Fig. 8: PDA-based colorimetric sensors for ammonia detection.

a Schematic illustration of self-assembled PDA vesicles prepared using the self-injection method. The DA monomer was first dissolved in ethanol and then injected into an aqueous phase at 85 °C to form self-assembled polydiacetylene particles. After cooling overnight, polymerization was initiated under UV irradiation (254 nm) to obtain blue-phase PDA. Upon exposure to ammonia vapor (NH₃), the PDA structure underwent a conformational change, producing a color shift from blue to red due to disruption of the π-conjugated backbone. b The colorimetric response of PDA to various ammonia concentrations (0–2000 ppm) shows a progressive color change from blue to red with increasing concentration, confirming the high sensitivity of PDA vesicles as a colorimetric sensing platform. Adapted from ref. ²⁰¹, copyright (Royal Society of Chemistry, 2020).