Almost all current electrochemiluminescent reagents require real-time electrochemical stimulation to emit light. Here, we report a novel electrochemiluminescent reagent, nitrogen-deficient graphitic carbon nitride (CN x ), that can emit afterglow electrochemiluminescence (ECL) after cessation of electric excitation. CN x obtained by post-thermal treatment of graphitic carbon nitride (CN) with KSCN has a cyanamide group and a nitrogen vacancy, which created defects to trap electrically injected electrons. The trapped electrons can slowly release and react with coreactants to emit light with longevity. The cathodic afterglow ECL lasts for 70 s after pulsing the CN x nanosheet (CN x NS-1.6)-modified glassy carbon electrode at −1.0 V for 20 s in 2.0 M PBS containing 1 mM K2S2O8. The afterglow ECL mechanism is revealed by investigation of its influencing factors and ECL wavelength. The discovery of afterglow ECL may open a new doorway for new significant applications of the ECL technique and provide a deeper understanding of the structure–property relationships of CN.
Biosensors capable of detecting cancer cell quantity are significant for cancer pathological investigation and prognosis. Herein, a facile electrochemiluminescent (ECL) biosensor is developed for cancer cell detection by comprehensively utilizing the features of functionalized graphitic carbon nitride (g-CN) nanomaterials like well film-forming capability and functionalization level tunability. The solid-state ECL biosensor is fabricated via a simple dropping-drying method by subsequent deposition of g-CN nanosheets/graphene oxide nanocomposites (CNNS/GO) as ECL emitter, folate functionalized g-CN quantum dots (FA-CNQDs) as cancer cell capture agent, and bull serum albumin as blocker to prevent nonspecific binding on glassy carbon electrodes. The strong and stable ECL emission of CNNS/GO along with the tunability of FA content in FA-CNQDs endow the ECL biosensor with competitive sensitivity, which is able to detect folate receptor-positive cancer cells (HepG2) in the concentration range of 100-104 cells/mL under optimal condition. Additionally, the proposed ECL biosensor shows high specificity, reproducibility and long-term stability as well as good reliability towards serum sample detection.
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