Abstract
Multi-walled carbon nanotubes (CNTs) decorated with zinc oxide nanoparticles (ZnO NPs) were prepared in isopropanol solution by a simple, room-temperature process and characterized from structural, morphological, electronic, and optical points of view. A strong interaction between ZnO and CNTs is fully confirmed by all the characterization techniques. ZnO-CNTs nanocomposites, with different weight ratios, were deposited as a dense layer between two electrodes, in order to investigate the electrical behaviour. In particular, the electrical response of the nanocomposite layers to UV light irradiation was recorded for a fixed voltage: As the device is exposed to the UV lamp, a sharp current drop takes place and then an increase is observed as the irradiation is stopped. The effect can be explained by adsorption and desorption phenomena taking place on the ZnO nanoparticle surface under irradiation and by charge transfer between ZnO and CNTs, thanks to the strong interaction between the two nanomaterials. The nanocomposite material shows good sensitivity and fast response to UV irradiation. Room temperature and low-cost processes used for the device preparation combined with room temperature and low voltage operational conditions make this methodology very promising for large scale UV detectors applications.
Highlights
Zinc oxide has received great attention in several application fields due to its sensitivity to environmental factors such as humidity, gas species and light irradiation
More effort still has to be concentrated on the study of sensitive materials that can operate as sensors at room temperature
We report on room-temperature, low-cost preparation of nanocomposite layers obtained by decorating multi-walled carbon nanotubes with zinc oxide nanoparticles and their applicability as sensitive layers for UV light detection at room temperature
Summary
Zinc oxide has received great attention in several application fields due to its sensitivity to environmental factors such as humidity, gas species and light irradiation. Much effort has been made to reduce the operating temperature to room temperature, mainly to reduce the energy waste during sensors operation and to avoid gas explosion in the presence of flammable and explosive gases To this aim, several approaches [9] have been explored, like doping with metals, modifying ZnO surface/defectivity or, preparing ZnO-based composites in order to increase the conductivity of the oxide [9,10,11,12,13,14,15,16]. Kwon et al [17] reported the synthesis of ZnO-decorated CNTs for gas sensing applications, but their procedure involved sputtering (for catalyst deposition) and high-temperature thermal processes (500 ◦C) for the growth of ZnO nanoparticles. The advantages of the methodology described in this paper with respect to previous works are: room temperature deposition on localized regions of the device, no need for post-deposition thermal annealing processes, very low voltage and room temperature operation of the devices, and an ultra-small sensitive area
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