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The photocatalyst S-scheme BiFeO3–g-C3N4 had been prepared by combining calcination and hydrothermal reaction. 10% BiFeO3–g-C3N4 composite showed the greatest photocatalytic effect during tetracycline hydrochloride degradation (TC-HCl, 99.7% removal) within 100 min. Meantime, the photocatalytic efficacy was further confirmed by the removal efficiency of ciprofloxacin(CIP, 98.2% removal). The formation of S-scheme heterostructure and matching valence band and conduction band may be responsible for the improved photocatalytic efficiency of BiFeO3–g-C3N4. This leads to the rapid separation of photo-induced carriers, increased electronic transport capacity, and extended carrier lifetime. A study was done on the potential mechanism by employing chemical scavenger experiment revealing the paramount role of O2−. The composite could maintain photocatalytically stable even after five consecutive reaction cycles. The recovery efficiency of 10% BiFeO3–g-C3N4 was high because of the magnetic property of BiFeO3, which was convenient for the recycling process. The produced photocatalyst has potential use in the field of photocatalysis, and this work provides a novel thought to raise the photocatalysts recovery efficiency during recycling. [ABSTRACT FROM AUTHOR]

Worldwide energy and environmental issues are forcing researchers to develop a green approach to produce a clean energy. However, traditional methods in reforming of fossil fuels to produce hydrogen (H2) are causing CO2 emission. Hydrogen is therefore an indirect greenhouse gas with a global warming potential. Hydrogen with high specific energy density can be considered as an efficient energy carrier as compared to fossil fuels. But hydrogen production from water splitting reaction has low efficiency, which limits its generation by green approach. For addressing this issue, different chemical hole scavengers have been applied, which is causing further environmental and economic problems. By using biomass as a hole scavenger to improve rate of H2 generation, environmental pollution can be controlled and value-added chemicals can be produced via its oxidation reaction. In this mini review, the effect of different influencing factors such as type of biomass feedstock, irradiation wavelength and intensity, and nature and function of applied photocatalysts in particular their structural/dimensional on the biomass photocatalytic reforming process to produce clean hydrogen will be discussed. Moreover, the fundamental principles of this process including kinetics and mechanism of the reaction will be also addressed. [ABSTRACT FROM AUTHOR]

Interaction of amorphous and crystalline TiO2 ultrafine particles (2–6 nm) with rutin results in the formation of colored nanomaterials of an excellent dispersity and enhanced colloidal stability in aqueous media. The FTIR and Raman spectra confirmed attachment of the rutin ligand via vicinal hydroxyl groups in a catechol-like fashion. The binding of rutin to amorphous TiO2 gives rise to spontaneous crystallization of the parent nanoparticles into hydrogen titanates (H2Ti3O7 and H2Ti12O25). Such structural transformations result in photosensitization toward visible light with enhanced efficiency of the charge separation and interfacial charge transfer processes, confirmed by detailed photoelectrochemical studies of the examined nanomaterials. The effectiveness of the photocatalytic ROS generation reactions was also strongly influenced by hydrogen peroxide, which plays a double role of a reactant prone to reduction and generation of hydroxyl radicals or a redox agent destroying the intra-band gap electronic states, suppressing thereby charge recombination. The photoinduced charge transfer processes lead to generation of various reactive oxygen species, which were detected by EPR using DMPO spin trap (HOO· detection) and in the reaction with terephthalic acid acting as a chemical scavenger (HO· detection). Complexation of TiO2 particles with rutin shifts the photogeneration of hydroperoxyl (HOO·) and hydroxyl (HO·) radicals toward visible light (λ > 400 nm). A triple effect of rutin attachment to titania was established. It consists in pronounced photosensitization, promotion of crystallization and enhancement of the colloidal stability of ultrafine titania particles. Environmental implications of these assets on the photoinduced redox reactions with hydrogen peroxide in aqueous solutions upon UV or visible light irradiation were also discussed. [ABSTRACT FROM AUTHOR]

BiOI microspheres were synthesized by using mild conditions under microwave irradiation and applying short reaction times. The effect of the reaction medium in the final morphology of BiOI was revised modifying the relative concentrations of 2-propanol and ethylene glycol (EG) used as solvents. The as-prepared samples were characterized by X-ray powder diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, N2 adsorption-desorption isotherms and photoluminescence measurements. The photocatalytic activity of BiOI was evaluated in the oxidation reaction of nitric oxide (NO) under visible-light irradiation. In particular, the samples with morphology of 3D flower-like microspheres prepared with EG showed the highest activity for NO removal (83%), maintaining its performance after several photocatalytic cycles. Besides the morphology of BiOI samples, the high photocatalytic activity was associated with the large surface area and the low rate of charge recombination observed in samples prepared with EG. The use of scavenger agents allowed to determine the predominant participation of holes (h+), electrons (e−) and superoxide ion (·O2−) in the reaction mechanism of the NO oxidation. [ABSTRACT FROM AUTHOR]

Supported cobalt oxides on mesoporous nitrogen-doped carbon (CoxOy/NC) were prepared by a simple pyrolysis method using cobalt acetate as the cobalt source and chitosan as the nitrogen and carbon source. The as-synthesized catalysts were characterized by XRD, N2 adsorption/desorption, SEM, TEM and XPS. It was found that chitosan was transformed to mesoporous carbon after pyrolysis at 900 °C under N2 atmosphere, while Co2+ was reduced to metallic Co covering with cobalt oxide, which was uniformly distributed in the surface of carbon. The catalytic performances were examined by Acid Orange 7 (AO7) degradation with H2O2 as an oxidant in bicarbonate aqueous solution. The dye was decolorized completely after 20 min at room temperature with the CoxOy/NC catalyst. The catalyst can be recycled up to four times without significant loss of activity. The addition of methanol as a hydroxyl radical scavenger confirmed that the radicals take part in the reaction as the major active species. In addition, intermediate products were identified by electrospray ionization-mass spectrometry during the degradation of AO7. [ABSTRACT FROM AUTHOR]

The synthesis of (6-ethyl-1,6-dihydropyrrolo[3,2-c]carbazol-2-yl)methanol 5 and (6-ethyl-6,11-dihydro-1H-dipyrrolo[3,2-c:2′,3′-g]carbazole-2,10-diyl)dimethanol 6 were achieved via the reduction of methyl pyrrolo carbazole carboxylate 3 and methyl dipyrrolo carbazole carboxylate 4, respectively. The structures of hydroxymethyl-pyrrolocarbazoles 5 and 6 were supported by FT-IR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1H and 13C NMR spectroscopy. The photophysical properties of the targeted compounds 3-6 were investigated by employing absorption and fluorescence spectroscopy in different common organic solvents. Also, the fluorescence lifetime (τF) of the compounds was measured utilizing a time-correlated single-photon counting technique in tetrahydrofuran. Antioxidant activities of compounds 3-6 were determined by employing three different assays, namely DPPH radical scavenging, ABTS cation radical decolarization and cupric reducing antioxidant capacity. The results revealed that the ABTS cationic scavenging activity assay was found to be the most sensitive method for the determination of inhibition values. [ABSTRACT FROM AUTHOR]

A deposition method was applied to synthesize a multicomponent photocatalyst based on apatite (HaP)-coated Ag/AgBr/Bi2WO6 (denoted as HaP/Ag/AgBr/Bi2WO6). Various techniques were applied to identify the synthesized photocatalyst. The photocatalytic activity of the prepared photocatalysts was examined using degradation of rhodamine B, methyl orange, and phenol as pollutants under visible-light irradiation. The results of the photocatalytic experiments showed that the HaP/Ag/AgBr/Bi2WO6 multicomponent composite exhibited excellent visible-light-driven photocatalytic activity. Meanwhile, studies on the photocatalytic activity determined that the simultaneous effects of the adsorption properties of HaP, the surface plasmonic resonance of the Ag nanoparticles, the photocatalytic activity of AgBr under visible light, and reactive oxygen species (ROS) contributed to the enhanced photocatalytic activity of the HaP/Ag/AgBr/Bi2WO6 composite. Moreover, based on studies conducted using radical scavengers, the main reactive species in the photocatalytic reaction for degradation of all the chemical pollutants were revealed and a photocatalytic mechanism for the degradation of organics over HaP/Ag/AgBr/Bi2WO6 is proposed. Furthermore, HaP/Ag/AgBr/Bi2WO6 exhibited good stability in cyclic photocatalytic trials. [ABSTRACT FROM AUTHOR]