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As an emerging type of optically active materials, chiral molecules-stabilized semiconductor quantum dots (QDs) have achieved extensive attention. Unfortunately, understanding of the optical characteristics of chiral QDs observed by circular dichroism (CD) spectroscopy remains a great challenge due to their rather weak signals. Herein, we successfully achieve much enhanced CD responses from l- or d-cysteine-stabilized wurtzite CdSe quantum rods (QRs) thanks to their unique optical anisotropy. Furthermore, the optical activity of CdSe QRs is explored to be improved and subsequently become stable with the geometrical aspect ratio (AR) increasing, and such change matches well with alternation of the polarization factor of CdSe QRs. A non-degenerate coupled-oscillator (NDCO) model is established to elucidate the optical activity of chiral QRs, and the positive and negative natures of the CD peaks appearing at the first exciton band are clearly assigned to different transition polarization along 4p → 5s and 4p → 5s, respectively. This work opens the door toward comprehension and design of optically active semiconductor nanomaterials.

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Nanocrystals (NCs) with identical components and sizes but different crystal structures could not be distinguished by conventional absorption and emission spectra. Herein, we find that circular dichroism (CD) spectroscopy can easily distinguish the CdSe nanoplatelets (NPLs) with different crystal structures of wurtzite (WZ) and zincblende (ZB) with the help of chiral L-or D-cysteine ligands. In particular, the CD signs of the first excitonic transitions in WZ and ZB NPLs capped by the same chiral cysteine are opposite. Theoretic calculation supports the viewpoint of different crystal structures and surfaces arrangements between WZ and ZB NPLs contributing to this significant phenomenon. The CD peaks appearing at the first excitonic transition band of WZ or ZB CdSe NPLs are clearly assigned to the different transition polarizations along 4p (x,y,z),Se → 5s Cd or 4p (x,y),Se → 5s Cd. This work not only provides a deep insight into the origin of the optical activity inside chiral semiconductor nanomaterials but also proposes the design principle of chiral semiconductor nanocrystals with high optic activity.

The Cu/SiO2 catalyst prepared by the ammonia evaporation hydrothermal method presented unprecedented stability (300 h) for glycerol hydrogenolysis to 1,2-propanediol.

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