Periodic Reporting for period 1 - DECAGON (Doping Colloidal Nanoplatelets: Synthesis, Self-assembly and Spectroscopy)
Reporting period: 2016-01-11 to 2018-01-10
Another aspect of the work performed by the Fellow was the stacking of CdSe NPLs. We showed that ribbons of stacked board shaped CdSe NPLs twist upon addition of oleic acid ligand, leading to chiral ribbons with several micrometer in length and well defined pith of ~400 nm. In order to assemble the NPL, the fellow used simple drying technique with successive additions of oleic acid during drying. After drying, the precipitate was re-dispersed in hexane and shows long ribbon ranging from 1-4 μm. Closer observation reveals that the ribbons are twisted. Instead of stacking face to face with edges parallel, consecutive NPL in the same thread are rotated by a small angle. We demonstrated that the chirality originates from surface strain caused by the ligand since the addition of various amounts of OA to a dispersion of NPL in hexane without drying, so as to prevent ribbon formation, lead to a twist of the individual NPLs. In this case, the NPL are not stacked and can therefore change their shape freely upon ligand addition hence the increase of OA surface concentration induces a transition of the individual NPL from a flat to a curved shape. This twist at the single-particle level propagates over the whole ribbon length through the release of stress when platelets are confined within stacked ribbons. This study has led to a publication in a prestigious journal (Science Advances) in Open Access for a better dissemination to the public. A press release has been issued by the CNRS about these results.
The fellow also continued his work on chirality of CdSe NPLs by adding a chiral ligand on surface of NPLs. This chiral NPLs results is in very preliminary stage and needs more experiment.
breakthroughs on both fundamental and applied standpoints.