AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Colloidal Nanoparticle Analysis using a LN-DMA-APM System
VIVEK RAWAT, Seongho Jeon, Xiaoshuang Chen, Siqin He, Derek Oberreit, Christopher Hogan Jr., University of Minnesota
Abstract Number: 713 Working Group: Instrumentation and Methods
Abstract Gas phase size and mass analysis techniques allow for determination of the morphologies and densities of particles in 25-500 nm range. While such techniques are readily applied to aerosol particles, for accurate measurements of colloidal particles in the gas phase it is necessary to aerosolize particles while preserving their size, mass, and shape distributions. Traditional nebulization techniques generate super-micrometer diameter droplets which have high residue content and hence lead to aggregation of particles and residue coating onto the particle surface during aerosolization. To overcome this issue, in this study, we employ a novel liquid nebulizer (LN) with an online ultra pure water dilution system and also a ball impactor. Aerosolization with this LN allows for preservation of particle size and morphology while removing the non-volatile residue that can mask aerosolized particle distributions. We applied the LN in series with a differential mobility analyzer (DMA), an aerosol particle mass analyzer (APM), and a condensation particle counter (CPC) to classify the nanoparticles based on their electrical mobility and mass to charge ratio. To infer accurate size and mass distributions from these measurements, we inverted two dimensional distributions in particle size and mass. Data deconvolution requires consideration of DMA and APM transfer functions as well as corrections for the particle charge distribution, CPC detection efficiency and transport losses in the system. The LN-DMA-APM-CPC system was specifically applied to wet milled silica and titania nanoparticles; suspensions were milled for different times to produce particles of variable morphology, as well as variable size and mass distributions. Measurements and data inversion techniques were also validated by examining polystyrene latex (PSL) nanoparticle standards and accurately determining their sizes and densities.