Performance and Selectivity toward Acetone against Various Gaseous Markers for Liver Diseases of Flame-Made Ir-Loaded In₂O₃ Nanoparticulate Sensors

In this work, iridium (Ir) loaded indium oxide (In2O3) nanoparticles made via a flame spray pyrolysis (FSP) technique for the first time were systematically investigated for acetone (C3H6O) detection at ppb levels. The structural data based on microscopic and spectroscopic analyses unveiled that 3-6 nm secondary metallic Ir nanoparticles were loaded on 8-15 nm cubic In2O3 nanoparticles with uniform dispersion at a low Ir content of 0.5 wt % or less. Sensing films fabricated from the powders via a spin-coating process were assessed for their gas-sensing properties toward four groups of breath gases including environmental gases, volatile organic compounds, volatile organic acids or short-chain fatty acids, and volatile sulfur compounds. From the test results, the optimum Ir loading level of 0.5 wt % yielded the highest response (S = 6.02-1000 ppb C3H6O) with a low detection limit of 10.7 ppb and good acetone selectivity against numerous breath gases at 300 °C. In addition, the 0.5 wt % Ir-loaded In2O3 sensor exhibited a modestly low acetone response decline of less than 25% in humid air (80%RH) at 300 °C. Consequently, the 0.5 wt % Ir-loaded In2O3 nanomaterial was attractive for sensitive detections of acetone at ppb levels applicable to medical applications, including initial screening of liver diseases.