Grant: Research Tools and Instruments - Category 1 (<$150,000)

The scanning mobility particle sizer (SMPS) requested in this grant application will be used to advance research on applications of cold fiber solid-phase microextraction (SPME) and needle trap devices for particle, particularly nanoparticle, collection and identification. Modified SPME devices made from metal fibers and fitted with cooling means will be evaluated for efficient nanoparticle collection. For this purpose, thermophoresis, a physical phenomenon in which a thermal gradient causes dispersed particles to drift towards the cooler surface, will be used. Thermophoretic deposition is nearly independent of particle size, and thus able to provide an unbiased sampling of airborne particulates. We propose to develop a new approach to thermophoretic collection of nanoparticles on a cold fiber in the SPME device, followed by a convenient interface to analytical instruments, to enable characterization of the matrix of the particle, as well as the chemical species adsorbed on its surface. To validate theoretical predictions and enable development of calibration procedures, we urgently need an SMPS to be used together with an aerosol generator, which we are building in our laboratory, to measure the size distribution of nanometer aerosols. Further, such system is required to conduct studies on permeabilities of particles through barriers. Mathematical models will be derived to explain the permeation process, and equations for calculating permeability will be deduced. Similarly, the effects of feed and permeate gas velocity, membrane module temperature, and humidity on the membrane permeabilities for nanoparticles will be investigated. The requested equipment will be used by at least two post-doctoral fellows and one graduate student, and developed methods will be applied to analyses of indoor and outdoor air, car exhaust, and different kinds of smoke, including cigarette smoke.