CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

depends strongly on the nature of the synthesis method and conditions employed [70-73]. For
example, Sharma, et al. [73] synthesised Y 2 O 3 :Eu nanoparticles having size in the range of
micrometers to nanometers with the help of organic surface modifiers like Tween-80 and
Emulsogen-OG. The authors observed a five fold enhancement in emission intensity from the
nanoparticles when 10 wt. % of surface modifier was added during the synthesis of Y 2 O 3 :Eu
nanoparticles. Taner and Wang [74] investigated the luminescence properties of Y 2 O 3 :Eu
nanoparticles prepared by flame spray pyrolysis method and compared it with that of
conventional pyrolysis method. The intensity of 5 D 1 emission of Eu 3+ ions from the C 3i site
(S 6 ) in Y 2 O 3 is significantly less compared to the emission from Eu 3+ ions in the C 2 site for
these samples. Igarashi, et al. [75] compared luminescence properties of bulk and
nanoparticles of Y 2 O 3 :Eu prepared using yttrium hydroxy carbonate precursor method and
established that the increase in ionicity of Eu-O bond due to decrease in particles size is
responsible for observed blue shift of excitation peak with decrease in particle size. Song and
co-workers [76, 77] have observed that the radiative and non-radiative transition rates of Eu 3+
ions in Y 2 O 3 :Eu nanoparticles increased with decrease in particle size and this is attributed to
the crystal lattice degeneration and surface effects. Further, ultraviolet (UV) light irradiation
on Y 2 O 3 :Eu nanoparticles has been found to reduce the intensity of Eu-O charge transfer peak
[78,89]. Temperature and particle size effect on photoluminescence properties of Y 2 O 3 :Tb
nanoparticles have also been investigated by the same authors. Based on the studies it has
been established that relative intensity of 5 D 4 → 7 F J transitions and oxygen defect emission ~
620 nm characteristic of Y 2 O 3 host are related to extent of thermal quenching process [80].
Tb 3+ concentration dependence on photoluminescence intensity of Y 2 O 3 :Tb nanoparticles is
investigated by Park, et al. [81]. These authors have observed that for Y 2 O 3 :Tb nanoparticles,
prepared by solution route followed by annealing at 400°C and containing 8 wt. % Tb 3+ ,
gave optimum intensity for green emission. Mukherjee, et al. [82] have observed a variation
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