In-situ Synthesis Of Nitrogen-doped Carbon-gold Nanocomposite For Electrochemical Determination Of Heavy Metal Ions

The pollution of heavy metal ions in groundwater has been a detrimental risk to natural environment and human health.Electrochemical method,as a promising and elegant technique,has been used extensively for detection of heavy metal ions due to its rapidity,high sensitivity,short analysis time,and easy portability.However,in spite of consecutive efforts made by the researchers,it is still desirable to solve the problem of low sensitivity and selectivity of the electrochemical detection Development of modified electrode materials is the key to obtain a good and reliable electrochemical performance.Carbon-based material,as the most promising material in the 21 st century,is widely used in modified electrode material because of its own unique physical,chemical and electrical properties,but pure carbon-based materials still have some shortcomings including hydrophobicity and poor electrical conductivity.Therefore,in order to improve the electrochemical performance,the pure carbon materials will be modified through doping or compounding with other materials.In this paper,two kinds of nitrogen-doped carbon-based materials with different morphologies were synthesized and used as the modified electrode materials.In addition,square wave anodic stripping voltammetry?SWASV?was selected for the detection of heavy metal ions.The main contents of our thesis are as follows:1.The nitrogen-doped porous carbon material?N-PC-Au?has been fabricated by an emulsion polymerisation-carbonisation approach.Various techniques such as scanning electron microscopy?SEM?,transmission electron microscopy?TEM?were characterized to clarify the morphology and structure of N-PC-Au.Besides,the cyclic voltammetric?CV?and electrochemical impedance spectroscopy?EIS?were also carried out to investigate electrochemical performance of N-PC-Au.The N-PC-Au modified electrode has been prepared for the electrochemical determination of trace Hg²⁺ through SWASV.The experimental parameters such as supporting electrolytes,p H,deposition time,and deposition potential were carefully studied.Under the optimum experimental conditions,the SWASV was adopted to detect different concentrations of Hg²⁺,resulting in a detection limit of 0.35 n M?S/N=3?,which was much lower than the guideline values in drinking water given by the WHO.The selectivity,interference and determination in real sample were also explored.The results indicate that the N-PC-Au is an excellent modified material.2.Nitrogen-doped hollow carbon spheres?N-HCS?have been prepared by using SiO₂ nanospheres as templates.The morphology and structure of N-HCS were characterized by relevant methods.The electrochemical performance of N-HCS was characterized by CV and EIS.Under the optimum experimental conditions?such as supporting electrolytes,p H,deposition time,and deposition potential?,the N-HCS modified electrode has been prepared to individually analyze different concentrations of Pb²⁺,Cu²⁺ and Hg²⁺.The N-HCS modified electrod exhibits the detection limit of 15 n M,17 n M,2.35 n M to Pb²⁺,Cu²⁺ and Hg²⁺,respectively.Moreover,the stability and repeatability of the N-HCS modified electrode were also investigated.3.The N-HCS modified electrode has been prepared for the simultaneous determination of Pb²⁺ and Hg²⁺ through SWASV.The simultaneous determination conditions?such as supporting electrolytes,p H,deposition time,and deposition potential?were investigated in detail.Under the optimum experimental conditions,we discuss the two types of test in co-detection of Pb²⁺ and Hg²⁺.