Res. Chem. Intermed.
, Vol. 31, No. 7–8, pp. 649–659 (2005)
Also available online - www.vsppub.com
Excitation energy transfer efﬁciency of dipole–dipole
interaction in a dye pair in polymer medium
and KRISHNA K. PANDEY
Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India
Institute of Wood Science and Technology, Malleswaram, Bangalore, 560006, India
Received 23 May 2004; accepted 9 June 2004
Abstract—Excitation energy transfer efﬁciency (η) of dipole–dipole interaction has been studied
in the dye pair 3,3
-dimethyloxacarbocyanine iodide (DMOCI) (donor) to o-(6-diethylamino-3-
diethylimino-3H-xanthen-9-yl) benzoic acid (Rhodamine B, RB) (acceptor) in polyvinyl alcohol
(PVA) thin ﬁlms by steady-state and ps time-resolved ﬂuorescence spectroscopy. In the presence of
the acceptor the ﬂuorescence intensity of the donor decreases, while that of the acceptor increases
as a function of the added acceptor concentration. Time-resolved study of the donor at various
acceptor concentrations suggest that the non-radiative energy transfer mechanism as proposed by
Förster is responsible for the observed behaviour along with some modiﬁcations at very low
acceptor concentrations. Modiﬁed η values have been simulated and compared with those obtained
experimentally. It is found that the value of η increases with acceptor concentration.
Keywords: Energy transfer efﬁciency; time-correlated single photon counting; 3,3
cyanine iodide; Rhodamine B.
The excitation energy transfer between a donor and an acceptor dye molecule
has received a lot of attention in last four decades [1–14] after the pioneering
works of Förster (dipole–dipole interactions)  and Dexter (higher multiple
interactions) . This is due to wide applications of energy transfer in the ﬁelds
of physics, chemistry and biology [15–17].
The excitation energy transfer between donor–acceptor molecules is known as
energy transfer, while that among donors is known as energy migration. In principle,
the excitation energy transfer process can be modulated by the excitation energy
migration and also by the material diffusion of the donor. However, the initial
model proposed by Förster  does not take in to account the cases of mobile
To whom correspondence should be addressed. E-mail: firstname.lastname@example.org