AIE-active photoresponsive Ir(III) complex as an oxidase mimic for ratiometric ascorbic acid detection.

Ascorbic acid (AA) sustains biological redox homeostasis, hence its rapid and precise detection bears important research value. Conventional nanozyme-based detection strategies are hampered by complicated synthesis, inflexible enzyme-like activity modulation, single detection mode and unsatisfactory anti-interference ability. In this work, an amino-modified Ir(III) complex with aggregation-induced near-infrared emission property was facilely synthesized. The product can self-assemble into photoresponsive oxidase-mimetic nanoparticles. Upon light irradiation, Ir-1 NPs exhibit remarkable catalytic performance and excellent stability, with a Michaelis constant of 5.5 mM in catalyzing o-phenylenediamine oxidation. A ratiometric fluorescent sensor was fabricated using the intensity ratio of I567/I682. It achieves linear detection of AA within 0.01-0.8 mM, with a low limit of detection at 2.1 μM (3σ/k) and superior selectivity. The sensor enables accurate quantification of AA in fruits and vitamin C tablets. This study offers a novel strategy for photoresponsive nanozyme design and a reliable analytical approach for AA detection in nutritional assessment.