Material composition engineering and device fabrication of perovskite nanocrystals (PNCs) in solution can introduce organic contamination and entail several synthetic, processing, and stabilization steps. We report three-dimensional (3D) direct lithography of PNCs with tunable composition and bandgap in glass. The halide ion distribution was controlled at the nanoscale with ultrafast laser–induced liquid nanophase separation. The PNCs exhibit notable stability against ultraviolet irradiation, organic solution, and high temperatures (up to 250°C). Printed 3D structures in glass were used for optical storage, micro–light emitting diodes, and holographic displays. The proposed mechanisms of both PNC formation and composition tunability were verified.
Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1−xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1−xWxTe2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1−xWxTe2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1−xWxTe2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1−xWxTe2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein.
It
is a challenge to fabricate three-dimensional carbon aerogels
based on natural renewable resources with stability, flexibility,
and versatility. Here, an ultralight, elastic, and hydrophobic multifunctional
reduced graphene oxide-konjac glucomannan (RGO-KGM) carbon aerogel
was fabricated by a three-step process of freeze-casting, freeze-drying,
and carbonization. In the freeze-casting process, three unique structural
RGO-KGM carbon aerogels were obtained by adjusting the position of
the PDMS mold on the homemade directional freezer. RGO-KGM carbon
aerogels possessed many excellent physicochemical properties, such
as ultralow density, high specific surface area, elasticity, hydrophobicity,
and controllable size. As an adsorbent, RGO-KGM carbon aerogels exhibited
high adsorption capacity for various organic solvents and oils, and
the maximum adsorption capacity reached up to 360 g/g. Therefore,
RGO-KGM carbon aerogels with good mechanical properties and reusability
shows promising prospects in the field of water treatment.
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