Photocontrolled Thermosensitive Electrochemiluminescence Hydrogel for Isocarbophos Detection

Endowing specificity and controllability with the electrochemiluminescence (ECL) thermosensitive hydrogels is vitally crucial to expanding their sensing applications. Herein, a novel photocontrolled thermosensitive electrochemiluminescence hydrogel (PT-ECL hydrogel) sensing platform with sufficient simplicity, specificity, and precise controllability is proposed, for the first time, by the integration of Ru(bpy)₃²⁺ (bpy = 2,2'-bipyridine) derivatives (signal reporter), split aptamers (recognition unites), and Au nanorods (AuNRs) (photothermal energy converter) into the poly(N-isopropylacrylamide) (pNIPAM) matrix. In the presence of the model target isocarbophos (ICP), the conjugation of two split aptamers initiated the ECL-resonance energy transfer (ECL-RET) between the Au nanorods and the Ru(bpy)₃²⁺ centers. Surprisingly, under the irradiation of near-infrared (NIR) light, the photothermal effect of AuNRs prompted the shrinkage of the hydrogel, resulting in the enhancement of the ECL-RET and further ∼7 times signal amplification. Consequently, the PT-ECL hydrogel sensing platform performed well for ICP detection with a low detection limit of 20 pM (S/N = 3) and a wide linear range from 50 pM to 4 μM, with great stability and repeatability. Obviously, the results showed that AuNRs utilized in this study served the role as not only the ECL-RET acceptor but also the photothermal converter to prompt the phase change of the PT-ECL hydrogel precisely and simply controlled by NIR light. Use of the proposed PT-ECL hydrogel detection scheme is a first step toward enabling a newly upgraded highly sensitive and selective hydrogel-based assay and also paving the way for the application of smart photothermal reagents.