Triplet-Triplet Annihilation Upconversion Based Nanosensors for Fluorescence Detection of Potassium

Typical ionophore-based nanosensors use Nile blue derived indicators called chromoionophores, which must contend with strong background absorption, autofluorescence, and scattering in biological samples that limit their usefulness. Here, we demonstrate potassium-selective nanosensors that utilize triplet-triplet annihilation upconversion to minimize potential optical interference in biological media and a pH-sensitive quencher molecule to modulate the upconversion intensity in response to changes in analyte concentration. A triplet-triplet annihilation dye pair (platinum(II) octaethylporphyrin and 9,10-diphenylanthracene) was integrated into nanosensors containing an analyte binding ligand (ionophore), charge-balancing additive, and a pH indicator quencher. The nanosensor response to potassium was shown to be reversible and stable for 3 days. In addition, the nanosensors are selective against sodium, calcium, and magnesium (selectivity coefficients in log10 units of −2.2 for calcium, −2.0 for sodium, and ...