Preparation of bi-functional silica particles for antibacterial and self cleaning surfaces

Synthesis of bi-functional silica particles by a simple wet chemical method is described where the mixture of ultra fine nanoparticles (1–3 nm) of titania and silver were attached on the silica particle surface in a controlled way to form a core–shell structure. The silica surface showed efficient bi-functional activity of photo-catalytically self cleaning and antibacterial activity due to nanotitania and nanosilver mutually benefiting each other’s function. The optimum silver concentration was found where extremely small silver nanoparticles are formed and the total composite particle remains white in color. This is an important property in view of certain applications such as antibacterial textiles where the original fabric color has to be retained even after applying the nanosilver on it. The particles were characterized at each step of the synthesis by X-ray photoelectron spectroscopy, UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron energy loss spectroscopy. Bi-functional silica particles showed accelerated photocatalytic degradation of methylene blue as well as enhanced antibacterial property when tested as such particles and textiles coated with these bi-functional silica particles even at lower silver concentration.

Schematic illustration of silica@TiO2, Ag core–shell particle formation and their bifunctional activity.Figure optionsDownload high-quality image (87 K)Download as PowerPoint slideHighlights
► Bifunctional silica with ultra fine titania and silver nanoparticles on its surface.
► Formation of silica@titania,silver core shell structure.
► Titania and silver enhance photocatalytic and antibacterial activity together.
► White colored composite due to ultra small nano silver size.
► Technologically important material which retains original colour of the substrate.