Fluorescent organic nanoparticles as chemosensor for nanomolar detection of Cs+ in aqueous medium

A new sensor 1 bearing mixed imine and amide linkages is synthesized with simple condensation reaction of diode amine with catechol carbaldehyde. The amide linkages may define the receptor pseudo cavity as these linkages are generally considered to provide rigidity to receptor design. The imine linkages are expected to be responsible for providing binding site as well as fluorescent signaling sub-unit. The 1 is evaluated for their sensor activities in a diverse range of solvents and it has shown the selective binding affinity for Cs+. In order to evaluate the sensor activity in aqueous medium, fluorescent organic nanoparticles (FONs) of receptor 1 are formed using re-precipitation method. FONs of 1 has shown AIE phenomenon in aqueous medium with enhancement in fluorescence intensity at λmax = 412 nm. Fluorescence emission profiles of these FONs have shown some changes in low and high pH range; however it remains stable in pH range 4–9, thus making them appropriate to use in environmental/biological samples. To the best of our knowledge, 1is representing the first example of FONs as chemosensor for nanomolar detection of Cs+ in aqueous media.