CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

obtained after 275 nm excitation is shown as an inset in Fig.72. Weak emission has been
attributed to the enhanced non-radiative decay of Ce 3+ ions in the present host.
Intensity (arb.units)
3000
2500
2000
1500
1000
500
Intensity
60
30
300
*
Tb 3+ Ce 3+
150
0
400 500 600
Wavelength (nm)
5
D 4
7 F 6
5 D 7 4
F 5 0
320 340 360
(c) Wavelength (nm)
(b)
(a)
5
D 4 7 F 4
5 D 4 7 F 3
0
450 500 550 600 650
Wavelength (nm)
Fig.72. Emission spectrum from nanoribbons/ nanoparticle of (a) SbPO 4 :Tb 3+ (5%), (b)
3+ 3+ 3+ 3+
SbPO4: Ce (2.5%), Tb (5%), and (c) SbPO 4 : Ce (2.5%),Tb (5%) dispersed in
silica. Samples were excited at 250 nm. Inset at the left side shows the emission
spectrum of TbPO 4 samples prepared by the identical method as that adopted for
other samples and the inset at the right side shows the Ce 3+ emission from SbPO 4 :
Ce 3+ (2.5%),Tb 3+ (5%) sample obtained after 278 nm excitation. The peak marked
“*” in the left inset is an artifact.
Intensity
Since the samples are powder in nature, it is not very accurate to compare the peak
intensities of the emission spectra, while comparing their luminescence properties. Instead,
the lifetime of the 5 D 4 level of Tb 3+ in these samples can be compared for judging their
luminescent efficiencies. The decay curve corresponding to the 5 D level of Tb 3+
4 obtained
after exciting the samples at ~ 250 nm (4f→5d transition of Tb 3+ ) and monitoring the
emission at ~ 544 nm ( 5 D 4 → 7 F 5 transition of Tb
3+ ) for these samples are shown in Fig.73.
The decay curves are found to be bi-exponential in nature for both SbPO :Tb 3+
4 (5 at %) and
3+
SbPO4:Ce (2.5%),Tb 3+ (5%) nanoribbons/ nanoparticles, and single exponential in nature for
3+
SbPO4:Ce (2.5%),Tb 3+ (5%) nanoribbons/ nanoparticles incorporated in silica. The measured
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