Bismuth Nano-Nest/Ti<sub>3</sub>CN Quantum Dot-Based\nSurface Plasmon Coupling Electrochemiluminescence Sensor for Ascites\nmiRNA-421 Detection

In this study, a novel surface plasmon-coupled electrochemiluminescence\n(SPC-ECL) biosensor was developed based on bismuth nano-nest and Ti₃CN quantum dots (Ti₃CN QDs). First, MXene derivative\nQDs (Ti₃CN QDs) with excellent luminescence performance\nwere prepared as the ECL luminescent. The N doping in Ti₃CN QDs can effectively improve the luminescence performance and catalytic\nactivity. Therefore, the luminescence performance of QDs has been\neffectively improved. Furthermore, the bismuth nano-nest structure\nwith a strong localized surface plasmon resonance effect has been\ndesigned as the sensing interface via the electrochemical deposition\nmethod. It was worth noticed that the morphology of bismuth nanomaterials\ncan be controlled effectively on the electrode surface by the step\npotential method. Due to the abundant surface plasmon hot spots generated\nbetween the bismuth nano-nests, the isotropic ECL signal of Ti₃CN QDs can be not only significantly enhanced by 5.8 times\nbut also converted into polarized emission. Finally, the bismuth nano-nest/Ti₃CN QD-based SPC-ECL sensor was used to quantify miRNA-421\nin the range of 1 fM to 10 nM. The biosensor has been successfully\nused for miRNA in ascites samples from gastric cancer patients, which\nindicated that the SPC-ECL sensor developed in this study has great\npotential for clinical analysis.