The Research Of Electrochemical Sensors For Heavy Metals Monitoring In Water Environment

With the enlargement of cities and development of industrialization, life sewageand industry waste water are drained into water environment. Heavy metals enteringinto water environment are severely endangering human health through drinking water,bioaccumulation and food chain etc. Therefore quantitative analysis of trace heavymetals is extremely important in water environment monitoring. This thesisconcentrates on the research of electrochemical sensors for heavy metals monitoring inwater environment, and the major contents of this thesis are given in the following.1) Heavy metals including zinc, cadmium, lead, copper, arsenic and mercury aredetermined by differential pulse stripping voltammetry. A series of experiments havebeen carried out to obtain optimized parameters, and experimental results are analyzedand discussed. We compare characteristics of different mercury film electrodes throughdipping or plating, and mercury plated carbon electrode is chosen to simultaneouslydetect Zn(Ⅱ), Cd(Ⅱ), Pb(Ⅱ) and Cu(Ⅱ) in water. Based on the gold electrode, As(Ⅲ)and Hg(Ⅱ) are determined.2) Based on microfabrication technology, such as oxidation, sputtering andphotolithography, a gold microelectrode array is developed. The size of the array is5.5×5.5mm~2, containing 30×30 gold disk microelectrodes. The diameter of eachmicroelectrode is 10μm, and microelectrodes are spaced 150μm with each other.Experiments and studies of the Hg-plated microelectrode array have been performedto detect heavy metals. Based on differential pulse stripping voltammetry, Zn(Ⅱ),Cd(Ⅱ), Pb(Ⅱ) and Cu(Ⅱ) are simultaneously determined. Moreover, with anautomatic-analyzer for heavy metals, Zn(Ⅱ), Cd(Ⅱ), Pb(Ⅱ) and Cu(Ⅱ) in pretreatedseawater sample are automatically detected.3) A gold microwire electrode is developed with simple methods. Based on themicrowire electrode, As(Ⅲ) can be measured in weak acidic even neutral conditionswhile using a more negative deposition potential. Hg(Ⅱ) and Cu(Ⅱ) can also besimultaneously determined. The microwire doesn't need to polish, and it is pretreatedthrough sonication and cyclic voltammetry. During the measurement, we can set shorter deposition time and a lower detection limit can be obtained.4) Based on microfabrication technology, a nanoband electrode array is developed.Gold and platinum materials are respectively deposited onto the front and back of asilicon substrate, as working electrode and counter electrode. The nanoband electrodearray includes three layers: substrate layer, electrode layer and insulation layer. The sizeof the array is 6mm×1cm, including 50 nanoband electrodes. The length of eachelectrode is 9.5mm, the width is 10μm, the thickness is 100nm, and nanobandelectrodes are spaced 100μm with each other. Base on the array, heavy metals in watercan be determined using electrochemical methods. Nanoband electrode array can berepolished, and has a longer lifetime than general microelectrodes. Nanoband electrodearray can be extended to multi-layers, which can detect different elementssimultaneously. Furthermore, it can be integrated into microfluidic systems, andanalytical speed can be enhanced.