Journal
JOURNAL OF COLLOID AND INTERFACE SCIENCE
Volume 315, Issue 1, Pages 123-127Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2007.06.064
Keywords
silica; colloids; zeta potential; surface charge; surface modification; alkoxysilane; stability; light scattering; nano-size
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The surfaces of commercial 30-nm colloidal silica particles were modified by reacting with functional silanes. The high specific surface area and reactivity of the particles due to the small size make the process susceptible to irreversible aggregation not found previously with larger particles. This study compares surface charge results from different reaction conditions and characterization methods. Measurements of the zeta potential as a function of pH and gelation kinetics shed light on the mechanism of instability in nano-sized silica suspensions. Experimental results showed that very stable particles can be suspended in a nonaqueous solvent after refluxing of the silica particles, while maintaining the original particles physical properties of size and electrochemical behavior. Extremely stable particles are obtained by ammosilane surface modification. Factors affecting susceptibility of small particles to irreversible aggregation caused by a nonaqueous solvent or a high concentration of a trialkoxysilane, including the large amount of reactive silanol groups on the surface gel layer of the particles, are discussed. (c) 2007 Elsevier Inc. All rights reserved.
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