Synthesis Of Three Hierarchical Carbon Nanocomposites And Properties Of Their Protein Sensor

Electrochemical biosensor is an analysis and detection equipment that identifies target detection substances through biometric probes fixed on the transducer and converts the concentration data into measurable electrical signals.It has been widely used in environmental analysis,medical diagnosis,food detection and other fields due to its advantages of simplicity,speed and efficiency.As an important branch of the electrochemical biosensor,the core component of the electrochemical protein sensor is REDOX protein,which can react with the substance to be measured and generate biochemical signals,providing a guarantee for the specific selectivity of the sensor.With the development of nanoscience and nanotechnology,many nanomaterials have been used as sensitizers for electrode modification,carbon-based nanomaterials have become one of the most attractive candidates for electrode modification due to their good biocompatibility,easy modification and excellent electrical conductivity.In particular,one-dimensional carbon nanomaterials,represented by carbon nanotubes and carbon nanofibers,are often selected as conductive substrates in the design of electrochemical sensing.The sensor platform constructed based on them can not only play the role of signal transmission,but also promote the direct electron transfer between the electrode interface and the electroactive center.However,the surface of carbon nanofibers is inert,which is not conducive to the direct adsorption of proteins,so surface modification or doping is often needed.In this paper,zinc oxide carbon nanofibers（ZnO-CNF）,hydroxyapatite hollow carbon nanofibers（HAP-HCNF）and gold nanoparticles/hydroxyapatite hollow carbon nanofibers（Au/HAP-HCNF）were prepared as the sensitizer of electrode modification.Furthermore,the direct electrochemical behavior of REDOX protein on the interface of CILE electrode was studied in detail as follows:（1）In this study,zinc acetate doped polyacrylonitrile nanocomposite fibers（（CH₃COO）₂Zn-PANF）were prepared by high pressure electrostatic spinning process.With this fiber as the skeleton,secondary nucleation method was adopted,and hexamethyltetramine was used as the growth control agent.Three-dimensional sheet zinc acetate nanostructures were in-situ grown on the surface of PANF using doped zinc acetate as crystal core.After high temperature carbonization,ZnO-CNF nanofiber composites with hierarchical structure were prepared.An electrochemical protein sensor（Nafion/Hb/ZnO-CNF/CILE）was constructed by using ionic liquid carbon paste electrode（CILE）as the base electrode and ZnO-CNF as the sensitizer on the sensor interface.Then,hemoglobin（Hb）and Nafion（Nafion/Hb/ZnO-CNF/CILE）were fixed on the surface of the electrode by layered coating method.The composites and their electrochemical biosensors were characterized by ultraviolet and infrared spectroscopy,scanning electron microscopy and electrochemical analysis.The results show that the composite not only has a good immobilization effect on hemoglobin,but also acts as the intermediary of electron transfer between hemoglobin and electrode.In addition,the electrochemical protein sensor has shown good electrochemical catalytic ability for Trichloacetic Acid（TCA）,showing good linear relationship in the concentration range of 0.77～230.00mmol/L,with the lowest detection limit of 0.25mmol/L（3σ）.（2）Hollow polyacrylonitrile nanofibers（（CH₃COO）₂Zn-HPANF）containing zinc acetate were prepared by coaxial high pressure electrostatic spinning technology using zinc acetate and polyacrylonitrile as precursors.A hollow carbon nanofiber（HCNF）containing mesoporous surface was synthesized by high temperature carbonization and phosphoric acid soaking.Using the mesoporous surface of the fiber as the scaffold,the release of calcium salt was controlled through the mesoporous surface,and the floral herarchical nanostructures（hydroxyapatite）were grown in situ on the surface of the carbon nanofibers without the addition of surfactants.Floral herarchical nanostructures confer larger specific surface area and more active sites.In addition,hydroxyapatite rich in hydroxyl functional groups can enhance the adsorption of proteins on carbon fiber surface and maintain its unique biological conformation,thus improving the catalytic activity of biological proteins.The electrochemical protein sensor（Nafion/Hb/HAP-HCNF/CILE）was constructed by using hydroxyapatite and hollow carbon nanofiber composites（HAP-HCNF）to modify the surface of the CILE electrode.The prepared electrochemical protein sensors showed excellent electrocatalytic ability for TCA and KBrO₃,where the linear detection range of TCA was 0.98～340.00 mmol/L,and the detection limit was 0.32 mmol/L（3σ）.The linear detection range of KBrO₃is0.03～10.00 mmol/L,and the detection limit is 0.011mmol/L（3σ）.（3）By electrochemical deposition,gold nanoparticles（Au NPs）were deposited on the surface of HAP-HCNF/CILE electrode to obtain a ternary nano-modified electrode,and then Hb and Nafion were modified on the surface.Finally,the electrochemical protein sensor（Nafion/Hb/Au/HAP-HCNF/CILE）was successfully constructed.The prepared electrochemical biosensors showed excellent electrocata-lytic ability on TCA,where the linear detection range of TCA was0.33～30.00,30.00～110.00 mmol/L,and the detection limit was 0.11 mmol/L（3σ）.When Au NPs were added,the electrochemical protein sensor showed a lower detection limit,from 0.32 mmol/L to 0.11 mmol/L.