Formation of nanostructured metallic glass thin films upon sputtering.

Morphology evolution of the multicomponent metallic glass film obtained by radio frequency (RF) magnetron sputtering was investigated in the present work. Two modes of metallic glass sputtering were distinguished: smooth film mode and clustered film mode. The sputtering parameters, which have the most influence on the sputtering modes, were determined. As a result, amorphous Ni-Nb thin films with a smooth surface and nanoglassy structure were deposited on silica float glass and Si substrates. The phase composition of the target appeared to have a significant influence on the chemical composition of the deposited amorphous thin film. The differences in charge transport and nanomechanical properties between the smooth and nanoglassy Ni-Nb film were also determined.

Self-organized patterning through the dynamic segregation of DNA and silica nanoparticles.

Exotic pattern formation as a result of drying of an aqueous solution containing DNA and silica nanoparticles is reported. The pattern due to segregation was found to critically depend on the relative ratio of nanoparticles and DNA, as revealed by polarization microscopy, scanning electron microscopy, and fluorescence microscopy. The blurred radial pattern that is usually observed in the drying of a colloidal solution was shown to be vividly sharpened in the presence of DNA. Uniquely curved, crescent-shaped micrometer-scale domains are generated in regions that are rich in nanoparticles. The characteristic segregated patterns observed in the present study are interpreted in terms of a large aspect ratio between the persistence length (∼ 50 nm) and the diameter (∼ 2 nm) of double-stranded DNA, and the relatively small silica nanoparticles (radius: 5 nm).

Synthesis of silica nanoparticles covered with silver beads.

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.