Synthesis And Biosensor Performance Of Ag-Cu Nanosheets

In recent years,the development of medicine makes the research of biosensor more and more in-depth and extensive,especially the nanomaterial biosensor for the detection of biological macromolecules has brought qualitative breakthrough.Artificial enzymes have attracted much attention from the scientific community because of their advantages such as low preparation cost,wide application conditions and diverse substrate species.Artificial nanomases show specific enzyme-like activities because of their special size and morphology.Using the characteristics of artificial enzymes to develop excellent properties of biosensors is the current research hotspot and difficulty.In this paper,the soft template method is used to synthesize Ag-Cu alloy nanosheets with diameter of 3～5 nm and thickness of 1～3 nm.Firstly,the ascorbic acid biosensor is constructed by ultraviolet absorption spectrometry（UV-Vis）.Subsequently,the peroxidase and catalase activities of Ag-Cu alloy nanosheets were studied and glutathione and dopamine were determined by colorimetry.The main research contents of this paper are as follows:（1）Ag-Cu alloy nanosheets with thickness of 1～3 nm and diameter of 3～5 nm were synthesized by soft template method in this study.These nanosheets are used to build sensors that measure ascorbic acid concentrations.After adding ascorbic acid,the initial UV-Vis absorption peak of Ag-Cu alloy nanosheets in aqueous solution was effectively quenched.When ascorbic acid concentration varied in the range of 5 to 250 mmol/L,the UV absorption intensity of the sensor also changed.Due to its wide detection range,high sensitivity and good stability,the Ag-Cu alloy sensor method may be a good alternative to the traditional ascorbic acid measurement method.（2）The Ag-Cu nanosheets prepared in this paper can catalyze the oxidation of 2,2-diazo-bis（3-ethyl-benzothiazol-6-sulfonic acid）diamammonium salts（ABTS）and 3,3’,5,5’-tetramethylbenzidine（TMB）,showing peroxidase like activity.By calculating the Mi constant and the maximum reaction rate,the Mi kinetic equation with ABTS and TMB as substrates was obtained.It was found that Ag-Cu nanosheets had stronger affinity for TMB substrate than natural peroxidase.The properties of Ag-Cu nanomases resembling catalase were confirmed by UV absorption spectroscopy and p H method.By testing the dependence of Ag-Cu nanocases on p H and temperature,it was found that the optimal p H of Ag-Cu nanocases acting as peroxide-like（POD-like）was in the range of 2-4,and the catalase-like activity（CAT-like）could be maintained under alkaline conditions,especially the highest activity at p H=13.And the p H inflection point of the activity of these two enzymes is about 6.The peroxidase activity of Ag-Cu nanomases increased stably at 20～80℃,indicating that Ag-Cu nanomases could exert peroxidase activity stably at high temperature.The peroxidase activity of Ag-Cu nanosheets can catalyze the oxidation of ABTS to 2,2-diazo-di（3-ethyl-benzothiazol-6-sulfonic acid）diamammonium oxide(ABTS_ox.).Glutathione and dopamine have reducing properties,which can inhibit the oxidation process of ABTS producing ABTS_ox..This study used this property to construct a simple and easy colorimetric detection method of glutathione and dopamine.（3）Ag-Cu nanosheets with different ratios of Ag/Cu were prepared,and the peroxidase activity of Ag-Cu nanosheets with different ratios was studied.It was found that the peroxidase activity of Ag-Cu nanosheets with Ag/Cu=4:1 was higher,which further confirmed that Cu particles can accelerate the electron transfer of nanase.Thus,the catalytic activity of the catalyst can be improved.Based on the peroxidase activity of Ag-Cu nanosheets,it was found that the higher the H₂O₂in the system,the higher the absorbance of the oxidation product of ABTS.This study made use of this property to produce a simple H₂O₂sensor.This study provides a new idea for improving the activity of peroxide-like enzymes and developing artificial nano-enzymes with stronger stability and higher detection efficiency.