Size and bandgap control in the solution-phase synthesis of near-infrared-emitting germanium nanocrystals.

Ruddy, Daniel A; Johnson, Justin C; Smith, E Ryan; Neale, Nathan R · ACS Nano · 2010

basic_science · Level V

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Abstract

We present a novel colloidal synthesis of alkyl-terminated Ge nanocrystals based on the reduction of GeI(4)/GeI(2) mixtures. The size of the nanocrystals (2.3-11.3 nm) was controlled by adjusting both the Ge(IV)/Ge(II) ratio and the temperature ramp rate following reductant injection. The near-infrared absorption (1.6-0.70 eV) and corresponding band-edge emission demonstrate the highly tunable quantum confinement effects in Ge nanocrystals prepared using this mixed-valence precursor method. A mechanism is proposed for the observed size control, which relies upon the difference in reduction temperatures for Ge(II) versus Ge(IV).

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