Effective surface-passivation of PbS nanocrystals in aqueous colloidal solution has been achieved following treatment with CdS precursors. The resultant photoluminescent emission displays two distinct components, one originating from the absorption band-edge and the other from above the absorption band-edge. We show that both of these components are strongly polarised but display distinctly different behaviours. The polarisation arising from the band-edge shows little dependence on the excitation energy while the polarisation of the above-band-edge component is strongly dependent on the excitation energy. In addition, time resolved polarisation spectroscopy reveals that the above-band-edge polarisation is restricted to the first couple of nanoseconds, while the band-edge polarisation is nearly constant over hundreds of nanoseconds. We recognise an incompatibility between the two different polarisation behaviours, which enables us to identify two distinct types of surface-passivated PbS nanocrystal.
@article{arxiv.cond-mat/0306310,
title = {Polarised Photoluminescence from Surface-Passivated PbS Nanocrystals},
author = {M. J. Fernee and J. Warner and A. Watt and S. Cooper and N. R. Heckenberg and H. Rubinsztein-Dunlop},
journal= {arXiv preprint arXiv:cond-mat/0306310},
year = {2009}
}