镱铥共掺杂的氟化镧纳米粒子的亮蓝色上转换发光(英文)

Bright Blue Upconversion Emission of LaF_3∶Yb^(3+),Tm^(3+) Nanoparticles

采用反胶束法合成镱铥共掺杂的氟化镧纳米粒子。这种反胶束是由微乳液作为合成媒介,这些分散的纳米粒子在化学成分、尺寸分布上是可控的。产物形貌经场发射扫描电镜和透射电镜表征。固态样品分散在乙醇中,在未经超声处理时,样品表现为玉米棒样的聚集。棒的平均直径和长度分别为110,575 nm。我们认为这种大量纳米粒子聚集成良好超结构是由于溶剂挥发,分子交叉链接或者表面活性剂分子附着于纳米粒子特殊晶面造成的。当样品经过超声处理后,由于超声振动破坏了上述因素,玉米棒形貌的聚集体转为大量纳米粒子。单个粒子的高分辨电镜显示出该纳米粒子的单晶结构。并且晶面间距约为0.366 nm,与纯氟化镧六角相[002]晶面相一致。样品在300℃退火30 min后的透射电镜照片显示纳米粒子的平均直径大约为35 nm,这与XRD结果相吻合。并且,这些纳米粒子表现出了良好的单分散性,并且在978 nm二极管激发下,纳米粒子呈现出亮蓝色上转换发光,这种上转换荧光粉在光电子或生物检测中有潜在的应用前景。

In this paper, discrete Yb^3＋ -Tm^3＋ co-doped LaF3 nanoparticles with controlled chemical composition and size distribution were readily synthesized using reverse mieelles with microemulsions as confined reaction media. The morphology of the final product was characterized by the FESEM and HRTEM images. When the solid sample disperses in the ethanol without ultrasonic treatment, it is maize cob-like aggregator. The average diameter and length of the maize cob are about 110 and 575 nm, respectively. We suggested that the nanoparticles assemble into well- defined superstructures arising from the solvent evaporation, molecular cross-linking or interaction from surfactant molecules attached to specific nanoparticles crystal faces. After ultrasonic treatment for 30 min, the maize cob-like aggregator turns into a lot of nanoparticles owing to ultrasonic breach above a series of factors. The HRTEM image taken from individual nanoparticles indicates the crystalline nature, and the interplanar spacing of - 0.366 nm corresponding to the [002 ] planes of pure hexagonal phase LaF3. The TEM image of the samples annealed at 300℃ for 30 minutes displays the average diameter of NCs increased to about 35 nm and is in good agreement with XRD result. In addition, the NCs exhibit nearly monodisperse property, which is in favor of optimizing luminescence of the sam- ple. The nanoparticles present a bright blue upconversion luminescence under the 978 nm excitation from a laser diode, which provides a promising upconversion phosphor for optoelectronic or biological applications.