Synthesis and Characterization of the ZnO/SnO2 Heterostructures obtained by Hydrothermal Method: Gas Sensor Applications

Abstract

Nowadays, the high agricultural productivity is related to use of the fertilizers, mainly the fertilizer nitrogen which are essentials for large crops, such as corn and rice. The main challenge in this area consists to improve the harnessing of the fertilizers, due the large losses of the nitrogen through volatilization process. This process consists in the oxidation of these sources on the soil which generates the NOx, a gas which contributes to global climate change and ozone depletion. Based on these findings, it is necessary to find efficient ways to detect and quantify NOx gas in the environment. Among the oxide materials which exhibit a good performance as gas sensor, the zinc oxide (ZnO) and tin oxide (SnO2) have been promising. Nevertheless, the electronic effects adverse during the charge separation process, and consequent formal signal (carrier's recombination) reduce the potential of these materials. Recently, the heterostructures combining two metal oxide semiconductors have been investigated as an alternative way to reduce the recombination process. Up to date, there are few studies about the gas sensing properties of the ZnO/SnO2 heterostructures under UV light illumination. Herein, we propose the synthesis of the ZnO and SnO2 nanostructured and ZnO/SnO2 heterostructures using hydrothermal treatment, and their applications as NOx sensor with and without UV light illumination. The ZnO/SnO2 heterostructures will be synthesized by sol-gel method assisted by hydrothermal crystallization, which allows the synthesis of both oxides and its heterostructures. The heterostructures will be prepared using different molar ratio Zn:Sn, besides the conventional characterization methods, we propose an investigation "in-situ" of the electronic structure and the short-order range structure using the X-ray absorption spectroscopy, to evaluate the effect of molar ratio Zn:Sn as well as the exposure to different gases, mainly NOx.