CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

particles. Thus the TEM studies also confirm the observed variation in particle size as a
function of Ga concentration.
Photoluminescence spectra of ZnGa 2 O 4 nanoparticles prepared with different Ga 3+
concentration are shown in Fig.97 (a) and corresponding excitation spectra are shown in
Fig.97 (b). The emission spectra (Fig.97 (a)) clearly reveal that with increasing the Ga
concentration, from 0.14 to 1.44 mmol, emission maxima shifts from 420 nm to 435 nm and
for further higher concentration of gallium, it starts shifting to lower wavelength side. This
again can be explained by considering the changes in the particle size with reactants
concentration. The host absorption (Band edge absorption) also shows similar trend as
evident from the excitation spectra (Fig.97 (b)) where the peak maximum shifts from 260 to
270 and then to 255 nm. Wavelength maximum corresponding to localised centres present in
ZnGa 2 O 4 nanoparticles also varied in a similar fashion.
(a) (b) (c)
(d) (e) (f)
Fig.96. TEM images (a, d), HREM images (b, e), SAED patterns (c, f) of ZnGa 2 O 4
nanoparticles prepared with 1.44 and 22.96 mmol Ga, respectively.
157