SBIR Phase I: Optical Detection and Sizing of Aerosol Nanoparticles (diameter detection limit below 2 nanometers)

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This Small Business Innovation Research Phase I project intends to fabricate, and test a condensation nucleus counter (CNC) of the turbulent-mixing type, with a detection limit below 2 nm particle diameter, and able to measure the size distribution of aerosol nanoparticles. A novelty of this apparatus is that its super-saturation level can be adjusted quickly and accurately along a wide range. This ability, along with the dependence between critical super-saturation and embryo diameter, will make it possible to measure in real time the size distribution of the nanometric fraction of the aerosol. It will be shown that the design of this CNC effectively delays the onset of homogeneous nucleation; uncharged particles smaller than 3 nm in diameter are readily activated; a detection limit below 2 nm for uncharged particles can be achieved by using the appropriate condensing vapor; and charged nanoparticles of arbitrary small size are detected. Note that this demonstrated detection limit is substantially smaller than that of the best CNC commercially available (TSI model 3025A, 3 nm detection limit). Three tasks have been identified to materialize the goals of this proposal: design and fabrication of a CNC prototype; experimental demonstration of the performance of the CNC; and execution of fundamental research on heterogeneous nucleation. The overall work will eventually lead to the commercialization of an improved CNC. The main fields of application include: bio-aerosol detection, air quality testing, environmental studies, particle emission testing, and materials, pharmaceutical and basic aerosol research. This turbulent-mixing CNC will enable the analysis of macromolecules via liquid chromatography with a very significant gain of sensitivity with respect to more common schemes. This analytical application has considerable commercial potential.