| The modern industry of China maintained a rapid development in recent decades, and heavy metal emissions from industrial waste are growing. Heavy metal is highly toxic and can cause damaging effects even at very low concentrations. They tend to accumulate in the food chain and in the body and can be stored in soft and hard tissues. It is of great significance to develop a fast and sensitive analysis of trace heavy metals for monitoring of the urban environment. Compared with other heavy metal detection methods, electrochemical stripping voltammetry exhibits the superiority of its fast multi-element capabilities, relative small volume, low cost of equipment, simple operation, and high sensitivity. This is in line with the trend of the development of modern sensors and their analysis instruments for miniaturization, integration and automatization.This work is mainly focused on the preparation of silicon nanowires (SiNWs) arrays and their surface modification by metal nanoparticles. The as-fabricated Au/SiNWs arrays will be developed as a new kind of microelectrode and applied for heavy metal analysis in natural water.The main contents of our work are listed as follows:Firstly, a novel gold nanoparticles modified silicon nanowires (SiNWs) electrode for anodic stripping analysis of heavy metal is prepared by metal-assisted chemical etching method and immersion plating in this paper. The structural and morphological properties of microelectrode were characterized by SEM (Scanning Electron Microsocop) and XRD (X-Ray Diffraction) technique. The dimension of SiNWs arrays prepared is about dozens of micrometer in length and hundreds of nanometer in diameter. Gold nanoparticles with radius of20nm has been grafted to silicon nanowires to improve the detection sensitivity of heavy metal since the large active electrode area and the strong adsorption ability toward heavy metal had been realized.Secondly, heavy metal elements, including cadmium, lead and copper were determined by differential pulse anodic stripping voltammetry and the experimental results were analyzed and discussed. A series of experiments had been carried out to obtain optimized parameters.0.1mol/L(pH=4.4) of HAc-NaAc buffer was used as the electrochemical cell electrolyte and accumulation time was of120s. The results indicated that gold-modified electrode displays the excellent linear behavior in the examined concentration (from0μgL-1to225μgL-1). Cd2+, Pb2+and Cu2+in0.1mol/L HAc-NaAc can be detected with the sensitivity of0.31μA/(μgL-1),0.97μA/(μgL-1) and0.44μA/(μgL-1) respectively. The corresponding detection limits are0.58μgL-1,0.26μgL-1and0.67μgL-1. The noise immunity and repeatability of the prepared electrode were also tested.Thirdly, the proposed electrode has been used to determine the trace levels of Pb+2and Cu+2in real water samples. The recovery rate of Pb2+and Cu2+is105%and99%. These results were verified by inductively coupled plasma emission spectrometer.Experiments show that the prepared electrode is suitable for rapid detection of cadmium, lead, copper and other heavy metals in environmental water samples by differential pulse stripping voltammetry.In conclusion, due to its high surface to volume ratio, silicon nanowires material has great potential application in the field of electrochemical sensors. The fabrication method is simple, and compatible with integrated circuits and micro-fabrication process. It can bring a novel idea for investigation of the integrated system on chip. |
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