Synthesis and characterization of germanium/Si-alkyl and germanium/silica core-shell quantum dots

Chung Sung Yang, Susan M. Kauzlarich, Y. C. Wang

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Abstract

Ge/Si-R and Ge/SiO2 core-shell nanoparticles have been synthesized by a solution route from the stepwise reactions of the Zintl salt, Mg2Ge, with SiCl4 and subsequently either RLi (R = butyl) or H2O2. High-resolution transmission electron microscopy (HRTEM) images show that the core part of these Ge/Si-R and Ge/SiO2 nanoparticles is crystalline and the d spacing of lattice fringes agrees with the {111} crystal plane (3.27 Å) of Ge. The average sizes (diameter) are 5.8(2.3) and 6.8(2.8) nm for Ge/Si-R and Ge/SiO2, respectively. Fourier transform-infrared (FTIR) spectra are consistent with alkyl groups bonded to the silicon surface in Ge/Si-R nanoclusters. Off-axis holography was performed for several Ge/SiO2 nanoparticles. The characterization of the ratio of radii and geometry between the core part and the outer sphere of Ge/SiO2 is presented. The reconstructed phase image from the hologram offers detailed information concerning the ratio of the shell thickness (R - r) to the radius of the core (r), Rr = (R - r)/r, by measuring the phase shift and the resultant phase contrast. The Rr value from the deconvoluted phase image of a 16 nm spherelike Ge/SiO2 is 0.264 (0.065). Photoluminescence (PL) spectra of both Ge/Si-R and Ge/SiO2 nanoclusters show a strong UV-blue PL with a peak centered between 400 and 410 nm. These results suggest that the UV-blue PL may be attributed to the core part of these nanoparticles.

Original languageEnglish (US)
Pages (from-to)3666-3670
Number of pages5
JournalChemistry of Materials
Volume11
Issue number12
Publication statusPublished - 1999

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ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

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