CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

units. Radiative recombination of this trapped electron with hole in valance band leads to
emission in the region 385 to 455 nm as schematically shown in Fig.93.
Fig.93. Schematic representation of possible energy transitions in ZnGa 2 O 4 nanoparticles.
5.3. Effect of precursor concentration on particle size: ZnGa 2 O 4 nanoparticles were
prepared in 25 ml EG and 10 ml water with different concentrations of reactants namely
gallium chloride and zinc acetate and XRD patterns of the resulting compounds are shown in
Fig.94. For samples prepared with 0.14 mmol of gallium, XRD patterns revealed the
formation of an amorphous product. This is probably due to very small size of the
nanoparticles of ZnGa 2 O 4 (as confirmed by FT-IR studies previously described). As the
precursor concentration increases, particle size increases up to certain concentration, i.e., 1.44
mmol of gallium and above that its starts decreasing and finally again giving rise to an
amorphous product at 22.96 mmol of gallium. The calculated crystal sizes are given in the
Table 13 as a function of the gallium concentration. This observed variation can be explained
based on nucleation and growth processes involved for the formation of ZnGa 2 O 4 particles.
At lower Ga 3+ concentration, both nucleation and growth are slower because ions are far
away and attaining the super-saturation condition is difficult. As a result, the particle sizes are
smaller. With increase in gallium concentration, growth becomes faster as compared to
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