Photoelectrochemical aptasensing of lincomycin based on a AgI-carboxylated multiwalled carbon nanotubes-BiOI Z-scheme heterojunction

Lincomycin (LIN) is a common antibiotic that is widely used in animal husbandry and other fields, and the residual problem caused by its abuse has attracted widespread attention. Herein, a novel AgI-carboxylated multiwalled carbon nanotubes (cMWCNT)-BiOI Z-scheme heterojunction material was synthesized via a one-pot hydrothermal method, modified on a fluorine-doped tin oxide (FTO) electrode surface, and used for detecting LIN. The photocurrent on the AgI-cMWCNT-BiOI/FTO photoelectrode is 4.6 times that on the control AgI-BiOI/FTO photoelectrode. An amino-functionalized LIN aptamer was fixed on the AgI-cMWCNT-BiOI/FTO photoelectrode by the cross-linking reaction between chitosan and glutaraldehyde, and then Ru(NH3)63+ was electrostatically attached to the LIN aptamer to increase the photocurrent response to the LIN binding. When LIN binds competitively with Ru(NH3)63+ to the aptamer, the photocurrent signal can be quantitatively decreased. Under optimized conditions, the anodic photocurrent at 0 V vs KCl-saturated calomel electrode in 0.1 M phosphate buffer (pH 7.0) containing 0.100 M ascorbic acid was linear with the common logarithm of LIN concentration from 10.0 pM to 500 nM, with a limit of detection of 2.8 pM (S/N = 3). Satisfactory recovery results were obtained in the analysis of cow milk samples.