Study On The Construction Of Electrochemical Sensor Based On Nanoporous Gold And Its Application In Rapid Detection Of Food

Electrochemical sensors are favored by many researchers because of their sensitivity,portability,and low cost in the field of rapid food safety detection.Recently,nanomaterials with different characteristics have emerged and were used as electrode modification materials,greatly expanding the application range of electrochemical sensors.In this paper,three different electrochemical sensors were constructed by using nanoporous gold(NPG),combined with other nanocomposites or electrochemical polymers as the electrode modification material.The electrochemical properties and performance of the electrochemical sensor was studied.Finally,those electrochemical sensors were applied to the detection of four food components.Main results are as followings:(1)Nanoporous gold(NPG)was prepared by etching,and an electrochemical sensor(NPG/GCE)was constructed.The CV and DPV electrochemical behaviors of ascorbic acid on the NPG/GCE were studied.The large specific surface area and unique three-dimensional network structure of NPG facilitated the adsorption of substances,and electro-catalyzed the oxidation-reduction reactions of the-OH in ascorbic acid.Thus,it increased response current of ascorbic acid,and could be used for the quantitative detection of ascorbic acid.Within a certain concentration range,the oxidation peak current value was linearly related to the ascorbic acid concentration.Linear regression equation:j(?A/cm²)=0.76526C_VC(?g/m L)+27.8992.The electrode preparation was simple and no sample pretreatment,avoiding the oxidation of ascorbic acid.As a result,rapid detection could be obtained.The equipment was easy to carry,and can meet the requirements of rapid on-site sample testing in food quality inspection.(2)The graphene/chitosan/ionic liquid nanocomposite(GO/CS/IL)was prepared and used to modify NPG/GCE to construct GO/CS/IL/NPG/GCE electrochemical sensor.The morphology of the nanocomposite were studied.Electctrochemical behaviors of different modified electrodes were investigated.The results showed that NPG and GO/CS/IL had synergistic effect,which made the novel GO/CS/IL/NPG/GCE have excellent electrochemical performance.The specific surface area of the prepared NPG/GCE was 0.3765 cm²,and the surface area was increased to 0.625 cm²when modified by GO/CS/IL.The GO/CS/IL increased the surface area of the electrode by nearly 1.66 times.The large specific surface area and good electronic properties of GO/CS/IL/NPG/GCE can promote the electron transfer.The GO/CS/IL/NPG/GCE showed the highest redox peak current response signal to amaranth,which could be used for the detection of amaranth in beverages.The detection concentration ranged from 8 n M to 1200 n M.The excellent electrochemical performance of GO/CS/IL/NPG/GCE improved the transfer rate of electrons.The lower detection limit(8 n M)and higher sensitivity(27.74 A M^-1 cm^-2)were compared with other relevant sensors reported in the literature.(3)The anodic stripping voltammetry behavior of Cd²⁺on GO/CS/IL/NPG/GCE electrode was investigated,which further expanded the application range of GO/CS/IL/NPG/GCE.The GO/CS/IL nanocomposite and NPG are both negatively charged on the surface of the electrode.Based on the electrostatic attraction,GO/CS/IL and NPG can adsorb positively charged heavy metals and improve the enrichment of heavy metals.The GO/CS/IL/NPG/GCE was successfully used for the determination of Cd²⁺in rice,and the curve equation:y(?A)=2.296 x+2.225(R²=0.990)was obtained.The recovery rate of the standard sample was 104%?106%,and the sensor had good anti-interference ability and stability for the detection of Cd²⁺.(4)On the surface of NPG/GCE electrode,mercaptoaniline was used as the functional monomer and 3-MCPD was used as the template molecule.The molecular im-printing polymers(MIP)was formed by electropolymerization and combined with the NPG/GCE to construct a new molecularly imprinted membrane electrochemical sensor(MIP/NPG/GCE).The hydroxyl group in 3-MCPD and the amino group in mercaptoaniline were crosslinked through hydrogen bonding.After template elution,a three-dimensional hole matching the structure of 3-MCPD was left on the surface of the electrode.The MIP/NPG/GCE electrode was characterized by iron ions in CV,EIS and DPV.The preparation conditions of the MIP were optimized.Finally,MIP/NPG/GCE was used for the detection of 3-MCPD.The results showed that the peak current value of iron has a linear relationship with the log value of 3-MCPD concentration within a certain range.The linear regression equation was:I(?A)=-3.76748 lgC+20.81759,(R²=0.998).The lowest detection limit was 1×10^-16 mol/L.The formed molecularly imprinted membrane had a specific recognition function for3-MCPD,and MIP/NPG/GCE showed excellent anti-interference ability and selectivity.