Research On The Preparation And Application Of Ratio Electrochemical Sensors Based On Precious Metal/graphene Composites

Carbon nanomaterials with different dimensions have received extensive attention in the fields of electrochemistry and other fields due to their excellent electrical,optical and mechanical properties.Among them,graphene is an important material of carbon nanomaterials,and has wide applications in electrocatalytic and electrochemical sensors due to its excellent mechanical tensile properties and rapid electron transfer.Graphene composites have the advantages,such as high sensitivity,large specific surface area,good biocompatibility,good electrical conductivity and rapid response.Graphene nanomaterials are compounded with metal nanoparticles,which can increase the specific surface area of the material at the electrode and also allow the sensor to have a fast rate of electron conduction.Based on the preparation of electrochemical sensors and their applications in analytical detection,this dissertation studied the rapid and simple preparation methods of the composites consisting of graphene materials and noble metal nanomaterials,and constructed a ratiometric electrochemical sensor（RES）for efficient and accurate detection of uric acid（UA）and creatinine（Crn）.Firstly,a novel and simple RES was developed and used to determine uric acid（UA）sensitively.Gold-silver bimetallic nanoparticles（Au-Ag NPs）were prepared and electrodeposited on the surface of a glassy carbon electrode（GCE）by one-step co-reduction reactiob,using HAuCl₄ and AgNO₃ as precursors.Graphene oxide（GO）reacted with thionin（TH）to form GO-TH through self-assembly.The Au-Ag NPs/GO/TH@GCE sensing platform was prepared by interactions between Au-Ag NPs,GO and TH.The electrochemical signal response of the sensing platform was recorded by square wave voltammetry（SWV）.With the increase of UA concentration,the peak intensity of redox current of UA increased regularly,while that of TH hardly changed.It allowed UA detection in practical samples and achieved a good linear range.Secondly,a new and effective creatinine RES was developed and used to determine creatinine（Crn）sensitively,based on creatinine-induced specific signal response and enzyme-free ratiometric signal detection strategy.The nanocomposite of polydopamine and reduced graphene oxide（PDA-rGO）was fabricated by a one-step hydrothermal reaction.PDA-rGO-NB complex was formed byπ-πstacking interactions between reduced graphene oxide（rGO）and Nile blue（NB）.Under cyclic voltammetry,copper nanoparticles（CuNPs）were prepared by electrochemical reduction of Cu²⁺ions on the surface of PDA-rGO-NB.A new CuNPs/PDA-rGONB@GCE sensing platform was constructed.The peak current intensity of I_Cu²⁺was regularly reduced due to specific interactions of nitrogen-containing center of creatinine with Cu²⁺.Experimental results confirmed that the sensing platform enabled high sensitive and selective detection of Crn.Based on functionalized GO-based nanocomposites and synergic advantages of GO and noble metals,RES was constructed for detection of small biomolecules.The functionalized graphene-noble metal nanocomposite as a modification material of the electrode enhanced the electrochemical signal and also played in a role of catalytic oxidation.This dissertation studied the applications of GO and precious metals for RES,showing great potential in the field of biological small molecule detection.