Tm^(3+)掺杂的NaYF_4微米颗粒中强烈的单带下转换荧光发射

Strong Single-Band Down-Conversion Emission in Tm^(3+)-Doped NaYF_4 Microparticles

采用柠檬酸钠辅助的水热方法合成了一系列具有不同长径比的Tm3+掺杂的β-NaYF4(NaYF:Tm3+)微米棒(盘).通过X射线衍射(XRD),扫描电子显微镜(SEM),能量色散X射线荧光光谱(EDX),傅里叶变换红外(FTIR)光谱和激光光谱学等手段对所制备的系列β-NaYF4微米棒(盘)进行了表征.XRD和SEM分析表明β-NaYF4微米棒(盘)的长径比依赖于前驱液的pH值,随着前驱液的pH值的增加,从长棒逐渐过渡到六角盘.光谱测量结果表明:一系列NaYF4:Tm3+微米晶体在656 nm脉冲激光选择激发下,均获得了强烈的单带近红外下转换荧光发射.系统研究了激发波长、环境温度和颗粒长径比对NaYF4:Tm3+微米晶体中单带近红外荧光强度的调控.结果表明:颗粒长径比越大,荧光强度越强.进一步探索了颗粒长径比调控的荧光增强机理,并提出了基于长径比控制的缺陷空位机理.

We synthesized Tm3＋-doped NaYF4 microcrystals with various length-to-diameter ratios by using a facile hydrothermal method assisted with sodium citrate from precursor solutions with various pH values. Theβ-NaYF4：Tm3＋ samples were characterized by using X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy-dispersive X-ray spectroscopy（EDX）, Fourier-transform infrared（FT-IR） spectroscopy, and photoluminescence spectroscopy. XRD and SEM show that as the pH of the precursor solutions increased,the morphology of the microcrystals changed from long rods to short microprisms to microplates. We also investigated the luminescence properties of the β-Na YF4：Tm3＋ hexagonal microdisks and microrods. By selectively exciting the NaYF4：Tm3＋ microcrystals with a 656-nm pulsed laser at a pulse duration of 10 ns, they exhibited a strong single-band down-conversion emission at 800 nm. We systematically studied how the excitation wavelength, temperature, and length-to-diameter ratio of the particles affected the luminescence intensity of their near-infrared（NIR） single-band emission. As the length-to-diameter ratio of the NaYF4：Tm3＋microcrystals increased, their luminescence intensity strengthened. Exploring the reason for this luminescence enhancement, we propose a mechanism based on vacancy defects.