CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

3+ 3+
Ce ions is in the ratio of around 40:60 for both SbPO 4 :Ce (2.5%), Tb 3+ (5%) nanoribbons/
nanoparticles as well as the nanoribbons/ nanoparticles dispersed in silica, suggesting that the
extent of energy transfer is approximately 60 %. The values are comparable with the energy
transfer efficiency estimated from the Ce 3+ emission in SbPO 4 host using the equation η = 1-
I/I0, where I and I 0 are the intensities of Ce emission in the presence and absence,
respectively of Tb 3+ ions. The comparable efficiency of energy transfer for the as prepared
nanomaterials and nanomaterials incorporated in silica matrix are understandable as the
phonon energies are comparable for both SbPO and SiO
4 2 lattices. Hence, identical extent of
quenching is expected for lanthanide ion excited states from these matrices. However, the
silica covering on the nanoribbons/ nanoparticles have additional advantage of removing the
asymmetric environment created at the surface by the stabilising ligands. Energy transfer
must also reflect in the Ce 3+ excited state lifetimes. However, the decay curves obtained
corresponding to the excited state of Ce 3+ were close to the instrument response (less than 1
ns) and hence the values could not be accurately calculated from the decay curves.
3+
It will be interesting to understand the mechanism of the energy transfer between the
3+ 3+ 3+ 3+
Ce and Tb ions. The energy transfer between Ce and Tb depends on extent of overlap
between donor (D) emission peak (Ce 3+ emission peak in the present case) and acceptor (A)
absorption peak (Tb 3+ excitation peak in the present case) and expressed by the equation 21
[69],
4 π | , *| | *, |
2
DA DA D ( ).
A (
P = < D A H D A> g E g E)
h
∫ dE……………….. (21)
where, P DA is the rate of energy transfer from donor to acceptor. The first term in the above
expression represents the transition dipole moment between the |D*, A> and |D, A*> states
via the interaction Hamiltonian H DA . D* and A* represent the excited state of the donor and
acceptor, H is the interaction Hamiltonian. The parameters g
DA
D(E) and g A (E) are normalized
population density function representing the optical line shapes of donor and acceptor
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