| Graphene with unique optical,electrical,mechanical properties and chemical stability,are widely used in electrochemical sensor,electrochemical catalyst,supercapacitor,lithium-ion batteries,and catalysis.In recent years,the composite of graphene and metal nanomaterials has become a research hotspot in the field of materials.The hybrid not only combines the advantages of the two materials,but also improves the electron conductivity,electrolyte transmission speed and catalytic activity of the composites by the electrochemical synergy.Graphene materials which are currently in use,including ordinary graphene sheets of several micrometers to tens of micrometers and nanometer graphenes of several nanometers,are mainly confronted with problems of large block of electron transport and poor conductivity of small size.In view of the main scientific problems,this project developed new graphene materials.Through the ingenious combination of graphene and nanomaterials,the electrochemical performance can be significantly improved to meet the needs of different applications.The 2D graphene is constructed into 3D graphene aerogel,and the porous flower-like F-Fe2O3 was designed and synthesized as a composite component.Finally,the self-assembly of F-Fe2O3 and graphene was achieved by a multiple gel method to form the F-Fe2O3@MGA composite.Porous flower-like F-Fe2O3 was synthesized by adjusting the reaction medium and polyvinylpyrrolidone as the template.The supercapacitor was used as a model to study the electrochemical properties of the composite.F-Fe2O3@MGA shows low impedance?4.624??,high diffusion coefficient(1.6×10-9 cm2 s-1),and high specific capacitance in 3 M KOH aqueous solution(1119 F g-1 at a current density of 1 A g-1)and high rate performance(630 F g-1 at 10 A g-1 current density and 492 F g-1 at 20 A g-1 current density).In addition,after 2000 cycles of F-Fe2O3@MGA in 3 M KOH aqueous solution,the capacitance can be maintained at 98.9%.These results show that F-Fe2O3@MGA has extremely high electron conductivity,mass transfer capacity,and cycle stability.Functionalized nano-graphene was designed and nickel-cobalt-sulfide?NiCo2S4?which is as a composite component was synthesized by one-step method.The two materials were combined by matching at the energy level to obtain the NiCo2S4/His-NG composite.Among them,tryptophan is used to functionalize nano-graphene.NiCo2S4 is a material with a quasi-spherical structure,which is obtained by using cobalt nitrate and nickel nitrate as precursors,L-cysteine as a sulfur source,and tert-butyl alcohol?TBA?as a template solvent.The electrochemical performance of the composites was also studied using a supercapacitor model.The specific capacity of NiCo2S4/Trp-NG at a current density of 1 A g-1 can reach1453.1 F g-1.In addition,high rate performance is exhibited(It is 642.5 F g-1 at 5 A g-1current density,455.6 g-1 at 20 A g-1 current density and cycle stability?discharge capacity loss is less than 5.2%after 5000 cycles?.These results indicate that the NiCo2S4/Trp-NG composite has structural stability and excellent electrochemical performance.NiCo2S4/Trp-NG composites were prepared as biosensors for the detection of glucose.Glucose oxidase was used as a recognition factor and glucose as a substrate to construct a detection system in pH 7.4 PBS buffer solution.The results showed that when the glucose concentration was in the range of 1×10-4-5×10-6 M,the current response of the sensor showed a good linear relationship with the glucose concentration,and the detection limit was1.67×10-7 M.This method has excellent reproducibility and stability and was successfully applied to the detection of glucose in serum samples.The structure,size,and morphology of nanomaterials were regulated.For the first time,nano-graphene/Co3O4 composites was directly prepared by in situ synthesis.Based on the n-type semiconductor characteristics of histidine-functionalized nanographene and p-type semiconductor characteristics of Co3O4,the two materials were composited to achieve the p-n junction effect,enabling electrochemical detection signals to be amplified and the sensitivity significantly improved.A hydroquinone sensor was constructed using Co3O4/His-NG as the electrode material.When the concentration of hydroquinone is in the range of2.0×10-9-8.0×10-4 M,the current response value of the sensor has a good linear relationship with the concentration of hydroquinone.The corresponding linear regression equation obeys the following formula:Ip=0.024C+0.752.Based on the signal-to-noise ratio?S/N=3?of these data,the detection limit of hydroquinone is 8.2×10-10 M.When the water environment sample was measured,it showed good anti-interference and stability,and the sample recovery rate was 98.0-104.0%. |
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