Stimulus-responsive electrochemiluminescence from self-assembled block copolymer and nonpolar carbon quantum dot composite nanospheres

A self-assembled superstructure composed of block copolymers with stimulus-response properties is attractive, but how to achieve electrochemiluminescence (ECL) with good stimulus responsiveness from biocompatible materials is a big challenge. Herein, F127/NPCD nanospheres comprising the block copolymer Pluronic F127 and nonpolar carbon quantum dots (NPCDs) are designed and prepared. The materials with hydrophobic interaction show excellent ECL stimulus response. The ECL mechanism is investigated by analyzing the cyclic voltammetry, ECL, photoluminescence, and electron paramagnetic resonance results. There are two secondary structures in the F127/NPCDs nanospheres, namely a hydrophobic layer and a hydrophilic layer. The hydrophobic layer contains a polyoxypropylene PPO moiety of F127 and NPCDs, and the hydrophilic layer contains polyoxyethylene PEO of F127. The hydrophilic layer as a repository of co-reactants can adsorb a large amount of SO₄^•– to excite the NPCDs in the nearby hydrophobic layers to produce ECL at a gentle voltage. In nonpolar solvents, separation of the NPCDs from F127 leads to insufficient contact between NPCDs and SO₄^•– , and hence, the NPCDs require excitation of a larger potential to produce ECL to exhibit the stimulus response via a unique turn-on mechanism. The in vitro cytotoxicity experiments indicate that the F127/NPCDs nanospheres have good cytocompatibility. The stimulus-responsive ECL nanospheres are broadly applied as biological microelectrode materials in biological monitoring, tissue component recognizing, drug distribution, and sustained release.