Study On Semiconductor Nanomaterials Based Photoelectrochemical Bioseneing

Photoelectrochemical biosensor is a new kind of electrochemical biosensor technique,which has develpoed rapid in recent years.And it developed on the combination of photoelectrochemical reaction process and specific biorecogination.The detecting principle of this newly sensing technique is the electrical signal can be brought from the electron transfer between analytes,photoelectrochemical active matrials and electrode.Photoelectrochemical biosensor possessed the advantages of optical mathods and electrochemical analytical techniques.Therefore,as a newly analytical technique,photoelectrochemical biosensor exhibiting features of high sensitivity,low background signal,inexpensive,simple facility and so on.Desipite lots of studies have been done for photoelectrochemical biosensor and it has obtained a rapid development in recent years,compared with traditional electrochemical analysis techniques,photoelectrochemical analysis method is still not matured.The analytical method of detection signals and photocurrent conversion efficiency of photoelectrochemical biosensor are insufficient.Therefore,it is necessary to develop new photoelectrochemical active materials and analytical method of detection signals.In this paper,semiconductor nanomaterials and nanocomposites were used as the photoelectrochemical active materials to assemble a series of photoelectrochemical biosensors,and the applications of these biosensors in DNA,proteins,antigens were also studied.The main research contents were described as follows:1.Enhanced photoelectrochemical sensing for MUC1 detection based on TiO₂/CdS:Eu/CdS cosensitized structureA novel ultrasensitive photoelectrochemical aptasensing was developed to detect mucin 1?MUC1?based on TiO₂/CdS:Eu nanocomposite.The TiO₂/CdS:Eu nanocomposite modified fluorine-doped tin oxide?FTO?electrode was prepared by successive ionic layer adsorption and reaction technique?SILAR?.Subsequently,SH-DNA?DNA1?,NH2-DNA?DNA2?and CdS-COOH QDs were successively incubated on the electrode surface.When the target MUC1 cleaved NH2-DNA from the electrode,the photocurrent response signal changed.The novel ultrasensitive photoelectrochemical aptasensing presented a highly selective,sensitive and reproductive detection of MUC1 from 1 nM to 5 ?M with a lower detection limit of 0.3 nM.At the same time,it also provided a good specificity,reproducibility,stability and promising strategy to detect a variety of other protein targets for early clinical diagnosis of different diseases.2.Photoelectrochemical sensor for DNA detection based on TiO₂/Au nano-composite structureA novel enhanced photoelectrochemical DNA sensor,based on a TiO₂/Au hybrid electrode structure,was developed to detect target DNA.The sensor was developed by successively modifying fluorine-tin oxide?FTO?electrodes with TiAO2 nanoparticles,gold?Au?nanoparticles,hairpin DNA?DNA1?,and CdSe-COOH quantum dots?QDs?,which acted as signal amplification factors.In the absence of target DNA,the incubated DNA 1 hairpin and the CdSe-COOH QDs were in close contact with the TiO₂/Au electrode surface,leading to an enhanced photocurrent intensity due to the sensitization effect.After incubation of the modified electrode with the target DNA,the hairpin DNA changed into a double helix structure,and the CdSe QDs moved away from the TiO₂/Au electrode surface,leading to a decreased sensitization effect and photoelectrochemical signal intensity.This novel DNA sensor exhibited stable,sensitive and reproducible detection of DNA from 0.1 p.M to 10 fM,with a lower detection limit of 3 fM.It provided good specificity,reproducibility,stability and is a promising strategy for the detection of a variety of other DNA targets,for early clinical diagnosis of various diseases.3.Label-free photoelectrochemical biosensor for highly sensitive detection of urokinase plasminogen activator based on CdS-g-C₃N₄ nanocompositeHerein,we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator?u-PA?,based on a g-C₃N₄/CdS nanocomposite.The prepared nanocomposite was characterized by transmission electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible absorption spectroscopy,and Fourier transform infrared spectroscopy,thus indicating that the nanocomposite was prepared successfully.In the typical process,the prepared nanocomposite was deposited on the surface of a bare FTO electrode.After being air-dried,the g-C₃N₄/CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA.In the presence of target u-PA antigen,the photocurrent response of the prepared biosensor electrode decreased significantly.The proposed novel photoelectrochemical biosensor exhibited good sensitivity,specificity,and reproducibility for u-PA detection,and a low detection limit of 33 fg· mL-1,ranging from 1 ?g·mL-10.1 pg·mL-1.The proposed strategy should provide a promising method for detection of other biomarkers.4.Photoelectrochemical immunoassay for human interleukin 6 based on the use of perovskite-type LaFeO₃ nanoparticles on fluorine-doped tin oxide glassA film of perovskite-type LaFeO₃ nanoparticles?NPs?was deposited on fluorine-doped tin oxide?FTO?conducting glass via dipping-lifting and calcination.The NPs were characterized by X-ray diffractometery and scanning electron microscopy and show that the NPs are evenly distributed on the surface of the glass.The modified glass was further coated with antibody against human interleukin 6?IL-6?to result in a photoelectrochemical immunoassay for IL-6.The device,on illumination with a xenon lamp,has a linear current response in the 0.1 pg mL-1 to 0.1 ug·mIL-1 IL-6 concentration range and a detection limit as low as 33 fg·mL-1.