jp2086818_si_001.pdf (5.86 MB)
Low-Temperature Synthesis of Magic-Sized CdSe Nanoclusters: Influence of Ligands on Nanocluster Growth and Photophysical Properties
journal contribution
posted on 2012-02-23, 00:00 authored by John C. Newton, Karthik Ramasamy, Manik Mandal, Gayatri K. Joshi, Amar Kumbhar, Rajesh SardarWe present a low-temperature (68–70 °C) synthesis
of green light-emitting, trioctylphosphine oxide-capped magic-sized
CdSe nanoclusters from the reaction of trioctylphosphine oxide–cadmium
acetate precursors with trioctylphosphine selenide. We observed continuous
growth of these magic-sized nanoclusters, which displayed a first
absorption peak at 422 nm and broad luminescence covering the entire
visible region. The diameter of the nanoclusters determined by transmission
electron microscopic measurement was ∼1.8 nm. Powder X-ray
diffraction analysis showed a sharp peak at low angle (2θ =
5.3°), confirming the formation of ultrasmall, magic-sized nanoclusters.
The nanocluster formation was also studied using different purities
of trioctylphosphine oxide. The synthetic protocol was extended to
the preparation of oleylamine-, ethylphosphonic acid-, lauric acid-,
and trioctylamine-stabilized magic-sized CdSe nanoclusters. Importantly,
the investigation showed that the nature of the cadmium precursors
plays a crucial role in the nanocluster growth mechanism. The applicability
of the trioctylphosphine oxide-capped nanoclusters was further investigated
through a ligand exchange reaction with oleylamine, which displayed
an extremely narrow absorption peak at 415 nm (full width at half-maximum
of 14 nm) and a band edge emission peak at 456 nm with a shoulder
at 438 nm.