Chan Yoon Jung

One-Step Synthesis of Structurally Controlled Silicate Particles from Sodium Silicates using a Simple Precipitation Process

Silicate particles with various types of internal structures were prepared via one-pot synthesis. Spherical particles with sizes of 50-100 nm could be obtained by a simple precipitation process with the addition of alcohol to an aqueous sodium silicate solution. By controlling the reaction conditions such as the precipitating solvent (different types of alcohols), reaction time, temperature, and addition rate, spherical silicate particles with hollow, porous, dense internal structures were synthesized without using an external template. In addition, the amount of Na in the silicate particles was effectively reduced by washing with hot water, acid, or ion-exchange resins. Spherical particles maintained their morphologies after heat treatment at 500 degrees C. Electron microscopy, N(2) adsorption/desorption measurements, ICP-OES, XRD analysis, and IR and (29)Si NMR spectrometry were performed to elucidate the chemical and physical properties of the obtained silicate particles. This method of synthesis could provide a commercial route to the simple, economical mass production of silica particles.

One-pot synthesis and surface modifications of organically modified silica (ORMOSIL) particles having multiple functional groups

Here we report a facile one-pot synthetic method for organically modified silica (ORMOSIL) particles having multiple functional groups and demonstrate the homogeneous distribution of functional groups in ORMOSIL particles by chemical reactions of each surface functional group with fluorescent dyes such as fluroescamine and rhodamine B isothiocyanate. Dye-tagged ORMOSIL particles having tri-functional groups are exhibited two fluorescent emission peaks at 475 (blue) and 570 nm (red), indicating the positions of functional groups. The surface reaction of these functionalized ORMOSIL particles with various organic or inorganic materials not only endowed additional functionalities and physical properties, but also produced metallic hybrid composite particles. Chemical and physical properties of functionalized ORMOSIL particles were characterized by FT-IR, solid state (13)C and (29)Si NMR, thermogravimetric analysis (TGA), electron microscopy (SEM and TEM), and X-ray diffraction (XRD) analysis.

Selective surface reactions for Janus ORMOSIL particles with multiple functional groups using an ordered monolayer film at liquid-liquid interface.

Monodispersed, submicron-sized Janus ORMOSIL particles with multiple functional groups were prepared by the selective surface reaction of a monolayer film formed at a hexane-water interface. A well-ordered monolayer film was obtained by self-assembly of ORMOSIL particles with multiple functional groups at hexane-water interface. The photopolymerization of an ordered monolayer containing ORMOSIL particles yields a rigid film strong enough to maintain its integrity for transfer and further chemical reaction. The chemical reaction of this ordered film with organic and inorganic functional groups produced Janus ORMOSIL particles with multiple functional groups. The morphologies, structures, and chemical compositions of monolayer films and Janus ORMOSIL particles were characterized by FT-IR, solid state NMR, X-ray diffraction (XRD), optical microscopy (OM), electron microscopies (SEM and TEM), and confocal laser scanning microscopy.