CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

in the ZnGa 2 O 4 lattice. It is known that In 3+ is heavier than Ga 3+ , as a result the energy
corresponding to GaO 6 unit in the ZnGa 2-x In x O 4 nanoparticles will be less than that in
ZnGa 2 O 4 . Hence, the λ max corresponding to emission and excitation of GaO 6 level shifts to
higher values with increase in the In 3+ content. The decay curve corresponding to the excited
state of blue emission from ZnGa 1.5 In 0.5 O 4 nanoparticles is shown in Fig.100 (b). It is found
to be bi-exponential in nature with lifetime values 0.49 μs (56 %) and 1.85 μs (44 %). The
faster component is due to surface GaO 6 units and longer component is due to GaO 6 present
in the bulk of the ZnGa 2 O 4 :In 3+ lattice. Since surface GaO 6 units are directly bound to EG
moiety, they will decay faster than bulk GaO 6 structural units.
(a)
(b)
Fig.99. (a) TEM image, (b) HRTEM image of ZnGa 1.5 In 0.5 O 4 nanoparticles. SAED pattern
from these nanoparticles is shown in the inset of Fig.99 (a)
Normalised intensity
1.0
0.8
0.6
0.4
0.2
x = 0
x = 0.05
x = 0.2
x = 0.5
Intensity (arb.units)
1000
100
λ exc
= 270 nm & λ em
= 455 nm
0.0
10
350 400 450 500 550 600 0 5 10 15 20
Wavelength (nm)
Time (μs)
(a)
(b)
Fig.100. (a) Emission spectra of ZnGa 2-x In x O 4 (x = 0, 0.05, 0.2, 0.5) nanoparticles after
exciting samples in the UV region (260 to 280 nm). (b) Decay profile corresponding
to blue emission from ZnGa 1.5 In 0.5 O 4 nanoparticles.
160