The Room Temperature Highly Sensitive Ammonia Gas Sensor Based on Polyaniline and Nitrogen-Doped Graphene Quantum Dot-Coated Hollow Indium Oxide Nanofiber Composite.

Hollow indium trioxide (InO) nanofibers fabricated via an effectively combined method of electrospinning and high-temperature calcination were coated with nitrogen-doped graphene quantum dots (N-GQDs) prepared by a hydrothermal process through electrostatic interaction. The N-GQD-coated hollow InO nanofibers served as a core for the synthesis of polyaniline (PANI)/N-GQD/hollow InO nanofiber ternary composites using in situ chemical oxidative polymerization. The chemical structure and morphology of the fabricated ternary composites were characterized using Fourier transform infrared, field-emission scanning electron microscopy, and transmission electron microscopy. The gas-sensing performances of the ternary composites were estimated by a homemade dynamic test system which was supplied with a real-time resistance acquisition platform at room temperature. The response value of the PANI/N-GQD/hollow InO nanofiber sensor with a loading of 20 wt% N-GQD-coated hollow InO nanofiber and an exposure of 1 ppm NH was 15.2, which was approximately more than 4.4 times higher than that of the PANI sensor. This ternary composite sensor was proved to be very sensitive in the detection of NH at a range of concentration between 0.6 ppm and 2.0 ppm at room temperature, which is crucial in the detection of hepatic or kidney disease in human breath. The PANI/N-GQD/hollow InO nanofiber sensor also revealed higher selectivity and repeatability when exposed to 1.0 and 2.0 ppm NH at room temperature. Because of the excellent selectivity and repeatability in the detection of 1.0 and 2.0 ppm NH at room temperature achieved in this study, it is considered that the PANI/N-GQD/hollow InO nanofiber composite sensor will be a favored gas-sensing material applied on human breath for the detection of hepatic or kidney disease.