All-in-one synthesis of mesoporous silicon nanosheets from natural clay and their applicability to hydrogen evolution

Silicon nanosheets have attracted much attention owing to their novel electronic and optical properties and compatibility with existing silicon technology. However, a cost-effective and scalable technique for synthesizing these nanosheets remains elusive. Here, we report a novel strategy for producing silicon nanosheets on a large scale through the simultaneous molten-salt-induced exfoliation and chemical reduction of natural clay. The silicon nanosheets thus synthesized have a high surface area, are ultrathin (similar to 5 nm) and contain mesoporous structures derived from the oxygen vacancies in the clay. These advantages make the nanosheets a highly suitable photocatalyst with an exceptionally high activity for the generation of hydrogen from a water-methanol mixture. Further, when the silicon nanosheets are combined with platinum as a cocatalyst, they exhibit high activity in KOH (15.83 mmol H-2 per s per mol Si) and excellent photocatalytic activity with respect to the evolution of hydrogen from a water-methanol mixture (723 mu mol H-2 per h per g Si).clos

Ambipolar Transport in Solution-Synthesized Graphene Nanoribbons

Graphene nanoribbons (GNRs) with robust electronic band gaps are promising candidate materials for nanometer-scale electronic circuits. Realizing their full potential, however, will depend on the ability to access GNRs with prescribed widths and edge structures and an understanding of their fundamental electronic properties. We report field-effect devices exhibiting ambipolar transport in accumulation mode composed of solution-synthesized GNRs with straight armchair edges. Temperature-dependent electrical measurements specify thermally activated charge transport, which we attribute to inter-ribbon hopping. With access to structurally precise materials in practical quantities and by overcoming processing difficulties in making electrical contacts to these materials, we have demonstrated critical steps toward nanoelectric devices based on solution-synthesized GNRs

Conjugated organic framework with three-dimensionally ordered stable structure and delocalized π clouds

Covalent organic frameworks are a class of crystalline organic porous materials that can utilize p–p-stacking interactions as a driving force for the crystallization of polygonal sheets to form layered frameworks and ordered pores. However, typical examples are chemically unstable and lack intrasheet p-conjugation, thereby significantly limiting their applications. Here we report a chemically stable, electronically conjugated organic framework with topologically designed wire frameworks and open nanochannels, in which the p conjugation-spans the two-dimensional sheets. Our framework permits inborn periodic ordering of conjugated chains in all three dimensions and exhibits a striking combination of properties: chemical stability, extended p-delocalization, ability to host guest molecules and hole mobility. We show that the p-conjugated organic framework is useful for high on-off ratio photoswitches and photovoltaic cells. Therefore, this strategy may constitute a step towards realizing ordered semiconducting porous materials for innovations based on two-dimensionally extended p systems.11521611sciescopu