English
Русский Surface modification of silica and titanium dioxide powders with silver nano- and microparticles by a thermal method
Abstract
Objectives: to modify silica powder synthesized by the sol–gel method and commercial titanium dioxide with silver particles via thermal decomposition of silver nitrate within oxide matrices. To carry out a comparative study of the morphology and distribution of silver on different supports in terms of their potential application in photocatalysis and as functional abrasive fillers in toothpastes. To determine the nanostructure and specific surface area of silica and to assess the influence of the porous structure of the support on the dispersion of the silver phase.
Methods. Silica was obtained by sol–gel synthesis based on tetraethoxysilane. Modification of titanium dioxide and silica with silver was performed by impregnation with a silver nitrate solution followed by thermal decomposition of the salt at 700 °C. The morphology and distribution of silver were investigated by scanning electron microscopy and energy-dispersive elemental analysis with mapping. The nanostructure and porosity of silica were characterized by Sears titration and methylene blue adsorption with calculation of Langmuir equation constants and specific surface area.
Results. It was shown that commercial titanium dioxide consists of coarse particles (medium size 35,4 µm), whereas the sol–gel synthesized silica has the form of microspheres with medium size 1,4 µm and is composed of primary nanoparticles of about ~3.7 nm. According to methylene blue adsorption data, the specific surface area of silica is about 10 m²/g, which corresponds to a mesoporous structure. It was found that, upon modification of titanium dioxide with silver, submicron and micron-sized silver particles (up to ~2 µm) are formed on its surface, whereas on mesoporous silica a more highly dispersed silver phase is produced, which is not size-resolvable in SEM mode but is uniformly distributed over the surface according to EDS mapping data.
Conclusions. The morphology of the silver phase strongly depends on the type and structure of the oxide support. Mesoporous nanostructured silica promotes the formation of more highly dispersed (nanosized) and uniformly distributed silver particles compared to commercial titanium dioxide, on the surface of which submicron and micron silver inclusions prevail. The obtained data can be used to optimize the photocatalytic and antibacterial properties of silver-containing composites, as well as to select the composition of abrasive fillers based on SiO₂@Ag and TiO₂@Ag for toothpastes and other oral hygiene products.
Methods. Silica was obtained by sol–gel synthesis based on tetraethoxysilane. Modification of titanium dioxide and silica with silver was performed by impregnation with a silver nitrate solution followed by thermal decomposition of the salt at 700 °C. The morphology and distribution of silver were investigated by scanning electron microscopy and energy-dispersive elemental analysis with mapping. The nanostructure and porosity of silica were characterized by Sears titration and methylene blue adsorption with calculation of Langmuir equation constants and specific surface area.
Results. It was shown that commercial titanium dioxide consists of coarse particles (medium size 35,4 µm), whereas the sol–gel synthesized silica has the form of microspheres with medium size 1,4 µm and is composed of primary nanoparticles of about ~3.7 nm. According to methylene blue adsorption data, the specific surface area of silica is about 10 m²/g, which corresponds to a mesoporous structure. It was found that, upon modification of titanium dioxide with silver, submicron and micron-sized silver particles (up to ~2 µm) are formed on its surface, whereas on mesoporous silica a more highly dispersed silver phase is produced, which is not size-resolvable in SEM mode but is uniformly distributed over the surface according to EDS mapping data.
Conclusions. The morphology of the silver phase strongly depends on the type and structure of the oxide support. Mesoporous nanostructured silica promotes the formation of more highly dispersed (nanosized) and uniformly distributed silver particles compared to commercial titanium dioxide, on the surface of which submicron and micron silver inclusions prevail. The obtained data can be used to optimize the photocatalytic and antibacterial properties of silver-containing composites, as well as to select the composition of abrasive fillers based on SiO₂@Ag and TiO₂@Ag for toothpastes and other oral hygiene products.