Synthesis and characterization of AgBr/SiO2 core/shell nanoparticles

Abstract

In the recent years there is tremendous demand of smaller devices over the bigger one because of its efficiency and portability. The nanoparticles are the building blocks to make the very small devices like small robot, micro-motor, small chips, microprocessor, sensor or carrier for drugs or storage for fuel cell etc. So small is not only beautiful but also powerful.
To improve the property of nanoparticle, composite or core/shell nanoparticles are synthesized. The core-shell nanoparticles are used in the field of biotechnology for drugs carrier, in electronic as semiconductor materials, in fuel-cell and also in chemical reaction. The easy and generalization of methods is required to prepare the core-shell nanoparticles. In this study we prepared core-shell nanoparticles, where AgBr is core and silica as a shell material. For preparation of core-shell nanoparticles, precipitation and the modified Stöber method were adopted. The surfactant is used to modify the surface of core particle so that core-shell nanoparticle will form. Before going to core-shell particles, the individual particles of AgBr and SiO2 were studied. Spherical AgBr nanoparticles were prepared in aqueous media in the absence and presence of surfactant. Smaller particles were obtained in pure aqueous media by increasing the reactant concentration. The coarsening rate constant for the particle formation was found to increase linearly with increasing reactant concentration. The presence of nonionic surfactant generated smaller particles than were obtained in pure aqueous media. The coarsening rate constant in the presence of TX-100 was always lower than that in the presence of pure aqueous media. In pure aqueous media, the temperature effect caused an increase in particle size as the temperature was increased from 20 to 30 °C, after which the change was not significant. In contrast, in the presence of TX-100, the change was not significant in the 20 - 30 °C temperature ranges, but a further increase to 40 °C resulted in a significant change in size. Silica is coated on AgBr nanoparticles by modified Stöber methods. The lowest particles size of the AgBr/SiO2 core-shell was 90±8 nm. The core-shell particle sizes varied from 95 nm to 430 nm. It is found that the bigger particle size found on higher concentration of TEOS. The CTAB surfactant assist-AgBr nanoparticles were isolated in silica shell, indicates CTAB concentration (0.1 mM) were optimal for the formation of monolayered structures on AgBr surfaces. The shell thickness was very thin 5 nm. The AgBr/SiO2 core/shell nanoparticles have been prepared within 100 nm by modified Stöber methods. The spherical composite materials are formed. The shell thickness can be controlled on varying the concentration of precursor’s solution. Silica can be coated on other material by modifying the surface of the core shell materials.