Alcohol selectivity of a room temperature-operated gas sensor based on TiO2 burr-like nanorods

Abstract

• A TiO 2 -based room temperature-operated gas sensor and a portable system were built. • The response increases as the carbon chain length of the alcohols increases. • The response decreases in the order of primary, secondary and tertiary alcohols. • Adsorption energy, electronegativity and steric hindrance affect alcohol selectivity. • A temperature-driven p-n response transition was observed and a novel sensing model was built by FT-IR and DFT analysis. High-temperature operation and poor selectivity are two main shortcomings of metal oxide (MOX)-based gas sensors. Gas selectivity is an important but complex issue. In this study, alcohol selectivity at room temperature was studied systematically from two dimensions: carbon chain lengths and isomers. A room temperature-operated alcohol sensor based on TiO 2 burr-like nanorods was developed. Its responses to alcohols increase as their carbon chain lengths increase, and decrease in the order of primary, secondary, and tertiary alcohols. Overall, a new relationship between the gas molecular structure and response is reported here: the more slender the gas molecule, the higher the response. A novel sensing mechanism is reported here by studying the anomalous p-type responses to the alcohols at room temperature and a temperature-driven p-n response transition. The mechanisms for all the above results were studied experimentally and theoretically by characterizing the reaction path using Fourier transform infrared spectroscopy and analyzing adsorption characteristics by density functional theory calculations. The anomalous p-type response is caused by the surface adsorption of the alcohols. The adsorption energies, electronegativity, and steric hindrance contribute to the gas selectivity together. Besides the fundamental research, a homemade portable system for on-field n-butanol concentration monitoring was built. This study provides new insights into the gas selectivity and development of room temperature-operated MOX-based gas sensors.