14-02-2013, 04:01 PM
Study on the Surface Acoustic Wave Sensor with Self-Assembly Imprinted Film of Calixarene Derivatives to Detect Organophosphorus Compounds
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ABSTRACT
The molecularly imprinted technology and the self-assembly technique were used together on the calixarene surface acoustic wave (SAW) chemical sensors to detect organophosphorus compounds. 25-(thioalkyl-alkoxy)-p-tertbutylcalix[4] arene with self-assembled monolayer character was the sensitive coating of the sensors. The sensors had a special re-sponse to organophosphorus compounds and the response frequency shift of this sensor to organophosphorus com- pounds in 0.1 mg/m3 was 350 Hz. The response frequency increased linearly with the increase of the concentration of DMMP in the range from 0.1 to 0.6 mg/m3. The possible explanation of the interaction between the coatings and or-ganophosphorus compounds was discussed.
Introduction
Nowadays, the SAW sensor technology to detect the poi-sonous and harmful gases is a focus in the sensor field. In 1992, Larry J. Kepley [1], for the first time, published a literature in which surface acoustic wave technique and self-assembly technique were put together to detect the compound Dimethyl Methylphosphonate (DMMP). The advantages of powerful selectivity, high sensitivity, short response time, simple membrane preparation and long usa- ge time were reported. Because calixarenes had the in- herent three dimensional structure and pre-organized cavi- ties as recognition sites, studies on their self-assembly researches were more and more valuable [2]. The particu- lar calixarene corpus molecules were assembled on the surface of a gum body, SiO2, gold and other metals. Then monolayer or multilayer self-assembly system could be formed and used in molecular recognition, chemical sen- sors and phase transfer catalysis, enzyme mimics etc, so it exhibited an extensive application prospect [3,4].
Experimental
Reagents and Apparatus
25-(Thioalkyl-alkoxyl)-p-tertbutylcalix[4]arene was synthe- sized by our laboratory and was liquid chromatography grade. Dimethyl Methylphosphonate (DMMP), Diisopro- pyl Methylphosphonate (DIMP), Isopropyl hydrogen met- hylphosphonate were reagent grade (Research Institute of Chemical Defence, China). The other chemicals were rea- gent grade (Beijing Chemical Reagent, Beijing, China).
For the instrumentations, a Surface Acoustic Wave dual delay line (the centre frequency 300 MHz, the area of delay line was 4 mm2 gold films), a Model Proteck C3100 Frequency Meter, (Korean Proteck company) was used in this article.
Imprinted Effectiveness and Anti-interference Experiments of the SAW-MIP Sensors
In order to further confirming the imprinted effectiveness, many other gases were chosen to carry on comparative experiment. Spirits, hydrocarbon, aldehyde, ketene, aro- matics, amines, organic acid, organophosphorus, herbosa smoke etc, about 30 kinds of interference gases whose concentrations were higher 100 - 1000 times than that of DMMP were detected. The experimental results were shown in Table 3:
It had been shown in Table 3, in general, common organic solvents and gases did not interference with the SAW-MIP sensors. Among them, because the structures of organophosphorus agrochemicals were similar to DMMP, their frequency shifted greatly, but to the imprinted effe- ctiveness of DMMP, their responses were obviously lower than that of DMMP at the same concentration. Moreover, organic amines and high concentration organic acids would also produce some influence on the examination,
Conclusion
In this paper, the SAW-MIP sensor to detect organophos- phorus has been detailly studied with 25-(thioalkyl-alko- xy)-p-tertbutylcalix[4]arene self-assembly molecular im- printed film. Because this kind of SAW-MIP sensor has strong selectivity, high sensitivity, great response frequency shift and good recovery for DMMP, it was possible to be applied to detection of the low concentration organophos- phorus gases or quickly early-warning and it could be widely applied in the future.