Enhanced Electrochemiluminescence of Graphitic Carbon Nitride by Adjustment of Carbon Vacancy for Supersensitive Detection of MicroRNA

Herein, a supersensitive biosensor was constructed by using graphitic carbon nitride with a carbon vacancy (V_C-g-C₃N₄) as an efficient electrochemiluminescence (ECL) emitter for detection of microRNA-21 (miRNA-21). Impressively, V_C-g-C₃N₄ could be prepared by formaldehyde (HCHO)-assisted urea ploycondensation, and the concentration of the carbon vacancy could be controlled by adjusting the dosage of HCHO to improve the ECL performance, in which the carbon vacancy could improve the charge carrier transfer to enhance the conductivity and it also could be used as an electron trap to prevent electrode passivation and facilitate the adsorption of coreactant S₂O₈^2– to accelerate its reduction. Compared with original g-C₃N₄, the introduction of carbon vacancies resulted in a significant enhancement of the ECL efficiency of V_C-g-C₃N₄. With the aid of improved cascade strand displacement amplification (IC-SDA), the ECL biosensor realized sensitive detection of miRNA-21 with a low detection limit of 3.34 aM. This successful strategy promoted the development of g-C₃N₄ in the ECL field to construct the sensitive biosensor for molecular and disease diagnoses.