Study On Synthesis And Stability Of AuNPs@PAMAM And Its Application In Electrochemical Analysis

Objective:In roder to improve the stability of gold nanoparticles,polyamide-amine（PAMAM）,a dendrimer compound,was used as templates to synthesize nanogold composites because there are a large number of molecular cavities in the PAMAM molecule.On this basis,AuNPs@PAMAM modified electrodes were used to establish the methods for the determination of bisphenol A（BPA）,4-hydroxy bicuculline andβ-amyloid.Methods:（1）Divergent method was used to synthesize 0.5-2.0 generation PAMAM.AuNPs@PAMAM was synthesized using citric acid three sodium as reductive agent and PAMAM as the templats in HAuCl₄ solution.AuNPs was obtained in HAuCl₄ solution without PAMAM samely using citric acid three sodium as reductive agent.The UV-Vis spectrophotometry was used to characterize the AuNPs@PAMAM and AuNPs solution.The particle size and Zeta potential of AuNPs@PAMAM and AuNPs solution were determined by laser particle sizer.（2）The AuNPs@PAMAM modified electrode was used for the electrochemical detection of BPA.The optimal solution pH,temperature and AuNPs@PAMAM concentration on AuNPs@PAMAM electrode were investigated by differential pulse method.Finally,the quantitative determination of BPA in real sample was carried out with AuNPs@PAMAM modified electrode as the electrochemical sensor.（3）Cyclic voltammetry was used to characterize the electrochemical behavior of 4-hydroxy bicuculline on AuNPs@PAMAM electrode.The method of determining the content of4-hydroxy bachydine was established.In addition,β-amyloid detection is achieved using AC impedance method on AuNPs@PAMAM electrode.Results:（1）The results showed that AuNPs@PAMAM can not be synthesized with G0.5-G1.5 PAMAM due to the macroscopical aggregation of nanoparticles.On the contrary,AuNPs@PAMAM was synthezed successfully with G2.0 PAMAM.G2.0AuNPs@PAMAM and AuNPs both have UV absorption with maximum absorption wavelength at 524 nm.G2.0 AuNPs@PAMAM show good stability in wide range of pH and salt concentration.（2）G2.0 AuNPs@PAMAM modified electrode has excellent electrocatalytic activity for BPA,the optimal conditions for the detection of BPA was studied and showed as follow:0.25 mmol/L HAuCl₄(C_{G2.0 PAMAM}:C_HAuCl4=3:1)for the synthesis of G2.0 AuNPs@PAMAM,25℃for detection solution temperature and pH 7.5.The electrochemical sensor based on G2.0 AuNPs@PAMAM nanocomposites has good electrochemical response to BPA.The linear relationship between peak current response and BPA concentration within the concentration range from1×10^-5to 5×10^-5mol/L as expressed:I_pa=0.0414 c+0.2791（μmol/L）with a correlation coefficient of 0.9962,the low detection limit is 2.0×10^-7mol/L,and the recovery rate was 101.3±8.9%.（3）G2.0AuNPs@PAMAM modified electrode show good clectrochemical catalytic activity for the oxidation of 4-hydroxy bicuculline,and the oxidation current showed excellent linear relationship with the concentration of 4-hydroxy between the range of 2×10^-6-10×10^-5mol/L,the linear relationship expressed as I_pa=0.0192c+0.1718 with a correlation coefficient of R²=0.9993,the low detection limit is 5.71×10^-7mol/L.（4）In addition,impedance analysis ofβ-amyloid on G2.0 AuNPs@PAMAM showed thatβ-amyloid content had a good linear relationship between 5×10^-6-2×10^-4mol/L and expressed as R_ct=5.9931c+408.54.The low detection limit was 7.7×10^-7mol/L.Conclusion:（1）AuNPs@PAMAM can be synthesized with G2.0 PAMAM successfully and show good stability.（2）Compared with bare gold electrode and AuNPs modifeied electrode,G2.0 AuNPs@PAMAM showed better electrocatalytic activity for BPA and it is better applied in baby bottle.（3）The AuNPs@PAMAM modified electrode showed a good electrochemical response to 4-hydroxybitrapane and can be applied in the determination of4-hydroxybicuculline.（4）The method forβ-amyloid detection was researched on AuNPs@PAMAM electrode through electrochemical impedance spectrum,which provides a methodological reference for the clinical diagnosis of Alzheimer’s disease.