Erkka Saukko

Publications (3)10.13 Total impact

• Article: On-Line Characterization of Morphology and Water Adsorption on Fumed Silica Nanoparticles

  Helmi Keskinen, Sami Romakkaniemi, Antti Jaatinen, Pasi Miettinen, Erkka Saukko, Joutsensaari Jorma, Jyrki M. Mäkelä, Annele Virtanen, James N. Smith, Ari Laaksonen
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  ABSTRACT: The first wetting layer on solid nanoparticles has direct implications on the roles these particles play in industrial processes and technological applications as well as in the atmosphere. We present a technique for online measurements of the adsorption of the first few water layers onto insoluble aerosol nanoparticles. Atomized fumed silica nanoparticles were dispersed from aqueous suspension and their hygroscopic growth factors (HGF) and number of the adsorbed water layers at subsaturated conditions were measured using a nanometer hygroscopic tandem differential mobility analyzer (HTDMA). Particle morphology was characterized by electron microscopy and particle density was determined by mobility analysis. The HGFs of the size-selected particles at mobility diameters from 10 to 50 nm at 90% relative humidity (RH) varied from 1.05 to 1.24, corresponding to 2–6 layers of adsorbed water. The morphology of the generated fumed silica nanoparticles varied from spheres at 8–10 nm to agglomerates at larger diameters with effective density from 1.7 to 0.8 g/cm3 and fractal dimension of 2.6. The smallest spheres and agglomerates had the highest HGFs. The smallest particles with diameters of 8 and 10 nm adsorbed two to three water layers in subsaturated conditions, which agreed well with the Frenkel, Halsey, and Hill (FHH) isotherm fitting. In comparison to the small spheres or large agglomerates, the compact agglomerate structure containing a few primary particles increased the number of adsorbed water layers by a factor of 1.5. This was probably caused by the capillary effect on the small cavities between the primary particles in the agglomerate.
  Aerosol Science and Technology 12/2011; 45(12):1441-1447. · 2.67 Impact Factor
• Source

  Available from: Annele Virtanen

  Article: On-Line Characterization of Morphology and Water Adsorption on Fumed Silica Nanoparticles

  Helmi Keskinen, Sami Romakkaniemi, Antti Jaatinen, Pasi Miettinen, Erkka Saukko, Joutsensaari Jorma, Jyrki M Mäkelä, Annele Virtanen, James N Smith, Ari Laaksonen
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  ABSTRACT: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan, sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
  Aerosol Science and Technology 01/2011; 4512:1441-1447. · 2.67 Impact Factor
• Article: Ion mobility distributions during the initial stages of new particle formation by the ozonolysis of α-pinene.

  Anna-Kaisa Viitanen, Erkka Saukko, Annele Virtanen, Pasi Yli-Pirilää, James N Smith, Jorma Joutsensaari, Jyrki M Mäkelä
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  ABSTRACT: An ion mobility spectrometer (IMS) was used to study gas phase compounds during nucleation and growth of secondary organic aerosols (SOA). In this study SOA particles were generated by oxidizing α-pinene with O(3) and OH in a 6 m(3) reaction chamber. Positive ion peaks with reduced mobilities of 1.59 cm(2)(Vs)(-1) and 1.05 cm(2)(Vs)(-1) were observed 7 min after α-pinene and ozone were added to the chamber. The detected compounds can be associated with low volatility oxidation products of α-pinene, which have been suggested to participate in new particle formation. This is the first time that IMS has been applied to laboratory studies of SOA formation. IMS was found suitable for continuous online monitoring of the SOA formation process, allowing for highly sensitive detection of gas phase species that are thought to initiate new particle formation.
  Environmental Science & Technology 11/2010; 44(23):8917-23. · 4.80 Impact Factor