Metastable γ-Bi2O3 tetrahedra: Phase-transition dominated by polyethylene glycol, photoluminescence and implications for internal structure by etch.

Metastable γ-Bi2O3 tetrahedra have been fabricated by a facile polyethylene glycol-assistance (PEG, Mw=400) one-step precipitation method at 70°C. The tetrahedra of 8μm are built up of ultrathin nanosheets via layer-by-layer self-assembly. X-ray powder diffraction, scanning electron microscopy, UV-visible spectrometer and fluorescence spectrophotometer were employed to characterize the obtained γ-Bi2O3. The morphology of the γ-Bi2O3 is significantly influenced by the feeding concentration of NaOH solution. Tetrahedra and incomplete tetrahedra whose edges are clipped in various degrees of γ-Bi2O3 can be obtained with different concentrations of NaOH solution. The uniform and ordered chains of PEG play a crucial role not only in the morphology, even more important in phase-transition of Bi2O3. The photoluminescence (PL) characteristic of the sample was investigated.