Studies On Analytical Applications Of Cu₂S@Co₃S₄ Heterostructures Based On Their Electrocatalytic And Peroxidase-like Activities

Alpha-fetoprotein（AFP）is an important plasma protein,mainly produced in the liver,yolk sac,and gastrointestinal tract of human embryo.The high level of AFP in Adult Serum is considered as a possible sign of malignant tumor,so AFP can be used as an important tumor marker in the diagnosis of cancer（such as liver cancer,esophageal cancer,etc.）.Hydrogen peroxide（H₂O₂）is one of the main forms of active oxygen in the cells of organisms.A proper amount of H₂O₂ can ensure its integrity and vitality,but excessive H₂O₂ may cause oxidative stress in the human body and cause a series of diseases（such as cancer,diabetes,etc.）.Glucose is a direct source of energy for cell metabolism.High blood sugar levels can lead to heart disease,blindness and other problems.Therefore,it is of great significance to develop efficient methods for sensitive detection of AFP,H₂O₂ and Glucose.Transition metal sulfides are widely used in the fields of batteries,electrocatalysis and supercapacitors because of their abundant natural reserves,low prices,and a variety of element valence states and crystal forms.Metal sulfide heterostructures formed by metal sulfides are expected to improve the catalytic performance.In this thesis,Cu₂S@Co₃S₄ heterostructures were prepared,and their electrocatalytic activity and peroxidase activity were studied.The sensitive detection of AFP,H₂O₂ and glucose was realized.The main content of this article is as follows:（1）Cu₂S@Co₃S₄ core-shell heterostructures were synthesized by growrh of amorphous Co（OH）₂ nanosheets on Cu₂O nanocubes at room temperature and one-step sulfuration of Cu₂O@Co（OH）₂ by a hydrothermal method.Due to the great synergetic effect between Cu₂S and Co₃S₄,the Cu₂S@Co₃S₄ heterostructures show high electrocatalytic activity toward H₂O₂ reduction.Under the optimal detection conditions,a label-free electrochemical immunosensor using Cu₂S@Co₃S₄ as the electrode material possesses a wide linear range for detecting AFP between 10^-3 and 100 ng m L^-1,with a detection limit as low as 0.6 pg m L^-1（S/N=3）.（2）The peroxidase-like activity of Cu₂S@Co₃S₄ heterostructures were studied,and the results showed that Cu₂S@Co₃S₄ can catalyze the conversion peroxidase substrate of 3,3,5,5-tetramethylbenzidine（TMB）to colored substance in the presence of H₂O₂.The catalytic kinetics of were studied,and the results show that Cu₂S@Co₃S₄ has a very small Michaelis-Menten constant（K_m）and a large maximum reaction rate(V_max).Based on the excellent peroxidase-like activity of Cu₂S@Co₃S₄,colorimetric detection of H₂O₂ and glucose was carried out,and the detection limits of H₂O₂ and glucose are 2.6 and 6.1μM,respectively.