Engineering Molecular Emission Centers of Carbon Dots to Boost the Electrochemiluminescence for the Detection of Cancer Cells

Despite the fact that electrochemiluminescent (ECL) performance of carbon dots (CDs) could be improved by modulating their surface defects, they are still restricted by inferior controllability and poor reproducibility. In this work, we disclosed a new approach for synthesizing luminescent groups rich in CDs (Lu-CDs) by engineering the luminol as molecular emission centers into the CDs, which exhibited an 80-fold stronger ECL intensity at an ECL onset potential of 0.6 V than the CDs without pre-implanted luminol. Different from the significant deviation between the ECL and fluorescence emission of other surface state-dominated CDs, the ECL emission of Lu-CDs was nearly consistent with its fluorescence emission at 465 nm, which was defined as the molecular emission dominated-ECL CDs herein. To prove this principle, the Lu-CDs were employed to construct an ECL biosensor for MCF-7 cell analysis based on the cell direct recognition and amplification strategy, which made the MCF-7 cells as nanomachines via specific binding with aptamer signal probes on the DNA triangular scaffold. The proposed biosensor displayed a wide detection range from 101 to 104 cell mL–1 and a low detection limit of 8.91 cells mL–1. Overall, this work not only presents a new strategy for preparing CDs with high controllability and excellent reproducibility but also provides a platform for tumor cell sensing.