Au@Pt Ultramicroelectrode Preparation And Analysis Application Research

Ultramicroelectrodes(UMEs)are a kind of electrodes with one-dimensional size in micrometer(10-6m)or nanoscale(10-9m).Usually,it is accustomed to call an electrode with one-dimensional size smaller than 25?m or less than the thickness of its diffusion layer as UME.UME shows several unique properties,such as the increased mass-transport rates,high sensitivity,less susceptibility to ohmic losses,steady-state response,and short response times.Considering the several typical attributes of UME,it has broad application prospects in single-cell analysis,single biomolecule detection,electrochemical biosensor and electrocatalysis,and so on.Therefore,it is of great importance to construct UMEs with different structures and properties and study its applications.There are three parts in this thesis,main contents are as follows:The chapter one of this thesis presents a brief review of the basic concept,features,fabrication,characterization and application of UME.Then the electrochemical DNA(E-DNA)biosensor and electrocatalysis were introduced in a simple way,respectively.In chapter two,an Au@Pt nanoflower UME was fabricated and used to study the rapid hybridization kinetics of DNA.In this work,the Au@Pt nanoflower UME was prepared by electrodeposition of gold on a platinum UME surface.Then it was used for the construction of the folding-based E-DNA sensors taking ATP as an example.The as-prepared ATP sensors showed rapid response to ATP due to both the enhanced mass transfer rate from the small size of UME and the reduced steric hindrance of nanoflower structure of the electrode.The hybridization reaction rate of DNA at Au@Pt nanoflower electrode increased with the decreasing of the size of UME.10 min is enough for the hybridization reaction between ATP aptamer and ATP at UME whose radius is smaller than 25 ?m(the critical dimension of UME),which is more rapid than that occurred at macroelectrode or in solution.Therefore,the E-DNA sensor prepared by this work is expected to achieve the detection of biomolecules(such as ATP molecules)quickly and specifically in microenvironments(such as single cells).In chapter three,an Au@Pt core-shell UME was fabricated and used for the study of its electrocatalytic activity.In this work,Au@Pt core-shell UME was prepared by a physical method,based on the difference in the melting point of gold and platinum,making gold melt and disperse on platinum wire surface.Then it was used for the study of electrocatalytic activity to formic acid and methanol.The results showed that the as-prepared Au@Pt core-shell UMEs exhibited preferable electrocatalytic oxidation activity to formic acid and methanol.It is also found that the Au@Pt core-shell UME presents its optimal electrocatalytic oxidation activity to formic acid and methanol when the ratio of gold/platinum is close to 1.In addition,this method for the preparation of Au@Pt core-shell UME does not involve complex chemical synthesis and expensive instruments.It has the advantages of simple operation,short time consuming and low cost.Therefore,this study has developed a new method for the preparation of alloy UMEs,and provides a new idea for the direct application of UMEs to the field of electrocatalysis.