| With the development of society and the improvement of people's health awareness,environmental pollution and health problems have received widespread attention.Due to the difficulty of metabolism,bioaccumulation and high toxicity of heavy metals,the hazards of heavy metal pollution are particularly prominent.Therefore,how to achieve fast and sensitive detection and monitoring of heavy metals is an urgent problem to be solved.The main research content of this thesis is to design and develop a variety of sensors with micro-nano structure or characteristics for different heavy metals detection,including gold nanoband eldctrode,gold nanoparticles-modified screen-printed carbon electrode(AuNPs-SPCE),graphene field effect transistor(GFET)array sensor and AlGaN/GaN field effect transistor(AlGaN/GaN FET)sensor.In this paper,the basics and working principle of electrochemical and FET sensors was introduced in detail.Four kinds of sensors were deeply studied and applied to heavy metal detection in water environment.In addition,a portable electrochemical detection system for on-site,fast heavy metal detection was built.The hardware and software design of the system were described in detail.The research work in this study was supported by Ministry of Science and Technology of China(973 Program)(Grant No.2015CB352101),Natural Science Foundation of NSFCRFBR Cooperation of China(Grant No.8171101322)and Major Research and Development Program of Zhejiang Province(Grant No.2017C03032).The major innovations of this study are listed below:1,A portable electrochemical detection system was designed and developed to realize on-site,rapid detection of various heavy metals in water environments.Combined with smart devices,a portable electrochemical detection system for heavy metal detection in water environment was designed.The portable electrochemical detection system can implement various electrochemical analysis methods such as cyclic voltammetry and differential pulse voltammetry.The portable electrochemical detector was modular in design,including a microprocessor based on a low-power MSP430 chip,a 16-bit digital-to-analog and analog-to-digital converter module,and a three-electrode detection module.The detector uses Wi-Fi or USB to communicate with smart devices such as PCs or mobile phones.For this purpose,microprocessor-based embedded software,PC software based on Visual Studio C++and Qt,and mobile control software based on Android were developed.It was verified by experiments that the system can realize the on-site and rapid detection of heavy metals in the water environment.2,The integrated design method of gold nanoband microelectrode sensor is improved,which realizes highly sensitive detection of trace mercury ions and has the advantages of long service life.The gold nanoband microelectrode is a nanometer-sized electrode processed by micro-nano processing technology,which has the characteristics of improving the sensitivity of heavy metal detection.In this paper,the design of gold nanoband microelectrode based on silicon processing technology is deeply studied,and the structure and characteristics of micro/nano electrode are analyzed.The sensor has a thickness of about 100 nm and has good sensitivity in the detection of mercury ions.As a nanometer-sized electrode,the sensor has good characteristics in tenns of nonlinear diffusion,mass transfer rate,current density,time constant,charge current,signal-to-noise ratio,and iR drop.3,The design method of low-cost AuNPs-SPCE was proposed and the sensor presented good capability for Cr(VI)detection with good sensitivity,reproducibility and selectivity.Gold nanoparticles-modified screen-printed carbon electrode(AuNPs-SPCE)were designed and AuNPs-SPCE has the advantages of screen printed electrodes and gold nanoparticles The relevant parameters of hexavalent chromium(Cr(VI))ion detection were optimized,including optimization of deposition time of AuNPs modification,selection of supporting electrolyte,optimization of scanning rate and solution pH.Based on the optimized experimental conditions,high sensitivity detection of Cr(VI)was achieved with a detection limit of 5.4 ?g/L.And the sensor has excellent repeatability,reproducibility and selectivity.Real samples were analyzed and the results were consistent with atomic adsorption spectrometry.5,A ssDNA-based graphene FET array sensor was designed to achieve ultra-sensitive and high-specificity detection of mercury ions.Aiming at the requirement of ultrasensitive detection of trace mercury ions in water environment,this paper proposes a design of common source graphene FET(GFET)array sensor.A novel biomolecular sensor was constructed by modifying specific ssDNA on graphene FET sensor.Through the characterization of the sensor and the testing of the sensor characteristics,the experimental parameters were optimized and determined to provide an ultrasensitive detection of trace mercury ions in the water environment.The experimental results show that the sensor was highly selective for mercury ions with a detection range from 100 pM to 100 n?M.4,A design method of FET sensor based on AlGaN/GaN was proposed,which optimizes the width-to-length ratio(W/L)parameters of the device and obtains higher detection sensitivity.Gallium nitride is a wide-bandgap semiconductor material,and the AlGaN/GaN structure generates two-dimensional electron gas(2DEG),which has extremely high electron mobility and greatly improves the performance of the sensor.Through modeling,the relationship between the series resistance and the current sensitivity is obtained,and there is an optimized W/L ratio which enables the largest current sensitivity.The efficiency of the sensor is decreased with larger W/L.Assuming identical W/L,VDS and surface sensitivity,the AlGaN/GaN-based sensor can deliver more than 40 times larger current sensitivity than Si-based ISFET according to the simulation and device model.The gate sensitive membrane could increase the surface sensitivity but decrease the transconductance,such that the current sensitivity is not necessarily increased. |
PDF Full Text Request