【作者】 邢苏洁；

【导师】 金利通；

【作者基本信息】 华东师范大学 ， 分析化学， 2010， 硕士

【摘要】 随着工农业生产的迅速发展,水体污染问题越来越严重,其中重金属是最主要的污染物质之一。重金属可以在水体中积累和作物体内残留,通过食物链进入人体内蓄积,构成对人体的潜在危害。人体内重金属含量过量时,会导致各种疾病的发生。水体重金属污染问题已引起全世界的高度重视和深入研究,对不同种类食品和水体中的重金属污染进行监测和分析研究,对于评价水体质量、保护人类健康和维持社会经济可持续发展具有重要的现实意义。纳米材料是指在三维空间中至少有一维处于1～100nm纳米尺度范围或由它们作为基本单元构成的材料。纳米复合材料是两种或两种以上不同纳米材料以不同方式组合而成的材料。虽然复合材料从问世至今只有短短数10年的历史,但由于它可以发挥各种组成物质的优点,克服了单一材料的缺陷,因此得到了广泛应用,被誉为是21世纪最有前途的材料之一。随着纳米技术的发展,纳米复合材料作为一种新型的电极材料在电化学检测和分析方面受到人们的日益关注。本论文制备并表征了一系列新型的化学修饰电极,同时将超声、模板沉积技术引入电化学中,进而提出对水中的重金属进行测定的新方法。所建立的方法简单,快速,灵敏度高,为重金属检测提供了一种全新的理念和思路。本论文内容共分五章：第一章绪论本章主要系统地介绍重金属污染的危害与检测技术的发展、化学修饰电极的制备与应用、超声合成纳米复合材料的原理和应用。并对这些领域的研究现状和与进展作了综述。第二章普鲁士蓝修饰玻碳电极应用于水体中痕量Cr(Ⅵ)的检测本章采用电化学沉积的方法制备普鲁士蓝,并将其作为工作电极应用于水体中痕量Cr(Ⅵ)的检测研究。普鲁士蓝在一定电位的作用下会发生氧化还原反应,其还原状态重新转化成电中性时会催化Cr(Ⅵ)还原成Cr(Ⅲ)。本实验考察了普鲁士蓝膜厚度、还原电位、电解质对Cr(Ⅵ)还原响应电流大小的影响。其线性范围为0.5-200ug／L,灵敏度为15±0.2 nA／ppb,经计算,检测限为0.15ug／L。此检测方法受共存金属离子和表面活性剂的影响较小。此方法制备简单,稳定性强,分析时间短。第三章AgNPs/Nafion纳米复合电极的制备及应用于水体中痕量Cr(Ⅵ)的检测本章以Ag纳米粒子修饰Nafion膜复合电极为工作电极,采用安培检测法直接检测水体中的Cr(Ⅵ)。阳离子交换剂Nafion能作为导电软模板,将Ag纳米粒子牢牢固定于电极表面,而电沉积得到的Ag纳米粒子粒径均匀,分布统一,显示出优异的催化性能。此AgNPs/Nafion纳米复合电极对Cr(Ⅵ)还原具有显著的灵敏度和选择性。Cr(Ⅵ)的线性范围为2-230ug／L,灵敏度为1.1nA／ppb,检测限为0.67ug／L。运用扫描电子显微镜(SEM),透射电子显微镜(TEM)对AgNPs／Nafion纳米复合电极的形貌进行表征。通过循环伏安(CV)考察AgNPs／Nafion纳米复合电极的电化学性质。研究结果表面,利用该电化学方法制备的AgNPs／Nafion纳米复合电极具有更大的电活性面积和更优异的电催化性能。此纳米复合电极成功应用于安培检测痕量Cr(Ⅵ)的研究。第四章超声合成Au/NHAP纳米复合材料应用于水体中铅和镉的检测本章以沉淀法合成的纳米级生物陶瓷羟基磷灰石为模板,在超声波作用下,合成Au/NHAP复合纳米材料,应用于实际水样品中铅和镉的检测。通过透射电子显微镜对此复合材料的形貌进行表征。羟基磷灰石纳米颗粒粒径均匀,阻止了金纳米颗粒的团聚,对铅和镉两种金属粒子有特异的吸附作用。此检测方法采用吸附-还原-溶出独立溶液环境,有效地排除了其他重金属离子的干扰。本方法独特新颖,合成简单,效果优异,成本低廉,在开发新型传感器方面有潜在的应用价值。第五章铂纳米管阵列电极应用于氧化检测痕量As(Ⅲ)的研究本章介绍了铂纳米管(PtNTs)阵列电极应用于氧化检测痕量砷As(Ⅲ)的研究。运用3-氨丙基三甲氧基硅烷(APS)修饰的多孔氧化铝模板(PAA)在含有AuCl4-溶液中,利用电化学沉积的方法得到高度有序PtNTs阵列结构。采用扫描电子显微镜(SEM)和X-射线衍射(XRD)对PtNTs阵列的形貌和结构进行表征。通过电化学研究表明,PtNTs阵列结构具有更大的有效面积和更高的催化性能。与Pt纳米粒子修饰玻碳电极(Pt-NPs/GC)和Pt盘电极相比,PtNTs阵列电极氧化检测痕量砷(Ⅲ)方面具有更优异的性能。50次重复测定20μM砷(Ⅲ)的相对标准偏差(RSD)为3.5%,检测限(S／N=3)为0.1μg／L,比文献报道的Pt-NPs/GC和Pt盘电极低1-2个数量级,证明该方法具有更高的灵敏度,对于痕量As(Ⅲ)的常规检测具有潜在的应用价值。更多还原

【Abstract】 The food security problem has been focused on for a long time. With the development of industrial and agricultural manufacture, food contamination is increasing serious, especially for heavy metals contamination. The residence time of most heavy metals in soils and plants is very long. Taken by plants, heavy metals may enter the food chain in significant amounts. Hence, people could be at risk of adverse health effects from consuming food grown in soils containing elevated metal concentrations. Considerable interest and extensive study have developed in the determination of heavy metals in food all over the world. Therefore, it is practically important for the detection of toxic heavy metals in different kinds of food and water in evaluating food quality, protecting human health and promoting sustainable development of economy and society.Nanomaterials are defined as the materials with domain ranges between 1 and 100 nm at least in one dimension, or materials that be composed of nanoscale units. Nanocomposite materials have recently been shown to represent a novel and developed rapidly nanomaterials, which are formed by no less than two solid phases with nanoscale size at least in one dimension. The nanoscale dispersed phase of composite materials not only remarkably increased interface areas of two phases, but also significantly enhanced interactions between two interfaces caused by nanosize effects. Difference from singular nanomaterials and nanophase, nanocomposite materials not only have the nanoscale units’basic properties:quantum size effect, surface effect, small size effect, quantum tunneling effect, dielectric confinement effect and so on, also exist new effects caused by combination of nano-structured materials such as quantum coupling effect and synergistic effect, making their general performances are better than the original single materials and be able to meet requirements for a variety of practical application. Nanocomposites are known as the most promoting materials in the 21st century. With the development of nano-technology, nanocomposites as a new type of electrode materials are applied in electrochemical detection and analysis by people’s growing concern.In this dissertation, some novel chemically modified electrodes were prepared and characterized. Introducing ultrasonic and template deposition technology into electrochemistry, some simplicity, reliability and high sensitivity methods for detection of heavy metals were described, which provides a new concept and ideas for detection of heavy metals. There are five chapters in this paper.Chapter 1 OverviewIn chaperl, a detail outline and reviews mainly on the hazards of heavy metal contamination, development of the heavy metal determination, the preparation and application of the chemically modified electrodes, the principal mechanism and the application of both ultrasound and template deposition.Chapter 2 A Simple and Sensitive Method for the Amperometric Detection of Trace Chromium (Ⅵ) Based on Prussian Blue Modified Glassy Carbon ElectrodeA simple and sensitive method for the amperometric detection of trace amount of chromium (Ⅵ) using a Prussian blue modified glassy carbon electrode (PB/GCE) is described here. The Everitts salt/Prussian blue redox couple of the PB film was found to mediate the Cr(Ⅵ) reduction, and the mechanism of electrochemical reaction was investigated. The effects of PB film thickness, applied potential and electrolyte solution on the current response of Cr(VI) reduction were thoroughly studied. Under the optimized conditions, the PB/GCE provided a wide linear range for Cr(Ⅵ) analysis from 0.5 to 200 ppb with excellent sensitivity (15±0.2 nA/ppb) and low detection limit (0.15 ppb). In addition, the modified electrode showed excellent stability, reproducibility and good resistance to other metal ions and surfactants. Finally, the proposed method was applied to detect trace Cr(Ⅵ) in wastewater with satisfactory results. The great advantages of the method were characterized by the simplicity, ease of preparation, stability, short analysis time and cost-efficiency.Chapter 3 Nafion Stabilized Silver Nanoparticles Modified Electrode And Its Application to Cr (Ⅵ) DetectionA silver nanoparticles/Nafion film composite material modified glassy carbon electrode(GCE) was prepared and used as a kind of superior electrochemical sensor for chromium(Ⅵ). Nafion(Nf), a cation-exchange polymer, was employed as the conductive matrix in which Ag nanoparticles(AgNPs) can be tightly attached to the electrode surface. AgNPs were obtained by direct electrodeposition and showed excellent catalytic ability toward Cr(Ⅵ) reduction. Such a designed AgNPs/Nafion shows outstanding sensitivity and selectivity to Cr(Ⅵ) reduction. A linear relationship between the reduction current and Cr(Ⅵ) concentration was obtained covering the concentration rang from 2 to 230 ppb with excellent sensitivity(1.1 nA/ppb) and low detection limit(0.67 ppb). The electrochemically formed AgNPs were characterized by SEM(scanning electron microscopy), TEM(transmission electron microscopy) and electrochemical techniques. Interference from other heavy metal ions such as Cr3+, Cd2+, Cu2+, and Hg2+ associated with Cr(Ⅵ) analysis could be effectively diminished. The practical application of the proposed sensor was carried out for determination of trace level of Cr(Ⅵ)in real water sample. The present electrode is reliable, stable, sensitive and low-cost.Chapter 4 Au/NHAP nanocomposite synthesized by ultrasound and its application to lead(Ⅱ) and cadmium(Ⅱ) detection in waterA novel nanocomposite was developed with hydroxyapatite as deposition template, NaOH as reductant, Au as catalyst via ultrasound. The novel sensor can be applied to detect Pb(Ⅱ) and Cd(Ⅱ) in water samples. The transmission electron microscopy (TEM) revealed the size of synthesized nanocompsite with nominal diameter of 20nm. The independent electrolytical environment prepared for the adsorption, reduction and stripping of heavy metals effectively prevented other coexist metals. The specific adsorption of Pb(Ⅱ) and Cd(Ⅱ) of hydroxyapatite allowed it to achieve low detection limits down to ppb level. The ultrasound preparation of nanocomposite made the deposited of Au nanoparticles well-distributed, which prevented its further agglomeration. The proposed method was outstanding for its ease of preparation, free of interference, low cost and can be applied in practical application.Chapter 5 Highly ordered platinum-nanotube arrays for oxidative determination of trace arsenic(Ⅲ)A novel method for the oxidative determination of trace arsenic(Ⅲ) was investigated on highly ordered platinum-nanotube (PtNTs) array electrodes. The PtNTs with a highly organized structure were fabricated by electrochemical deposition of platinum in a 3-aminopropyltrimethoxysilane-modified porous anodic alumina template (PAA) in solution containing AuC14-. The morphologies and structures of PtNTs arrays electrode were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical experiments proved that the PtNTs array electrode exhibited larger effective area and high catalytic properties, which have better performance for As(Ⅲ) analysis in comparison with platinum nanoparticles-coated GCE (Ptnano/GCE) or Pt foil electrode. The PtNTs array electrode showed to provide better reproducibility and higher sensitivity. The limit of detection (LOD) was typically 1-2 orders of magnitude lower than that of Ptnano/GCE or Pt foil electrode, suggesting that the proposed method has potential application values for trace As(Ⅲ) analysis.更多还原