Phenylene-ethynylene trication as an efficient fluorescent signal transducer in an aptasensor for potassium ion

► Novel aptasensor is optimized by tuning the fluorophore-aptamer interactions. ► The system exhibits K+ detection limit below 1.0 μM with wide linear dynamic range. ► The fluorophore-aptamer-K+ interactions are characterized by CD spectra. ► The sensing system is applied for rapid K+ assays in real urine samples. ► As little as 30 μM K+ can be detected, even in the presence of 4800-fold of Na+.