Breath visualization: Colorimetric detection of acetone gas using ion-pairing dyes based on hollow silica particles

The detection of over 200 volatile organic compounds in exhaled breath has highlighted their potential in diagnosing diseases and monitoring health. Particularly, acetone has emerged as a key biomarker for monitoring ketosis in both healthy individuals and those diagnosed with diabetes. Although equipment-based gas sensor systems such as high-performance liquid chromatography are commonly used for acetone gas detection, they are expensive and require preprocessing. To address these challenges, we developed a cost-effective colorimetric sensor that uses silica-based hollow nanoparticles (SHNPs) and offers enhanced selectivity. We fabricated spherical and uniformly sized SHNPs and infused them with methyl red and brilliant green (M–B ion-pairing dye) to develop colorimetric sensors for acetone gas detection. The optimal color change response occurred at a particle size of 52 (±3.4) nm and shell thickness of 7 (±1.1) nm within the SHNPs, indicative of a significant increase in surface area. Furthermore, the use of hollow silica with a water barrier effect protected the dye, enabling acetone gas detection even in environments with 80% relative humidity. Notably, a substantial color change (Δ130) was noticeable in only 1 min. This robust sensor enables sensitive and rapid naked-eye detection of low concentrations of acetone gas (1 ppm). Consequently, the proposed methodology holds promise for real-time visualization of acetone gas and can be easily integrated into other colorimetric gas sensor systems to enhance both sensitivity and simplicity.