Fig. 2: The pH-indicator-coated PDMS sponges enable selective, linear, real-time colorimetric detection of NH₃, TMA, and H₂S.

a The figure presents the fabrication of pH indicator-coated PDMS sponges designed for selective gas detection. The process begins with sugar dissolution to create porous PDMS sponges, followed by applying three pH indicators (BPB-PIL, TET-PIL, Cu-PAN). b–d Response curves demonstrate the sensors’ sensitivity to gases such as NH₃, TMA, and H₂S, with linear correlations (R²) supporting their detection accuracy. e–h Time-dependent brightness measurements reveal real-time sensor responses during gas introduction and removal. Simultaneously, comparing response times highlights the distinct sensitivities of BPB-PIL to NH₃ and TET-PIL to TMA (The color legend assigns blue to NH₃, yellow to TMA, purple to H₂S, dark green to C₂H₅OH, red to CH₃COCH₃, pink to CO, turtle to C₈H₈, dark blue to C₈H₁₀, and brown to NO₂.). i Color intensities change across various gas concentrations, demonstrating their effectiveness for gas detection.