Shinar R, Liu G, Porter M D
Microanalytical Instrumentation Center, Ames Laboratory-USDOE, and Department of Chemistry, Iowa State University, 50011, USA.
Anal Chem. 2000 Dec 15;72(24):5981-7. doi: 10.1021/ac0009548.
The use of graphite particles (1-2 microm) as coatings on quartz crystal microbalances (QCMs) for detection and monitoring of toluene and other volatile organic compounds (VOCs) is described. Unlike the more commonly used polymeric coatings with low glass transition temperatures (Tg), particulate graphitic coatings are not as susceptible to loss of acoustic energy when coating thickness or operational temperature increases. This situation enables the use of relatively thick coatings, which increases the absolute amount of vapor sorbed in the coating and, consequently, lowers the level of detection and enhances operation over a wide temperature range. The use of small size particles also results in a coating with a more porous structure, which facilitates uptake and release of VOCs in comparison to coatings made from high Tg polymers, which have a lower porosity. These attributes, coupled with the inherent stability of graphitic materials, make particulate graphite coatings especially suitable for applications at high temperatures. The advantages of using particulate graphite as a coating on QCMs are demonstrated by comparison to the performance of a few low-Tg polymers [i.e., poly(isobutylene) and poly(diphenoxyphosphazene)] and high-Tg polymers (i.e., polystyrene).
本文描述了使用石墨颗粒（1 - 2微米）作为石英晶体微天平（QCM）的涂层，用于检测和监测甲苯及其他挥发性有机化合物（VOC）。与更常用的低玻璃化转变温度（Tg）的聚合物涂层不同，颗粒状石墨涂层在涂层厚度或操作温度增加时，不太容易损失声能。这种情况使得可以使用相对较厚的涂层，这增加了涂层中吸附的蒸汽绝对量，从而降低了检测限，并在很宽的温度范围内增强了操作性能。使用小尺寸颗粒还会导致涂层具有更多孔的结构，与由高Tg聚合物制成的孔隙率较低的涂层相比，这有利于VOC的吸收和释放。这些特性，再加上石墨材料固有的稳定性，使得颗粒状石墨涂层特别适用于高温应用。通过与几种低Tg聚合物[即聚异丁烯和聚二苯氧基磷腈]和高Tg聚合物（即聚苯乙烯）的性能进行比较，证明了在QCM上使用颗粒状石墨作为涂层的优势。
