Preparation, purification, and characterization of aminopropyl-functionalized silica sol

Abstract

A new, simple and "green" method was developed for the surface modification of 20 nm diameter Stöber silica particles with 3-aminopropyl(diethoxy)methylsilane in ethanol. The bulk polycondensation of the reagent was inhibited and the stability of the sol preserved by adding a small amount of glacial acetic acid after appropriate reaction time. Centrifugation, ultrafiltration and dialysis were compared in order to choose a convenient purification technique that allows the separation of unreacted silylating agent from the nanoparticles without destabilizing the sol. The exchange of the solvent to acidic water during the purification yielded a stable colloid, as well. Structural and morphological analysis of the obtained aminopropyl silica was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared (FTIR), 13 C and 29 Si MAS nuclear magnetic resonance (NMR) spectroscopies, as well as small angle X-ray scattering (SAXS). Our investigations revealed that the silica nanoparticle surfaces were partially covered with aminopropyl groups, and multilayer adsorption followed by polycondensation of the silylating reagent was successfully avoided. The resulting stable aminopropyl silica sol (ethanolic or aqueous) is suitable for biomedical uses due to its purity.

Hollow organosilica beads as reference particles for optical detection of extracellular vesicles

“…The colloidal stability of the HOBs, which describes the aggregation properties of the beads, was evaluated by zeta potential measurements. We found highly negative zeta potentials (− 56.6 mV for HOB200 and − 58.1 mV for HOB400), which we associated with the dissociation of surface silanol groups . The highly negative zeta potentials suggest that HOBs have excellent colloidal stability in water at pH 7.4.…”

Direct Immobilization of Gadolinium Complex on Silica Particles and Their MRI Properties

“…ζ-potentials of the SiO 2 particles were negative in a range of pH examined, that is, the ζ-potential did not become positive even at the low pHs, though an absolute value of the ζ-potential was lowered with a decrease in pH. SiO 2 particles show such tendency of ζ-potential for pH [16,17]. Since the ζ-potential approached to zero at pH below 2.0, the obtained SiO 2 particles had an iso-electric point in a range of 1.5-2.…”

High-concentration Photochemical Upconverters

“…Silica nanoparticles (NPs) were prepared, functionalized with amino-propyl groups and purified according to literature procedures [7]. Tetraphenyl carboxylic acid palladium (II) porphyrin was then loaded onto the particles by adding a stock solution of porphyrin in DMF to the silica NP-NH 2 sol.…”