Multisignal Conversion Electrochemiluminescence Strategy Based on Nanozyme-Enhanced Nitrogen-Vacancy/Oxygen-Doped g-C₃N₄ for the Detection of Cholesterol

The high and stable signal intensity of electrochemiluminescence (ECL) is crucial for establishing highly sensitive ECL biosensors. Here, nitrogen-vacancy/oxygen-doped carbon nitride (OCNNV-650) was first used as an ECL emitter, significantly improving the low ECL activity and poor dispersion of graphitic carbon nitride (g-C₃N₄) through a molecular engineering strategy. It is particularly noteworthy that Fe₃O₄@MoS₂ peroxidases, as coreaction accelerators, are the key to achieving the first and last "signals on", promoting the production of more SO₄^•- and even promoting the production of •OH radicals when cholesterol is electrocatalyzed to produce H₂O₂. The intermediate "signal off" is induced by nitrogen and sulfur codoped carbon dots (NS-CDs), which significantly reduce the ECL detection background by hindering the electron transfer between SO₄^2- and SO₄^•-. The optimized sensor detects 0.31 μM cholesterol with a broad detection range (0.1 μM-0.1 mM). The "on-off-on" strategy facilitates multipathway ECL emission of OCNNV-650 with high and stable signal intensity, presenting a new method to develop ECL biosensors with high sensitivity and real-time accurate detection for disease prevention and human health care.