Excellent isoprene-sensing performance of In2O3 nanoparticles for breath analyzer applications

Abstract We report the sensing performance of In2O3 nanoparticles (NPs) synthesized by a co-precipitation method for the detection of isoprene. The as-synthesized In2O3 NPs exhibited excellent isoprene-sensing performance compared to other previously reported isoprene sensors based on metal-oxide semiconductors. Under an exposure of 1 ppm isoprene at an optimal operating temperature of 350 ℃, the In2O3 NP sensor showed the highest sensing response of ∼231 with a rapid response time of ∼3 s. The low detection limit was approximately 0.001 ppm of isoprene. Furthermore, the In2O3 NP sensor showed a good long-term stability for 90 days by controlling the annealing time. In addition, for the sensor’s practical applications to a breath isoprene analyzer, we tested the sensing ability of the In2O3 NPs by integrating the sensor into a miniaturized gas analyzer based on gas chromatography (GC). The results revealed that the In2O3 NP sensor is sensitive and can distinctly detect 1 ppm isoprene and 10 ppm H2 within ∼100 s in a mixture gas with other breath gases, such as acetone, CO2, CO, and CH4. Our study demonstrated the potential of the In2O3 NP sensor for application in breath isoprene analyzers by controlling the sensor’s annealing time and adopting the GC system.