Electrochemiluminescence sensing platform for ultrasensitive DNA analysis based on resonance energy transfer between graphitic carbon nitride quantum dots and gold nanoparticles

Electrogenerated chemiluminescence (ECL) of semiconductor quantum dots (QDs) is considered as a powerful technique in the fabrication of biosensor, however, the inherent toxicity of the heavy metal ion containing in QDs limits their further applications. Thus, searching for environment-friendly luminescent nanomaterials with high electrochemiluminescence (ECL) efficiency is an urgent goal. In this work, a solid-state method under low temperature was adopted to prepare graphitic carbon nitride quantum dots (g-CNQDs). By using coreactant K2S2O8, a strong cathodic ECL signal of g-CNQDs could be observed in phosphate buffer. A novel ECL resonance energy transfer procedure was constructed between g-CNQDs (emitter) and gold nanoparticles (acceptor). A signal probe was formed by connecting gold nanoparticles at the hairpin DNA (Hai-DNA) terminal. When the signal probe was anchored on g-CNQDs, ECL resonance energy transfer occurred due to the ECL quenching of gold nanoparticles to g-CNQDs. This phenomenon decreased the ECL signal. In the presence of target DNA (T-DNA), the looped structure of Hai-DNA could be destroyed by T-DNA, and gold nanoparticles were separated from g-CNQDs. Accordingly, the ECL resonance energy transfer procedure was hindered, and the ECL signal was recovered again. The ECL intensities exhibited linear correlation with the logarithm of T-DNA concentration from 0.02 fM to 0.1 pM, and the limit of detection was 0.01 fM (3 sigma). With the developed ECL resonance energy transfer system, good selectivity and high sensitivity were achieved in T-DNA detection.