Research On Biomolecules And Ions By Constructing Electrochemical Sensors Based On Gold Nanowires

The electrochemical sensor can convert the chemical reaction signal of the substance to be tested through the electrode surface into an electrical signal.It has the advantages of good selectivity,fast signal response,and high detection sensitivity.Precious metal elements are widely used in the fields of catalysis,analysis and medicine due to their special optical,thermodynamic and electrocatalytic properties.Nano-gold particles are widely used in nanoelectronics,optoelectronics,catalysis,biomolecular labeling,sensing and biosensing with highly application potential owing to their high electron transfer rate,high catalytic activity,large specific surface area,and good electrical conductivity as well as their special optical properties.The single-component of noble metal nanoparticles holds the simple function and the application defects such as poor electrical conductivity and unstable structure.In order to overcome these challenges,a variety of gold nanomaterials with different shapes have been investigated.Gold nanowires achieved the high attention from the researchers for their unique electrical properties,catalytic properties and biocompatibility.The work of this thesis uses self-assembly method to synthesize gold nanowires on ITO conductive glass,and the further modification of gold nanowires with4-mercaptobenzoic acid.The electrochemical sensors based on this material for different biologically active substances have been constructed,and have been used to detect the species of dopamine,pyrophosphate and alkaline phosphatase(ALP).The practical applications of the material were also studied.Three aspects of this work have been summarized as following:1.Building an electrochemical sensor based on gold nanowires for detecting dopamineThe self-assembly method was used to prepare gold nanowire-modified ITO conductive glass and construct the Au NWs/ITO working electrode.The introduction of MBA(4-mercaptobenzoic acid)functionalized gold nanowires realizes the selective detection of dopamine(DA).By optimizing the synthesis conditions and test conditions,the optimal preparation conditions and excellent performance of dopamine electrochemical sensor were obtained.The experimental results show that under the best experimental conditions,the linear detection concentration of dopamine measured by differential pulse voltammetry is 0.05-175μmol/L(R~2=0.989),and the minimum detection limit of dopamine is 0.031μmol/L.The as-prepared gold nanowires show the good selectivity and sensitivity,and were able to effectively reduce the interference from ascorbic acid and uric acid in the actual sample detection.Dopamine in blood and urine has been detected by adding standard method using the as-prepared electrode.2.Indirect detection of pyrophosphate based on the electrochemical response of gold nanowires to copper ionsThrough the chelation of the carboxyl group on 4-mercaptobenzoic acid with copper ions and with the well-known fundamental that pyrophosphoric acid and copper ions will chelate and compete with MBA to bind copper ions,the Au NWs/ITO electrode is designed to detect pyrophosphate acid by monitoring the signal change of copper ions.The experimental results achieved under the optimal experiment conditions show that the linear range of the prepared sensor for detecting pyrophosphate acid is 0.1-10μmol/L,and the lowest detection limit is 0.035μmol/L.The sensor has good anti-interference ability to achieve selective detection of pyrophosphate acid.3.Electrochemical sensors constructed with gold nanowires for indirect detection of alkaline phosphatase activityBy leveling the competitive binding effect of pyrophosphate and copper ions in the work of Part II,this work used self-assembly of copper ions on the as-prepared Au NWs/ITO electrode and used pyrophosphate to competitively bind copper ions to indirectly detect alkaline phosphatase(ALP).The detection principle is that ALP can hydrolyze its substrate pyrophosphate to release copper ions,and the released copper ions generate electrochemical signals on the electrode to achieve indirect detection of alkaline phosphatase activity.The constructed sensor can selectively detect alkaline phosphatase activity,and can achieve specific detection in the presence of ATP and phosphate.The concentration linear range of electrochemical detection is 60-180 U/L,and the lowest detection limit is 12.75 U/L.