Single Metal-organic Precursors Research Articles

Enhanced response and selectivity of H2S sensing through controlled Ni doping into ZnO nanorods by using single metal organic precursors

We report on enhancing the selectivity and response of room (23 °C) and high temperature H2S gas sensing through controlled Ni doping (0–10 at%) into ZnO nanorods (NRs) grown with a facile solution growth method using a single hybrid bimetallic metal-organic precursor (nickel/zinc acetylacetonate). The morphology, microstructure, surface chemistry and photoluminescence properties of the as-grown NRs are extensively examined. The gas sensing results are discussed in terms of doping concentration, operating temperature, gas type, gas concentrations and relative humidity. The optimal response toward 100 ppm of H2S reaches 3.1 at 23 °C and increases to 45.3 at 200 °C for 8 at% Ni-doped ZnO NR sensors, where the corresponding response/recovery time at 23 °C and 200 °C also reaches 76/160 and 48/60 s, respectively. The same sensor exhibits high H2S selectivity over other gases, including CH4, CH3OH and C2H5OH. The enhancement of gas sensing is attributed to increasing the number of active sites for adsorption of oxygen and target gases on the surface through incorporation of Ni3+ over Ni2+ ions. At 23 °C, the sensing mechanism is related to the formation of a 7 nm-thick ZnS layer over the NRs through reactions between H2S and adsorbed oxygen.

Cu doped ZnO nanorods with controllable Cu content by using single metal organic precursors and their photocatalytic and luminescence properties

Controlled doping into nanomaterials is an enabling technology for functional nanodevices, but still challenging. We report the accomplishment of a facial growth method of controlling Cu doping concentration into ZnO nanorod arrays systematically as an example by faith transfer of Cu content in single hybrid bimetallic organic precursors, zinc copper acetylacetonate, to the end ZnO nanorod arrays using solution method. The incorporation of Cu content is demonstrated to vary from 0 at.% to 10 at.% with a step of 2 at.%, where the control over the accuracy of Cu content can be better. The as-synthesized nanorods of around 150 nm in diameter are characterized by single crystallinity. The systematic Cu incorporation is proved by energy dispersive spectroscopy and X-ray diffraction. Photoelectron spectroscopy shows that the ratio of Cu+2 to Cu+1 varies accordingly, an increasing trend with total Cu doping concentration. The optical and photocatalytic properties of the Cu-doped ZnO nanorods are thus studied. The results reveal that the photodegradation of methyl orange is facilitated with Cu doping and the role of multi-valences of Cu ions on surface is proposed. Several unique features in photoluminescence also accompany with Cu doping, including the UV peak shift toward longer wavelength, the decrease of UV/visible intensity ratio, the increase of visible light emission and the shift of visible light emission from green to orange.