An inner filter effect-based upconversion fluorescence sensor using TPPS-Co²⁺ complexes for rapid detection of...

An inner filter effect (IFE)-based upconversion fluorescence nanosensor was developed for the sensitive detection of roxithromycin (ROX) residues in food. Core-shell NaYF₄,Er@NaYF₄ upconversion nanoparticles were used as the fluorescence donor and a tetraphenylporphyrin tetrasulfonic acid cobalt complex (TPPS-Co²⁺) as the energy acceptor. Owing to the spectral overlap between the UCNP emission at 653 nm and the absorption of TPPS-Co²⁺, efficient fluorescence quenching was achieved under 980 nm excitation. Upon the addition of ROX, competitive coordination with Co²⁺ disrupted the TPPS-Co²⁺ complex, resulting in fluorescence recovery at 653 nm. The recovered fluorescence exhibited a linear response to ROX over the range of 1-1000 ng/mL, with a detection limit of 0.05108 ng/mL. The sensor showed a rapid response (10 min) and excellent selectivity. In honey samples, recoveries ranged from 98.29% to 102.59% with coefficients of variation of 1.15%-5.16%, demonstrating its potential for the rapid determination of ROX residues in food.