The Construction And Application Research Of Nano-ZnO Electrochemical Biosensor

Electrochemical biosensors have the advantages of rapid detection, high sensitivity, stable performance etc, and have a huge application potential in the area of food safety. Based on the summary and analysis of milk quality testing methods both home and abroad, a nano-ZnO modified electrochemical biosensor was built using nanotechnology and micro-fabrication techniques, the sensor was used in the detection of pathogenic microorganisms in milk. The main research contents are as following:1) Nano-ZnO electrochemical biosensor fabrication. Firstly, photolithography peeling process were used to build interdigitated gold electrode electrodes in three different sizes that is 30?m, 50?m, 70?m. Nano-ZnO film produced by electrochemical deposition method was modified on the gold electrode surface, by the characterization of electron microscopy scanning and cyclic voltammetry the Nano-ZnO film distributed on the electrode surface was dense and uniform. Then, the modified interdigitated electrode sensor was encapsulated. Finally, the pre-experiment of the sensor was carried out with the test sample of the ultra pure water and the normal milk. It turned out that the best AC test signal amplitude parameter set range is from 100 m V to 500 m V, and the optimal frequency parameters set range is from 100 Hz to 1MHz.2) Nano-ZnO electrochemical biosensor was used to carry out the milk quality evaluation.(E. coli was used as the pathogenic microorganisms in milk). Electrochemical impedance spectroscopy(EIS) technique was used to detect milk samples. The sensor has a stable performance when the amplitude of the signal is between 100 ~ 500 m V.NanoZnO thin film effectively increased the specific surface area of the gold electrodes, changed the impedance characteristics, increased the detection sensitivity. Five different gradients of milk samples were detected with three sensors in different size, the nanoZnO biosensor which the electrode width and space is 70?m has the highest detection accuracy. In the frequency domain, the electrochemical impedance spectra can be completely distinguished the milk samples of 0, 2.94×105, 6.1×105, 9.9×105and 1.9367×106CFU/m L, the experimental data was used to fit the equivalent circuit of milk, The equivalent circuit model of the system was obtained. The relationship between the elements of the equivalent circuit model and the measurement system is analyzed, found that the CPE and Warbury were closely related to the concentration of bacteria, the relationship between two variables and the bacteria content was almost linear in bacteria milk samples with no more than 1 million CFU/m L, and the milk samples with different gradients of bacteria can be detected.