Model of the PbSe|CdSe core|shell NC
structure evidencing the octahedral
shape of the PbSe core (A). HR-TEM images of a PbSe|CdSe core|shell
NC (B) and PbSe/CdSe Janus-like NCs (C). The latter are obtained after
thermal annealing at 200 °C of initial core|shell NCs. The bottom-left
particle clearly shows that the volume of the CdSe shell was significantly
larger than that of the PbSe core, consequently the PbSe/CdSe heterointerface
is considerably different from that observed for equal volume bihemispheres,
in the sense that it is no longer a flat interface, as can be clearly
observed for the two top-right NHCs. (D) The mechanism of the thermally
induced structural transformation from core|shell to Janus-like NHC
is schematically depicted. Reproduced from [Grodzinska, D.; Pietra,
F.; van Huis, M. A.; Vanmaekelbergh, D.; de Mello Donega, C. Thermally
induced atomic reconstruction of PbSe/CdSe core/shell quantum dots
into PbSe/CdSe bihemisphere heteronanocrystals J. Mater. Chem. 2011, 21, 11556–11565]. Copyright
2011 American Chemical Society.