The Application Of Photocathode Biosensor

Photoelectrochemical biosensing assays based on photocathodes can overcome the inherent disadvantages of photoanode based biosensor assays.Unlike the photoanode,the internal electron reduction reaction takes place at the photocathode/electrolyte interface,and oxygen is the electron acceptor.This causes the reducing component that is adsorbed from the electrolyte solution having no effect on the reduction reaction.As a resul,a true photocurrent response of photocathode itself is obtained.Based on this,we have synthesized BiOI nanosheets and CuInS₂ microflower p-type semiconductor materials,which have high dielectric constants,high carrier mobility,and strong carrier effects.This thesis was focused on the preparation photocathode biosensors constructed using BiOI nanosheets and CuInS₂ microflowers as photosensitive materials to detect thrombin,Pb²⁺,and miRNA.The main contents include:?1?A novel multi-functional PEC biosensor platform based on hemin G quadruplex enhancement and gold nanoparticles?AuNPs?quenching the PEC signal of Bi OI nanosheets was developed.The p-type semiconductor BiOI nanosheet was used as the cathode photosensitive material,and the hemin G quadruplex and AuNPs were used as electron transfer bodies.When the target thrombin is absent,the hemin G quadruplex is farther away from the BiOI nanosheets and the AuNPs are closer to the Bi OI nanosheets.At this time,the electron transfer between the AuNPs and the BiOI nanosheets plays a dominant role,resulting in the quenching of photoelectric signal.When the target thrombin was present,the hemin G quadruplex was closer to the BiOI nanosheets and the AuNPs was released.At this time,the photoinduced electron transfer between the hemin G quadruplex and the BiOI nanosheets plays a dominant role,resulting in the enhancement of photocurrent response.The photocurrent response shows a good linear relationship with the logarithm of thrombin concentration,in range of 8.75×10^-14mol/L to 8.75×10^-9mol/L.?2?A novel multi-functional PEC biosensing platform based on Fc enhancement and AuNPs quenching the PEC signal of BiOI nanosheets was developed.The p-type semiconductor BiOI nanosheets are still used as cathode photosensitive materials,and Fc and AuNPs are used as electron transfer bodies.When the target Pb²⁺is not present,the Fc is far away from the BiOI nanosheets and the AuNPs are closer to the BiOI nanosheets.At this time,the electron transfer between the AuNPs and the BiOI nanosheets plays a dominant role,resulting in the quenching of photoelectric signal.When the target Pb²⁺is present,the Fc is close to the BiOI nanosheets and the AuNPs is released.At this time,the photoinduced electron transfer between the Fc and the BiOI nanosheets plays a dominant role,resulting in enhancement of photocurrent response.The photocurrent response shows a good linear relationship with the logarithm of Pb²⁺concentration,in range of 5.0×10^-12mol/L to 1.0×10^-6mol/L.?3?Photoelectrochemical biosensing platform based on CuInS₂ microflowers as photosensitive material was developed.Using p-type semiconductor CuInS₂ microflowers as the cathode photosensitive materials,enzymatic cleavage amplification was used for cyclic amplification of the target miRNA.TATA-binding protein was used for electron blocking,which lead to the signal decreased in the presence of the target miRNA.In the absence of the target miRNA,the PEC signal does not change.The photocurrent response shows a good linear relationship with the logarithm of mi RNA concentration,in range of 1.0×10^-15mol/L to 1.0×10^-6mol/L.