THE DEVELOPMENT OF A NEW THERMOPHORETIC PRECIPITATOR FOR SCANNING-TRANSMISSION ELECTRON-MICROSCOPE ANALYSIS OF ULTRAFINE AEROSOL-PARTICLES

A thermophoretic precipitator specifically for collecting ultrafine aerosol samples onto electron microscope support grids has been designed, and built. The precipitator has been designed to deposit particles of diameter less than 100 nm discretely onto support grids, with uniform deposition velocity across the size range, in addition, it has been designed to be compact, and portable. Preliminary investigations indicate it to give discrete deposits suitable for single particle analysis. Qualitatively, particle deposition velocity appears uniform between 4 and 30 nm, with a slight decrease towards higher diameters, although this is yet to be confirmed by comparison with reference particle size distribution analysis methods. Particle distribution on the microscope grid was shown to be uneven on a millimeter scale, but relatively even on a micrometer scale, enabling good characterization of the deposit.