Micro-nano Opto-electronic Integrated Sensor Chip And Its Application For Heavy Metals Detection In Aquatic Environment

Contamination of aquatic environment by heavy metals gets more and more serious with the rapid development of industry. They can do harm to the whole ecological systems, including humans, even if they are present in extremely low concentrations. Some of them can not be metabolized in vivo, which means that once they enter the human body, they won’t be degradable. Thus the development of in-situ and on-line heavy metals detection in aquatic environment is of great significance.Electrochemical sensors are one of the most useful electroanalytical techniques for heavy metals detection due to their fast, sensitivity, selectivity and simultaneously determination of various elements. In this paper, the voltammetric properties of micro and nano amperometric electrodes are analyzed, and the principle of light addressable potentiometric sensor (LAPS) is illustrated. Moreover, the miniaturization, integration and wireless sensor network are studied. As a result, microelectrode array (MEA) and nanoband electrode array are developed and improved. In addtition, micro-nano opto-electronic integrated sensor chips are present based on stripping voltammetry and potentiometric method. Besides, a node for wireless sensor network is established. This study is supported by the National High Technology Research Program (863Program) and the National Key Basic Research Program (973Program).The major work of this study is as follows:1) Au-MEA is fabricated based on the standard micro fabrication technology. The ratio of interelectrode distance to the electrode diameter of the MEA is10:1to get a collective current response while maintaining the excellent features of single microelectrodes. The electrochemical properties including detection potential window, real surface area and the length of diffusion layer are analyzed. The Au-MEA can be directly used for the detection of Pb2+and Cu2+in the pure water-background samples. The detection sensitivities are23nA/μg and12nA/μg, respectively, and the detection limits are1.8μg/L and3.5μg/L.2) Detection conditions including pH of the analyte solutions, preconcentration potential, preconcentration time and sweep rate are optimized for the mercury film Au-MEA. It can be utilized to simultaniously detect pure water-background samples of Zn2+, Cd2+, Pb2+and Cu2+. The detection sensitivities are33nA/μg,19nA/μg,65nA/μg and23nA/μg, respectively, and the detection limits are4.5μg/L,0.5μg/L,1.2μg/L and1.5μg/L. In addition, the mercury film Au-MEA is applied to the detection of Cd2+, Pb2+and Cu2+in sea water-background samples, where agreements are found with the standard analytical method (Atomic absorption spectrometry, AAS).3) A double-side nanoband electrode array, which consisted of50gold working electrodes and50platinum auxiliary electrodes is developed. Surface analysis and electrochemical behavior of Au nanoband electrode array are studied. The detection sensitivities for Pb2+and Cu2+in pure water-background samples are105nA/μg and88.5nA/μg, respectively, and the detection limits are0.97μg/L and0.73μg/L, which are both better than that of Au-MEA. Besides, the concentrations of Pb2+and Cu2+in sea water-background samples detected by Au nanoband electrode array are9.47±0.78μg/L and5.41±0.57μg/L, respectively, close to the values validated by AAS (10±0.6μg/L and5±0.4μg/L).4) The detection of Zn2+, Cd2+and Pb2+in pure water-background samples by enviorenmental friendly bismuth film Au nanoband electrode array is also studied. The sensitivities are17nA/μg,28nA/μg and154.4nA/μg, respectively, which for Cd2+and Pb2+are proved to be the best.5) Micro-nano opto-electronic integrated sensor chips are developed and studied. In these chips, MEAs or nanoband electrode array are intergrated with LAPS on a same silicon substrate. A node of wireless sensor network is supposed based on the integrated sensor chips and the flow system. Self-calibration model are established based on the multiple linear regression equation set, which is verified through the bias potentials and stripping currents of Zn2+, Pb2+and Cu2+obtained from the integrated sensor chips.