Abstract:

The heavy metal ion pollution of hexavalent chromium (Cr(Ⅵ)) in water is serious in China. An electrochemical sensor for hexavalent chromium (Cr(Ⅵ)) detection is proposed based on graphene nanomaterial. The graphene nanomaterial modified gold electrode (rGO/Au) was prepared by using the method of electrochemical reduction of graphene oxide (GO). The surface morphology and structure of rGO/Au were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM) technologies. The direct electrocatalytic reduction of Cr(Ⅵ) on the surface of rGO/Au was studied by using electrochemical methods such as square wave voltammetry (SWV), cyclic voltammetry (CV) and linear sweep voltammetry (LSV), etc. The preparation conditions were optimized which include GO reduction potential and reduction time, as well as the detection parameters, such as detection potential, pH and concentration of electrolyte. Without preconcentration step, the linear relationship between Cr(Ⅵ) concentrations and current responses on the rGO/Au was investigated by using amperometry method. The experimental results showed that graphene nanomaterial has electrocatalytic activity for Cr(Ⅵ) reduction. A good linear relationship between Cr(Ⅵ) concentrations and current responses was obtained from 5 to 2000 μg·L^-1, with a low detection limit of 0.5 μg·L^-1 (S/N ≥ 3). The modified electrode was resistant to some common metal interference ions, such as Cr(Ⅲ), Ni(Ⅱ), Cu(Ⅱ), Mg(Ⅱ) and Mn(Ⅱ). And the response current decreased less than 10% compared to the initial value after 11 successive measures, which showed a relative good stability. The advantages of the proposed electrochemical sensor are simple, fast, friendly environmental and reusable, which made it possible to apply the sensor for rapid detection of Cr(Ⅵ) in water.

Key words: graphene, nanomaterial, heavy metal ion Cr(Ⅵ), electrocatalytic reduction, electrochemistry, sensor

摘要：

针对我国水质重金属六价铬（Cr（Ⅵ））污染问题突出，提出了一种基于石墨烯纳米材料的水质Cr（Ⅵ）电化学传感器。采用电化学方法还原氧化石墨烯，构建石墨烯纳米材料修饰金电极（rGO/Au）。采用扫描电子显微镜（SEM）和透射电子显微镜（TEM）技术表征了rGO/Au的表面形貌和结构；采用方波伏安法、循环伏安法和线性扫描伏安法等电化学方法研究了Cr（Ⅵ）在rGO/Au表面的直接电催化还原行为，优化了氧化石墨烯的电化学还原电位和还原时间，以及支持电解质pH、浓度和检测电位等实验参数；采用计时电流法，在无须预富集的条件下，考察了Cr（Ⅵ）浓度与rGO/Au响应电流之间的线性关系。实验结果表明，石墨烯纳米材料对Cr（Ⅵ）有明显的电催化还原活性，计时电流响应值与Cr（Ⅵ）浓度呈良好的线性关系，线性范围为5～2000μg·L^-1，最低检测限为0.5 μA·L^-1（S/N≥3）。所制备的rGO/Au具有对常见其他重金属干扰离子（Cr（Ⅲ）、Ni（Ⅱ）、Cu（Ⅱ）、Mg（Ⅱ）和Mn（Ⅱ））较好的抗干扰性能，11次连续测定后，响应值相对初始值下降幅度小于10%，表明该修饰电极具有较好的稳定性。本研究提出的电化学传感器具有检测方法简单、快速、环保以及可重复使用的优点，能够应用于水质重金属Cr（Ⅵ）的快速测定。

关键词: 石墨烯, 纳米材料, 重金属Cr(Ⅵ), 电催化还原, 电化学, 传感器