Versatile Photoelectrochemical Biosensing for Hg2+and Aflatoxin B1Based on Enhanced Photocurrent of AgInS2 Quantum Dot-DNANanowires Sensitizing NPC-ZnO Nanopolyhedra

:eliminating false positives or negatives in analysis has been achallenge. Herein, a phenomenon of polarity-switching photocurrent of AgInS2quantum dot (QD)-DNA nanowires reversing nitrogen-doped porous carbon-ZnO (NPC-ZnO) nanopolyhedra was found for thefirst time, and a versatilephotoelectrochemical (PEC) biosensor with a reversed signal was innovativelyproposed for dual-target detection. NPC-ZnO is a photoactive material withexcellent PEC properties, while AgInS2QDs as a photosensitive material matchNPC-ZnO in the energy level, which not only promotes the transfer ofphotogenerated carriers but also switches the direction of PEC current.Furthermore, in order to prevent spontaneous agglomeration of AgInS2(AIS)QDs and improve its utilization rate, a new multiple-branched DNA nanowire wasspecially designed to assemble AgInS2QDs for constructing amplified signalprobes, which not only greatly increased the load of AgInS2QDs but also furtherenhanced the photoelectric signal. When the target Hg2+-induced cyclic amplification process generated abundant RDNA, the DNAnanowire signal probe with plenty of QDs was linked to the NPC-ZnO/electrode by RDNA, generating greatly amplified polarity-reversed photocurrent for signal"ON"detection of Hg2+. After specific binding of the target (aflatoxin B1, AFB1) to its aptamer, thesignal probes of AIS QD-DNA nanowires were released, realizing signal"OFF"assay of AFB1. Thus, the proposed new PECbiosensor provides a versatile method for detection of dual targets and also effectively avoids both false positive and negativephenomena in the assay process, which has great practical application potential in both environmental and food analysis