Abstract

The influences of electrochemical reduction degrees of reduced graphene oxide (rGO)-based electrode on its electrochemical sensing performance toward heavy metal ions (HMIs) were investigated. Initially, graphene oxide was synthesized by the modified Hummers’ method. Then, rGO films with different degrees of electrochemical reduction were prepared by using the cyclic voltammetry (CV) technique in different numbers of voltammetric cycles x (where x = 3, 6, 9, and 12). The structural and morphological characterizations of different degrees of reduction for rGOx were carried out by using ultraviolet–visible spectroscopy, attenuated total reflection-infrared, X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The charge transfer rate of rGOx modified glassy carbon electrodes (rGOx/GCEs) was investigated by CV and electrical impedance spectroscopy measurements using a standard ferri/ferrocyanide system. These modified electrodes were further investigated to achieve the best electrochemical performance toward HMIs detection. The modified electrode with six voltammetric cycles (rGO6/GCE) exhibited considerable improvements related to the stability, sensitivity, and well-oxidation potential definition for cadmium ion (Cd²⁺) and lead ion (Pb²⁺). The deposition potential, pH value, and accumulation time were optimized. The simultaneous electrochemical detection of Cd²⁺ and Pb²⁺ was performed using differential anodic stripping voltammetry technique under optimized conditions in the presence of bismuth ion (Bi³⁺). The Bi/rGO6/GCE was selected as the desired electrode and employed to detect the Cd²⁺ and Pb²⁺ at different concentrations within a linear range between 10 and 50 μgL⁻¹. The detection limits for Cd²⁺ and Pb²⁺ were 1.2 and 0.2 μgL⁻¹, respectively; with a signal to noise ratio (S/N = 3). Finally, the repeatability and reproducibility were investigated which exhibited excellent stability with relative standard deviations equal to 2.9 and 0.7% for Cd²⁺ and Pb²⁺ respectively, and similar linear range with detection limits.

Graphic abstract

中文翻译：

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控制氧化石墨烯基电极的还原度以提高对重金属离子的感测性能

摘要

研究了还原型氧化石墨烯（rGO）基电极的电化学还原度对其对重金属离子（HMIs）的电化学传感性能的影响。最初，通过改良的Hummers方法合成氧化石墨烯。然后，使用循环伏安法（CV）在不同数量的伏安循环x（其中x = 3、6、9和12）。rGOx的不同还原程度的结构和形态表征是通过使用紫外可见光谱，衰减的全反射红外，X射线衍射，原子力显微镜，场发射扫描电子显微镜和能量色散X射线进行的光谱学。rGOx修饰的玻碳电极（rGOx / GCEs）的电荷转移速率通过使用标准亚铁/亚铁氰化物系统的CV和电阻抗光谱测量进行了研究。进一步研究了这些修饰电极，以实现针对HMI检测的最佳电化学性能。具有六个伏安循环（rGO6 / GCE）的修饰电极在稳定性，灵敏度，²⁺）和铅离子（Pb ²⁺）。优化了沉积电位，pH值和累积时间。在最优化条件下，在存在铋离子（Bi ³⁺）的条件下，采用差分阳极溶出伏安法进行Cd ²⁺和Pb ²⁺的同时电化学检测。选择Bi / rGO6 / GCE作为所需的电极，并用于检测10至50μgL ^-1之间的线性范围内不同浓度的Cd ²⁺和Pb ²⁺。Cd ²⁺和Pb ²⁺的检出限为1.2和0.2μgL ^-1， 分别; 信噪比（S / N = 3）。最后，对重复性和重现性进行了研究，结果显示出极好的稳定性，Cd ²⁺和Pb ^2+的相对标准偏差分别为2.9和0.7％，线性范围与检测限相似。

图形摘要