Abstract
INTRODUCTION
The investigation of the fundamental process that enables and predicts phase change is of great interest. Both homogeneous and heterogeneous nucleation/condensation processes are applied for e.g. nanoparticle
synthesis, but also are responsible for new particle formation (NPF) in the atmosphere and thus, affect our climate and human health.
With advances in aerosol instrumentation towards smaller and smaller particles an increasing attention was drawn to the investigation of the process of heterogeneous nucleation for seed particles close to the Kelvin
diameter. With the introduction of the ultrafine condensation particle counter (CPC) by Stolzenburg and McMurry in 1991 particle detection down to about 3 nm became possible. For a long time the Kelvin diameter was seen as a fundamental lower detection limit for the CPCs. However, this assumption could not
hold some experimental investigations. Seto et al. (1997) found that ions of about 1.5 nm could be activated in a turbulent mixing CNC (condensation nuclei counter). Gamero and de la Mora (2000) used dibutylphthalate vapor and showed that there was no lower limit to the particle size that could be activated. The
definite confirmation, that detection below the Kelvin limit is possible, was provided by observations of Winkler et al. (2008) in an expansion type CPC using monodisperse particles down to about 1 nm. A universal theory predicting heterogeneous nucleation especially for particles smaller than the Kelvin
diameter is still missing. Many seed properties that were found to have an influence on nucleation, e.g. polarity and chemical composition, are not considered in classical models such as the classical nucleation theory (CNT). The development of a theory is complicated also due to the lack of meaningful experimental
measurements. Accurate experimental measurements of activation probabilities require highly homogeneous nuclei and supersaturations (Fernandez de la Mora, 2010). This still is difficult to achieve using general state-of-the-art aerosol instruments.
In this study we were able to overcome these experimental difficulties by using highly specialized aerosol instruments that can meet both of the prerequisite; firstly, a high resolution and transmission DMA for the size selection of highly monodisperse seed ions of defined chemistry and both polarities; and secondly, an
expansion type CPC, exposing the seed ions to a homogeneous supersaturation. In addition to the experimental work we compared the results to existing theories by applying the classical nucleation theory (CNT) for the case of insoluble and perfectly wetting seed particles.
The investigation of the fundamental process that enables and predicts phase change is of great interest. Both homogeneous and heterogeneous nucleation/condensation processes are applied for e.g. nanoparticle
synthesis, but also are responsible for new particle formation (NPF) in the atmosphere and thus, affect our climate and human health.
With advances in aerosol instrumentation towards smaller and smaller particles an increasing attention was drawn to the investigation of the process of heterogeneous nucleation for seed particles close to the Kelvin
diameter. With the introduction of the ultrafine condensation particle counter (CPC) by Stolzenburg and McMurry in 1991 particle detection down to about 3 nm became possible. For a long time the Kelvin diameter was seen as a fundamental lower detection limit for the CPCs. However, this assumption could not
hold some experimental investigations. Seto et al. (1997) found that ions of about 1.5 nm could be activated in a turbulent mixing CNC (condensation nuclei counter). Gamero and de la Mora (2000) used dibutylphthalate vapor and showed that there was no lower limit to the particle size that could be activated. The
definite confirmation, that detection below the Kelvin limit is possible, was provided by observations of Winkler et al. (2008) in an expansion type CPC using monodisperse particles down to about 1 nm. A universal theory predicting heterogeneous nucleation especially for particles smaller than the Kelvin
diameter is still missing. Many seed properties that were found to have an influence on nucleation, e.g. polarity and chemical composition, are not considered in classical models such as the classical nucleation theory (CNT). The development of a theory is complicated also due to the lack of meaningful experimental
measurements. Accurate experimental measurements of activation probabilities require highly homogeneous nuclei and supersaturations (Fernandez de la Mora, 2010). This still is difficult to achieve using general state-of-the-art aerosol instruments.
In this study we were able to overcome these experimental difficulties by using highly specialized aerosol instruments that can meet both of the prerequisite; firstly, a high resolution and transmission DMA for the size selection of highly monodisperse seed ions of defined chemistry and both polarities; and secondly, an
expansion type CPC, exposing the seed ions to a homogeneous supersaturation. In addition to the experimental work we compared the results to existing theories by applying the classical nucleation theory (CNT) for the case of insoluble and perfectly wetting seed particles.
| Original language | English |
|---|---|
| Publication status | Published - 26 Jun 2017 |
Austrian Fields of Science 2012
- 103008 Experimental physics
- 105904 Environmental research
- 103039 Aerosol physics
