Ultra-low-temperature reversible thermochromism and contactless bacterial sensing by chalcone-functionalized polydiacetylene

Polydiacetylenes are a class of conjugated polymers exhibiting unique color and fluorescence transformations. Here, we report the synthesis and remarkable chromatic properties of polymerized diacetylene displaying a chalcone headgroup. Specifically, the exposure of drop-casted chalcone-diacetylene films to HCl allowed diacetylene polymerization through modulating the ion-pair interactions and hydrogen bonding between adjacent chalcone residues. The HCl-treated chalcone-polydiacetylene films displayed reversible thermochromism even at very low temperatures (down to -50 degrees C). In addition, the polymerized films exhibit specific color and fluorescence transformations selectively induced by ammonia vapor, ascribed to scavenging of the HCl residues and resultant blending of the distinctive colors/fluorescence of both chalcone moieties and the polydiacetylene network. The ammonia sensing capabilities of the HCl-treated chalcone-polydiacetylene films were employed for high-sensitivity visible detection of bacterial growth and food spoilage, in varied temperatures and under various humidity conditions. Notably, the simple synthesis, sensitive chromatic response of the chalcone-polydiacetylene-HCl films and the demonstrated feasibility of visual early detection of food spoilage in a broad temperature range furnish significant practical advantages compared to existing food monitoring technologies.

Automated summary

Polymerized chalcone-diacetylene films exhibited remarkable chromatic properties, with reversible thermochromism and selective color and fluorescence transformations induced by ammonia vapor. These films were utilized for high-sensitivity visible detection of bacterial growth and food spoilage in varied temperatures and humidity conditions, offering practical advantages compared to existing food monitoring technologies.