Effects of Gold Nanoparticles on Quantum Dot Electrochemiluminescence Obtained Using a DNA Electrochemiluminescence Sensor

Gold nanoparticles (AuNPs) have a high extinction coefficient and a strong surface plasmon resonance, the latter of which is influenced by the size of AuNPs and the surrounding environment. In this article, a DNA electrochemiluminescence (ECL) sensor was fabricated based on the distance-dependence of semiconductor nanocrystals' ECL signal to AuNPs. AuNPs were first deposited on the surface of glassy carbon electrode (GCE) by cyclic voltammetry (CV). The mercaptopropionic acid-capped CdS quantum dots (QDs) used in this study can covalently bind with amino-terminated double-stranded DNA (dsDNA), via the -CO-NH bond to obtain a QDs-dsDNA compound. The QDs-dsDNA compounds were assembled on the surface of AuNPs via an Au-S bond, using the other distal of dsDNA that is labeled with thiol, to create the CdS QDs-DNA/AuNPs/ GCE ECL sensor. Experimental conditions, such as the QDs-dsDNA density on the surface of electrode and the deposition method of AuNPs, were then optimized. The surface properties of different modified electrodes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS). The effect of AuNPs on the ECL intensity of CdS QDs was investigated by controlling the DNA which lies between the AuNPs and the CdS QDs. The ECL signal was affected significantly by the length and type of DNA strands. The sensor was used to detect DNA damage from environmental pollutants and exhibited a highly sensitive response.