Poly(styrene-block-vinylpyrrolidone) beads as a versatile material for simple fabrication of optical nanosensors.

A versatile platform for designing optical nanosensors is proposed. The "sensing chemistries" are entrapped into the poly(styrene-block-vinylpyrrolidone) nanobeads having the average size of 245 nm in aqueous media. Addressable staining into the core or the shell of the beads results in nanosensors for essential analytes such as dissolved oxygen, temperature, pH, chloride, and copper ions. Two immobilization procedures are developed: staining in the polystyrene core is performed from a tetrahydrofuran/water mixture (50:50 v/v) and staining in the poly(vinylpyrrolidone) shell is achieved by using the ethanol/water mixture (70:30 v/v). The oxygen and temperature indicators should be preferably immobilized into the core, whereas nanosensors for ions are manufactured by staining into the shell. In the case of the lipophilic pH indicators both procedures result in similar pKa values. The unique properties of the beads make them promising for sensing and imaging even in very complex media, multianalyte sensing, and monitoring of very fast processes.