Iodine Ions Mediated Formation of Monomorphic Single-Crystalline
Platinum Nanoflowers
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Abstract
Well-defined and strikingly monomorphic single-crystalline
Pt nanoflowers
were successfully synthesized through the addition of a large amount
of iodine ions into polyol process (5 mM H<sub>2</sub>PtCl<sub>6</sub>, 30 mM KI, and 50 mM PVP in ethylene glycol solution at 160 °C).
The detailed structures of the Pt nanoflowers were studied with high-resolution
TEM, indicating that high-quality production of the Pt nanoflowers
could be obtained when the KI concentration was increased to six times
of H<sub>2</sub>PtCl<sub>6</sub>. The size of Pt nanoflowers could
be tuned by changing the concentration of H<sub>2</sub>PtCl<sub>6</sub> with the constant Pt/I ratio (1:6). The formation process of the
nanoflowers was investigated by the UV–vis and EXAFS spectroscopic
studies, demonstrating that the iodine ions played a key role in inducing
the formation of the single-crystalline Pt nanoflowers. After the
addition of iodine ions into the polyol synthesis, the Pt–I
complex was formed and reduced by different kinetics compared with
that of H<sub>2</sub>PtCl<sub>6</sub> to induce the overgrowth of
Pt nanocrystals. Additionally, a small portion of iodine element was
found to be strongly adsorbed on the surfaces of Pt nanoflowers, which
probably also favored the anisotropic overgrowth of Pt nanocrystals
resulting in the single-crystalline Pt nanoflowers. A comprehensive
set of systematic studies on the synthesis factors (the concentrations
of Pt precursor, iodine ions and PVP, reaction temperature, different
kinds of Pt precursors and reaction atmosphere) was also reported
