Influence of Surface Coating on Structural and Photoluminescent Properties of CaMoO4:Pr Nanoparticles

• Published in: Journal of fluorescence Vol. 24; no. 4; pp. 1253 - 1262
• Main Authors: Ansari, Anees A., Parchur, A. K., Alam, M., Labis, J., Azzeer, Abdallah
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-07-2014
• Subjects: Analytical Chemistry; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biomedicine; Biophysics; Biotechnology; Original Paper; Band gap energy; Absorption spectra; Photoluminescence; Calcium molybdate nanoparticles
• ISSN: 1053-0509; 1573-4994
• DOI: 10.1007/s10895-014-1409-9

CaMoO
4
:Pr(core), CaMoO
4
:Pr@CaMoO
4
(core/shell) and CaMoO
4
:Pr@CaMoO
4
@SiO
2
(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 CaMoO
4
and SiO
2
shell (~12 nm) around the CaMoO
4
: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 MoO
4
2−
(533 nm) and Pr
3+
4f
2
 → 4f
2
, with multiple strong
3
H
4
 → 
3
P
2
,
1
D
2
 → 
3
H
4
and
3
P
0
 → 
3
 F
2
transitions located at ~490, 605 and 652 nm, respectively. The emission intensity of the CaMoO
4
:Pr@CaMoO
4
core/shell and CaMoO
4
:Pr@CaMoO
4
@SiO
2
core/shell/shell nanoparticles increased ~4.5 and 1.7 times,respectively, with respect to those of CaMoO
4
:Pr core nanoparticles. This indicates that a significant amount of nonradiative centers existing on the surface of CaMoO
4
:Pr@CaMoO
4
core/shell nanoparticles can be eliminated by the shielding effect of CaMoO
4
shells.