Laser and Spectroscopy Laboratory, Department of Applied Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
Methods Appl Fluoresc. 2017 Dec 18;6(1):015003. doi: 10.1088/2050-6120/aa8c61.
Ho/Yb/Tm/Li:Gd(MoO) nanophosphors successfully synthesised via solid state reaction method have been structurally and optically characterised. Under 980 nm diode laser excitation the nanophosphors emit intense blue, green, red and NIR emissions peaking at ∼476 nm, ∼543 nm, ∼646 nm and ∼798 nm corresponding to the G → H (Tm), F, S → I (Ho), F → I (Ho) and H → H (Tm) transitions respectively. The upconversion emission intensity enhancement in the Ho-Yb-Tm-Li:Gd(MoO) nanophosphors for the green band is found to be ∼367, ∼50 and ∼9 times compared to the singly Ho doped, Ho-Yb co-doped and Ho-Yb-Tm tri-doped Gd(MoO) nanophosphors. The enhancement observed has been explained on the basis of energy transfer process and local field modifications around the rare earth ions. The energy transfer efficiency ∼5% is determined in the tridoped nanophosphors. The interaction involved between rare earth ions for energy transfer process is found to be dipole-dipole type. On changing the Tm ions concentration the colour emitted from the tridoped nanophosphors is tuned from near white to blue region. In the tridoped nanophosphors, on varying the pump power the colour tunability has been observed.
采用固态反应法成功合成了 Ho/Yb/Tm/Li:Gd(MoO) 纳米荧光粉，并对其进行了结构和光学特性的表征。在 980nm 激光二极管激发下，纳米荧光粉发出强烈的蓝色、绿色、红色和近红外发射，分别在 ∼476nm、∼543nm、∼646nm 和 ∼798nm 处出现峰值，对应于 G→H（Tm）、F、S→I（Ho）、F→I（Ho）和 H→H（Tm）跃迁。与单掺 Ho、Ho-Yb 共掺和 Ho-Yb-Tm 三掺 Gd(MoO)纳米荧光粉相比，Ho-Yb-Tm-Li:Gd(MoO)纳米荧光粉的绿光上转换发射强度分别增强了 ∼367、∼50 和 ∼9 倍。观察到的增强是基于稀土离子周围的能量转移过程和局部场修饰来解释的。在三掺杂纳米荧光粉中确定了能量转移效率 ∼5%。发现稀土离子之间的能量转移过程涉及偶极-偶极相互作用。通过改变 Tm 离子浓度，可以调节三掺杂纳米荧光粉发出的颜色从近白色到蓝色区域。在三掺杂纳米荧光粉中，随着泵浦功率的变化，观察到了颜色可调谐性。
