CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

slower lifetime components are attributed to Dy 3+ ions present at the surface and bulk of the
nanoparticles, respectively.
Intensity (arb.units)
Intensity (arb.units)
12000
λ exc
= 253 nm
8000
4000
10000
8000
6000
4000
2000
0
4 F 9/2
6 H 15/2
4 F 9/2
6 H 13/2
4 F 9/2
6 H 9/2
400 450 500 550 600 650 700
Wavelength (nm)
(a)
λ em
= 574nm
0
200 250 300 350 400
1
0.5 1.0 1.5 2.0
Wavelength (nm)
Time (ms)
(c)
(d)
Fig.113. Emission spectrum (a) and photograph of emission (b) obtained after excitation at
253 nm from CaWO 4 :Dy 3+ nanoparticles. Corresponding excitation spectrum and
decay curve monitored at 574 nm emission are shown in Fig.113 (c and d).
Intensity (arb.units)
1000
100
10
(b)
λ exc
= 253 nm & λ em
= 575 nm
6.9. Luminescence studies on Sm 3+ doped CaWO 4 nanoparticles: Emission spectrum
obtained from 2 at % Sm 3+ doped CaWO 4 nanoparticles after excitation at 253 nm is shown
in Fig.114 (a). The spectrum consists of three peaks at 565, 602 and 645 nm and is attributed
to 4 G 5/2 Æ 6 H 5/2 , 4 G 5/2 Æ 6 H 7/2 and 4 G 5/2 Æ 6 H 9/2 transitions, respectively of Sm 3+ present in
the CaWO 4 lattice. Orange emission visible to naked eye, observed from Sm 3+ doped CaWO 4
nanoparticles in methanol is clear from the photograph shown in the Fig.114 (b). The
excitation spectrum monitored at 602 nm emission of Sm 3+ is shown in Fig.114 (c). It
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