Ionophore-Based Potassium Selective Fluorescent Organosilica Nano-Optodes Containing Covalently Attached Solvatochromic Dyes

Abstract

Fluorescent nanoprobes containing ionophores and solvatochromic dyes (SDs) were previously reported as an alternative to chromoionophore-based nano-optodes. However, the small-molecular SDs are prone to leakage and sequestration in complex samples. Here, we chemically attached the SDs to the surface of organosilica nanospheres through copper-catalyzed Click chemistry to prevent dye leakage. The nano-optodes remained well responsive to K+ even after exposure to a large amount of cation-exchange resin, which acted as a sink of the SDs. The potassium nanoprobes exhibited a dynamic range between 1 μM to 10 mM and a good selectivity thanks to valinomycin. Preliminary sensing device based on a nylon filter paper and agarose hydrogel was demonstrated. The results indicate that the covalent anchoring of SDs on nanospheres is promising for developing ionophore-based nanoprobes.