Comment on 'Semiconductor nanocrystals: structure, properties, and band gap engineering' [Acc. Chem. Res. Vol 43 (2) pp 190, (2010)]

Surface traps and associated emission in quantum dots (QDs) sought a lot of research attention because of the fundamental interests apart from their influence on the emission characteristics. In ref [Acc. Chem. Res. Vol 43 (2) pp 190, 2010] the hole traps (h-traps) are depicted close to the conduction band (CB) for CdSe QDs while discussing the emission mechanism. However, notably electron traps (e-traps) are close to CB and h-traps are supposedly close to the valance band, especially in anion rich CdSe QDs. Although such emission (so called deep-trap) is a well known phenomenon, the energetic locations of these traps and the associated discrepancy require further attention. Hence the distinction between e, h-traps and their energetic location within the band gap is addressed in a general context, which is essentially a revisit to the surface states. Finally this general description is put to the context of surface states of CdSe QDs.