Study On The Preparation And Application Of Transition Metal (Oxide)/graphene Sensing Materials

Transition metal-oxide nanomaterials have high electrochemical activity,low redox potential and good biocompatibility and has been widely used in the fields of sensing,energy storage,catalysis,biomedicine and so on.However,most of the materials prepared at present have the defects of large particle size,poor dispersibility and electronic conductivity,resulting in the inherent excellent electrochemical properties of the materials are far from being reflected.Therefore,the development of electrode materials with adjustable size structure,good dispersibility and excellent conductivity is of great siginificance for the overall improvement of electrochemical performance.In order to solve the problem of traditional electrode material has low utilization rate of active substances caused by large particle size and small specific surface area.Through the "slow release effect" of graphene quantum dots on transition metal ions a method for adjusting the size and structure of nanomaterials by histidine functionalized graphene quantum dots was established.The imidazole functional group introduced by the edge of the graphene quantum dot sheet forms a stable complex with Cu2+,and then the CuO-His-GQD composite material is obtained through slow oxidation treatment.The in-situ synthesis of graphene quantum dots and CuO achieves a clever combination of p-type semiconductors and n-type semiconductors,resulting in a similar "p-n junction" interface,making CuO-His-GQD composites exhibit higher electrocatalytic activity.Hydroquinone sensor was constructed with CuO-His-GQD as electrode material.The differential pulse voltammetry(DPV)was used to detect hydroquinone and showed a good linear relationship in the concentration range of 1.0×10-7~1.0×10-4 M.The corresponding regression equation was Ip=0.5753 C + 17.093.R2 = 0.999,and the detection limit(S/N = 3)is 3.1 × 10-7 M.The CuO-His-GQD electrode exhibited excellent antiinterference and stability when measured in environmental water samples.Point at the problem of low conductivity of metal semiconductor oxide,a method of insitu recombination of Ni2+ with histidine functionalized graphene quantum dots was established to construct a nano-building with a three-dimensional network porous structure.At the same time of realizing particle size control,the oxidized Ni O-His-GQD compound is subjected to high-temperature thermal reduction by inert gas to form Ni-His-GQD.On the one hand,the intimate contact between Ni nanoparticles and His-GQD greatly shortens the gap between the two complexes,resulting in faster electron migration speed;On the other hand,the conductive(Ni)/semiconductor(His-GQD)catalytic interface formed in clocse contact can produce Stokes diode-like structures,accelerate the migr-ation rate of hole carriers in the semiconductor,and exhibit good electrocatalytic activity.An enzyme-free glucose electrochemical sensor was prepared with Ni-His-GQD electrode material,which showed good electrocatalytic activity.The concentration of glucose was detected by amperometric analysis,and showed a good linear relationship in the concentration range of 5.0×10-6~2.0×10-3 M.The calibration curve was Ip=20.89 C + 1.7713,R2=0.9884,and the detection limit(S/ N = 3)is 1.7 ×10-6 M.And it shows high accuracy in human serum samples.To solve the problem of the poor dispersibility of metal nanomaterials and the large agglomeration of active sites caused by particle agglomeration,a histidine functionalized graphene quantum dot-graphene hybrid(His-GQD@rGO)was designed.The graphene functionalized graphene quantum dot imidazole group in the graphene-graphene quantum dot hybrid is coordinated with Ni2+ and Co2+ to form a three-dimensional graphene network system supporting Ni and Co complexes.A graphene-graphene quantum dot hybrid with nickel-cobalt ions fixed as a precursor,and a nickel-cobalt-histidine graphene quantum dot @graphene composite electrode(NiCo-His-GQD@rGO)material is formed by high temperature thermal reduction in the next step of inert gas.Using the supercapacitor model to investigate the electrochemical performance of the composite electrode material,the Ni Co-His-GQD@rGO electrode has a capacity of up to 1250 F g-1 at a current density of 1 A g-1,at a current density of 10 A g-1.It can still maintain 64% capacity and exhibit excellent rate performance.Differential pulse voltammetry was used for dopamine content detection and showed a sensitive electrochemical response in phosphate buffer solution at p H=7.0.When the dopamine concentration was in the range of 6.0×10-8~5.0×10-5 M,the DPV peak current showed a good linear relationship with the dopamine concentration.The corresponding calibration curve was Ip=0.554 C + 21.706,R2=0.9985,The detected limit(S/N=3)is 2.0×10-8 M,and it has been successfully applied to the detection of dopamine content in urine with high stability and antiinterference.