In-situ formation coreactant promoters via pre-oxidation to enhance electrochemiluminescence of Eu-doped methionine-stabilized Au nanoclusters and application in label-free molecularly imprinted sensor of neuron specific enolase

Pre-oxidation is a simple and effective strategy to enhance the electrochemiluminescence (ECL) of Au nanoclusters. But the pre-oxidation ECL enhancement mechanism is still not clear. Herein, an in-situ formation immobilized coreactant promoters mechanism was proposed and verified by using Eu-doping methionine-stabilized Au nanoclusters (Met-AuEuNCs) as the model, with the ECL intensity 3.72-fold of that of Met-AuNCs. The ECL of Met-AuEuNCs was further enhanced 24.3-fold via pre-oxidation in 100 mM triethanolamine (TEOA) at the potential step of 1.0 V for 60 s, obtained a high ECL quantum yield of 143 %. The pre-oxidized Met-AuEuNCs reserved 20.1-fold ECL enhancement ratio after storing for 12 h and generated intense self-ECL in the absence of coreactant. Immobilized coreactant and coreactant promoters were formed in situ during pre-oxidation stage and enhanced the ECL of Au nanoclusters. A low potential step (e.g., 0 V, 5 s) was useful to activate the immobilized coreactant promoters for higher ECL enhancement ratio. The pre-oxidation enhancement strategy is valid only in the presence of anodic coreactants and Au nanoclusters. The pre-oxidation mechanism was applied in molecularly imprinted polymer (MIP) based ECL sensor, using neuron specific enolase (NSE) as the model analyte, with the detection limit of 6.3 fg mL −1 . The re-binding of the MIP film to NSE blocked the accesses between Met-AuEuNCs and TEOA in the pre-oxidation, activation and ECL measurement, decreased the ECL of Met-AuEuNCs. The pre-oxidized MIP-ECL sensor offered higher sensitivity than that in normal MIP-ECL mode without pre-oxidation and activation treatments.