CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

5 D 0
7 F 2
level to 7 F 7 7
1 , F 2 , F 3 and 7 F 3+
4 levels of Eu ions. The transitions 5 D 0 → 7 F 5
1 and D 0 → 7 F 2 are
purely magnetic and electric dipole allowed respectively. The relative intensity ratio of
5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 transition, known as the asymmetric ratio of luminescence, is a very
sensitive parameter which depends on the environment around Eu 3+ ions [234, 235]. The
3+ 3+
value is found to be 2.2 for 2.5 at % Eu containing sample. With increasing Eu content
(i.e. for 5 at % Eu 3+ containing sample) the asymmetric ratio decreases to 1.0 (Fig.56 (b)).
Significant change in the asymmetric ratio of luminescence indicates a drastic change in the
environment around Eu 3+ ions, which could be due to the formation of separate Eu 3+
containing phase. It can be either the pure EuPO or a complex of Eu 3+
4 formed with ligands
(glycerol) present in the reaction medium.
5
D 0
7 F 1
5 D 0
7 F 4
5
D 0
7 F 3
(c)
Normalised intensity
(b)
(a)
550 600 650 700 750
Wavelength (nm)
Fig.56. Emission spectrum from GaPO 4 nanoparticles containing (a) 2.5 at % and (b) 5 at %
Eu 3+ ions. The corresponding pattern from EuPO 4 nanoparticles is shown in Fig.56
(c). All samples were excited at 260 nm.
To check this aspect, emission spectrum from pure EuPO 4 sample prepared in an identical
method as that used for GaPO 4 nanoparticles is shown in Fig.56 (c). The pattern is same as
that of 5 at % Eu 3+ containing GaPO nanoparticles. The asymmetric ratio of luminescence is
4
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