CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

In pure EG an amorphous product is formed. As volume of H 2 O increases in the reaction
medium, the crystallinity of nanoparticles also increasing as can be seen from the line width
of the diffraction peaks. In pure H 2 O, average crystal size is found to be the highest. Average
crystallite size of ZnGa 2 O 4 nanoparticles obtained with different EG-water solvent ratio is
given in Table 12. The increase in particle size with increase in water to solvent ratio can be
explained based on two aspects. The first one is as that with increase in water content urea
hydrolysis becomes more effective and the second one is that the viscosity decreases with
increase in water content facilitating diffusion of monomer towards the growth site.
Table 12: Calculated average crystallite size of ZnGa 2 O 4 nanoparticles as a function of EG-
H 2 O ratio.
No. of moles
of Zn 2+
(mmol)
No. of moles
of Ga 3+
(mmol)
Vol. of H 2 O
(ml)
Vol. of EG
(ml)
Crystallite
size (nm)
1.43 2.86 35 0 10
1.43 2.86 25 10 8
1.43 2.86 15 20 7
1.43 2.86 10 25 5
1.43 2.86 5 30 1
1.43 2.86 0 35 -
To confirm the nature of product obtained while EG only was used as the solvent, FT-
IR studies were carried out on the sample and the pattern is compared with that of samples
prepared with EG-water mixture and are shown in Fig.91. Nanoparticles prepared in pure
water shows two bands at 450 and 600 cm -1 and are attributed to Ga-O and Zn-O stretching
vibrations, respectively of ZnGa 2 O 4 [265]. The samples prepared in 25 ml EG and 10 ml
water displayed these bands but appeared at a slightly higher frequency. Further, two other
bands at 850 and 1050 cm -1 also appeared (Fig.91). The 1050 cm -1 peak is assigned to the C-
H bending of EG molecules present on the surface of nanoparticles. The bands at 450 and
600 cm -1 shifted to higher frequency and have become broader with increase in the EG to
water ratio in the solvent. This is attributed to the reduction of particle size with increase in
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