Ultraviolet Detection and Photocatalytic Activity of Nanostructured LaCoO3 Prepared by Solution-Polymerization

Abstract

LaCoO3 is a p-type semiconductor material with unique electrical and magnetic properties and has been one of the most studied cobalt-based perovskites. Its narrow bandgap energy (∼2.2 eV) suggests its possible application for detecting radiation in the ultraviolet and visible light regions. With this goal, nanostructured LaCoO3 was prepared by the solution-polymerization method. The calcination at 700°C produced nanostructured sheets of single-phase LaCoO3, with plenty porosity. The electrical characterization was performed on thick films prepared by depositing a suspension of the perovskite on alumina substrates. The variation of resistance caused by the exposure to radiation was used to evaluate its sensing properties. As UV source, a light emitting diode (LED) with wavelength (λ) of 365 nm was used. The detection of light with larger λ was also investigated. The results show uniform response patterns in numerous on/off cycles. Moreover, a proportional decrease of resistance with optical irradiance was observed. This can be explained by the increase on the number of electrical charge carriers produced by the incoming photons. Since the photocatalytic properties of a semiconductor material are associated to the surface formation of electrical charged species, the degradation of green malachite using LaCoO3 (in powder) was evaluated.