Photoelectrochemical aptasensing of oxytetracycline based on a BiVO 4 -carboxylated graphene-WO 3 Z-scheme heterojunction.

A new BiVO 4 -carboxylated graphene (cG)-WO 3 Z-scheme heterojunction was constructed on a fluorine-doped tin oxide (FTO) substrate electrode by ultrasonic mixing and cast-coating for determination of oxytetracycline (OTC). Since cG can absorb visible light and well match with the energy levels of WO 3 and BiVO 4 to promote the charge separation and transfer, the photocurrent on the BiVO 4 -cG-WO 3 /FTO photoelectrode is 4.4 times that on the control BiVO 4 -WO 3 /FTO photoelectrode. An amino-functionalized OTC aptamer was fixed on the BiVO 4 -cG-WO 3 /FTO photoelectrode by the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide mediated amide reaction, and then hexaammonium ruthenium(III) (Ru(NH 3 ) 6 3+ ) was attached to the OTC aptamer to increase the photocurrent response to the OTC binding. Under the optimized conditions, the photocurrent on the BiVO 4 -cG-WO 3 /FTO photoelectrode at 0 V vs SCE was linear with the common logarithm of OTC concentration from 0.01 nM to 500 nM, with a limit of detection of 3.1 pM (S/N = 3). Satisfactory recovery results were obtained in the analysis of real water samples.