The spindle-like, tubular, and tire-like hematite were successively fabricated by a facile, one-step hydrothermal procedure, which is of great importance in facilitating the controllable-synthesis process of commercial industrialization. A mechanism involving a formation-dissolution process was proposed based on the X-ray diffraction, scanning electron microscopy, trans-mission electron microscopy, and high-resolution transmission electron microscopy analysis. It was demonstrated that the presence of phosphate ions during the reaction process is crucial to the morphology evolution of hematite. Their different ad-sorption ability on the different crystallographic planes of hematite and a coordination effect with ferric ions could promote the preferential dissolution of the spindle-like hematite precursors along the long axis [001] from the tips down to the interior, and thus yield the tubular and tire-like hematite one by one with the increasing reaction time. The magnetic measurements have also been performed to investigate the different magnetic properties such as coercivity and low-temperature transition behavior of three different hematite nanostructures.
采用溶剂热法成功的制备出了不同核壳结构NaYF4基上转换发光材料。利用X射线衍射、透射电子显微镜和荧光光谱等对产物进行表征,探讨反应时间对核壳结构纳米粒子发光强度的影响。结果表明:α-NaYF4@β-NaLuF4:Yb,Er纳米粒子的发光强度随反应时间的增加越来越强,反应时间为24 h时,成功制备出尺寸约为50 nm的核壳纳米粒子,并且随着反应时间延长六方相晶体的衍射峰强度逐渐增高,发光强度逐渐增强。活性壳α-NaYF4:Yb,Er@β-Na Lu F4:Yb纳米粒子的发光强度比惰性壳α-NaYF4:Yb,Er@β-NaLuF4纳米粒子的发光强度高,这得益于活性壳层包含敏化剂Yb3+,敏化剂可以吸收激发能量,并将能量传递给核内的激活剂,从而提高材料的发光强度。
