Ohira Shin-Ichi, Miki Yusuke, Matsuzaki Toru, Nakamura Nao, Sato Yu-ki, Hirose Yasuo, Toda Kei
Department of Chemistry, Kumamoto University, Kumamoto, Japan.
Tsukuba Laboratories, Taiyo Nippon Sanso Corporation, Ibaraki, Japan.
Anal Chim Acta. 2015 Jul 30;886:188-93. doi: 10.1016/j.aca.2015.05.045. Epub 2015 Jul 8.
Industrial gases such as nitrogen, oxygen, argon, and helium are easily contaminated with water during production, transfer and use, because there is a high volume fraction of water in the atmosphere (approximately 1.2% estimated with the average annual atmospheric temperature and relative humidity). Even trace water (<1 parts per million by volume (ppmv) of H2O, dew point < -76 °C) in the industrial gases can cause quality problems in the process such as production of semiconductors. Therefore, it is important to monitor and to control trace water levels in industrial gases at each supplying step, and especially during their use. In the present study, a fiber optic gas sensor was investigated for monitoring trace water levels in industrial gases. The sensor consists of a film containing a metal organic framework (MOF). MOFs are made of metals coordinated to organic ligands, and have mesoscale pores that adsorb gas molecules. When the MOF, copper benzene-1,3,5-tricarboxylate (Cu-BTC), was used as a sensing material, we investigated the color of Cu-BTC with water adsorption changed both in depth and tone. Cu-BTC crystals appeared deep blue in dry gases, and then changed to light blue in wet gases. An optical gas sensor with the Cu-BTC film was developed using a light emitting diode as the light source and a photodiode as the light intensity detector. The sensor showed a reversible response to trace water, did not require heating to remove the adsorbed water molecules. The sample gas flow rate did not affect the sensitivity. The obtained limit of detection was 40 parts per billion by volume (ppbv). The response time for sample gas containing 2.5 ppmvH2O was 23 s. The standard deviation obtained for daily analysis of 1.0 ppmvH2O standard gas over 20 days was 9%. Furthermore, the type of industrial gas did not affect the sensitivity. These properties mean the sensor will be applicable to trace water detection in various industrial gases.
诸如氮气、氧气、氩气和氦气等工业气体在生产、传输和使用过程中很容易被水污染，因为大气中水蒸气的体积分数很高（根据年平均气温和相对湿度估算约为1.2%）。即使工业气体中存在痕量水（体积分数<1 ppmv的H₂O，露点<-76°C）也会在诸如半导体生产等过程中引发质量问题。因此，在工业气体的每个供应环节，尤其是在使用过程中，监测和控制痕量水含量非常重要。在本研究中，对一种用于监测工业气体中痕量水含量的光纤气体传感器进行了研究。该传感器由包含金属有机骨架（MOF）的薄膜组成。MOF由与有机配体配位的金属构成，具有吸附气体分子的介孔。当使用金属有机骨架材料苯-1,3,5-三甲酸铜（Cu-BTC）作为传感材料时，我们研究了Cu-BTC在吸附水时颜色在深度和色调上的变化。Cu-BTC晶体在干燥气体中呈深蓝色，在潮湿气体中则变为浅蓝色。利用发光二极管作为光源、光电二极管作为光强检测器，开发了一种带有Cu-BTC薄膜的光学气体传感器。该传感器对痕量水表现出可逆响应，无需加热来去除吸附的水分子。样气流量不影响灵敏度。获得的检测限为40 ppbv。对于含有2.5 ppmv H₂O的样气，响应时间为23秒。对1.0 ppmv H₂O标准气体进行20天的每日分析所得到的标准偏差为9%。此外，工业气体的类型不影响灵敏度。这些特性意味着该传感器将适用于各种工业气体中的痕量水检测。
