Research On The Fabrication And Application Of Photoelectrochemical Biosensor

Photoelectrochemical (PEC) technology was on the basis of the electrochemical with light as Ihe excitation source signal, current signal as the signal detection, to achieve energy conversion, testing analysis and energy utilization. Due to different kind of excitation source and signal detection, the background signal of PEC method is quite low, which could improve the sensitivity. Because the advantages, such as:high detection sensitivity and selectivity, simple operation steps, and low cost, PEC biological analysis was widely used in clinical analysis, environmental pollution monitoring and other fields.Variety methods were proposed to improve the sensitivity of the sensor, such as energy transfer, sensitization or co-sensitization structure, etc. Under the background of these studies, this paper is committed to development some new PEC biosensors with high sensitivity and selectivity. This thesis involved nanometerials, PEC analysis technology, aptamer. It focuses on the application of PEC biological analysis, the main contents are as follows:1. Highly sensitive and selective photoelectrochemical biosensor for Hg2+ detection based on dual signal amplification by exciton energy transfer coupled with sensitization effectA highly sensitive and selective PEC biosensor for Hg2+ detection was developed based on the synergistic effect of exciton energy transfer (EET) between CdS quantum dots (QDs) and Au nanoparticles (NPs) coupled with sensitization of rhodamine 123 (Rh123) for signal amplification. First, the TiO2/CdS hybrid structure obtained by depositing CdS QDs on TiO2 film was employed as a matrix for immobilizing probe DNA (pDNA). Next, Rh123 was introduced into the pDNA terminal, and then Au NP labeled target DNA (Au-tDNA) was hybridized with pDNA to form a rod-like double helix structure. The detection of Hg2+ was based on a conformational change of the pDNA after incubating with Hg2+. In the absence of Hg2+, Rh123 was located away from the electrode surface due to the DNA hybridization, leading to inhibition of the sensitization effect and meanwhile the occurrence of EET between CdS QDs and Au NPs resulting in photocurrent decrease. However, after incubating with Hg2+, the rod-like double helix was disrupted and the energy transfer was broken, the photocurrent recovered, and meanwhile the folded pDNA made the labeled Rh123 move closer to the electrode surface, leading to the formation of the sensitization structure, which evidently increased the photocurrent intensity. The sensitivity of the biosensor for Hg2+ detection was greatly enhanced for the dual signal amplification strategy. The linear range was 10 fM to 200 nM, with a detection limit of 3.3 fM. This biosensor provides a promising new platform for detecting various heavy metal ions at ultralow levels.2. Enhanced photoelectrochemical aptasensor for ultrasensitive Pb2+ detection based on MoS2-CdS:Mn nanocomposites and sensitized structureA highly sensitive PEC biosensor for Pb2+ detection was developed based on the MoS2-CdS:Mn nanocomposites (NCs) and the sensitized structure. The MoS2-CdS:Mn NCs was prepared in a one-step synthesis in the solution of MoS2 nanosheets, which was obtained by ultrasonic method. First, the MoS2-CdS:Mn NCs was modified on the electrode as the matrix of the biosensor. Then, the aptamer probe DNA was anchored on the electrode through the classic EDC coupling reaction between carbonyl groups on the surface of the CdS:Mn and the amino groups of the probe DNA. Next, the target DNA and the sensitive element, CdTe-NH2 QDs, were introduced to the electrode step by step. The detection of Pb2+ was based on conformational change of the aptamer after incubating with Pb2+. In the absence of Pb2+, CdTe-NH2 QDs was located away from the electrode surface due to the DNA hybridization, leading to inhibition of the sensitization effect. However, after incubating with Pb2+, the rod-like double helix was disrupted and meanwhile the folded pDNA made the labeled CdTe-NH2 QDs move closer to the electrode surface, leading to the formation of the sensitization structure, which evidently increased the photocurrent intensity. The sensitivity of the biosensor for Pb2+ detection was greatly increased for the signal amplification strategy. The linear range was 50 fM to 100 nM, with a detection limit of 16.7 fM...