Design of chemosensors and dynamic anticounterfeiting inks based on colloidal nanoprecipitated polymers

Fluorescent polymer nanoparticles have received considerable attention over the past few decades, because of their various responses to physical and/or chemical stimuli, showing great potential for their applications in chemosensing and anticounterfeiting. Nowadays, the fabrication and development of polymer chemosensors with multi-responsivity to multiple chemical targets are highly considered. In this study, (co)polymers with well-controlled molecular weights and narrow molecular weight distributions were synthesized via reverse atom transfer radical polymerization. Fluorescent polymer nanoparticles with the ability to sense pH, CO2, acidic and basic vapors, and polarity were prepared by physical incorporation of fluorescein via a facile nanoprecipitation method. Morphological studies showed that these smart nanoparticles have a spherical shape with an average size of lower than 150 nm. UV-vis and fluorescence spectroscopy analyses showed that the variation of pH, incorporation of CO2 into the aqueous medium, and variation of the polarity of polymers changed the intensity ratio of absorption and emission wavelengths. The fluorescent nanoparticles were printed on biocompatible cellulosic papers, which showed different fluorescence emissions at various pH values and also upon exposure to acidic/basic vapors. This confirms the high potential of these nanoparticles to be used as chemical sensors and also in the high-level anticounterfeiting field. Fluorescent polymer nanoparticles, prepared by physical incorporation of fluorescein during the nanoprecipitation of the polymers, showed applications in high-level anticounterfeiting and chemical sensing of pH, CO2, and acidic and basic vapors.