Study On A New Liquid Crystal Sensor Functionalized Only With Copper Ions

In recent years, the hazards to environmental security and threats tohomeland defense from organophosphorus substances are increased.However, all the pre-existing detection methods have some shortcomings.Recently proposed liquid crystal (LC) biosensors can be applied todetection of many agents with fast, high sensitivity, high specificity andreusability. According to past achievements on LC biosensors, we carry outa new type of LC biosensor for detection of organophosphorus. The majorworks as follows:(1) functionalization of the surface of glass substrate with copper ions,a liquid crystal sensor is fabricated and used to observe the effect of thecopper ions on the orientation of the LC molecules5CB supporting on thesubstrate. We find that the orientational change of liquid crystal on thesubstrate surface is realized. The perpendicular orientation of liquid crystalis confirmed by optical characterization which is significantly differentfrom the one not sprayed with copper ions.(2) Measuring the saturation solubility of copper ions in5CB. Becausethe concentration of copper ions affects the change in orientation of the LC, in order to deeply analyze the mechanism of the perpendicular orientationof LC molecules on the substrate surface functionalized only with copperions, the saturation solubility of copper ions in LC is determined to about0.68mmol/L by using atomic absorption spectrometer.(3) Detection of organophosphorus such as DMMP with the presentedLC sensor. The results showed that the response time only tens of seconds,furthermore, the sensor can detect ppb-level concentration of DMMP anddo not respond to the interferences such as water, ethanol, toluene andacetone. We also find that the LC sensor can store for a long time withoutlosing sensing performance when using the copper ions of1-5mmol/L toprocess the substrate of the presented sensors.(4) The contrast study on the detecting performance of the LC sensorfunctionalized only with copper ions with the one processed with SAM.Under the same conditions, the results revealed that the two LC sensors canreach similar detecting performance with respect to response time, limit ofdetection, selectivity and anti-interference. Compared to the latter,moreover, it has advantages of more simple preparation process, lower-costand so on.