A novel synthetic technique for gold nanosheets and hollow gold nanocapsules is developed. When aqueous HAuCl4 (pH 10, 1 mL) layered on C4mimPF6 (1-butyl-3-methylimidazolium hexafluorophosphate, 1 mL) was illuminated vertically with a super high pressure mercury lamp, gold nanosheets with thickness of ca. 30 nm are formed. The gold nanosheets are face-centered cubic (fee) single crystals with an atomically flat (111) surface as determined by electron diffraction analysis. Photoreduction of Au(III) ions did not proceed when aqueous HAuCl4 solution (pH 10) was photoirradiated in the absence of ionic liquid. Therefore, photoreduction occurs at the ionic liquid/water interface, and photo-excited C 4mimPF6 molecules may act as sacrificial electron donors to reduce Au(OH)4- ions. We also conducted the photoreduction by using microdroplets of C4mimPF6 in water. Ultrathin gold nanosheets with thickness of ca. 10 nm are obtained by photoilluminating mixture of C4mimPF6 (1 mL) and aqueous HAuCl4 (pH 10, 1 mL) under vigorous stirring. To our surprise, in the TEM observation of ultrathin gold nanosheets, moiré fringes are observed for overlapped portions. The observation confirms that the ultrathin gold nanosheets are single crystalline with homogeneous thickness. On the other hand, when a mixture of C4mimPF6 (1.8 mL) and aqueous HAuCl4 (pH 10, 0.2 mL) was illuminated under vigorously stirring, hollow gold microspheres with diameter less than 3 μm are obtained. In this case, water microdroplets in C4mimPF6 seem to act as template for the formation of hollow gold spheres.
|Number of pages||2|
|Publication status||Published - Dec 1 2005|
|Event||54th SPSJ Symposium on Macromolecules - Yamagata, Japan|
Duration: Sep 20 2005 → Sep 22 2005
|Other||54th SPSJ Symposium on Macromolecules|
|Period||9/20/05 → 9/22/05|
All Science Journal Classification (ASJC) codes