反应温度对Na_(3)ScF_(6)∶Yb/Er纳米晶的发光和形貌的影响

Effect of Reaction Temperature on the Luminescence and Morphology of Na_(3)ScF_(6)∶Yb/Er Nanocrystals

稀土离子掺杂上转换发光材料(UCNP)在太阳能电池、固体激光、彩色显示、生物成像等领域有着巨大的应用潜力,因而受到广泛的关注。在稀土元素中,钪(Sc)元素既处于第三主族的顶端,又处于过渡元素开始的地方,且具有最小的离子半径,因而具有异于Y,Gd和Lu基材料的物理、化学性质。Na_(3)ScF_(6)化学性质稳定,声子能量低,是一种新型高效的基质材料,但是目前对其研究依然较少。基于此,采用熔剂热方法,以油酸(OA)和十八烯(ODE)作为溶剂,保持OA∶ODE=10 mL∶10 mL和NaF∶Ln^(3+)=4∶1不变,调节反应温度为260,280和300℃时合成了一系列的单斜相Na_(3)ScF_(6)∶Yb/Er纳米晶。研究结果表明:在合成温度为260℃时,样品为单斜相的Na_(3)ScF_(6)∶Yb/Er(PDF No.47-1221)纳米晶,粒径在20 nm左右;反应温度为300℃时,样品为单斜相的Na_(3)ScF_(6)∶Yb/Er(PDF No.20-1221)纳米晶,粒径在18 nm左右,结晶度高,分散性好。在280℃时为单斜相的PDF No.47-1221和PDF No.20-1221二者的混合相,样品形貌均一,分散性好,粒径在30 nm左右。在980 nm激光的激发下,随着反应温度从260℃升高到300℃,样品上转换发光颜色从红光转化为绿色光,发射光强显著增加,约为原来的3.1倍。随后,在反应温度为300℃时,讨论了样品形貌随时间的演化。仅通过调节反应温度,即实现了Na_(3)ScF_(6)∶Yb/Er纳米晶上转换发光颜色的可控输出,这不仅提供了一种红绿光的调节方法,而且补充了钪基氟化物的研究,拓宽了钪基纳米材料的应用范围。

At present,rare-earth ion-doped up-conversion luminescent materials(UCNP)have attracted widespread attention due to their massive potential of practical application in various fields like color display,biological imaging,solar cells,photodynamic therapy,solid-state lasers and more.Among various rare earth elements,Sc is situated at the top of the third main group and at the beginning of the transition element.With the minimum ionic radius,it demonstrates different physical and chemical properties to Y,Gd,and Lu-based materials.Although Na_(3)ScF_(6)is regarded as a new and efficient host material for its consistent chemical properties and low phonon energy,there are still few studies focusing on it.Allowing for this,the solvothermal method was adopted in this study,with oleic acid(OA)and octadecene(ODE)as complexing agents.On the basis of OA∶ODE=10 mL∶10 mL and NaF∶Ln^(3+)=4∶1,a series of monoclinic Na_(3)ScF_(6)∶Yb/Er nanocrystals were synthesized at the temperature of 260,280,and 300℃,respectively.The phase,microstructure and upconversion luminescence properties of the samples were characterized by X-ray diffractometer,transmission electron microscope and fluorescence spectrometer,respectively.Research indicates:when the reaction temperature reached 260℃,the sample was monoclinic Na_(3)ScF_(6)∶Yb/Er(PDF No.47-1221)nanospheres with a particle size of about 20 nm;when the reaction temperature reached 300℃,the sample was monoclinic phase Na_(3)ScF_(6)∶Yb/Er(PDF No.20-1221)nanocrystals with a size of about 18 nm,exhibiting high crystallinity and excellent dispersion.Having a mixed phase of PDF No.47-1221 and PDF No.20-1221 at 280℃,the sample demonstrated uniform morphology and excellent dispersion,with a particle size of about 30 nm.Under the excitation of a 980 nm laser,the upconverted luminescence color of the sample shifted from red light to green light when the reaction temperature was raised from 260 to 300℃,while the luminous intensity showed a significant increase to about 3.1 times the original level.Moreover,a discussion was conducted about the evolution of the sample morphology with time at 300℃.This work achieves a controllable output of Na_(3)ScF_(6)∶Yb/Er nanocrystal upconversion luminescence color only by adjusting the reaction temperature,which not only provides a simple method for the regulation of red and green light,but also complements scandium-based fluoride and broadened the application scope of scandium-based nanomaterials.