Synthesis of nanosize silica in aerosol OT reverse microemulsions

Journal Article · Wed Mar 01 04:00:00 EST 1995 · Journal of Colloid and Interface Science; (United States)

DOI:https://doi.org/10.1006/jcis.1995.1064· OSTI ID:6492917

Arriagada, F J; Osseo-Asare, K ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

Silica nanoparticles were synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/decane/ammonium hydroxide reverse microemulsions via the base-catalyzed hydrolysis of tetraethoxysilane (TEOS). The fluorescence spectra of 1,3,6,8-pyrenetetrasulfonic acid (PTS) trapped in the water pools indicate that free water molecules do not become available until the water-to-surfactant molar ratio (R) exceeds about 10. At R values below about 4, no particles are produced. Under these conditions, the surfactant molecules are closely packed at the interface and the water molecules are strongly bound to the surfactant polar groups and the sodium counterions; the net result is to inhibit TEOS hydrolysis. As R increases from 5 to 9.5, the diameter of the resulting particles increases, and the size distribution decreases. These trends are rationalized in terms of changes in the local concentration of hydrolyzed TEOS species in the reversed micellar pseudophase, coupled with the protective action of the surfactant film. The fact that the final particle sizes exceed the diameters of the corresponding water pools indicates a role for intermicellar matter exchange in the particle growth process. The dispersions are not stable, and gel-like precipitates eventually form. The low dispersion stability is attributed to the presence of sodium ions and to the possible decrease in pH caused by the hydrolysis of the AOT surfactant molecules. This surfactant has been used in a number of applied investigations involving membrane chemistry, protein separations, metal separations, solar energy conversion, and nanoparticle synthesis.

• OSTI ID: 6492917
• Journal Information: Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 170:1; ISSN 0021-9797; ISSN JCISA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHALCOGENIDES
CHEMICAL REACTIONS
COLLOIDS
CONCENTRATION RATIO
DECOMPOSITION
DISPERSIONS
EMULSIONS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROLYSIS
LYSIS
MICROEMULSIONS
MINERALS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
SILANES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SOLVENT PROPERTIES
SOLVOLYSIS
SURFACTANTS
SYNTHESIS