CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

measurements, it is confirmed that increase in particle size and associated decrease in the
concentration of surface quenching sites are responsible for the improved emission from the
nanoparticles heated at high temperatures. In continuation of this work, detailed studies were
carried out on lanthanide doped CaWO 4 nanoparticles and their luminescence properties are
described below.
6.7. Luminescence studies on Tb 3+ doped CaWO 4 nanoparticles: Emission spectrum from
as prepared 2 at% Tb 3+ doped CaWO 4 nanoparticles excited at 253 nm is shown in Fig.112
(a). The spectrum consists of four sharp peaks at 490, 545, 590 and 621 nm and are attributed
to the 5 D 4 Æ 7 F 6 , 5 D 4 Æ 7 F 5 , 5 D 4 Æ 7 F 4 and 5 D 4 Æ 7 F 3 transitions, respectively of Tb 3+ ions
present in the CaWO 4 lattice.
Intensity (arb.units)
20000
15000
10000
5000
λ exc
= 253 nm
7
F6
5
D4
5 D 4
7 F 5
0
400 500 600 700
Wavelength (nm)
(a)
7
F4
5
D4
7
F3
5
D4
(b)
16000
λ exc
= 253 nm & λ em
= 545 nm
Intensity (arb.units)
12000
8000
4000
0
λ em
= 545 nm
200 250 300 350 400
Wavelength (nm)
Intensity (arb.units)
1000
100
10
0 2 4 6 8 10
Time (ms)
(c)
(d)
Fig.112. Emission spectra (a) and photograph of emission (b) obtained after excitation at 253
nm from CaWO 3 :Tb 3+ nanoparticles. The corresponding excitation spectrum and
decay curve monitored at 545 nm emission are shown in Fig.112 (c and d),
respectively.
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