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3-Aminopropyltrimethoxysilane (APTMS) was used as ligand to prepare ZnO@APTMS, Cu(2+)-doped ZnO (ZnO:Cu@APTMS) and ZnO quantum dots (QDs) with chemisorbed Cu(2+) ions at their surface (ZnO@APTMS/Cu). The dots have a diameter of ca. 5 nm and their crystalline and phase purities and composition were established by X-ray diffraction, transmission electron microscopy, UV-visible and fluorescence spectroscopies and by X-ray photoelectron spectroscopy. The effect of Cu(2+) location on the ability of the QDs to generate reactive oxygen species (ROS) under light irradiation was investigated. Results obtained demonstrate that all dots are able to produce ROS (OH, O2(-), H2O2 and (1)O2) and that ZnO@APTMS/Cu QDs generate more OH and O2(-) radicals and H2O2 than ZnO@APTMS and ZnO:Cu@APTMS QDs probably via mechanisms associating photo-induced charge carriers and Fenton reactions. In cytotoxicity experiments conducted in the dark or under light exposure, ZnO@APTMS/Cu QDs appeared slightly more deleterious to Escherichia coli cells than the two other QDs, therefore pointing out the importance of the presence of Cu(2+) ions at the periphery of the nanocrystals. On the other hand, with the lack of photo-induced toxicity, it can be inferred that ROS production cannot explain the cytotoxicity associated to the QDs. Our study demonstrates that both the production of ROS from ZnO QDs and their toxicity may be enhanced by chemisorbed Cu(2+) ions, which could be useful for medical or photocatalytic applications., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This work presents the first preparation using the Solution Precursor Plasma Spray process of heterostructured films associating ZnO nanorods (NRs) and various metal oxides (CuO, Fe 2 O 3 and Co 3 O 4) by Solution Precursor Plasma Spray process. These CuO/ZnO, Fe 2 O 3 /ZnO and Co 3 O 4 /ZnO films exhibit hierarchically chocolate sticks-like, dandelion-like or chrysanthemum-like surface morphologies. These heterostructures were confirmed by SEM, XRD, EDS and Raman analyses. The bandgaps of heterostructured films are narrower than that of pure ZnO. The CuO/ZnO film exhibits the highest photocatalytic activity both under UV and visible light irradiation for the degradation of the Orange II dye due to the homogenous distribution of CuO at the surface of ZnO. The high photocatalytic performances originate from the increased visible light absorption and from the effective separation of charge carriers in CuO/ZnO films compared to ZnO NRs. • Hierarchically heterostructured ZnO nanorods films originally deposited via the SPPS route • Heterostructured films generally exhibited better photocatalytic performance than pure ZnO • Suitable distribution of coupled narrow-bandgap metal oxides play important role in photocatalytic activities. [ABSTRACT FROM AUTHOR]

Heterostructured ZnO photocatalysts for the degradation of organic pollutant are mainly synthesized by conventional chemical methods, suffering from long duration, multi-steps, and post-treatment of the powder-formed catalysts after usage. In this paper, Solution Precursor Plasma Spray (SPPS) process is demonstrated to be a fast and efficient method for the one-step preparation of MnO/ZnO and CuO/ZnO heterostructured films for photocatalytic applications. The ratios between MnO or CuO and ZnO materials in the films were easily adjusted by varying the molar ratio of Mn(OAc) 2 or Cu(OAc) 2 relative to Zn(OAc) 2 during the SPPS synthesis. To optimize the microstructure of selected CuO/ZnO films, two alternative spraying patterns were also developed. The modified films (Cu20-ZnO-A and Cu20-ZnO-B) were partly composed of nanorods (NRs) instead of conventional irregular particles. The MnO/ZnO and CuO/ZnO films exhibit narrower bandgap than pure ZnO films. The photocatalytic performances of the ZnO based films were evaluated for the degradation of the Orange II dye. Cu20-ZnO and Cu20-ZnO-B films exhibit the highest degradation efficiency under UV light and visible light, respectively. For example, the SPPS deposited Cu20/ZnO films could almost remove 90% of Orange II within 3 h of UV light irradiation. Moreover, this study not only reveals that SPPS is of high potential for the deposition of heterostructured metal oxide films in rapid one-step, but also points out an efficient spraying strategy for adjusting the nanostructured morphologies in these films. Unlabelled Image • SPPS process was firstly employed to prepare heterostructured MnO/ZnO and CuO/ZnO films for photodegradation. • Particles with nanorods morphology are pioneering observed in CuO/ZnO films. • CuO/ZnO films exhibit the highest photocatalytic activity for the degradation of the Orange II dye. [ABSTRACT FROM AUTHOR]

The light photoresponse, the separation of photogenerated charge carriers and the specific surface area are of great importance for the development of semiconductor‐based photocatalysts. We report the anchorage of small‐sized ZnO nanorods with a length of ca. 38 nm at the surface of graphitic carbon nitride (gCN) sheets. The gCN loading in the ZnO/gCN composites was varied and the materials characterized by TEM, XRD, XPS, BET and UV‐vis diffuse reflectance spectroscopy. The ZnO/gCN (10 %) composite exhibits a high photocatalytic activity for the degradation of dyes (Orange II, Resazurin and Reactive Black 5) under visible light irradiation of low intensity (2.5 mW/cm2) and for salicylic acid under simulated sunlight irradiation (5 mW/cm2). These results are supported by photoluminescence, photocurrent and electrochemical impedance spectroscopy measurements. The photocatalytic activity originates from synergistic effects in ZnO/gCN composites including a high specific surface area (60.4 m2/g), an enhanced visible light absorption capacity and the charge carriers separation. The ZnO/gCN photocatalyst exhibits a high stability and could be reused up to ten times with no loss of efficiency. A mechanism is proposed for the degradation of dyes using the ZnO/gCN composites. Synergy. The growth of ZnO rods at the surface of graphitic carbon nitride sheets affords photocatalysts with high activity under visible light irradiation due to the improvement of separation efficiency of photogenerated electron‐hole pairs and to the increase of specific surface area. [ABSTRACT FROM AUTHOR]

Small-sized ZnO rods with an average length of ca. 180 nm and a diameter of ca. 16 nm were successfully associated to reduced graphene oxide (rGO) via a solvothermal reaction conducted in ethanol. A set of characterization including TEM, SEM, XRD, BET, Raman spectroscopy and UV–vis absorption confirm that the ZnO/rGO composite is composed of highly dispersed ZnO rods bound to rGO nanosheets. The photocatalytic activity of the ZnO/rGO composite was investigated under solar light and under visible light irradiation using the Orange II dye in aqueous solution. Results indicate that the ZnO/rGO composite containing 10 wt% rGO used under solar light irradiation exhibit the highest photocatalytic activity and that the kinetic of reduction is of pseudo-fist-order. The photocatalyst is only weakly sensitive to pH changes and to the presence of inorganic salts or to glucose in the reaction medium. In addition, the reusability of the ZnO/rGO composite was studied and the results demonstrate that the photocatalyst can be reused up to fifteen times with nearly negligible loss of activity. The high photocatalytic performances can be attributed to the high specific surface of ZnO rods, to the enhanced visible light absorption of the ZnO/rGO composite and to the strong decrease of charge carrier recombinations originating from the association of ZnO rods with rGO. [ABSTRACT FROM AUTHOR]