Síntese e caracterização de molibdato de cério pelo método hidrotérmico assistido por micro-ondas: aplicação como sensor de gás ozônio

Abstract

Materials based on metallic molybdates have attracted many studies, due to their properties leading to numerous technological applications in several areas, such as: photoluminescence, photocatalysis and resistive gas sensors. In this work, we performed the synthesis of cerium molybdate (Ce2(MoO4)3) nanocrystals via the coprecipitation method followed by the microwave-assisted hydrothermal (MAH) treatment at 150 °C during different times (15, 30, and 60 min). This study showed that the effect of the MAH treatment time influenced the microstructural, optical and ozone gas-sensing properties. X-ray diffraction (XRD) and Raman spectroscopy measurements revealed that the samples presented a single-crystalline phase with scheelite-type tetragonal structure. Field emission gun scanning electron microscopy (FEG-SEM) images showed that MAH conditions favored changes in the morphology of the Ce2(MoO4)3 nanocrystals. In addition, transmission electron microscopy (MET) revealed that the interplanar distances corresponding to the main peak found in the XRD diffractogram, and the SAED confirmed that the samples are polycrystalline with concentric rings. The photoluminescence (PL) measurements indicated a significant increase in the PL emission with the time MAH, suggesting an increase in the intrinsic defects formed during the synthesis. The gas-sensing performance of cerium molybdate nanocrystals in relation to ozone sub-ppm levels was also investigated. The experiments revealed complete recovery and good repeatability as well as a good sensor response, which was improved in the sample synthesized in the longer time of the HMO.