Research On Construction And Application Of Biosensors Based On Novel Photoactive Materials

As an important substance regulating human physiological activities,the content ofbiomolecules in human body reflects various physiological indexes.The development of highly sensitive biomolecular detection methods can help people reveal the processes of the generation,storage and transformation of biomolecules in living system,and further explore the mechanism of life activities.As an important means to detect biomolecules,biosensors are playing an increasingly important role in precision medicine,clinical diagnosis and other fields.As a new chemical detection method,photoelectrochemical（PEC）biosensor is developed on the basis of electrochemical sensor and photochemistry.The detection principle of PEC sensor technology is to monitor the change of photocurrent or photovoltage caused by the reaction between the photoactive material and the analyte.In the detection process,the photoactive material is excited,and the photogenerated electron-hole pairs are transferred between the electrode and the photoactive material to obtain the photocurrent signal of the anode or cathode.The PEC biosensor separates the input signal（optical signal）and the output signal（electrical signal）.It inherits the advantages of the two signals and makes the background signal of this detection method very small and has high sensitivity.However,compared with the mature electrochemistry and photochemistry,the development of PEC is still not mature enough,for example,the photoelectric active material and detection mode are relatively single,and the photoelectric conversion rate is low.In this paper,a series of PEC biosensor platforms with high sensitivity and good selectivity were constructed by preparing new photoactive materials,and its detection performance and sensing principle were discussed.The main research contents are as follows:1.One–step synthesis of three-Dimensional porous Cu@Cu₂O agerogel networks for photocathodic sensing of Cysteine.The development of photoactive materials with low price,simple preparation,and stable signal has always been a hotspot in the field of photoelectrochemistry.In this chapter,the three-Dimensional porous Cu@Cu₂O aerogel composite was synthesized by simple one-step method,and it was applied to the construction of PEC biosensor for the detection of Cysteine（Cys）.Thanks to the prepared aerogels are highly porous,ultralow density and has a large specific surface area,the Cys in the system can be easily diffused and combine in the three-Dimensional Cu@Cu₂O aerogel composite.Under the optimized experimental conditions,Cu@Cu₂O aerogel composite showed excellent linear range（0.05-5μmol/L）and lower detection limit of 0.01μmol/L when detecting Cys.Compared with the previous biosensor detection Cys methods,our proposed sensor is simple to operate and does not require complex equipment and high-temperature heating operation.The results show that the sensor has good sensitivity,selectivity and stability.2.Construction of photocathodic bioanalytical platform based on Z-scheme polyimide/CdS composite assisted by dual-catalysis systemHerein a signal-on photoelectrochemical enzyme biosensor is successfully designed for sensitive monitoring of hypoxanthine based on the Z-scheme composite of polyimide/CdS.Xanthine oxidase（XOD）is integrated into the polyimide/CdS composite to construct an enzyme sensor.Due to its unique properties,polyimide（PI）not only has the ability of semiconductor to separate and transfer photogenerated electron-hole pairs,but also acts as a peroxide mimic enzyme to catalyze the reduction of H₂O₂,while the introduction of CdS is conducive to the light absorption of PI,and can also transfer the photogenerated electrons and holes generated by PI in time to obtain a more stable and larger photocurrent signal.Unlike the common O₂-dependent suppression of the signal,it is found that the cathode photocurrent becomes larger with the increase of the substrate concentration in a certain range.This interesting phenomenon is ascribed to the dual-catalysis system formed by the synergistic action of XOD and polyimide,and the use of cathode photocurrent also avoids the interference from reducing substances in the system.The constructed enzyme biosensor has a wide detection range from 10.0μmol/L to 10.0mmol/L and exhibits favorable analytical performance including good selectivity,sensitivity and high stability.