CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

the EG to water ratio. For samples prepared in pure EG, FT-IR spectra is similar to that of
samples prepared in solvents containing both EG and water. Hence, it is confirmed that the
product formed when EG alone is used as the solvent is also ZnGa 2 O 4 . Poor crystallinity can
be due to the very small particle size of ZnGa 2 O 4 when EG alone is used as solvent. Further,
the relative intensity of band corresponding to C-H vibration increases with increase in the
EG volume in the solvent. It indicates that the nanoparticles are stabilized effectively by EG
molecules. The increase in line width and blue shift of the peaks can be explained as follows.
With decrease in particle size, number of atoms on the surface (which are having unsaturated
coordination) increases and this leads to distortion in the lattice of ZnGa 2 O 4 nanoparticles.
Further, small particles of ZnGa 2 O 4 in general must have higher electronic/vibrational energy
levels compared to bulk ZnGa 2 O 4 . These two effects lead to broadening of the IR absorption
peak and shifting of its maximum to higher frequency values.
% of Transmittence
60
40
20
35 ml EG
25 ml EG + 10 ml H 2
O
35 ml H 2
O
400 600 800 1000 1200
Wavenumber (cm -1 )
Fig.91. FTIR spectra of ZnGa 2 O 4 nanoparticles prepared in solvents containing different
amounts of EG and water.
Photoluminescence spectra of all these samples obtained after excitation in the range of
250-300 nm are shown in Fig.92 (a) and the corresponding excitation spectra are shown in
Fig.92 (b). The emission maximum is found to vary from 385 to 455 nm with increase in the
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