Humidity-activated ammonia sensor based on mesoporous AlOOH towards breath diagnosis

Abstract

Discrimination and quantitation of ammonia (NH3) exhaled from human beings using oxide chemiresistors has shown great potential for non-invasive and direct diagnosis of helicobacter pylori gastropathy and end-stage renal disease. Herein, a newly humidity-activated sensor employing AlOOH that synthesized by a simple approach consisting of in-situ etching treatment and hydrothermal method is designed and demonstrated. The humidity-activated AlOOH sensor exhibits a high selectivity and response toward ppb-level of NH3 under 98 % relative humidity at room temperature, neglecting the water poisoning effect on gas-sensing characteristics. The enhanced adsorption of NH3 at abundant BrØnsted acid sites, and the effective ammonium ionic transmitting pathway induced by adsorbed moisture are proposed as the reasons behind the humidity-activated gas-sensing mechanism. Analysis using direct current analysis, complex impedance spectra and temperature programmed desorption (TPD) are performed to verify the above proposals. This study provides new pathway for rapid and stable detection of NH3 in human breath.