Supporting InformationFig. S1 In-situ TEM observation of the FeWO 4 flowers turning under electron beam. (a-b) show the 6-folded feature of a flower when initially exposed to electron beam during observation and tilting of the sample holder. (c-i) revealed a series of turning sequences of the same flower, after exposing to the focused electron beam for about 10 min. When shifting the beam towards the flower, it started to turn over, projecting a platelet shape at some stage, images (c) and (i). Damage on the surface was also observed due to the irradiation of the high density electron beam (TEM operated at 200 KeV). Pictures from (c-i) were taken at an interval about 40 s. The scale bar in the images is same.
Anisotropic heterostructures are of significant importance in creating novel nanomaterials and realizing their application potentials. Here we report a study on structural evolution and photoluminescence of zinc-blende CdSe-based CdSe/ZnS core/shell nanocrystals with variations of the ZnS shell growth. When raising the shell growth temperature, the structure of CdSe/ZnS can be tuned from sphere to near triangle, and to branched ones, including a tetrapod-like structure. But fast interface diffusion and alloying at high growth temperature will corrupt the branched structure and induce a blue shift in the luminescence spectrum. For tetrapod-like CdSe/ZnS nanocrystals, the growth of ZnS exhibits a pattern of first elongating and then branching, which is accompanied by rising, steady, and descending phases of the photoluminescence quantum yield. This study shows the shape tuning and interface alloying of CdSe/ZnS nanocrystals, and reveals that a moderate growth temperature is necessary for obtaining tetrapod-like CdSe/ZnS nanocrystals.
In this work, the effect of pulsed high magnetic field on the integral intensity of the electric-dipole emission spectrum of Eu 3+ in YVO 4 :Eu 3+ and GdVO 4 :Eu 3+ single crystals was studied and the results showed magnetic field induced luminescence suppression in YVO 4 :Eu 3+ and luminescence expansion in GdVO 4 :Eu 3+ . The single crystals were prepared by the optical floating zone method. The strong effect of the magnetic field on the splitting and emission of 5 D 0 -7 F 2 and 5 D 0 -7 F 4 transitions in Eu 3+ was investigated. The integral luminescence intensities of Eu 3+ are proportional to the magnetic field at higher than 15 T. For GdVO 4 :Eu 3+ , the integral intensity increases with the strengthening of magnetic field, and is completely opposite to that for YVO 4 :Eu 3+ . In this study, the dependence of luminescence integral intensity on the magnetic field was proposed to be the result of the structural change induced by high magnetic field which changes the symmetry of Eu 3+ ions in single crystals.
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