CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

The spectrum shows strong emission peaks around 590 and 615 nm, which are
characteristic of magnetic and electric dipole allowed 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 transitions,
respectively of Eu 3+ . Besides this peak, there are two more weak peaks centered at 651 and
700 nm due to 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 transitions, respectively of Eu 3+ ions. The relative
intensity ratio of the electric to magnetic dipole allowed transition, known as the asymmetric
ratio of luminescence, is a sensitive parameter, which depends on the electronic environment
around Eu 3+ ions. The asymmetric ratio of luminescence is found to be 3.4 and is comparable
with the value observed for of bulk Sb 2 O 3 samples (~ 3.3) prepared in presence of Eu 3+ ions
(Fig.47 (c)). The higher intensity of electric dipole transition compared to the magnetic dipole
transition and associated high asymmetric ratio value shows that the Eu 3+ ions are in a noncentro
symmetric environment.
To confirm the fact that the Eu 3+
ions are not forming separate europium
oxide/hydroxide phase, Eu 3+ ions were subjected to the same chemical treatment as that done
for Sb 3+ for preparing Sb 2 O 3 nanorods and the precipitate was subjected to luminescence
measurements. XRD and infrared patterns of precipitate indicated that the product is
amorphous europium hydroxide. Figure 48 shows the emission spectrum from the as
prepared europium hydroxide sample subjected to 395 nm excitation. The pattern is found to
be quite different from the Sb 2 O 3 sample prepared in presence of Eu 3+ ions. The asymmetric
ratio of luminescence is calculated to be ~1.6. The higher asymmetric ratio of Eu 3+ emission,
in Sb 2 O 3 sample prepared in presence of Eu 3+ ions, compared to europium hydroxide phase
(prepared by the same procedure as that of Sb 2 O 3 ) shows that Eu 3+ ions in Sb 2 O 3 sample have
a different environment and are not existing as separate europium hydroxide phase. The
excitation spectrum (inset in Fig.48) also reveals that the Eu 3+
ions have different
environment in both the samples. These results are further supported by the lifetimes
corresponding to the 5 D 0 level of Eu 3+ ions in the sample, as shown in Fig.49.
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