Res. Chem. Intermed.
, Vol. 34, No. 1, pp. 31–41 (2008)
Also available online - www.brill.nl/rci
Detection of shallow electron traps in quantum-sized CdS
particles using dithiolenes
J. A. JACOB, N. BISWAS, T. MUKHERJEE and S. KAPOOR
Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
Received 21 June 2007; accepted 23 August 2007
Abstract—Photophysical characteristics of capped and uncapped CdS particles have been investi-
gated in aqueous solution. It is seen that the ﬂuorescence spectrum shifts towards lower energies in
the presence of toluene dithiol (TDT) and dimercaptophthalic acid (DMPA). This shift, which is due
to quenching of shallow traps, is more predominant with TDT. Also, the presence of excess Cd
at the surface of the CdS particles facilitates the binding of dithiolenes.
Keywords: CdS particles; ﬂuorescence; dithiolenes.
There has been sustained interest in recent years in electron transfer across semicon-
ductor–liquid interfaces, metal oxide–liquid interfaces and their diverse applications
in solar energy conversion, waste treatment, synthesis of new materials and photo-
electrochemical devices . The discovery of a size quantization effect in semi-
conductor particles [2, 3] has especially enhanced interest in photo-electrochemical
processes at individual particles of semiconductor nanoparticles. These particles,
having a large speciﬁc surface, are susceptible to any change taking place at their
surface. Therefore, surface derivatization could be exploited to change the elec-
tronic properties of these materials. This aspect has important implications in their
applications in optoelectronics and microelectronics [4, 5].
Molecular modiﬁcation of the surface is often attempted to understand the
processes involved in the transfer of charge across the interface [6–8]. Control
of the surface properties of semiconductor colloidal particles is important for the
fundamental understanding of the photophysical and photochemical properties of
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