Diffusion coefficients for some organic and organometallic compounds using quartz crystal microbalance

Abstract

The diffusion coefficient data for organometallic substances are scarce in the literature. A recently developed quartz crystal microbalance (QCM) system has been used to measure the binary diffusion coefficients. The system consists of a QCM with a driving oscillator circuit, a closed Stefan tube, a temperature controlled unit, a data logger, and a frequency counter. The QCM crystal is placed on the top of a Stefan tube and its active surface is coated with a thin layer of the substance. On the other end of the Stefan tube highly adsorptive charcoal powder is placed. Thus a mass concentration gradient is established in the diffusion tube. The rate of mass loss from the QCM was then used to determine the binary diffusion coefficient in air. Diffusion coefficients of polyaromatic hydrocarbons anthracene and phenanthrene and some organometallic compounds (e.g. ferrocene, aluminium acetylacetonate and chromium acetylacetonate) in air at various temperatures are reported.