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Issue 24, 2011
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Progress in coagulation rate measurements of colloidal dispersions

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Abstract

This article reviews recent advances in coagulation rate measurements of colloidal dispersions, with emphasis on the turbidity method. For turbidity method, measurement of the coagulation rate relies upon the turbidity change resulting from the coagulation process, and the measuring sensitivity significantly depends on particle size and the wavelength used. There exists a “zero sensitivity” blind point for measurement at a specific wavelength, suggesting that such measurements should be performed at a wavelength some distance from the blind point. The major difficulty in determining absolute coagulation rate constant (CRC) by light scattering and turbidity measurements is how to theoretically solve the scattering problem of 2-particle aggregates. The T-matrix method accurately solves this problem, showing its superiority over various earlier theoretical approximations (applicable only to small particles). Results from studies on effects of forward scattering, multiple scattering, etc., provide guidelines for choosing proper particle size and volume fraction for the allowed margin of measurement error. Most of these findings on turbidity methods are also valid or applicable to other scattering methods. Finally, we introduce a new microscopic approach to assess the colloidal stability at individual particle levels, by means of directly observing artificially induced collision with the aid of optical tweezers.

Graphical abstract: Progress in coagulation rate measurements of colloidal dispersions

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Publication details

The article was received on 01 Jul 2011, accepted on 31 Aug 2011 and first published on 07 Oct 2011


Article type: Review Article
DOI: 10.1039/C1SM06237A
Citation: Soft Matter, 2011,7, 11298-11308
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    Progress in coagulation rate measurements of colloidal dispersions

    S. Xu and Z. Sun, Soft Matter, 2011, 7, 11298
    DOI: 10.1039/C1SM06237A

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