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An effective and reproducible preparation of silica sol nanospheres via a modified sol-gel process has been described. Monodisperse and stable silica sol nanospheres with uniformsize were successfully obtained through the optimized synthesis in which the mixture of tetraethyl orthosilicate(TEOS) and ethanol was followed by the addition of water and ammonium hydroxide(NH 3) separately, and the size of silica sol spheres was strictly controlled in the range of 25-119 nm with a narrow size distribution by fi ne adjustment of several reaction parameters. Results showed that in the presence of low concentration of TEOS, spheres size rose fi rst and reached maximum when H 2 O concentration was up to 66 g/L. However, the diameter of silica sol spheres decreased above 66 g/L of H 2 O concentration. Furthermore, it was also found that the size and size distribution of silica sol nanospheres were affected by NH 3 concentration. As NH 3 concentration increased from 15 to 35 g/L, the diameter declined from 83 to 64 nm. Nevertheless, higher NH 3 concentration would result in relatively broad size distribution, and gelation occurred when NH 3 concentration reached 44 g/L. In addition, the effect of the different feed rates of NH 3 on the size growth of silica sol nanospheres was also discussed.
An effective and reproducible preparation of silica sol nanospheres via a modified sol-gel process has been described. Monodisperse and stable silica sol nanospheres with uniformsize were successfully obtained through the optimized synthesis in which the mixture of tetraethyl orthosilicate (TEOS) and ethanol was followed by the addition of water and ammonium hydroxide (NH 3) separately, and the size of silica sol spheres was strictly controlled in the range of 25-119 nm with a narrow size distribution by fi ne adjustment of several reaction parameters. Presence of low concentration of TEOS, spheres size rose fi rst and reached maximum when H 2 O concentration was up to 66 g / L. However, the diameter of silica sol spheres decreased above 66 g / L of H 2 O concentration. it was also found that the size and size distribution of silica sol nanospheres were affected by NH 3 concentration. As NH 3 concentration increased from 15 to 35 g / L, the diameter decl ined from 83 to 64 nm. Nevertheless, higher NH 3 concentration would result in relatively broad size distribution, and gelation occurred when NH 3 concentration reached 44 g / L. In addition, the effect of the different feed rates of NH 3 on the size growth of silica sol nanospheres was also discussed.