Liquid phase deposition (LPD) of silica from soluble silicates has been performed in the presence of dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS) and sodium dodecylbenzyl sulfate (SDBS). The morphology of the silica varies between semi-ordered uniform spheres to low porosity agglomerates, with the choice and concentration of the surfactants. The agglomerate structures depend on the charge of the surfactant (and hence the retention of micelles under acidic LPD conditions and/or the ionic character of the surfactant solution), the critical micelle concentration (as compared to the concentration of the silica precursor), and the ionic strength of the solution. The application of surfactant micelles as templates for LPD silica is counter to a previous proposal that suggested the ionic strength of the silicate solution would cause the collapse of the ionic vesicles. The size of spherical silica particles is controlled by the relative concentration of the surfactant and the LPD precursor.

Single walled carbon nanotubes (SWNTs) have been coated with fluorine-doped silica by liquid phase deposition (LPD) using a silica–H2SiF6 solution and a surfactant stabilized solution of SWNTs. The coating of individual SWNTs versus small ropes is controlled by the choice of surfactant. Since the LPD reaction is performed close to the isoelectric point of the silica, some of the SiO2–SWNTs are fused together but the SWNTs remain individual in these composite structures. The SiO2–SWNTs have been characterized by SEM, TEM, Raman and IR spectroscopy, and XPS. Raman fluoresence is maintained even with coatings >50 nm. Using the relative intensity of the Raman G peak and the 8,3 SWNT fluorescence as a convenient measure of bundling, it may be shown that any decrease of fluoresence during growth is not due to changes in ionic strength or pH, as a consequence of addition of the LPD solution or the presence of HF as a side product in the deposition. The Raman D and G modes show no change in intensity, while the Fano line increases, both suggesting that no sidewall functionalization or proton adsorption of the SWNTs occurs during coating. The UV-visible-near infrared spectra shows a red shift in the first Van Hove transitions of the coated SWNTs inferring that the SWNTs in SiO2–SWNTs are in a more polarizable and inhomogeneous environment than that of surfactant solutions. Mats of SiO2–SWNT may be deposited onto silicon and gold substrates and through lithography may be patterned by etching off selected areas of the silica coating.

Liquid phase deposition of silica in the presence of fullerenol C60(OH)n, results in the formation of uniform silica spheres, whereas the use of C60 gives large non-uniform agglomerates as a result of homogeneous nucleation. Raman and UV spectroscopy indicate the C60 is retained as the core of the silica spheres.

Single walled carbon nanotubes (SWNTs) have been coated with silica by the addition of a silica/H2SiF6 solution to a surfactant-stabilized solution of SWNTs. The thickness of the coating is controlled by reaction time, while the coating of individual SWNTs versus small ropes is controlled by the choice of surfactant. Individual nanotubes encased by a silica coating show retention of the characteristic Raman fluorescence. Selective etching of the silica coating allows for the exposure of either one end of the tubes or the central section. Exposure of the ends results in the formation of spontaneous interconnects between isolated SWNTs.