一维四棱柱状Bi2O3纳米棒的微乳法合成及光性能

Synthesis of One Dimensional Quadrangular Prism Bi2O3 Nanorods by Reverse Microemulsion and Optical Properties

纳米氧化铋是一种重要的功能材料,其可控制备一直是研究的热点。以TritonX-100/正庚烷/正戊醇/水为微乳液体系,采用反相微乳法合成了一维四棱柱状Bi2O3纳米棒。采用X射线衍射（XRD）和扫描电镜（SEM）表征了煅烧温度和煅烧时间对Bi2O3样品晶型和微观形貌的影响。表征结果表明,随煅烧温度增加,产物由四方相β-Bi2O3向单斜相α-Bi2O3转变,样品为一维四棱柱状纳米棒,其直径为50～100 nm,长为300～600 nm。对前驱体的形成机制进行分析发现,定向附着、自组织和奥斯瓦尔德熟化在微乳体系合成纳米材料的过程中起到了重要作用。紫外-可见光谱（UV-Vis）分析表明,亚稳相β-Bi2O3（550 nm）相比稳定相α-Bi2O3（460 nm）具有更宽的可见光响应范围和更窄的禁带宽度（分别为2.30和2.74 eV）,属于电子从价带跃迁到导带引起的吸收,为Bi2O3的直接带隙吸收。荧光光谱（PL）表明β-Bi2O3在400～600nm具有宽的发射谱带,466 nm处的强蓝带发射归属于Bi3＋的3P1→1S0跃迁和O2-→Bi^3＋荷移跃迁,562 nm处绿峰归属于晶体表面氧空位和生长过程中形成的缺陷。

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 TritonX-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.