Application of Half Mini DMA for Sub 2 nm Particle Size Distribution Measurement in an Electrospray and a Flame Aerosol Reactor


Conventional Differential Mobility Analyzers (DMA) have had limited success in classifying sub 2 nm particles with high resolution, primarily due to diffusion broadening. High flow DMAs have been able to overcome this limitation and achieve high-resolution classification of sub 2 nm particles, by maintaining laminar flow at high Reynolds numbers. A Half Mini DMA was compared with a Nano DMA (TSI model 3085) for sub 2 nm size distribution measurements of organic ions generated by electrospray of tetra-heptyl ammonium bromide (THAB) solution and aerosols generated by a premixed flat flame reactor. Obscurities in ion peak measurements with the Nano DMA indicated a higher diffusion effect. Calculations of the diffusing transfer functions indicated that the Half Mini DMA deviated significantly from ideal conditions, possibly due to the higher demands for a more precise electrode placement and a smaller surface roughness, since it is operated at a high sheath flow rate. The Half Mini DMA was then applied to study the formation of flame-generated aerosols in the sub 2 nm range. This is the first reported measurement of these clusters in an aerosol reactor. The effects of the flame synthesis precursor (titanium (IV) isopropoxide), the Kr-85 radioactive neutralizer, and the tubing materials on the flame aerosol size distribution measurements were investigated. After the introduction of titanium (IV) isopropoxide, several discrete peaks were detected, suggesting discrete cluster formation during the initial stages of TiO2 particle synthesis. The addition of a radioactive neutralizer balanced the size distribution of flame aerosols by changing the charging mechanisms. Compared with copper tubing, silicone conductive tubing generated extremely high positive ion contamination after neutralization.


Civil, Architectural and Environmental Engineering


This work was partially supported by the National Science Foundation; the Nano Research Facility (NRF) at Washington University in St. Louis, a member of the National Nanotechnology Infrastructure Network (NNIN) ; and the Solar Energy Research Institute for India and the United States (SERIIUS) , funded jointly by the U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, under Subcontract DE-AC36-08GO28308 to the National Renewable Energy Laboratory, Golden, Colorado) and the Government of India, through the Department of Science and Technology under Subcontract IUSSTF/JCERDC-SERIIUS/2012 .

Keywords and Phrases

Aerosols; Atmospheric movements; Flame synthesis; Laminar flow; Particle size analysis; Positive ions; Radioactivity; Reynolds number; Silicones; Size distribution; Surface roughness; Titanium dioxide; Tubing; Flame aerosol reactor (FLAR); Half Mini DMA; Nano-DMA; Neutralizer; Sample tube; Sub 2nm; Particle size; Ammonia; Anion; Bromine derivative; Copper; Ion; Silicone; Tetraheptyl ammonium bromide; Unclassified drug; Neutralization; Particle size; Pollution; Reynolds number; Size distribution; Aerosol; Analyzer; Article; Calculation; Contamination; Differential mobility analyzer; Diffusion; Electrode; Electrospray; Flamer aerosol reactor; Flow rate; Laminar flow; Measurement; Particle size; Priority journal; Reactor; Nano DMA; Sample tube contamination

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Article - Journal

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© 2014 Elsevier, All rights reserved.

Publication Date

01 May 2014