一维四棱柱状Bi纳米棒的微乳法合成及光性能

Bismuth oxide is an important functional material, and its controllable preparation has always been a hot spot for research. One dimensional quadrangular prism Bi₂O₃ nanorods were controllably synthesized successfully by a reverse microemulsion route with Triton X-100/n-heptane/n-amyl alcohol/water as microemulsion system. X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) were employed to characterize the obtained Bi₂O₃ products. The results showed that with the increase of calcination temperature, tetragonal β-Bi₂O₃ transformed into monoclinic α-Bi₂O₃. The as-prepared one dimensional quadrangular prism nanorods were 50~100 nm in diameter and 300~600 nm in length. Formation mechanism analysis of the precursor showed that oriented attachment, self-organization and Ostwald ripening played important roles in the formation of the microstructure. Ultraviolet-visible diffuse reflectance spectrum showed that the metastable β-Bi₂O₃ sample presented photoabsorption property from UV light region to visible light range (absorption band edge was 550 nm, longer than that of stable α-Bi₂O₃ of 460 nm), belonging to the absorption caused by electron transition from valence band to conduction band, which was Bi₂O₃ direct band gap absorption. The band gap of the β-Bi₂O₃ was estimated to be 2.30 eV, which was lower than that of α-Bi₂O₃ of 2.74 eV. The fluorescence spectrum of quadrangular prism β-Bi₂O₃ nanorods showed broad emission (400~600 nm) with a strong blue emission peak at ~466 nm due to Bi³⁺ luminescence from the ³P₁ excited states to the ¹S₀ ground state. The green peak at ~562 nm was from an impurity trap associated with oxygen vacancies interacting with interfacial bismuth vacancies.