Proceedings of nanoGe September Meeting 2017 (NFM17)
Publication date: 20th June 2016
Surface chemistry modification of as-synthesized colloidal inorganic semiconductor nanocrystals (QDs), commonly referred to as ligand exchange, is mandatory towards effective QD-based optoelectronic and photocatalytic applications. The widespread recourse to ligand exchange procedures is leading to uncover, somehow serendipitously, the marked impact exerted by chemical species at nanoscopic surfaces on the ground state optoelectronic properties of QDs: indeed, QD surface modification has been shown to induce, among others, band edge energy shifting,[1] optical band gap reduction,[2] and broadband optical absorption enhancement[3] to an extent beyond any expectation based on commonly accepted models. However, the proposed explanations to these experimental findings often contradict each other, albeit observed for analogous QD systems, thus providing elusive answers to the questions raised by the observed phenomena.
Here I discuss such contradictions and suggest a comprehensive description of the colloidal QD electronic structure that relies on the notion of inherent ligand/core orbital mixing, thus suggesting the inadequacy of conceiving ligands at the QD surface as molecular dipoles or dielectric shell.
[1] a) M. Soreni-Harari et al., Nano Lett. 2008, 8, 678; b) P. R. Brown et al., ACS Nano 2014, 8, 5863.
[2] a) R. Koole et al., J. Phys. Chem. 2007, 111, 11208; b) A. Wolcott et al., J. Phys. Chem. Lett. 2011, 2, 795; c) M. T. Frederick et al., Nano Lett. 2011, 11, 5455; d) M. T. Frederick et al., Nano Lett. 2013, 13, 287.
[3] a) C. Giansante et al., J. Am. Chem. Soc. 2015, 137, 1875; b) D. Debellis et al., Nano Lett. 2017, 17, 1248.
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