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We have studied the dynamics of directed, multistep energy transport in a class of fractal-like dendrimeric molecules. For particular forms of these highly branched phenylacetylene dendrimers, both theory and experiment put the lowest excitation energy at the center (locus) of the supermolecule. This results in a structurally symmetric and ordered exciton funnel, with a well-directed energy gradient. We have designed and synthesized a derivative of these dendrimers with a perylene moiety at the locus, which acts as an energy trap for the directed exciton funnel. Spectroscopic evidence indicates transfer efficiency of 98% from the photoabsorbing dendrimer backbone to the perylenic trap.

Twinned growth behaviour in the rapidly emerging area of two-dimensional nanomaterials still remains unexplored although it could be exploited to fabricate heterostructure and superlattice materials. Here we demonstrate how one can utilize the twinned growth relationship between two two-dimensional materials to construct vertically stacked heterostructures. As a demonstration, we achieve 100% overlap of the two transition metal dichalcogenide layers constituting a ReS2/WS2 vertical heterostructure. Moreover, the crystal size of the stacked structure is an order of magnitude larger than previous reports. Such twinned transition metal dichalcogenides vertical heterostructures exhibit great potential for use in optical, electronic and catalytic applications. The simplicity of the twinned growth can be utilized to expand the fabrication of other heterostructures or two-dimensional material superlattice and this strategy can be considered as an enabling technology for research in the emerging field of two-dimensional van der Waals heterostructures.

Improved properties arise in transition metal dichalcogenide (TMDC) materials when they are stacked onto insulating hexagonal boron nitride (h-BN). Therefore, the scalable fabrication of TMDCs/h-BN heterostructures by direct chemical vapor deposition (CVD) growth is highly desirable. Unfortunately, to achieve this experimentally is challenging. Ideal substrates for h-BN growth, such as Ni, become sulfides during the synthesis process. This leads to the decomposition of the pregrown h-BN film, and thus no TMDCs/h-BN heterostructure forms. Here, we report a thoroughly direct CVD approach to obtain TMDCs/h-BN vertical heterostructures without any intermediate transfer steps. This is attributed to the use of a nickel-based alloy with excellent sulfide-resistant properties and a high catalytic activity for h-BN growth. The strategy enables the direct growth of single-crystal MoS2 grains of up to 200 μm(2) on h-BN, which is approximately 1 order of magnitude larger than that in previous reports. The direct band gap of our grown single-layer MoS2 on h-BN is 1.85 eV, which is quite close to that for free-standing exfoliated equivalents. This strategy is not limited to MoS2-based heterostructures and so allows the fabrication of a variety of TMDCs/h-BN heterostructures, suggesting the technique has promise for nanoelectronics and optoelectronic applications.

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