Intense pulsed light-based synthesis of hybrid TiO2–SnO2/MWCNT doped Cu-BTC for room temperature ammonia sensing

Abstract

Ammonia gas is an irritating and corrosive gas commonly used in fertilizers, refrigerants and cleaners. In this work, a sensitive and selective nanocomposite film is fabricated on a quartz crystal microbalance (QCM) with hybrid TiO₂–SnO₂/multi-walled carbon nanotube (MWCNT) doped Cu-BTC for detection of trace amounts of ammonia under ambient conditions. Cu-BTC exhibits excellent porosity for gas sensing, but its poor stability in the presence of water and ammonia limits the long term viability. Hybrid TiO₂–SnO₂/MWCNT doping prevents the framework decomposition and improves longevity. The nanocomposite film is rapidly synthesized under ambient conditions using a facile intense pulsed light (IPL) technique to stimulate in situ growth. IPL also assists in the thermal conversion of anatase TiO₂ to rutile TiO₂. This functionalized nanocomposite film-based QCM sensor demonstrates ammonia gas sensing capability with a limit of detection estimated to be 0.77 ppm and strong stability even under humid conditions. The sensor exhibits reversibility during cyclic testing and a minimal drift suggesting that the reaction mechanism is primarily surface adsorption. Changes in the motional resistance and resonance frequency of the sensor can be linearly related to the ammonia gas concentration.