Study And Application Of The Electrochemical Biosensors Based On Gold Nanoparticles/Graphene Modified Electrodes

Electrochemical sensors have been popular since it was created because of its advantages of fast and accurate detection rate,high sensitivity,simple operation,low price.How to build a sensitive,stable and reusable sensor interface is the key question that researchers want to resolve.Nanomaterials,such as graphene and gold nanoparticles are attractive in biosensors because of their high conductivity,large volume-to-surface area,as well as good biocompatibility.Especially the oxygen-containing functional groups at the edge of the graphene oxide have played a key role in the adsorption of heavy metal ions and the enzyme reactions.In this paper,we mainly focused on gold nanoparticles and graphene oxide which were covalently modified to the electrode surface by the aryldiazonium salt chemistry,and prepare high sensitive electrochemical sensors for detection of heavy metal ions and biological molecules.Based on above understanding,the main contents of this paper are as follows:(1)First of all,AuNPs were modified with the mixed layers of 4-nitrobenzene and 4-carboxyl benzene.Then the terminal nitro groups on AuNP surfaces were reduced to amine and then diazonium in the solution of HCl containing NaNO2 to form Au-Ph-N2+Cl-.Then the prepared AuNPs can be covalently modified to the gold electrodes through Au-C bond to form the Au-Ph-AuNP interface.Finally,glutathione was attached to the functional AuNPs,by the formation of peptide bond to fabricate the Au-Ph-AuNP-GSH sensing interface,which was used to detect Cd2+.The analysis performance of this electrochemical sensor for detection of Cd2+ was evaluated by different experimental parameters.This is the first reported sensor studying in-situ covalent bonding aryldiazonium salt modified AuNP on the electrode to detect metal ions.(2)The gold electrode surface was modified with 4-aminophenyl.The terminal amino groups were then reduced to diazonium in the solution of HCl containing NaNO2 to form Au-Ph-N2~+Cl-.Then the modified gold electrode was immersed in GO solution.GO was covalently modified on the gold electrode surface through the C-C bond by scanning cyclic voltammetry.The characterization results from electrochemistry and X-ray photoelectron spectroscopy(XPS)have confirmed that GO has been successfully modified to the gold electrodes,which can be,used for the detection of Pb2+,Cue+,Hg2+,simultaneously.For comparison,gold electrodes modified with 4-aminophenyl followed by GO through amide bonds were.also used to detect these three kinds of heavy metal ions.The analytical performace of two types of sensor interfaces were explored and compared.(3)We prepared the RGO/AuNP ananocomposited in order to improve the conductivity of sensing interfaces.RGO was firstly modified with 4-nitrophenyl to achive RGO-Ph-NO2,and then AuNPs were decorated into the RGO interface by in situ reduction of HAuCl4 to get RGO/AuNPs ananocomposites.Electrochemistry,Uv-Vis,FT-IR,and TEM were used for characterization of prepared nanomaterials,which demonstrated that AuNPs have been loaded on RGO sheets vastly.Then RGO/AuNPs nanocomposites were modified on the glassy carbon electrode surface by means of electrochemical methods followed by the attachment of glucose oxidase.The prepared enzyme biosensor were successfully used for the detection of glucose with high sensitivity.