Highly Activated Polyporous Silver Film By Etching And Its Electrochemical Determination Of Trichoroacetic Acid

Chloroacetic acid is a common organic halogenated pollutant,so it has an important application prospect to study efficient and rapid detection technology of trichloroacetic acid content.A highly activated polyporous silver film was constructed on the outer ring of silver wire by simple voltammetric etching for electrochemical detection of environmental pollutant trichloroacetir acid.The highly activated polyporous silver film was characterized by scanning electron microscopy?SEM?,X-ray diffractometer?XRD?,and photo-electron energy spectrum?XPS?.The surface roughness of the modified silver wire was analyzed by constant-potential step,the electrochemical performance of the modified silver wire was investigated by cyclic voltammetry,and the catalytic performance of the modified silver wire was investigated by chronoamperometry.Due to the excellent conductivity of the silver wire,and the large specific surface and high catalytic performance after modification,it was applied to thr electrochemical detection of trichloroacetic acid.The results showed that this new electrochemical sensor had high sensitivity,selectivity,stability.?1?Using inorganic anions as the etching activation solution,the voltammetric etching effects of different types and control conditions on silver wire were investigated.Select different anions,such as HCO₃^-,CO₃^2-,NO₃^-,OH^-,SO₄^2-,F^-,Cl^-,Br^-,I^-,the comparative study found that chlorine ions of halogen element were the best choice.It is futher preferable to influence the concentration of chlorine ions?Cl^-?and the voltanmmetric etching laps on the preparation of highly active porous silver film.The experimental results show that the optimal concentration of Na Cl is 0.5 mol·L^-1,the voltanmmetric etching cycle is 2 weeks.The surface roughness of the silver wire after activation was measured by potentiostatic step experiment to be 144.8 cm²·cm^-2.Result of SEM indicated that the surface of silver wire after activation showed a porous structure with a pore diameter of about 0.3?m and a porous membrance thickness of 4.5?m.Compared with the pristine silver wire electrode(roughness 1.7cm²·cm^-2),the elecrtrochemically active surface area increased 85 times after activation.The activated polyporous silver film displayed lower detection limit of 70nmol·L^-1?R²=0.9983?in the range of 0.1-518.1?mol·L^-1.It also showed good repeatability and reproducibility,and had excellent anti-interference performance and long-term stability.?2?In view of the fact that the target detection object trichloroacetic acid contains three Cl atoms,based on the voltammetric etching mechanism,it is conceivable that the chlorine element in the trichloroacetic acid molecule may also become effective chlorine activated by etching.Therefore we used trichloroacetic acid as the etching solution and modified the surface microstruct of the metal silver wire by voltammetry to construct a silver wire activated electrode with the target detection substance trichloroacetic acid imprinted etching.Using SEM,XRD,EDS and other characterization results,it can be seen that using trichloroacetic acid as the activation solution to modify the surface of the metal silver wire can obtain a porous silver film skeleton structure richer than inorganic anion etching.During the etching process,trichloroacetic acid molecules bonded by chlorine atoms are introduced into the microstructure of the silver wire surface,which enhances the surface roughness and improves the true electrochemical surface area.The electrode surface is imprinted with a high degree of matching with trichloroacetic acid.The active site makes the modified silver wire electrode obtain higher electrocatalytic activity.By optimizing the preparation conditions of the blot etching process,such as the concentration of trichloroacetic acid,voltanmmetric etching laps,and the cyclic voltammetry scanning range during the blot etching process.The experimental results show that the best preparation conditions contain the concentration of trichloroacetic acid is 0.5 mol·L^-1,the number of etching cycles is 20 weeks,and the cyclic voltammetry scan range is-0.6?1.0V.The true chemical surface area of the highly active porous silver membrane is 753.2 cm²·cm^-2,which is 426 times higher than the surface of the bright silver wire and 5 times higher than the silver wire etched by Cl^-ion voltammetry.It was used for the electrochemical detection of trichloroacetic acid.The concentration range of trichloroacetic acid was 0.05-313.2?mol·L^-1,and the lower detection limit was 35 nmol·L^-1?R²=0.9997?.The newly prepared modified silver wire electrode also has excellent repeatability,reproducibility,long-term stability,and anti-interference performance.