Neha Hebalkar

Silica-silver core-shell particles for antibacterial textile application.

The silica-silver core-shell particles were synthesized by simple one pot chemical method and were employed on the cotton fabric as an antibacterial agent. Extremely small (1-2 nm) silver nanoparticles were attached on silica core particles of average 270 nm size. The optimum density of the nano silver particles was found which was sufficient to show good antibacterial activity as well as the suppression in their surface plasmon resonance responsible for the colour of the core-shell particle for antibacterial textile application. The change in the density and size of the particles in the shell were monitored and confirmed by direct evidence of their transmission electron micrographs and by studying surface plasmon resonance characteristics. The colony counting method of antibacterial activity testing showed excellent results and even the least silver containing core-shell particles showed 100% activity against bacterial concentration of 10(4) colony counting units (cfu). The bonding between core-shell particles and cotton fabric was examined by X-ray photoelectron spectroscopy. The antibacterial activity test confirmed the firm attachment of core-shell particles to the cotton fabric as a result 10 times washed sample was as good antibacterial as that of unwashed sample. The bacterial growth was inhibited on and beneath the coated fabric, at the same time no zone of inhibition which occurs due to the migration of silver ions into the medium was observed indicating immobilization of silver nanoparticles on silica and core-shell particles on fabric by strong bonding.

Enhancement of photoluminescence in manganese-doped ZnS nanoparticles due to a silica shell

Zinc sulphide nanoparticles doped with manganese (ZnS:Mn) have been stabilized using thioglycerol [HSCH2CH(OH)CH2OH] molecules. The nanoparticles (∼1.7 nm) are highly stable and exhibit photoluminescence at ∼600 nm when excited with ultraviolet light. For increasing luminescence and stability the particles are further treated with tetraethylorthosilicate (TEOS)[Si(C2H5O)4] in an aqueous medium, yielding either a disordered silica matrix or spherical core-shell particles of up to ∼900 nm size with strongly enhanced luminescence under certain conditions. Photoluminescence, excitation spectroscopy, transmission electron microscopy, energy dispersive analysis of x-rays, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy measurements have been performed for the characterization of the ZnS:Mn nanoparticles alone, in the silica matrix as well as in spherical silica shells. Among other things, the analysis indicates that the thioglycerol capping has been affected by the coating neither in...

Properties of zinc sulphide nanoparticles stabilized in silica

Zinc sulphide nanoparticles have been synthesized in silica matrix using sol-gel method. It is observed that silica could be loaded with zinc sulphide over a very wide range of concentration without changing the nanoparticle size. A strongly luminescent zinc sulphide-silica composite, thermally stable even upto ∼700°C was thus obtained. Several techniques like UV absorption, photoluminescence, x-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetry and photoelectron spectroscopy have been performed to analyse the ZnS-silica composites.

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 others 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.

Synthesis and characterization of silica-titania core-shell particles

Nearly monodispersed particles of silica were prepared and coated with uniform layers of titanium dioxide in anatase phase by hydrolysis and condensation of titanium butoxide. The coating thickness could be altered by adjusting the concentration of reactants (titanium butoxide and water) and the amount of added silica particles. Different coating thicknesses were deposited and studied using optical absorption spectroscopy, electron microscopy and Fourier transform infra-red spectroscopy. It was found that silica particles of size 170 ±5 nm were coated with 23±5 nm thick layer of titanium dioxide. Alternatively titania particles of size 340±5 nm were synthesized by controlled hydrolysis of titanium ethoxide in the presence of sodium chloride. These particles were further coated with 135±5 nm thick layer of silica to investigate changes in properties after changing the shell material

Synthesis and Characterization of Mercaptoethanol Capped Zinc Oxide Nanoparticles Capped with Organic Molecules

Synthesis of Zinc oxide (ZnO) nanoparticles has been carried out using a chemical route. Stability of the size has been achieved using mercaptoethanol as surface capping molecules. Infra red spectroscopy and x‐ray photoelectron spectroscopy analysis confirm the presence of capping molecules on the ZnO particle surface. Strong green photoluminescence was observed at ∼534 nm from all the nanoparticles.

Synthesis and Investigation of ZnS Nanoparticles Adsorbed On Functionalised Silica Particles

Abstract The synthesis of monodispersed ZnS nanoparticles (~1.2 nm) stabilised with thioglycerol molecules which have been attached to functionalised silica particles is reported. The coupling agent used was 3-aminopropyltrimethoxysilane. The chemical bonding was studied by Fourier transform infrared spectroscopy. TEM of these particles clearly shows a uniform coating of ZnS on silica particles. These SiO2@ZnS core shell particles were also studied using characterisation techniques such as optical absorption spectroscopy, X-ray diffraction and EDAX.