Preparation Of Multi-metal Sulfide Composite Nanomaterials And Their Application In Photoelectrochemical Sensors

In recent years,cancer has become a major health burden worldwide,and therefore,the ability to achieve quantitative detection of biomarkers is crucial for early diagnosis of cancer.Photoelectrochemical（PEC）immunosensing technology has shown great potential in the fields of bioanalysis and clinical detection due to its advantages such as low background signal and high sensitivity.One of the core elements for constructing a high-sensitivity photoelectrochemical sensor lies in the selection of a suitable photoactive material.Metal sulfides have attracted a lot of attention because of their narrow band gap,good optoelectronic properties,low cost and tunable chemical properties.However,the fast recombination rate of photogenerated electron-hole pairs limits the application of metal sulfides in photoelectrochemical sensors,and one way to overcome the disadvantages of metal sulfides is to compound them with semiconductors to form heterostructures.Based on this,in this thesis,multi-metal sulfide composite nanomaterials were prepared to improve their photoelectric properties and stability,and used to construct photoelectrochemical immunosensors for the detection of tumor markers.The main work is as follows:（1）In this study,a signal burst photoelectrochemical immunosensor was constructed to detect carcinoembryonic antigen（CEA）using NiS quantum dot-modified CdS-deficient nanospheres as a photoelectrochemical sensing platform and flower-like CuS as a signal tag.In this work,NiS quantum dots were modified onto CdS-deficient nanospheres by hydrothermal synthesis,and the CdS@NiS heterostructure could improve the carrier separation efficiency and promote the charge migration,resulting in a strong photocurrent from CdS@NiS.By annealing,CdS@NiS was more tightly bound and stronger photocurrent signal was obtained,on which the PEC sensor was constructed.CuS was used as a signal tag to form a CuS-Ab₂biocouple with Ab₂,and the spatial site resistance of CuS-Ab₂ and the competition between CuS and CdS@NiS substrate material for light absorption made the photocurrent intensity of the PEC sensor significantly reduced.Based on the above strategy,a highly sensitive PEC immunosensor was constructed to achieve the sensitive detection of CEA.Under the optimal experimental conditions,the constructed PEC sensor responded to CEA in the range of 0.1pg/m L～50 ng/m L with a detection limit of 0.042 pg/m L（S/N=3）.In addition,the sensor exhibited good stability,selectivity and reproducibility,and the detection of human serum samples indicated that the constructed sensor has a good development prospect in the field of bioanalysis.（2）In this study,a sandwich-type photoelectrochemical immunosensor was constructed to detect cytokeratin 19 fragment（CYFRA 21-1）using CdS/In₂S₃ composite nanomaterials as a photoelectrochemical sensing platform and snowflake-like Cu₂S as a signal tag.In this work,CdS/In₂S₃ composite nanomaterials with better photoelectrochemical properties and stability were prepared by a hydrothermal synthesis method.Through annealing experiments,CdS/In₂S₃generated a tighter interface and obtained a stronger photocurrent signal,which was used as a substrate to construct a highly sensitive PEC sensor.Cu₂S was used as a signal tag to form a Cu₂S-Ab₂ biocouple with Ab₂,because the spatial site resistance of Cu₂S-Ab₂ would impede the contact between the substrate material and AA,reducing the hole removal efficiency of the substrate material,and Cu₂S would also compete with the substrate material for light absorption,making the photocurrent signal get significantly burst.Based on the above strategy,a highly sensitive PEC immunosensor was constructed to achieve the detection of CYFRA 21-1.The response range of the constructed PEC sensor for CYFRA 21-1 was 0.1 pg/m L～50 ng/m L with the detection limit of 0.034 pg/m L（S/N=3）under the optimal experimental conditions.The application of the assay on human serum samples verified that the prepared PEC immunosensor has good selectivity and high sensitivity,and the sensor exhibited satisfactory stability,selectivity and reproducibility.（3）In this study,Ti O₂/Cd In₂S₄ composite nanomaterials were used as a photoelectrochemical sensing platform and Ce O₂ was used as a signal tag to construct a signal burst photoelectrochemical immunosensor to detect glycoantigen 15-3（CA15-3）.In this work,Ti O₂ electrode was prepared first,and then Cd In₂S₄ was modified onto the electrode to construct a Ti O₂/Cd In₂S₄ heterostructure.Ti O₂/Cd In₂S₄ heterojunction has good photoelectrochemical properties and high stability,which can be used as a substrate to construct a highly sensitive photoelectrochemical immunosensor.Ce O₂ is used as the signal tag because the Ce O₂-Ab₂biocouple can not only impede the efficiency of AA removal of electrode holes by spatial site resistance,but also compete with the substrate material for light absorption,inhibit the transfer of electrons,burst the photocurrent signal,and amplify the signal change.Under the optimal experimental conditions,the response of the sensor to CA15-3 ranged from 0.001 U/m L～50U/m L with a detection limit of 0.0004 U/m L（S/N=3）.The application of the assay on human serum samples indicates that the constructed sensor provides a good platform for achieving efficient detection of human serum samples with hypersensitivity,and the sensor exhibits good stability,selectivity and reproducibility at the same time.