Preparation Of Gold Nanoparticles Biosensors And Its Application In Heavy Metal Detection

The harmful heavy metal ions produced by the geochemical cycle and human production activities have posed a serious threat to the natural environment and human health.Among them,silver ion（Ag⁺）and mercury ion(Hg²⁺)are the most common highly toxic heavy metal ions.Because they are not naturally degradable and have strong biological enrichment,they can lead to a series of disorders of human mechanism,damage human health,and destroy the normal life of human beings.In recent years,a series of real-time and effective heavy metal detection technologies have been developed.However,these traditional detection methods require expensive and complex instruments,which limits their practical application.Electrochemical sensors based on the selective binding of heavy metal ions to specific DNA bases have great application potential because of their simple and portable instrument,short detection time,easy electrode modification and the ability to be used in cloudy or colored samples.Nanomaterials used as sensing platforms play an important role in promoting signal amplification and accelerating electron transfer.Au NPs has become a very attractive biosensor material because of its unique properties,such as simple preparation process,numerous preparation methods,high chemical stability,high electrical conductivity,good biocompatibility and large electroactive surface area.Therefore,this paper constructs a biosensor by modifying the gold nanoparticle electrode working electrode,and detects trace heavy metals Ag⁺and Hg²⁺by electrochemical method respectively.The main contents are as follows:（1）Au NPs/Au modified electrode was prepared on the surface of conventional Au electrode by self-assembly of 1,3-Dimercaptopropane Trimethylene Dithiol（SH-C₃H₆-HS）and Au NPs nanoparticles.Compared with Au electrode,Au NPs/Au electrode effectively improved the loading rate and subsequent hybridization efficiency of single-stranded DNA.Ag⁺can be captured by cytosine base（C）to form stable double helices of C-C mismatched DNA.Based on this principle,the Ag⁺sensing interface was optimized and characterized by electrochemical impedance（EIS）.Then,Ag⁺was highly selectively detected by scanning electrochemical microscopy（SECM）.The results show that the linear range of the sensor for Ag⁺is 50-400 nmol/L,and the detection limit is 40 nmol/L（S/N=3）.In addition,this novel detection method has good stability,selectivity,stability and practical application value.（2）In the conventional gold electrode（Au）surface electrodeposition Gold Nanoparticles（Au NPs）as a substrate,and optimize the potential and electrodeposition time,compared with the Au electrode,increase quantity of the introduction of the ss DNA to Au NPs/Au electrode,then the sulfur under 50℃（Th）rely on pansy thymine bases（T）is combined with the specificity of Hg²⁺embedded ss DNA quickly inside the double helix,and through the electrochemical impedance（EIS）,Scanning electron microscope（SEM）characterization of Hg²⁺sensor interface,and finally,using differential pulse voltammetric（DPV）for determining the content of Hg²⁺.The results show that the linear range of Hg²⁺is 10-100 nmol/L and the detection limit is as low as7.4 nmol/L（S/N=3）under the optimal conditions.In addition,the sensor has good selectivity and practical application.