CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

the other hand the Eu 3+ lifetime has been found to increase after co-doping with Tb 3+ ions.
The lifetime values are given in the Table 11. The increase in lifetime corresponding to 5 D 0
level of Eu 3+ and decrease in lifetime corresponding to 5 D level of Tb 3+
4 in co-doped samples
compared to singly doped samples further confirms the energy transfer from Tb 3+ ions to
Eu 3+ ions.
Intensity (arb.unts)
400
300
200
100
0
λ exc
= 255 nm
5% Tb, 5% Eu
5% Tb
Intensity (arb.units)
8000
6000
4000
2000
500 550 600 650 700 750
200 250 300 350 400
Wavelength (nm)
Wavelength (nm)
(a)
(b)
1
λ exc
=255 nm, λ em
= 543em
Normalised intensity
0.1
0.01
0
5% Tb
5% Tb, 5% Eu
5% Tb, λ em
= 545 nm
5% Tb, 5% Eu, λ em
= 615 nm
1E-3
0 2 4 6 8 10
Time (ms)
(c)
Fig.87. (a) Emission spectra from BiPO 4 :Tb 3+ (5 at%) and BiPO 4 :Eu 3+ (5 at%),Tb 3+ (5 at%)
nanomaterials after excitation at 255 nm. The corresponding excitation spectrum is
shown in Fig.87 (b). Decay curve corresponding to 5 D 4 level of Tb 3+ from these
samples are shown in Fig 87 (c).
3+ 3+
Table 11. Lifetime values of excited states of Tb and Eu ions in BiPO 4 nanorods.
sample Lifetime of τ 1 (ms) τ 2 (ms)
3+
BiPO 4:5% Eu
5 3+
D 0 level of Eu 0.34 (30 %) 1.72 (70 %)
3+
BiPO 4 :5% Tb
5
D 4 level of Tb 3+ 0.36 (15 %) 2.44 (85 %)
BiPO 4 :5%Eu 3+ , 5% Tb 3+ 5 D 4 level of Tb 3+ 0.19 (27%) 1.77 (73%)
5 D 0 level of Eu 3+ 0.66 (14 %) 2.8 (86%)
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