CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

onds in the GaO 6 octahedra. Based on photoluminescence studies of a variety of gallium
compounds containing GaO 6 octahedra [182, 198-201] the emission around 435 nm has been
attributed to recombination of electrons trapped at oxygen vacancies and hole trapped at Ga 3+
vacancies present in GaOOH. Peaks around 360 and 280 nm characterize corresponding
excitation spectrum. UV-visible optical absorption studies [182] have revealed that GaOOH
has an optical band gap of ~ 4.4 eV (~280 nm) and hence the excitation peak around 280 nm
is assigned to the excitation of electron from valence band to conduction band of GaOOH.
The other excitation peak around 360 nm is attributed to excitation of electrons from valence
band to defect levels (oxygen vacancies) present in the lattice. Existence of energy transfer
from hosts like Ga 2 O 3 to lanthanide ions is used as criteria to confirm the lanthanide ion
incorporation in host. In order to find out whether lanthanide ions are incorporated in the
GaOOH lattice, detailed luminescence experiments were carried out for lanthanide ions
doped GaOOH samples and are described below.
1.0
excitation
emission
Normlised intensity
0.8
0.6
0.4
0.2
0.0
200 300 400 500 600
Wavelength (nm)
Fig.26. Emission spectrum obtained after 280 nm excitation and excitation spectrum
corresponding to 435 nm emission from GaOOH nanorods prepared in the absence of
any Eu 3+ ions.
Figure 27 (right) shows the emission spectrum of GaOOH nanorods prepared in the
presence of different concentrations of Eu 3+ ions. Peaks around 590 and 615 nm, which are
due to the magnetic, characterize the emission spectrum and electric dipole allowed 5 D 0 → 7 F 1
and 5 D 0 → 7 F 2 transitions, respectively of Eu 3+ ions. The emission spectrum is the same for all
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