Preparation and enhanced photoluminescence property of ordered ZnO/TiO2 bottlebrush nanostructures

A Facile Route to the Preparation of Highly Uniform ZnO@TiO2 Core-Shell Nanorod Arrays with Enhanced Photocatalytic Properties

Design and synthesis of ZnO@TiO2 core-shell nanorod arrays as promising photocatalysts have been widely reported. However, it remains a challenge to develop a low-temperature, low-cost, and environmentally friendly method to prepare ZnO@TiO2 core-shell nanorod arrays over a large area for future device applications. Here, a facile, green, and efficient route is designed to prepare the ZnO@TiO2 nanorod arrays with a highly uniform core-shell structure over a large area on Zn wafer via a vapor-thermal method at relatively low temperature. The growth mechanism is proposed as a layer-by-layer assembly. The photocatalytic decomposition reaction of methylene blue (MB) reveals that the ZnO@TiO2 core-shell nanorod arrays have excellent photocatalytic activities when compared with the performance of the ZnO nanorod arrays. The improved photocatalytic activity could be attributed to the core-shell structure, which can effectively reduce the recombination rate of electron-hole pairs, significantly increase the optical absorption range, and offer a high density of surface active catalytic sites for the decomposition of organic pollutants. In addition, it is very easy to separate or recover ZnO@TiO2 core-shell nanorod array catalysts when they are used in water purification processes.

Seedless growth of ZnO nanorods on TiO2 fibers by chemical bath deposition

Seedless growth of ZnO nanorods on TiO₂ microfibers was reported, and the growth mechanism was demonstrated.

A facile low-temperature approach to designing controlled amorphous-based titania composite photocatalysts with excellent noble-metal-free photocatalytic hydrogen production

A microporous amorphous-based titania composite photocatalysts has been fabricated using a facile low-temperature (120 °C) synthetic method. Notably, we have successfully prepared the various stages of the amorphous/crystalline heterostructure by simply adjusting the pH value. The high-pH sample favors the formation of amorphous based titania composite structure. Additionally, the BET surface area of the sample increases with the increasing of the pH value, reaching a maximum of 358 m(2) g(-1) when the pH value is 12. Unexpectedly, the H2 productivity of amorphous-based composite photocatalyst without noble metal co-catalyst increases significantly with the increasing pH value, which is attributed to the quickly increasing amorphous, and the highly active catalytic centers created by the synergistic effect between crystalline TiO2 and amorphous ZnO. This study demonstrates that it is possible to improve the properties of the amorphous-based composite photocatalyst by properly modifying the synthesis conditions. The approach presented herein can be applied to the research of controlled amorphous-based composite photocatalytic systems.

Decoration of ZnO Nanorods with Coral Reefs like NiO Nanostructures by the Hydrothermal Growth Method and Their Luminescence Study

Composite nanostructures of coral reefs like p-type NiO/n-type ZnO were synthesized on fluorine-doped tin oxide glass substrates by hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. This investigation shows that the adopted synthesis leads to high crystalline quality nanostructures. The morphological study shows that the coral reefs like nanostructures are densely packed on the ZnO nanorods. Cathodoluminescence (CL) spectra for the synthesized composite nanostructures are dominated mainly by a broad interstitial defect related luminescence centered at ~630 nm. Spatially resolved CL images reveal that the luminescence of the decorated ZnO nanostructures is enhanced by the presence of the NiO.

Microwave-assisted and conventional sol-gel preparation of photocatalytically active ZnO/TiO2/glass multilayers

For the first time a combination of microwaves and/or the conventional treatment method was used to dry and heat multilayered sol-gel ZnO/TiO2/glass structures. Compact or porous TiO2 films were deposited as a bottom layer, covered with a ZnO film. The structures were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM). Only peaks of wurtzite ZnO crystalline phase were registered on the X-Ray diffractograms. The microwave irradiation leads to a formation of poorly crystallized multilayers with very small crystallites and enhanced surface roughness. This results in a better photocatalytic activity of these structures than the structures of the samples treated conventionally. It was established that the morphology of the bottom titania layer affects the reaction of photocatalytic degradation of Malachite Green dye (MG). The structures with the compact bottom TiO2 films showed higher activities than those on porous TiO2 films. This study offers an energy saving method of producing ZnO/TiO2/glass multilayered structures of various morphologies and pronounced photocatalytic properties. The method does not involve any calcination step, normally applied to achieve a good degree of crystallization. This makes the method suitable for protecting substrates of low thermal stability.

Microstructure and optical properties of Ag-doped ZnO nanostructures prepared by a wet oxidation doping process

Silver-doped zinc oxide (Ag:ZnO) nanostructures were prepared by a facile and efficient wet oxidation method. This method included two steps: metallic Zn thin films mixed with Ag atoms were prepared by magnetron sputtering as the precursors, and then the precursors were oxidized in an O(2) atmosphere with water vapour present to form Ag:ZnO nanostructures. By controlling the oxidation conditions, pure ZnO and Ag:ZnO nanobelts/nanowires with a thickness of ∼ 20 nm and length of up to several tens of microns were synthesized. Scanning electron microscopy, transmission electron microscopy, cathodoluminescence and low temperature photoluminescence (PL) measurements were adopted to characterize the microstructure and optical properties of the prepared samples. The results indicated that Ag doping during magnetron sputtering was a feasible method to tune the optical properties of ZnO nanostructures. For the Ag:ZnO nanostructures, the intensity of ultraviolet emission was increased up to three times compared with the pure ones. The detailed PL intensity variation with the increasing temperature is also discussed based on the ionization energy of acceptor in ZnO induced by Ag dopants.

Heterogeneous lollipop-like V2O5/ZnO array: a promising composite nanostructure for visible light photocatalysis

ZnO/V(2)O(5) core-shell nanostructures have been prepared by a two-step synthesis route through combined hydrothermal growth and magnetron sputtering. After annealing under oxygen ambience, a ZnO/V(2)O(5) heterogeneous lollipop-like nanoarray formed. The microstructure and crystal orientation of those nanolollipops were investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), which show single crystal structure. The optical properties were characterized by UV-vis spectroscopy and showed quite different absorption curves for the as-deposited and annealed samples. The ZnO/V(2)O(5) nanolollipops demonstrated excellent photocatalytic activity in terms of decomposing 2,6-dichlorophenol (2,6-DCP) under visible light, indicating their promising potential as catalysts for industrial wastewater and soil pollution treatments.

Enhanced visible photoluminescence of V(2)O(5) via coupling ZnO/V(2)O(5) composite nanostructures

V(2)O(5) films capped by a thin ZnO layer had been prepared by sputtering method at room temperature. The initial smooth films transferred to porous composite nanocrystals and nanorods after annealed at 500 degrees C, and enhanced visible light emission was observed. This tremendous enhancement was attributed to the coupling between V(2)O(5) nanorods and ZnO nanoparticles as well as the improved V(2)O(5) crystallinity. Prominent vibrational fine structures of the photoluminescence spectra were also observed.