Showing papers by "George Biskos published in 2006"
TL;DR: In this paper, the deliquescence and efflorescence relative humidity values of 6- to 60-nm NaCl particles were measured using a tandem nano-Differential Mobility Analyzer.
Abstract: The deliquescence and efflorescence relative humidity values of 6- to 60-nm NaCl particles were measured using a tandem nano-Differential Mobility Analyzer. The deliquescence relative humidity (DRH) increased when the dry particle mobility diameter decreased below approximately 40 nm. The efflorescence relative humidity (ERH) similarly increased. For example, the DRH and ERH of 6-nm particles were 87% and 53%, respectively, compared to 75% and 45% for particles larger than 40 nm. Power law fits describing the nanosize effect are: DRH(d m) = 213 d m −1.6+ 76 and ERH(d m) = 213 d m −1.65+ 44, which are calibrated for 6 < d m < 60 nm with less than 1% RH uncertainty and where d m is the dry particle mobility diameter (nm). Two independent methods were used to generate the aerosol particles, namely by vaporizing and condensing granular sodium chloride and by electrospraying a high-purity sodium chloride aqueous solution, to investigate possible effects of impurities on the results. The DRH and ERH values were...
161 citations
TL;DR: In this article, a hygroscopic tandem nano-differential mobility analyzer was used to demonstrate prompt deliquescence and efflorescence of ammonium sulfate particles having diameters from 6 to 60 nm.
Abstract: Literature reports have differed on the possibilities of discontinuous and continuous (i.e., prompt and nonprompt) deliquescence and efflorescence of aerosol particles in the nanosize regime. Experiments reported herein using a hygroscopic tandem nano-differential mobility analyzer demonstrate prompt deliquescence and efflorescence of ammonium sulfate particles having diameters from 6 to 60 nm. Apparent nonpromptness can be induced both by operation of the experimental apparatus and by interpretation of the measurements, even though the underlying phase transitions of individual particles remain prompt. No nanosize effect on the relative humidity values of deliquescence or efflorescence is observed for the studied size range. Smaller hygroscopic growth factors are, however, observed for the nanoparticles, in agreement with thermodynamic calculations that include the Kelvin effect. A slightly nonspherical shape for dry ammonium sulfate particles is inferred from their hygroscopically induced reconstruction between 5 and 30% relative humidity. Our results provide a further understanding of nanoparticle behavior, especially relevant to the growth rates of atmospheric nanoparticles.
155 citations
TL;DR: In this article, the hygroscopic growth factors of NaCl particles having dry mobility diameters of 6 to 60 nm were measured using a tandem nano-differential mobility analyzer.
Abstract: [1] The hygroscopic growth factors of NaCl particles having dry mobility diameters of 6 to 60 nm were measured using a tandem nano-Differential Mobility Analyzer. The growth factors steadily decreased within detection limit for dry sizes below 40 nm. The decrease is quantitatively predicted by a model that includes the Kelvin effect and a size-dependent shape factor. This factor is not tuned to the data but rather is grounded in theoretical predictions from literature. Agreement in growth factors for particles generated by two independent methods (namely, vaporization-condensation and electrospray), as well as observations of prompt deliquescence, indicates the absence of significant chemical impurities.
110 citations