Studies On Photoelectrochemical Biosensors Based On Functionalized Semiconductor Nanocomposites

In recent decades, increasing attention has been paid to photoelectrochemical (PEC) sensors developed from solar cells due to their desirable analytical performance. With the further development of materials science, especially nanosemiconductor, new photoactive species will emerge constantly. Preparing photoelectrochemically active electrodes with high incident photon-to-electron conversion efficiency (IPCE) can improve the sensitivity of PEC sensors. Combined with biotechnology, novel approaches in PEC biosensors will be developed by expanding range of the types of analytes and exploiting ingenious signaling mechanism. Based on the p-n heterojuction architecture, we exploited two kinds of PEC biosensors. The major contents were described as follows:1. A case of application for general photoelectrochemical enzymatic analysis based on acetylcholine esterase antibodies on BiOI Nanoflakes array/TiO2 NPs electrodeThis work develops a novel PEC biosensor that can be established without surface-confinement procedure to immobilize enzyme as biorecogniton element for probing various analytes of interest. We first prepared a BiOI nanoflakes (NFs)/TiO2 nanoparticles (NPs) p-n heterojunction as the photoelectrode, on the basis of which acetylcholine esterase(AChE) antibody was introduced via the bridging of protein A.In such a system, enzyme could keep its optimal state in the solution if in the absence of inhibitor; otherwise, the degree of enzyme inhibition would correlate closely with the concentration of inhibitor. After immunoreaction between AChE and its antibody, the inhibitor concentration could then be determined by the biocatalytic reaction-controlled PEC response. Integrated with other enzyme-based biosystems, this simple configuration could serve as a general method for assaying enzyme inhibition or activities.2. BiOI NFS/TiO2 NTs arrayed p-n heterojunction and its application for photoelectrochemical bioanalysisWe developed sensitive detection of cancer biomarker vascular endothelial growth factor (VEGF) by using the p-n heterojunction comprised of p-type BiOI nanoflakes (NFs) array and n-type TiO2 nanotubes (NTs) array. Due to the unique arrayed structure and the synergy effect of photoelectrochemistry in the formed p-n junction, the synthesized configuration has superior excitation efficiency and thus excellent photoresponsibility. Then, the fabricated p-n heterojunction was integrated with an exquisite bioassay protocol for addressing VEGF using a sandwich immunoassay with glucosedehydrogenase (GDH) as the enzyme tags. This approach provided a sensitive response to VGEF in a wide range from 10 pg mL-1 to 1 ng mL-1 with a detection limit of 10 pg mL-1.This work not only presents a simple BiOI NFs array/TiO2 NTs array p-n heterojunction for general applications in the broad photochemistry areas, but also opens a different horizon for current development of advanced PEC biomolecular detection.