Dimitri Golberg

Self-catalyst growth and optical properties of novel SnO2 fishbone-like nanoribbons

Self-catalyst growth of novel SnO2 fishbone-like nanoribbons has been achieved, for the first time, via a thermal oxidation of elemental Sn powder using Fe3(NO3)3 as oxidizing agent at 1100 °C. X-ray powder diffraction and Raman scattering reveals that as-grown product has the phase structure of the rutile form of SnO2. Scanning electron microscopy shows that the synthesized product displays interesting fishbone-like ribbon morphology, in which numerous secondary and sub-secondary branches are grown at right angles on the main stems. Transmission electron microscopy indicates that the main stem of the ribbons grows along the [1 1 0] crystal direction, while the branches grow along [-1 1 0] (or [-1 1 0]) crystal direction. A room temperature photoluminescence spectrum of the present SnO2 ribbons shows a strong green emission at ∼500 nm. Possible growth mechanism of these ribbons was briefly discussed.

MoO3-promoted synthesis of multi-walled BN nanotubes from C nanotube templates

Abstract Large-scale synthesis of BN multi-walled nanotube (MWNT) ropes from C MWNT templates was carried out. A mixture of B 2 O 3 and MoO 3 was used as an oxidizing agent during a chemical reaction involving C MWNT oxidation in a flowing nitrogen atmosphere at 1773 K. Encapsulation of Mo-based clusters into the BN MWNTs was simultaneously achieved. The morphology, atomic structure and chemical composition of MWNTs synthesized at 1773 K with and without MoO 3 promoter were compared by means of high-resolution transmission electron microscopy and electron energy loss spectroscopy. A striking increase in BN MWNT yield and self-assemblage of tubes into ropes were discovered under MoO 3 -promoted synthesis.

Nanophotonic switch: gold-in-Ga2O3 peapod nanowires.

A novel metal-insulator heterostructure made of twinned Ga2O3 nanowires embedding discrete gold particles along the twin boundary was formed through a reaction between gold, gallium, and silica at 800 degrees C during simple thermal annealing. The Au-in-Ga2O3 peapods spontaneously crystallized under phase separation induced by the formation of twin boundaries. The nanostructures were analyzed by field emission scanning (FESEM) and transmission electron microscopes (FETEM), and their photoresponse was investigated using a double-frequency Nd:YAG laser with a wavelength of 532 nm on a designed single-nanowire device. The surface plasmon resonance (SPR) effects of embedded Au nanoparticles are proposed to be responsible for the remarkable photoresponse of these novel structures.

Mg2Zn11–MgO belt-like nanocables

A simple CVD process was developed to synthesize Mg2 Zn11-MgO core-shell nanocables. Typically, the nanocables had square-like cross-sections and were 30-150 nm wide, while the Mg2Zn11 cores were only several nanometers in widths. The MgO sheath had single-crystalline cubic structure and stretched along the [1 0 0] direction. The longitudinal directions of single-crystalline cores were in the [3 1 2] direction of cubic Mg2Zn11. The formation of nanocables is discussed.