CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

observed after excitation at 250 and 220 nm. Excitation spectrum corresponding to 545 nm
emission from these nanoparticles/ nanoribbons is shown as an inset in Fig.64 (b). Along with
less intense sharp peaks characteristic of intra 4f transitions of Tb 3+ ions, broad peak around
250 nm, which is characteristic of 4f→5d transition of Tb 3+ ions is also observed. The host
absorption around 220 nm characteristic of SbPO 4 is not clearly observed as it is masked
under the intense 4f→5d transition peak. The intensity of 250 nm peak increases with
increasing Tb 3+ concentration in SbPO nanoparticles/ nanoribbons.
4
To confirm incorporation of lanthanide ions in the SbPO 4 host, pure EuPO4 and
TbPO 4 samples were prepared in a manner identical to the synthesis of SbPO :Eu 3+
4 and
SbPO 4:Tb 3+ . No emission could be seen from TbPO4 sample under all excitation
wavelengths, whereas weak emission with asymmetric ratio of luminescence 0.78 has been
observed from EuPO sample (Fig.65).
4
Intensity(arb.units)
2.0
1.5
1.0
0.5
7
F1
5
D0
7
F2
5
D0
0.0
550 600 650
Wavelength(nm)
Fig.65. Emission spectrum of EuPO sample obtained after 250 nm excitation.
4
Poor emission from these samples has been attributed to the significant quenching due
to decreased Eu 3+ -Eu 3+ distance brought about by high lanthanide ion concentration. The
asymmetric ratio of luminescence, which is very sensitive to the Eu 3+ local environment, is
quite different for EuPO
3+
(0.78) as compared to SbPO :Eu (1.14). Observation of strong Eu
4 4
and Tb 3+ emission from SbPO 4 :Eu 3+ and SbPO :Tb 3+ along with quite different values of
4
119