PSMA/PEI core-shell nanoparticles with pH indicator for colorimetric CO₂ gas detection

In this study, we developed an optical colorimetric sensor based on poly(styrene-co-maleic anhydride) (PSMA)/ polyethylene imine (PEI) core-shell nanoparticles (PSMA/PEI) for CO₂ gas detection. When the contents of MA was 20 wt%, the PSMA had the uniform particle size distribution. Moreover, PSMA/PEI core-shell nanoparticles were prepared by PEI graft. To compose optical colorimetric sensors for CO₂ gas detection, PSMA nanoparticles (core part) were prepared and then impregnated with thymol blue, cresol red, and phenol red, respectively. Furthermore, we observed the retention of color change at CO₂ gas sensor. In the presence of CO₂ gas (0.1%), thymol blue sensors of optical colorimetric changed in 0.5 min (E=15536) and 5 min (E=35645), respectively. The optical CO₂ gas sensor was exhibited the largest color change (E=37859) at relative humidity of 30%. Optical CO₂ gas sensor of core-shell type would enable variable application of optical gas sensor system with high sensitivity and visualization.