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Aggregation of Nanosized Colloidal Silica in the Presence of Various Alkali Cations Investigated by the Electrospray Technique

Artikel i vetenskaplig tidskrift
Författare Ann-Catrin J. H. Johnsson
Peter Greenwood
Magnus Hagström
Zareen Abbas
Staffan Wall
Publicerad i Langmuir
Volym 24
Nummer/häfte 22
Sidor 12789
Publiceringsår 2008
Publicerad vid Institutionen för kemi
Sidor 12789
Språk en
Länkar dx.doi.org/10.1021%2Fla8026122
Ämnesord Silica, Nanoparticles, Colloid, Electrospray, Aggregation, DLVO
Ämneskategorier Kemi

Sammanfattning

The slow aggregation process of a concentrated silica dispersion (Bindzil 40/220) in the presence of alkali chlorides (LiCl, NaCl, KCl, RbCl, and CsCl) was investigated by means of mobility measurements. At intervals during the aggregation, particles and aggregates were transferred from the liquid phase to the gas phase via electrospray (ES) and subsequently size selected and counted using a scanning mobility particle sizer (SMPS). This method enables the acquisition of particle and aggregate size distributions with a time resolution of minutes. To our knowledge, this is the first time that the method has been applied to study the process of colloidal aggregation. The obtained results indicate that, independent of the type of counterion, a sufficient dilution of the formed gel will cause the particles to redisperse. Hence, the silica particles are, at least initially, reversibly aggregated. The reversibility of the aggregation indicates additional non-DLVO repulsive steric interactions that are likely due to the presence of a gel layer at the surface. The size of the disintegrating aggregates was monitored as a function of the time after dilution. It was found that the most stable aggregates were formed by the ions that adsorb most strongly on the particle surface. This attractive effect was ascribed to an ion−ion correlation interaction.

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