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Few-layer and large-size BNNSs with a high yield of 26% are successfully prepared by a simple method.

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Lots of top-down approaches by weakening the van der Waals interaction between adjacent layers and breaking up the covalent chemical bonds in each layer have been reported to prepare QDs of layered materials due to the stacked structures. However, much attention has been focused on graphene and layered transition-metal dichalcogenides (TMDs), seldomly on layered transition-metal oxides (TMOs). Herein, a modified top-down method combining intercalation and thermal exfoliation is reported to prepare high-yield QDs of layered MoO 3 . Alkylamine was first intercalated into MoO 3 layers to weaken the van der Waals forces. Then, the covalent bonds in each MoO 3 layer were broken down under a sudden increase in gas pressure generated by the decomposition of alkylamines after rapid heating. These fractured particles were further incised to QDs by sonication. The as-prepared MoO 3 QD dispersion showed a plasmon resonance after simulated solar light illumination. Surprisingly, their plasmon peak red shifted with an extended illumination time, which was different from the reported MoO 3 nanosheets. This reported method is expected to extend to other QDs of layered materials providing that their bulk materials can also be intercalated.

With the current development of microelectronic technology, thermally conductive and electrically insulating encapsulation materials are in urgent demand. Hexagonal boron nitride nanosheets (BNNSs) possess a highly anisotropic thermal property. Therefore, the thermal conductivity of the BNNSs-based composites can be dramatically increased through the orientation of fillers. However, it is still difficult to well align BNNSs at high loadings due to the intensive aggregation. Herein, highly ordered thermoplastic polyurethane elastomer (TPU)/BNNSs composites are successfully fabricated by the combination of filler modification and magnetic alignment. The effective covalent modification with 2,4-tolylene diisocyanate (TDI) greatly increases the dispersibility of fillers, thus making it easy to well orient BNNSs at high loadings. The highly aligned fillers result in much higher in-plane thermal conductivity than the composites filled with disordered or less-ordered unmodified BNNSs. The thermal conductivity is as high as 5.15 W m À1 K À1 at 30 wt% loading. Moreover, the composite simultaneously exhibits low dielectric constant, low dielectric dissipation factor and excellent thermomechanical properties. These results reveal the promising application of such highly-ordered composites in advanced electronic packing. Fig. 9 (a) Storage modulus and (b) tan delta of the blank TPU resin and different composites with 10 wt% fillers. 43388 | RSC Adv., 2017, 7, 43380-43389 This journal is

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