The Application Of New Piezoelectric Gas Sensor In The Detection Of Bacteria

Piezoelectric sensor has many advantages, such as broad sensing object, high sensitivity, easy to operate, and on-line detection etc and can be widely used in many area, such as analytical chemistry, life science, environmental monitoring etc. In this thesis, the new microbial sensing methods were presented base on the non-mass response of piezoelectric sensor which related to some characteristics of microbial growth and metabolism. The new methods are simple to operate and broaden their application in environmental monitoring and life science. The detection is rapid and accurate. The main work of this thesis could be summarized as follows:1. A new polypyrrole/polyimide-piezoelectric quartz crystal(PQC) sensor was proposed to detect ammonia. polypyrrole/polyimide was used as conduct electrode and directly connected to piezoelectric quartz crystal in series. The effect of P-toluene sulfuric acid on polymerization, ferric chloride on treating of polypyrrole and humidity on dertermination were investigated in detail. The response of polypyrrole/polyimide-piezoelectric quartz crystal sensor to ammonia was studied both in theory and experiment. Proposed ammonia sensor can applied to environmental monitoring and clinic diagnosis.2. The polypyrrole ammonia sensor was proposed to detect urease-producing bacteria. Compared with series piezoelectric quartz crystal(SPQC) sensor, it is more sensitively. Three culture mediums were used as test culture mediums in our experiment. The results showed that all three culture medium can be used as test culture medium in proposed system, but in SPQC system, only YC broth can be used. Proteus vulgaris was detected using proposed method .The detection time had a linear relationship with the logarithm value of the initial concentration of Proteus vulgaris in the rang of 8–3.2×108cell ml-1. Staphylococcus epidermidis and Klebsiella pneumoniae were also determined in this paper, which proved the feasibility of the proposed method.3. A new method based on series piezoelectric quartz crystal sensor detecting carbon dioxide was developed to detect fungi, the response mechanism is potassium hydroxide(KOH) reacted with carbon dioxide, which cause the changes of conductance in KOH solution,and then the changes of conductance can be monitored by SPQC. The effect of sensitivity was the concentration of KOH solution was discussed. The linear relationship equation between the frequency detection time (FDT) and the logarithm of the initial number of bacteria was derived (logN0=10.7296-0.2436t), experimentally and theoretically, which applied to determine the number of cells in culture. The method was also applied to detect Candida albicans, Candida parapsilosis, Candida krusei, Candida tropicalis, Candida lusitaniae. Compared with SPQC, forty strains of clinic fungi were detected by this method. Good results were obtained.