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Preparation Of Au/graphene Nanocomposites And Their Application For Novel Nonenzymatic Glucose Sensor

Posted on:2016-06-14Degree:MasterType:Thesis
Country:ChinaCandidate:H H ShuFull Text:PDF
GTID:2381330482973961Subject:Materials Physics and Chemistry
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The reliable and fast determination of glucose is an important research topic in several fields,such as the pharmaceutical industry,food processing and blood glucose sensing.The clinical conditions of diabetes mellitus are well known and well understood,yet remain a growing concern as the prevalence of the disease increases worldwide at an alarming rate.A number of life-threatening and life-impeding conditions greatly affect the diabetic community,resulting in a much greater risk of cardiac,nervous,renal,ocular,cerebral and peripheral vascular diseases.Treatment has become a far more sophisticated science,with self-testing becoming increasingly more compact and accurate,and continuous glucose monitoring now obtained from practical commercial sensors.Glucose sensors are therefore a highly active area of sensor research.Much effort has been focused on developing suitable glucose sensors with high selectivity and sensitivity,good stability,fast response,and low cost.It is well known that traditional sensor based on glucose oxidase(GOx)usually shows good selectivity and high sensibility.However,it is lack of stability due to the intrinsic nature of enzyme.Their activity is easily affected by temperature,pH and toxic chemicals,and this is difficult to overcome.Therefore,the nonenzymatic glucose sensors have been developed in which the noble metal nano-materials are often used as the catalysts to substitute the enzyme.The majority of these sensors rely on the current response of glucose oxidation directly at the surface of the nanomaterials.Thus the non-enzymatic biosensor exhibited much higher stability for a long period and resistance ability to the environmental factors than the glucose biosensor using enzyme.Many efforts have been tried for the study of non-enzymatic glucose sensors using various metals(Pt,Pd,Au,Cu,Ni),and metal alloys(Pt-Pb,Pt-Ru,Pt-Au,Ni-Pd).However,the low sensitivity and limited supply of some noble metal prevented them from being an efficient commercial catalyst.With the development of nanotechnology,various metal nanomaterials have appeared.The unique interface effect,micro size effect and quantum effect of nanostructure can accelerate the electron transfer rate,improve catalytic activity,and thus increase the sensitivity of glucose sensors.While in the process of materials preparation,the application of surfactants,bridging agents and organic solutions might reduce the electrocatalytic activity because of blocking of the active sites.So challenges still exist in the preparation of nano-materials with a clean surface and a high catalytic ability.Gold nanoparticles have a great application in the field of glucose sensing,due to the unique properties of gold nanostructures,such as good conductivity,useful electrocatalytic activity,and biocompatibility.Graphene,a novelty two-dimensional carbon material,has a dense honeycomb crystal structure.The unique structure makes it has extraordinary properties,including high specific surface,strong mechanic strength,superior electrical conductivity,thermal stability and good biocompatibility.And it can be used as supporting material to reduce the use amount of noble metal and improve the electron transfer rate at the same time,leading to an enhanced performance of composites.Due to the excellent performance of noble metal/graphene nanocomposites,it has caused the widely research interest on experimental and theoretical,especially in the biosensor research field.This work will focus on:the fabrication of different morphologies gold nanostructures(AuNSs)and gold/graphene nanocomposites(Au/gra),and the study of their electrocatalytic activity.The main work includes the following three parts:First,we tried electrodeposition method,pulsed laser deposition(PLD)and seed mediated growth method to fabeicated gold nanomaterials with different morphology and structures,such as three-dimensional dendritical-like gold nanostructures(DGNs),gold nanoparticles(AuNPs),gold nanoclusters(AuNCs),etc.The gold nanomaterials were used as catalysts for non-enzyme glucose sensing,which showed good catalytic activity and stability for glucose oxidation.The electrochemical results show that gold nanomaterials with different morphology and structures have different sensitivity,test potential and linear range to glucose sensing,which were related to active area of catalysts on the surface of electrode.Then,in order to further enhance the catalytic activity of gold nanomaterials,the graphene was used as supporting materials.Using potentiostatic electrodeposition method to synthesis gold and graphene nanocomposites,in which the reduction of graphite oxide and Au precursor were carried out simultaneously during electrodeposition without any extra steps.The obtained Au/gra nanocomposites was characterized by field-emission SEM and TEM,the results show that Au nanoparticles have successfully supported on the surface of graphene sheets,and the nanocomposites uniformly modified on the electrode with 3D porous structures.Based on cyclic voltammetry and amperometric results,Au/gra efficiently catalyzed the oxidation of glucose in neutral media(0.1 M PBS,pH 7.4)and exhibited rapid response time,broad linear range,good stability,and high sensitivity.These results demonstrated that the Au-gra is promising for nonenzymatic detection of glucose.In the end,we studied the catalytic activity of different metal for glucose sensing.The Pt-based catalysts also have high sensitivity for glucose oxidation.AA was adopted as reductant used to successful prepares platinum/graphene composites(PtNCs/gra)via one step chemical reduction method.Polyvinyl Pyrrolidone(PVP)was added during the one-step reductive process so as to improve the dispersity of PtNCs on the graphene and decrease the size of PtNCs.The TEM and SEM results show that with the assistant of PVP,Pt nanoclusters appeared with smaller particle size and narrower particle size distribution.The large the specific surface area of highly dispersed Pt nanoclusters and excellent electrical conductivity of graphene contribute to the improvement of catalytic activity and stability for the glucose sensing.
Keywords/Search Tags:Au nanostructure, Graphene, Electrodeposition method, Electrochemical test, Non-enzymatic glucose sensors
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