Quantitative Determination Of Trace Glucose Based On SERS And Electrochemical Method

Glucose is a very important substance which can provide energy after oxidation in human body.But when the concentration of glucose is too high,people will get diabetes.Diabetes can cause great harm to human body and some complications.In addition,glucose plays an important role in chemical industry,fermentation process and food industry.Therefore,rapid,trace,quantitative and on-line detection of glucose concentration is of great significance for human health and industrial production.Surface Enhanced Raman Scattering(SERS)has been widely used in biology,medicine,chemistry,food safety and other fields to achieve rapid quantitative detection of some substances in the reaction due to its advantages of rapidity and convenience compared with chromatography and mass spectrometry.Because the Raman scattering cross section of glucose is small and the adsorption with the substrate is weak,so it is difficult to directly detect the concentration of glucose by SERS.Therefore,this paper uses SERS technology to indirectly detect the concentration of glucose by enzymatic reaction.And enzymatic assay is of great significance in detecting the concentration of glucose in the complex process of components.Enzymatic-free method has the advantages of strong stability and low cost,which can meet the requirements of daily use,so it is particularly important to explore an enzyme-free detection method.The electrochemical sensor can oxidize some substances directly and detect them quantitatively according to the current response of different concentration substances,thus avoiding the participation of enzymes.Therefore,the electrochemical enzymatic-free method was also used to achieve rapid quantitative detection of glucose concentration.In this paper,Au foam substrate with high SERS enhancement and electrochemical properties was prepared.After rapid quantitative detection of glucose by enzyme method,a rapid quantitative detection of glucose concentration was realized by enzyme free method.The main contents are as follows1.Rapid and quantitative determination of glucose from 1×10-7 to 1.5×10-2 M was achieved by SERS under enzymatic conditions.In this paper,gold is first reduced to silicon substrate by chemical reduction to obtain the Au/Si substrate.It is used as the conductive electrode in the later experiment and also as the gold crystal seed to achieve the formation of Au foam.By adding the negative voltage at the two ends of the Au/Si substrate by electrochemical deposition,the H2SO4 and NH4Cl in the electrolyte generate bubbles on the electrode surface,while gold is reduced to form Au foam substrates with bubbles as templates.By optimizing the composition of the electrolyte,it is found that when the electrolyte is NH4Cl,H2SO4 and HAuC14,the pore size of the Au foam substrate is uniform and the morphology is the best,and enhancement of SERS is also the best.R6G molecule is used as the dye molecule for Raman testing,and it can detect the signal of 1×10-7M R6G solution with Au foam,proving that it has strong SERS detection accuracy and enhancement.2.Rapid and quantitative determination of glucose from 1×10-7 to 1.5×10-2 M was achieved by SERS under enzymatic conditions.Because the SERS signal of direct detection of glucose is weak,we have explored a new method to transform and amplify the Raman signal of glucose.In the first step,glucose is oxidized to H2O2,then tetramethylbenzidine(TMB)is oxidized to charge transfer complex(CTC)by H2O2.The Raman signal of CTC is strong and easy to be detected.It can indirectly convert the detection of glucose into the detection of CTC signal,that is,the concentration of glucose can be measured indirectly by the amount of CTC.In the process of study,the factors that may affect CTC detection,such as enzymes,gluconolactone,H2O2,TMB,etc.were excluded.The linear relationship between the concentration of H2O2 and the integral area of CTC Raman characteristic peak in the second step was found,which provided a basis for finding the linear relationship between the concentration of glucose and the intensity of CTC signal.By combining the two reactions,the linear relationship between the concentration of glucose and the integral area of CTC Raman characteristic peaks was finally determined The detection limit of glucose was 1×10-7 M.The established linear relationship was verified for the accurate detection of glucose.The results showed that the indirect method of SERS could detect the concentration of glucose quickly,sensitively and accurately.3.Rapid and quantitative determination of glucose from 5×10-7 to 1.2×10-2 M without enzyme was realized by electrochemical technique.Because the activity of enzymes is influenced by environment,which will affect the accuracy of glucose detection,so we also studied how to detect the concentration of glucose by enzyme-free method.The electrochemical activity of Au foam electrode,Au/Si electrode and Si electrode in H2SO4,NaOH and glucose solution were tested without enzyme.Because of its unique structure,foamed gold has large surface area,which allows it to adsorb more glucose molecules to form more AuOH catalyzing the oxidation of glucose.Therefore,it has strong electrochemical activity and can oxidize glucose.After that,the current response of glucose was detected.It was found that different glucose concentration corresponded to different current response.A fast,sensitive and accurate i-t curve was established.The linear relationship between glucose concentration and current response was established by using this curve,and the detection limit of glucose was determined to be 0.14 ?M.The selectivity,stability and reproducibility of Au foam glucose sensor were further studied.The results showed that the sensor had good selectivity,long time stability and good reproducibility for the detection of glucose under the condition of no enzyme.In addition,the glucose biosensor is also applied to the detection of glucose concentration in human serum,and accurate data are obtained.SERS method and electrochemical method were used to detect three concentrations of samples respectively,and compared with the results of commercial sensors.The results showed that Au foam sensor has good detection accuracy and can be applied to the quantitative detection of glucose in real life,so it has good application prospects.