Synergistic sensing properties of a standalone portable prototype using an integrated graphitic carbon nitride–carbon nanotube film for ultra-sensitive and selective acetone detection

Abstract

Selective room-temperature detection of ultra-low concentrations of the biomarker gas acetone remains challenging due to the limited analyte interaction with the sensor substrates. Carbon nanotube (CNT)-based sensors, although offering high surface area and conductivity, often lack sufficient selectivity for specific gases. To address this limitation, we developed a new method using graphitic carbon nitride (g-C₃N₄) to coat CNT films, creating a sensitive and selective sensor for acetone. Two types of g-C₃N₄, synthesized from urea (GCN-U) and thiourea (GCN-T), were used to enhance the sensor performance. The GCN-U-coated sensor showed exceptional results, exhibiting a twenty four-fold increase in resistance upon acetone exposure, a limit of detection of 2.3 parts per billion and rapid response and recovery times of 5 and 12 seconds, respectively. The enhanced and selective performance is attributed to g-C₃N₄ defects (pyrrolic-N and pyridinic-N), which enable selective chemical binding with acetone and reduce diffusional limitations through high-density heterojunctions at the CNT/g-C₃N₄ interfaces. A small, portable prototype was made and tested, successfully detecting acetone across a wide concentration range (1–50 ppm) and remaining reliable for six months. This work represents a shift from static sensors to highly interactive sensing platforms, advancing point-of-care VOC monitoring for diagnostic applications.