Nonporous Silica Nanoparticles for Nanomedicine Application

Synthesis and surface functionalization of silica nanoparticles for nanomedicine.

The influence of the small ionic surfactant sodium dodecyl sulfate (SDS) on the evaporation of drying colloidal droplets is quantitatively investigated. The addition of SDS leads to a significantly more uniform deposition of colloidal particles after evaporation (i.e., the so-called “coffee-ring effect” is dramatically altered). We understand this phenomenon in the context of circulating radial Marangoni flows induced by the variation of SDS concentration along the air–water interface. Video microscopy permits the direct visualization of the colloidal particles involved in these flows, revealing a surprisingly stable “Marangoni eddy” that prevents particle deposition at the drop perimeter.

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Surfactant-Induced Marangoni Eddies Alter the Coffee-Rings of Evaporating Colloidal Drops

Nucleation seeding is a new approach to control the kinetics of cement hydration. It is known that nano-silica has an accelerating effect on cement hydration. It is assumed that the surface of these particles act as a nucleation site for C–S–H-seeds which then accelerate the cement hydration. In this case the acceleration should depend on the particles surface area. To verify this, nano-silica particles of different sizes and specific surface areas were synthesised. The acceleration of cement hydration clearly correlates with the total surface size of the added particles, which was varied by either using smaller particles or higher concentration of particles in the cement lime. Additional in situ-XRD experiments show that the consumption of C3S and the formation of portlandite are accelerated by the addition of nano-silica. In both cases the surface size is the major factor for the hydration kinetics.

The influence of nano-silica on the hydration of ordinary Portland cement

Sol-Gel processing of silica nanoparticles and their applications.

Control over the synthesis of monodisperse silica particles up to mesoscopic scale is generally made difficult due to intrinsic limitation to submicrometric dimensions and secondary nucleation in seeded experiments. To investigate this issue and overcome these difficulties, we have implemented single step processing by quantifying the effects of the progressive addition of a diluted tetraethyl orthosilicate solution in ethanol on the size and monodispersity of silica particles. Contrary to particles grown in seeded polymerization, monodisperse particles with size up to 2 μm were synthesized. Moreover, the particles exhibit a final diameter (df), which varies with V-1/3 over more than 2 orders of magnitude in rate of addition (V). On the basis of a kinetic study in the presence of addition showing that particle growth is limited by the diffusion of monomer species, we developed a diffusion-limited growth model to theoretically explain the observed df(V) behavior and quantitatively retrieve the measured amp...

Nozawa K

Papers

Smart Control of Monodisperse Stöber Silica Particles: Effect of Reactant Addition Rate on Growth Process