A label-free aptasensor for ultrasensitive Pb2+ detection based on electrochemiluminescence resonance energy transfer between carbon nitride nanofibers and Ru(phen)32+

A label-free aptasensor was developed for ultrasensitive detection of Pb2+ based on electrochemiluminescence resonance energy transfer (ECL-RET) from graphitic carbon nitride nanofibers (CNNFs) to Ru(phen)32+. The CNNFs synthesized via a facile two-step hydrolysis-electrolysis strategy showed intense and stable ECL signal by taking advantages of amplifying and stabilizing effect of carbon nanotubes and Au nanoparticles. After the specific hybridation between capture DNA and Pb2+ specific aptamer, Ru(phen)32+ could be captured onto CNNFs modified electrode by effectively intercalating into the grooves of double-strand DNA, thus triggering the ECL-RET and leading to highly enhanced ECL intensity. The presence of Pb2+ would result in the detachment of Ru(phen)32+ and then the inhibition of ECL-RET. Then Pb2+ concentration could be quantified based on ECL change before and after introduction of Pb2+. The target recycling based on exonuclease I (Exo I) mediated digestion of Pb2+-aptamer complex was implemented to further improve the sensitivity. These synergistic amplification strategies enabled the aptasensor to be ultrasensitive for Pb2+ determination with a detection limit of 0.04 pM. The proposed probe was utilized to analyze environmental samples with satisfactory results.