In this article, we show how advanced hierarchical structures of topological defects in the so-called smectic oily streaks can be used to sequentially transfer their geometrical features to gold nanospheres. We use two kinds of topological defects, 1D dislocations and 2D ribbon-like topological defects. The large trapping efficiency of the smectic dislocation cores not only surpasses that of the elastically distorted zones around the cores but also the one of the 2D ribbon-like topological defect. This enables the formation of a large number of aligned NP chains, within the dislocation cores that can be quasi-fully filled without any significant aggregation outside the cores. When the NP concentration is large enough to entirely fill the dislocation cores, the LC confinement varies from 1D to 2D. We demonstrate that the 2D topological defect cores induce a confinement that leads to planar hexagonal networks of NPs. We then draw the phase diagram driven by NP concentration, associated with the sequential confinements induced by these two kinds of topological defects. Owing to the excellent large-scale order of these defect cores, not only the NP chains but also the NP hexagonal networks can be oriented along the desired direction, suggesting a possible new route for the creation of either 1D or 2D highly anisotropic NP networks. In addition, these results open rich perspectives based on the possible creation of coexisting NP assemblies of different kinds, localized in different confining areas of a same smectic film that would thus interact thanks to their proximity but also would interact via the surrounding soft matter matrix.

Fluorescent semiconductor nanoplatelets (epitaxial quantum wells) can be synthesized with excellent monodispersity and self-assembled in highly-ordered structures. Modifications of their electronic and luminescence properties when stacked, due to strong mechanical, electronic or optical interactions between them, have been the topic of intense recent discussions. In this paper, we use Fourier imaging to measure the different dipole components of various nanoplatelet assemblies. By comparing different measurement conditions and corroborating them with polarimetric analysis, we confirm an excellent precision on the dipole components. For single nanoplatelets, only in-plane dipoles (parallel to the platelet plane) are evidenced. For clusters of 2-10 platelets and chains of 30-300 platelets, on the other hand, a clear out-of-plane dipole component is demonstrated. Its contribution becomes more significant as the number of platelets is increased. We review possible explanations and suggest that the added out-of-plane dipole can be induced by strain-induced nanoplatelet deformations.Semiconductor nanoplatelets (NPLs) 1 are quasi-two-dimensional atomically flat nanoemitters with intense, spectrally monodisperse 2 and anisotropic 3-6 emission and potential applications in light-emitting devices 7 , photovoltaic cells 8 , field effect transistors 9 and lasers 10 . Fluorescence studies usually consider, as much as possible, isolated emitters, either by spectroscopy of dilute solutions or by single-molecule microscopy. Interactions between compact assemblies of stacked emitters are however receiving increased attention. In optoelectronics, for instance, these interactions must be understood as they can either be detrimental to a device's efficiency or allow new energy transfer strategies 8,[11][12] . Semiconductor platelets are an ideal model system for studying such interactions because they have a pronounced tendency to spontaneous cofacial stacking [13][14] and because, when stacked, their interactions should be strong as they present high absorption cross-section [15][16] , low Stokes shift and large in-plane dipoles 3,[5][6] which can be aligned parallel at very short distance (2-5 nm) from each other [17][18] . For instance, a second emission peak appears at low temperatures for stacked NPLs and was tentatively attributed to phonon coupling 13 , p-state

Fluorescent emitters like ions, dye molecules or semiconductor nanoparticles are widely used in opto-electronic devices, usually within densely-packed layers. Their luminescence properties can then be very different from when they are isolated, because of short-range interparticle interactions such as Förster resonant energy transfer (FRET). Understanding these interactions is crucial to mitigate FRET-related losses and could also lead to new energy transfer strategies. Exciton migration by FRET hopping between consecutive neighbor fluorophores has been evidenced in various systems but was generally limited to distances of tens of nanometers and involved only a few emitters. Here we image selfassembled linear chains of CdSe nanoplatelets (colloidal quantum wells) and demonstrate exciton migration over 500-nm distances, corresponding to FRET hopping over 90 platelets. By comparing a diffusion-equation model to our experimental data, we measure a (1.5 ps) -1 FRET rate, much faster than all decay mechanisms, so that strong FRET-mediated collective photophysical effects can be expected.