Ansari Anees A, Parchur A K, Alam M, Labis J, Azzeer Abdallah
King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia,
J Fluoresc. 2014 Jul;24(4):1253-62. doi: 10.1007/s10895-014-1409-9. Epub 2014 May 29.
CaMoO4:Pr(core), CaMoO4:Pr@CaMoO4 (core/shell) and CaMoO4:Pr@CaMoO4@SiO2 (core/shell/shell) nanoparticles were synthesized using polyol method. X-ray diffraction (XRD), thermogravimatric analysis (TGA), UV-vis absorption, optical band gap energy analysis, Fourier transform infrared (FTIR), FT-Raman and photoluminescence (PL) spectroscopy were employed to investigate the structural and optical properties of the synthesized core and core/shell nanoparticles. The results of the XRD indicate that the obtained core, core/shell and core/shell/shell nanoparticles crystallized well at 150 °C in ethylene glycol (EG) under urea hydrolysis. The growth of the CaMoO4 and SiO2 shell (12 nm) around the CaMoO4:Pr core nanoparticles resulted in an increase of the average size of the nanopaticles as well as in a broadening of their size distribution. These nanoparticles can be well-dispersed in distilled water to form clear colloidal solutions. The photoluminescence spectra of core, core/shell and core/shell/shell nanoparticles show the characteristic charge transfer emission band of MoO4 (2-) (533 nm) and Pr(3+) 4f(2) → 4f(2), with multiple strong (3)H4 → (3)P2, (1)D2 → (3)H4 and (3)P0 → (3) F2 transitions located at ~490, 605 and 652 nm, respectively. The emission intensity of the CaMoO4:Pr@CaMoO4 core/shell and CaMoO4:Pr@CaMoO4@SiO2 core/shell/shell nanoparticles increased ~4.5 and 1.7 times,respectively, with respect to those of CaMoO4:Pr core nanoparticles. This indicates that a significant amount of nonradiative centers existing on the surface of CaMoO4:Pr@CaMoO4 core/shell nanoparticles can be eliminated by the shielding effect of CaMoO4 shells.
采用多元醇法合成了CaMoO4:Pr（核）、CaMoO4:Pr@CaMoO4（核/壳）和CaMoO4:Pr@CaMoO4@SiO2（核/壳/壳）纳米颗粒。利用X射线衍射（XRD）、热重分析（TGA）、紫外-可见吸收、光学带隙能量分析、傅里叶变换红外（FTIR）、傅里叶变换拉曼（FT-Raman）和光致发光（PL）光谱研究了合成的核及核/壳纳米颗粒的结构和光学性质。XRD结果表明，在尿素水解条件下，所获得的核、核/壳和核/壳/壳纳米颗粒在乙二醇（EG）中于约150°C时结晶良好。CaMoO4和SiO2壳层（约12 nm）在CaMoO4:Pr核纳米颗粒周围生长，导致纳米颗粒的平均尺寸增加，同时尺寸分布变宽。这些纳米颗粒可以很好地分散在蒸馏水中形成澄清的胶体溶液。核、核/壳和核/壳/壳纳米颗粒的光致发光光谱显示了MoO4(2-)（533 nm）和Pr(3+) 4f(2) → 4f(2)的特征电荷转移发射带，分别在约490、605和652 nm处有多个强的(3)H4 → (3)P2、(1)D2 → (3)H4和(3)P0 → (3)F2跃迁。相对于CaMoO4:Pr核纳米颗粒，CaMoO4:Pr@CaMoO4核/壳和CaMoO4:Pr@CaMoO4@SiO2核/壳/壳纳米颗粒的发射强度分别增加了约4.5倍和1.7倍。这表明CaMoO4壳层的屏蔽效应可以消除CaMoO4:Pr@CaMoO4核/壳纳米颗粒表面存在的大量非辐射中心。
