challenges, i.e., energy and water crises as well as environmental pollution. Bismuth tungstate (Bi2WO6), an outstanding Aurivillius phase perovskite, has attracted intensive attention as a visiblelight-responsive photocatalyst because of its non-toxicity, low cost, and outstanding physicochemical characteristics, i.e., nonlinear dielectric susceptibility, ferroelectric piezoelectricity, pyroelectricity, catalytic behavior, modifiable morphology, strong oxidation power, and good photochemical stability. However, the photocatalytic activity of bare Bi2WO6 is restricted because of the inherent drawbacks such as poor light-harvesting efficiency, weak reduction potential, relatively low specific surface area, the fast recombination rate of photoinduced charge carriers, and thus poor quantum yields of photocatalytic reactions. Moreover, the impossibility of simultaneous strong redox ability (demanding wide bandgap) and high light-harvesting efficiency (requiring narrow bandgap) is considered as a big challenge for the practical application of Bi2WO6. Undeniably, the construction of Z-scheme photocatalytic systems is recommended strategy to overcome the above-mentioned disadvantages because of the efficient spatial separation of photogenerated charge carriers and the boosting the redox performance. This review summarizes the principles and recent developments on Z-scheme photocatalytic systems with special emphasis on the Bi2WO6-based photocatalysts, including the types, photocatalytic mechanisms and practical applications. Moreover, major differences between type-II heterojunction and Z-scheme photocatalyst have also been discussed. Additionally, the significant role of unique structures (e.g., core-shell and 2D/2D) for the improvement of photocatalytic activity of Z-scheme photocatalyst has been presented. Indeed, Bi2WO6-based Zscheme photocatalysts have exhibited superior photocatalytic activity for various applications. For example, they show high photocatalytic activity towards water/wastewater treatment (removal of organic and inorganic pollutants, as well as microorganisms), air purification (decomposition of volatile organic compounds and inorganic matters), green energy conversion (e.g., generation of H2 and CH4 fuels under solar irradiation), and organic synthesis. It is thought that this remarkable activity of Bi2WO6-based Z-scheme photocatalysts might be attributed to the efficient solar light harvesting, separation and further transfer of charge carriers and strong redox ability. To the best of our knowledge, the present paper is the first attempt to summarize the Bi2WO6-based Zscheme photocatalytic reactions, providing important insights and up-to-date information for the scientific community to fully explore the potential of Bi2WO6-based photocatalysts for renewable environmental remediation, energy conversion, and chemical synthesis

In Silico-Based Repositioning of Phosphinothricin as a Novel Technetium-99m Imaging Probe with Potential Anti-Cancer Activity

l-Phosphinothricin (glufosinate or 2-amino-4-((hydroxy(methyl) phosphinyl) butyric acid ammonium salt (AHPB)), which is a structural analog of glutamate, is a recognized herbicide that acts on weeds through inhibition of glutamine synthetase. Due to the structural similarity between phosphinothricin and some bisphosphonates (BPs), this study focuses on investigating the possibility of repurposing phosphinothricin as a bisphosphonate analogue, particularly in two medicine-related activities: image probing and as an anti-cancer drug. As BP is a competitive inhibitor of human farnesyl pyrophosphate synthase (HFPPS), in silico molecular docking and dynamic simulations studies were established to evaluate the binding and stability of phosphinothricin with HFPPS, while the results showed good binding and stability in the active site of the enzyme in relation to alendronate. For the purpose of inspecting bone-tissue accumulation of phosphinothricin, a technetium (99mTc)–phosphinothricin complex was developed and its stability and tissue distribution were scrutinized. The radioactive complex showed rapid, high and sustained uptake into bone tissues. Finally, the cytotoxic activity of phosphinothricin was tested against breast and lung cancer cells, with the results indicating cytotoxic activity in relation to alendronate. All the above results provide support for the use of phosphinothricin as a potential anti-cancer drug and of its technetium complex as an imaging probe

Development of Sulfur-Doped Graphitic Carbon Nitride for Hydrogen Evolution under Visible-Light Irradiation

Developing eco-friendly strategies to produce green fuel has attracted continuous and extensive attention. In this study, a novel gas-templating method was developed to prepare 2D porous S-doped g-C3N4 photocatalyst through simultaneous pyrolysis of urea (main g-C3N4 precursor) and ammonium sulfate (sulfur source and structure promoter). Different content of ammonium sulfate was examined to find the optimal synthesis conditions and to investigate the property-governed activity. The physicochemical properties of the obtained photocatalysts were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), specific surface area (BET) measurement, ultraviolet-visible light diffuse reflectance spectroscopy (UV/vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and reversed double-beam photo-acoustic spectroscopy (RDB-PAS). The as-prepared S-doped g-C3N4 photocatalysts were applied for photocatalytic H-2 evolution under vis irradiation. The condition-dependent activity was probed to achieve the best photocatalytic performance. It was demonstrated that ammonium sulfate played a crucial role to achieve concurrently 2D morphology, controlled nanostructure, and S-doping of g-C3N4 in a one-pot process. The 2D nanoporous S-doped g-C3N4 of crumpled lamellar-like structure with large specific surface area (73.8 m(2) g(-1)) and improved electron-hole separation showed a remarkable H-2 generation rate, which was almost one order in magnitude higher than that of pristine g-C3N4. It has been found that though all properties are crucial for the overall photocatalytic performance, efficient doping is probably a key factor for high photocatalytic activity. Moreover, the photocatalysts exhibit significant stability during recycling. Accordingly, a significant potential of S-doped g-C3N4 has been revealed for practical use under natural solar radiation