| The safety of drinking and using water is a topic of common concern all over the world.With the development of the Internet of Things for Water Quality Monitoring,water environment grid-based online monitoring network which consist by a large number of sensors can efficiently monitor the real-time conditions of natural water bodies,identify water quality problems in advance,and governance them.The monitoring indicators are complex and diverse,mainly including physical quantity indicators,chemical quantity indicators,biomass indicators,etc.Among them,nitrite is an important indicator of eutrophication of water pollution.At present,sensors based on optical principles are difficult to meet the grid monitoring requirements because Large volume and high cost.Therefore,there is an urgent need for a miniaturized,low-cost,mass-manufacturable,multi-parameter integration,and low-power sensor to meet the needs of the sensing Io T construction.In this thesis,integrated nitrite sensor chips were designed and prepared in batches to achieve the miniaturization,integration,and batch manufacturing of chemical sensors based on the principle of electrochemical cyclic voltammetry by MEMS micro-nano manufacturing technology.This thesis mainly completes the following work:1.An Ag/Ag Cl reference electrode chip with integrated nano-channel array was prepared.The experimental results indicate that as-prepared Ag/Ag Cl RE has a longer use life due to thpotential change of the reference electrode potential in the 3000s continuous test is only 0.1m V,which is far less than the change amount(1.8m V)of the traditional commercial reference electrode CHI111.The RE shown a better stability and consistency because the change of the reference potential was only 1.3m V in the buffer with range of 0.003M-0.03M and the relative standard deviation of the reference potential of the five reference electrodes selected arbitrarily is only 4.3%.2.The integrated nitrite sensor chip was prepared in batches.It showed a good linear relationship between the sensing signal and the nitrite concentration(R~2=0.998)by cyclic voltammetry method with a detection linear range was 100μM-10 m M and the detection limit was 27μM,sensitivity was 20.49μA/m M.CV method also has been used to demonstrate the advantages of high consistency(RSD<4.2%)and high reproducibility(RSD<2.6%)of the sensors prepared in batches.The linearity between the amount of nitrite added and the increase of the current value(99.6%)was high in constant voltage(0.91V),and in the case of coexistence of nitrite and 6 kinds of interferences,the sensor showed High selectivity for nitrite detection;3.A possible method to improve the performance of the sensor was initially explored.After sulfuric acid activation of the Au electrode,the detection limit of nitrite was reduced from 27μM to 9μM.And after nano-silver was electrodeposited by the electrode surface,the voltage at the oxidation peak was reduced from 1.17V to 0.78V.These studies were the basis for further research in the future.A miniaturized,integrated nitrite sensor chip was prepared by micro-nano manufacturing technology in this thesis,which provides a solution for chemical sensors batch manufacturing and an idea for multi-parameter integration and chip-based of traditional water quality sensors. |
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