Construction Of Electrochemical Sensors Based On Two-dimensional Nanomaterials And Their Application In The Detection Of Small Biomolecules

Two-dimensional nanomaterials exhibit unique electronic and physical properties due to their inherent low dimensionality and quantum confinement effects,which has garnered great attention.The properties of two-dimensional nanomaterials,such as high mechanical flexibility,high specific surface area,numerous active sites,chemical stability,and superior electrical and thermal conductivity render two-dimensional nanomaterials great choices as alternative electrode materials in electrochemical field.Especially,two-dimensional layered nanomaterials have excellent heterogeneous electron transfer ability,large specific surface area,good adsorption ability and good biocompatibility,which make them an ideal electrode-fixed surface and modified material,and have great application value in electrochemical biosensing.The properties can be improved by nanostructure regulation,thickness control,surface modification,which will make the two-dimensional nanomaterials have a broader development space and promising application.In this paper,different two-dimensional layered nanomaterials and their composites were prepared,and applied in the field of electrochemical biosensing.1.An enzyme-free glucose electrochemical sensor based on ultrathin nickel-cobalt phosphate two-dimensional?2D?nanosheets was constructed.A simple one-step hydrothermal method was used to prepared 2D ultrathin nickel-cobalt phosphate nanosheets.Transmission electron microscopy?TEM?and scanning electron microscopy?SEM?were applied to observe the morphology of nanomaterials which were synthesized under different reaction time and different Ni/Co ratios.And the influence of nanomaterials,structure on the electrochemical performance for glucose oxidation was investigated.It was found that the thinnest nickel-cobalt phosphate nanosheets synthesized with a Ni/Co ratio of 2:5 showed the best electrocatalytic activity for glucose oxidation.And the ultrathin nickel-cobalt phosphate nanosheet was used as an electrode material to construct a non-enzymatic electrochemical sensor for glucose detection,which showed excellent electrochemical performance,such as wide linear range?2.0×10-6?4.5×10-3 M?,low detection limit?0.4?M?and good stability and reproducibility.We also used the as-prepared sensor to measure the glucose in human serum.These superior performances prove that the ultrathin 2D nickel-cobalt phosphate nanosheet is promising material in the field of electrochemical sensing.2.A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles?AuNPs?decorated Ni metal-organic-framework?MOF?/Ni/NiO nanocomposite.Two-dimensional Ni-MOF nanosheets were synthesized by solvothermal method,and then Ni-MOF/Ni/NiO/C nanocomposites were prepared by one-step calcination of Ni-MOF in argon atmosphere.AuNPs were loaded onto the surface of Ni-based nanocomposites by electrostatic adsorption to improve electrocatalytic activity,and finally Au-Ni nanocomposites were prepared.Cyclic voltammetric?CV?study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto the large surface of Ni-MOF/Ni/NiO/C nanocomposites.Amperometric study manifested that the calibration curves of electrochemical sensors based on Au-Ni nanocomposites toward glucose oxidation showed a good linear relationship between 4.0×10^-7?9.0×10^-4 M?correlation coefficient R²=0.9996?.The sensitivity was as high as 2133.5 mA M^-1 cm^-2 and the detection limit was as low as 0.1?M.We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results.It is believed that AuNPs decorated Ni-MOF/Ni/NiO/C nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications.3.Molybdenum disulfide nanosheets/gold nanorod?MoS₂-AuNRs?hybrids were prepared and immobilized catalase?CAT?to construct electrochemical biosensors for detection of H₂O₂ released from living cells.FT-IR,UV-vis and Raman spectra showed that MoS₂-AuNRs nanocomposites provided a biocompatible microenvironment for the immobilization of CAT molecules and retained their natural structure and biological activity.The results of direct electrochemical measurements indicated that compared with MoS₂ nanosheets and AuNRs modified electrodes,CAT exhibited a faster surface-controlled electron transfer process on the MoS₂-AuNRs composite electrode,and the electron transfer rate constant?ks?is 1.07 S^-1 and the Michaelis constant is 0.10 mM.MoS₂-AuNRs nanocomposites has a large surface area and can be used for enzyme adsorption.It provided a good matrix for accelerating DET between enzyme and electrode,and greatly improved the sensitivity of detection of H₂O₂.The constructed electrochemical biosensor showed excellent electrochemical performance,such as a wide linear range(5.0×10^-7 M to 2.0×10^-4 M),high sensitivity(187.4 mA M^-1 cm^-2)as well as low detection limit?0.1?M?.The as-prepared biosensor also realized monitoring the trace concentrations of H₂O₂ released from SP2/0 living cells.