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A physical model for the growth mechanism of amorphous carbon nanotubes (ACNTs) (namely, 'open tips growth and carbon clusters (Cn,n>6) adding') has been proposed in this letter. Based on Tersoff-Brenner [Phys. Rev. B 37, 6991 (1988) and Phys. Rev. B 42, 9458 (1990)] and Lennard-Jones potential energy functions, a mathematic relationship for the growth of ACNTs was established. The predicted diameters of ACNTs from this physical model were in the range of 5-25 nm. The predicted values were in agreement with the experimental measurements in the range of 7-20 nm. [ABSTRACT FROM AUTHOR]

Aluminum hydroxide nanocrystals consisting of an amorphous shell and crystalline core are fabricated by pulsed laser ablation of an aluminum target in water. The colloid consisting of nanocrystals with a uniform size exhibits a size-independent photoluminescence (PL) band at ∼383 nm. According to the PL excitation spectra and time-resolved PL decay analysis, this PL band originates from oxygen vacancies in the amorphous shell and Förster energy transfer occurs between the oxygen vacancy levels in the crystalline core and amorphous shell. These phenomena are found to alter the PL excitation spectra. [ABSTRACT FROM AUTHOR]

The Ge–Ge optical phonon peak at 300 cm-1 acquired from amorphous SiO2 films embedded with Ge nanocrystals by Raman scattering is sensitive to the Si content. When the Si concentration is high, a thin GeSi interfacial layer forms around the Ge nanocrystals. A tensile stress is produced to partially offset the compressive stress imposed by the SiO2 matrix on the Ge nanocrystals, consequently downshifting the frequency of the optical phonon and increasing its linewidth. Theoretical calculation based on phonon confinement and compressive effects discloses that the interfacial layer plays a crucial role in the optical phonon behavior. [ABSTRACT FROM AUTHOR]