基于提取两级催化发光信号以鉴别醚蒸气的传感器

A Sensor System for Identifying Ether Vapors Based on Extracting Two-stage Cataluminescence Signals

本研究基于两个催化敏感材料,建立了一种鉴别不同醚蒸气的新方法.分别让四种醚蒸气经过纳米MgO(或ZrO2)表面进行催化发光(Cataluminescence,CTL)反应(称其为一级反应),产生CTL响应信号I1.再让反应后的尾气作为新的反应物经过纳米MgO(或ZrO2)表面进行CTL反应(称其为二级反应),产生新的CTL响应信号I2.实验发现:在波长425 nm、流速220 mL/min、温度240℃的检测条件下,四种醚蒸气分别依次经过MgO-MgO和ZrO2-MgO材料时产生的一、二级CTL信号比值I1/I2是常数,不随浓度变化而变化,可以鉴别和区分不同的醚蒸气.通过改变分析气体流经ZrO2-MgO的方向,可以得到每种醚蒸气的四组CTL强度比值I1/I2,据此可获得多维信息来增强传感器鉴别醚蒸气的能力.该传感器具有稳定性好、造价低和鉴别能力强的优点.

The study established a new method of identifying different ether vapors by detecting the cataluminescence （CTL） intensities of both ether vapors and its reaction residual gas （including undecomposed analytes and reaction products） on two catalytic materials. In our work, we designed a sensor system： two cylindrical ceramic heaters （inner diameter=4 mm, length=8 cm） sintered with nanosized MgO or ZrO2 about 0.2 mm thick on the surface were placed into two quartz tubes （diameter= l em, length= 10 cm） respectively （the catalytic materials could be the same or different on two ceramic heaters. Two quartz tubes were connected by a polytetrafluoroethylene （PTFE） tube （35 mX 0.4 mmX 0.3 mm） which en- sured that the signal peaks of each ether vapor and its reaction residual gas could be separated. Four kinds of ether vapors （dimethyl ether, ethyl ether, isopropyl ether and n-butyl ether） were investigated in the sensor system. Firstly, CTL signal I1 was generated when each ether vapor passed through nano-MgO or ZrO2 （the first order reaction）. Then residual gas from first reaction was regarded as a new reactant and continued to be oxidized on nano-MgO or ZrO2, generating new CTL signal 12 （the second order reaction）. The CTL signals were measured using a photomultiplier in the BPCL Ultra Weak CTL Ana- lyzer, and the data was processed by Origin 7.5. It was found that for each ether vapor the ratio of luminescent response sig- nals （11/12） was constant despite different concentrations of ether vapor under the optimal conditions of wavelength of 425 nm, temperature of 240 ~C, and flow rate of 220 mL/min. Therefore the sensor could identify and distinguish different ether vapor. In the research, we obtained four groups of I/I2 values for each ether vapor by changing the direction of gas flow passing through ZrO2 or MgO （four groups： MgO-MgO, MgO-ZrO2, ZrOz-ZrOz and ZrOz-MgO）. According to different luminescent intensity ratios of ether vapor on different combinations of sensitive materials, we could enhance the sensor＇s capacity of distinguishing different kinds of ether vapor by collecting multidimensional data and information. The linear range of four ether vapors was 50- 1000 ppm and the detection limits were below the allowable concentration of ether vapor in the air. Furthermore, some common pollutants in the air such as formaldehyde, benzene, toluene and ammonia would not affect the results of the analysis. This method could quickly and easily identify different ether vapors. Meanwhile, the resid- ual gas of dimethyl ether from both first and second order reactions on MgO-MgO surface were analyzed by gas chromato graph to demonstrate the possible mechanism of the CTL reaction in this sensor.