Static light scattering of concentrated silica dispersions in apolar solvents

Helden, A.K. Van; Vrij, A.

doi:10.1016/0021-9797(80)90570-6

Cited by 100 publications

(44 citation statements)

References 37 publications

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“…However, Van Helden et al 7 have already reported the presence of carbon in the composition of Stöber silica particles. They assumed that the carbon content determined gravimetrically originates from unhydrolyzed ethoxy groups and calculated that the particles contain 91.5% weight silica, 5.25% water and 0.97% ethoxy groups.…”

Section: Discussionmentioning

confidence: 99%

“…They carried out a systematic study of the reaction parameters and after some major changes of the experimental conditions he has obtained suspensions of quasi-monodisperse silica spheres. After this pioneering work, Stöber silica particles have been used as model colloids in a large number of experimental *e-mail: fernagal@iqm.unicamp.br investigations [7][8][9][10] . Based on the Stöber method, Kaiser 11 prepared completely porous silica particles by co-hydrolysis and subsequent condensation of tetraethoxysilane and an n-alkyltrialkoxysilane in a mixture of ethanol, water and aqueous ammonia.…”

Section: Introductionmentioning

confidence: 99%

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Core-and-shell nature of Stöber silica particles

Leite

Souza

Galembeck

2001

J. Braz. Chem. Soc.

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Duas amostras diferentes de partículas monodispersas de sílica de Stöber foram examinadas por microscopia eletrônica de transmissão analítica, utilizando-se diferentes tipos de imagens: campo-claro, campo escuro, imagens espectrais e mapas de distribuição elementar. As partículas (141 e 36 nm de diâmetro efetivo) contêm domínios de relação elementar O/Si e, portanto, de grau de hidratação muito variável, que coexistem com partículas medindo poucos nanômetros de diâmetro e com relação O/Si elevada, que aparecem dispersas no fundo das imagens. As imagens de campo claro e de perda de energia revelam que as partículas maiores possuem uma morfologia do tipo caroço-casca e as cascas das partículas possuem uma quantidade maior de domínios com razão O/Si maior, comparada com o interior da partícula, o que é atribuído ao acúmulo de domínios mais hidratados na casca, e também à presença de compostos de carbono, contaminantes da sílica. Por outro lado, as partículas menores (diâmetro efetivo = 36 nm) não são esféricas nem têm morfologia caroço-casca, embora também sejam formadas por domínios de composições químicas muito diferentes. Os vários mecanismos de formação de partículas apresentados na literatura são discutidos, considerando-se estes novos resultados.Two different samples of monodisperse Stöber silica particles were examined in the analytical transmission electron microscope, using different imaging modes: bright-field, dark-field, energyloss and elemental distribution maps. The particles (effective diameters = 141 and 36 nm) are formed by domains of variable O/Si ratio, which is consistent with a variable degree of hydration, and they coexist with particles with a high O/Si ratio measuring a few nanometers only, which appear dispersed in the picture background. Bright-field and energy-loss images of the larger particles show a core-and-shell morphology, and the shells have a higher amount of high-O/Si domains as well as contaminating carbon compounds. On the other hand, the smaller particles (effective diameter = 36 nm) are also formed by distinct domains, but their morphology is neither spherical or core-and-shell. The mechanisms for particle formation presented in the literature are discussed, considering the present findings.Keywords: colloidal silica, transmission electron microscopy, energy-filtered imaging, silica particle microchemistry J. Braz. Chem. Soc., Vol. 12, No. 4, 519-525, 2001. Printed in Brazil ©2001 Soc. Bras. Química 0103 -5053 $6.00+0.00 IntroductionUniform fine particles are interesting as model systems in the study of adsorption and catalysis, as well as in the study of size-dependent solid state properties such as quantum confinement 1 and superplasticity 2,3 . There have been significant achievements concerning the preparation of uniform colloid dispersions, both inorganic 4 and organic 5 . However, uniformity has often been considered only in relationship to particle size and shape, and little information is currently available concerning the uniformity of chemical composition of particl...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Core-and-shell nature of Stöber silica particles

Leite

Souza

Galembeck

2001

J. Braz. Chem. Soc.

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“…At moderate pH, these anions provide a long-range electrostatic repulsive interaction between individual particles. In order to neutralize the surface charge for studies of short-ranged interactions, these charges can be removed by surface esterification (22,24,(32)(33)(34).…”

Section: Silica Particlesmentioning

confidence: 99%

Optical Trapping of Titania/Silica Core-Shell Colloidal Particles

Viravathana

Marr

2000

Journal of Colloid and Interface Science

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“…This formalism has been successfully implemented in the analysis of light scattering [8], small angle X-ray (SAXS) [9] d an small angle neutron scattering (SANS) [lo] on dispersions of colloidal particles with steep short ranged repulsive interactions [ll].…”

Section: Introductionmentioning

confidence: 99%