Studies On The Biosensors Based On Optical-Electrical Effects Of Quantum/Semiconductor Nanotube Composite

In this paper, we constructed a signal-on ECL histidine sensor and high sensitivity PEC immunosensor by combining electrogenerated chemiluminescence (ECL) or photoelectrochemical (PEC) analysis techniques with functionalized TiO2 nanotube arrays (TiNT).In chapter 1, we give a detailed description on the principle, classification and biosensing applications of ECL biosensor and PEC biosensor. Then we summarized applications of the nanomaterials in biosensing.In chapter 2, we developed a switchable ECL sensor for specific recognition of Ni2+ histidine based on CdTe/TiNT composite nanostructure. Firstly we assembled L-cysteine capped CdTe QDs into TiNT, ang the resultant CdTe/TiNTs showed a strong ECL signal. When the Ni2+ions were introduced into the composite nanotubes, they reacted with amino and carboxyl groups on CdTe QDs surface. The ECL signal got weak or even quench. After we added histidine into the system, due to the high affinity of histidine to Ni2+ions were dissociated from the surface of Hcy-capped CdTe QDs. Subsequently, the ECL signals restored. The sensor shows high sensitivity, good specificity, and rapid analysis speed.In chapter 3, a highly sensitive photoelectric immunosensor based on CdS/TiNT composite nanotube array was developed. CdS nanocrystals (NCs) were decorated homogeneously on TiNT by chemical bath deposition method. The resultant CdS/TiNT composite showed stable photoelectric response in the visible light region (400 nm). When Au nanoparticles (Au NPs) were introduced into the system as the carriers of the second antibody, the photocurrent was greatly attenuated because the reaction of between alkaline phosphatase (ALP) and 3-indole-hydroxy acid disodium salt (3-IP) could reduce Ag+to Ag with the catalysis of Au NPs. Both the steric effects of nanoparticles and the excition-plasmon interaction between CdS and Ag NPs participate could attenuate the photocurrent. If we didn’t deposit Ag, the detection linear range of antigen was 1.0×10-14～1.0×10-8g mL-1, the detection limit was only 1.0×10-15g mL-1. When the ALP reacted with 3-IP to deposit Ag NPs, detection linear range of antigen was 1.0×10-18～1.0×10-8 g mL-1, and the detection limit is reduced to 1.0×10-19g mL-1,Furthermore, the sensitivity also increased significantly. By this way, we achieved a sensitive immunosensor signal magnification. It provides a promising approach for the application of PEC in immunosensing.