Graphene acid-hollow metal oxides composites for gas sensor

Abstract

Innovation in the gas sensors science and technology have great importance for the sustainable development of new materials with better performance. The research project concerns the evaluation of the use of graphene acid (GA) in the n-type (e.g., SnO2, CeO2, WO3) and p-type (e.g., CuO, Co3O4, Cr2O3) metal oxide semiconductors (MOS). The GA-MOS composites must improve the sensitivity, selectivity and response time of gas sensors, mainly for volatile organic compounds (VOCs). GA is a novel graphene derivative with a quasi-stoichiometric amount of carboxylic acid functional groups and going to be synthesized by the re-oxidation of graphene oxide. The hollow nano-microstructured MOS was going to be prepared from hard templates such as SiO2, soft templates (nano or microemulsions), Ostwald ripening during microwave-assisted hydrothermal synthesis or Kirkendall effect during heating in air. GA-MOS composites will be prepared by the ultrasonic spray. It is expected that GA increases the surface area of the composites and contributes to the selective adsorption of gasses by the action of their carboxylic groups (via hydrogen bonds). On the other hand, the main benefits of the hollow structures of the MOS would be the better diffusivity of the gasses in their internal and external layers and also the increase in the number of pores in the shell of the oxides. The number of active sites for adsorption of oxygen and analyte gas molecules is also increased in hollow structures. The sensorial responses going to be evaluated in the presence of different concentrations (in the ppm and ppb ranges) of VOCs (e.g., acetone, acetaldehyde, ethanol, methanol, benzene, xylene, and toluene) and high relative humidity (e.g., up to 98%). The proposal is original because it is intended to study a new derivative of graphene in hollow MOS composites to obtain more sensitive, selective and with quick response times compared to those already described in the literature. It should be noted that GA has not yet been applied as a gas sensor. Besides the scientific impact, it is sought the increment in the training of human resources at the undergraduate and postgraduate levels. (AU)