A novel ultrasensitive electrochemical sensor based on a hybrid of rGO/MWCNT/AuNP for the determination of lead(II) in tea drinks

In this study, an ultrasensitive novel electrochemical sensor based on graphene oxide-modified multiwalled carbon nanotubes and gold nanoparticles (rGO/MWCNT/AuNP) was constructed for the electrochemical detection of free lead (Pb2+). To assemble the electrochemical sensor, the hybrid of rGO/MWCNT/AuNP was adhered to a glassy carbon electrode (GCE) through chitosan (CS). Then, to connect the aptamer on the sensor securely, the 5 '-thiolate aptamer was modified on rGO/MWCNT/AuNP through Au-S covalent bonding. When the sensor was in the presence of Pb2+, the G-quadruplex, in which the aptamer interacts with Pb2+, led to decreased electron transfer, causing the peak of differential pulse voltammetry (DPV) to decline. Finally, the Pb2+ was quantified by the value of the decreasing peak. The remarkably low limit of detection of the sensor was 7.1 x 10-6 nmol/mL toward Pb2+, and the linear range was 5 x 10-5-0.2 nmol/mL under optimal conditions. Furthermore, the sensor displayed superior selectivity and can be used to detect the content of lead in tea drinks for practical application. Above all, the electrochemical sensor may be used to determine the trace amount of free Pb2+ in food and other industries.