Synthesis of Silica Nanoparticles Covered with Silver Beads

Abstract

Procedures for producing silica nanoparticles suitable for further amino functionalization and subsequent decoration with silica beads were investigated in a comparative way. Several methods, one based on tetrapropylammonium hydroxide, the classical Stöber synthesis, and two with amino acids (either lysine or arginine) as catalysts were employed and followed by means of DLS, SAXS, and TEM. The amino acid methods proved to be by far the most satisfactory ones, yielding highly spherical and monodisperse nanoparticles with a tunable size range of 15-100 nm. The surface of the particles could be functionalized with propylamine, which enabled to obtain positive surface charge at low pH and to tune the zeta potential by the pH in the range of +/- 40 mV. Finally, the modified particles were used to reduce silver (I) ions at high pH, leading to the formation of very small silver beads covering the silica surface and yielding a nanocomposite with a "raspberry" structure. Interestingly, this could be achieved without using any complementary reducing agent besides the particles themselves, thereby opening a very simple path to the formation of composite metal containing colloidal systems.

Noble metal/silica “raspberry” type hybrids: Synthesis and functionalization

“…S2. The same result was detected in all the cases and similar metal decorated SiO 2 NPs have been observed before [6,36,37] but not so far for Ru NPs. Although there are some Ru NPs seen in the TEM that are not adsorbed on the SiO 2 particles (which could also be an artefact of the preparation, for instance due to shear forces).…”

“…This architecture can be accomplished by decorating a larger NP with patches or smaller NPs of a second type. This may lead to a "raspberry-like" structure, such cases have been observed involving SiO 2 NPs for polymethylmethacrylate (PMMA)@SiO 2 [4], polystyrene (PS)@SiO 2 [5], Ag@SiO 2 [6], or SiO 2 NPs of different size [7]. Such nanocomposites have been used for applications in catalysis [1,8] or sensing [9].…”

Preparation of Polymer Brush Grafted Anionic or Cationic Silica Nanoparticles: Systematic Variation of the Polymer Shell

“…Silica nanoparticles (SiO 2 -NPs) were synthesized with a modified Stoeber method with TEOS as precursor but using l -lysine as catalyst, where the size and polydispersity can be well controlled and tuned by the reaction time, temperature, and stirring speed. , Here we synthesized three NPs with diameters of 50, 70, and 140 nm. Successful amino functionalization was achieved with APTS in water . The amino group was then reacted with BIBB to place the initiator group on the surface.…”

Size and Cell Type Dependent Uptake of Silica Nanoparticles

“…The 60 and 200 nm SiO 2 NP were synthesized as published [52], while 15 nm particles were from a commercial source (Ludox SM, obtained as a 30% wt. suspension in H 2 O, Sigma-Aldrich, Taufkirchen, Germany).…”

“…Primary sizes and morphology of SiO 2 NP were measured by transmission electron microscope (TEM,Tecnai G 2 20 S-TWIN, FEI, Oregon, USA) as published elsewhere [52]. The hydrodynamic diameters of SiO 2 NP were examined by dynamic light scattering (DLS) (Zetasizer Nano ZS, Malvern, Herrenberg, Germany) at room temperature.…”