Effects of zinc precursor, basicity and temperature on the aqueous synthesis of ZnO nanocrystals

The effects of the zinc salt precursors, the reaction temperature and the alkaline ratio b (b = [OH-]/[Zn2+]) on the aqueous synthesis of ZnO nanocrystals were investigated. Depending on the type of the zinc precursor, Zn5(OH)8Cl2·H2O or Zn5(OH)8(NO3)2.2H2O lamellar phases were obtained at room temperature (20°C) when the alkaline ratio is lower (0.5 ≤ b ≤ 1, 6 ≤ pH ≤ 6.4). When the reaction temperature increased to 95 °C, zinc hydroxide chloride monohydrate was obtained in one case whereas zinc oxide was formed in the other, and no lamellar phase of Zn5(OH)8(NO3)2.2H2O was obtained. Thermal decomposition of the two lamellar phases was carried out and mainly showed that Zn5(OH)8(NO3)2.2H2O was completely decomposed to ZnO when the annealed temperature reached ~250 °C while Zn5(OH)8Cl2·H2O was totally transformed to ZnO at about 400 °C, a higher comparative temperature that confirms the better thermal stability of the zinc hydroxide chloride monohydrate.Keywords: Oxides, ZnO, chemical synthesis, X-ray diffraction, crystal structure, luminescenc

Heterostructured Photocatalysts Associating ZnO Nanorods and Ag-In-Zn-S Quantum Dots for the Visible Light-Driven Photocatalytic Degradation of the Acid Orange 7 Dye

Heterostructured photocatalysts associating ZnO nanorods (NRs) sensitized by quaternary Ag-In-Zn-S (AIZS) quantum dots (QDs) were prepared by depositing AIZS QDs at the surface of ZnO NRs followed by thermal treatment at 300 °C. The ZnO/AIZS catalysts were characterized by X-ray diffraction, electron microscopy, UV-vis diffuse spectroscopy and by photoelectrochemical measurements. Their photocatalytic activity was evaluated for the bleaching of the Acid Orange 7 (AO7) dye under visible light irradiation. Results show that the association of ZnO NRs with 10 wt% AIZS QDs affords the photocatalyst the highest activity due to the enhanced visible light absorption combined with the improved charge separation. The ZnO/AIZS(10) photocatalyst degrades 98% AO7 in 90 min under visible light illumination, while ZnO NRs can only decompose 11% of the dye. The ZnO/AIZS(10) photocatalyst was also found to be stable and can be reused up to eight times without significant alteration of its activity. This work demonstrates the high potential of AIZS QDs for the development of visible light active photocatalysts

High performance Ce-doped ZnO nanorods for sunlight-driven photocatalysis

Ce-doped ZnO (ZnO:Ce) nanorods have been prepared through a solvothermal method and the effects of Ce-doping on the structural, optical and electronic properties of ZnO rods were studied. ZnO:Ce rods were characterized by XRD, SEM, TEM, XPS, BET, DRS and Raman spectroscopy. 5% Ce-doped ZnO rods with an average length of 130 nm and a diameter of 23 nm exhibit the highest photocatalytic activity for the degradation of the Orange II dye under solar light irradiation. The high photocatalytic activity is ascribed to the substantially enhanced light absorption in the visible region, to the high surface area of ZnO:Ce rods and to the effective electron–hole pair separation originating from Ce doping. The influence of various experimental parameters like the pH, the presence of salts and of organic compounds was investigated and no marked detrimental effect on the photocatalytic activity was observed. Finally, recyclability experiments demonstrate that ZnO:Ce rods are a stable solar-light photocatalyst

Tunable morphologies of ZnO films via the solution precursor plasma spray process for improved photocatalytic degradation performance

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Copper octacarboxyphthalocyanine as sensitizer of graphitic carbon nitride for efficient dye degradation under visible light irradiation

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Bismuth oxybromide/reduced graphene oxide heterostructure sensitized with Zn-tetracarboxyphthalocyanine as a highly efficient photocatalyst for the degradation of Orange II and phenol

International audienceThe preparation of heterostructured photocatalysts associating BiOBr, reduced graphene oxide (rGO) and zinc tetracarboxyphthalocyanine (ZnPc(CO2H)4) and their performance for the degradation of the Orange II dye and of phenol are reported. The BiOBr/rGO/ZnPc(CO2H)4(0.25) photocatalyst displays a superior activity than BiOBr and BiOBr/rGO, indicating that ZnPc(CO2H)4 enhances both the visible light absorption and the charge carrier separation, which is confirmed by photoluminescence, photocurrent responses and electrochemical impedance spectroscopy Nyquist plots. Scavenging experiments show that the main active species involved in the degradation of Orange II and phenol are superoxide radicals and holes and a mechanism is proposed. Due to its high stability, the BiOBr/rGO/ZnPc(CO2H)4(0.25) catalyst shows high potential for real environmental remediation

Core/shell rGO/BiOBr particles with visible photocatalytic activity towards water pollutants

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