Di Wu,Jiao Shi,Xiaoming Zheng,Jinxin Liu,Weidong Dou,Yongli Gao,Xiaoming Yuan,Fangping Ouyang,Han Huang
One-dimensional (1D) atomically thin crystals have attracted considerable interest due to their unique properties and potential applications. Herein, the chemical vapor deposition (CVD) growth of molybdenum disulfide (MoS 2 ) nanoribbons on sapphire(0001) supported monolayer MoS 2 flakes without catalysts as well as the characterizations by means of Raman and photoluminescence (PL) spectroscopy, optical microscopy (OM), atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM). The Raman and PL results is reported, as well as OM images reveal that such MoS 2 nanoribbons grow on monolayer MoS 2 flakes. STEM and selected area electron diffraction (SAED) results reveal that they are grown along the 〈 10 1 ¯ 0 〉 direction with atomically sharp edges. Controlled experiments show that the deficiency of sulfur vapor at the beginning of growth induced 1D MoO x S 2− x crystals as precursors. The subsequent sulfurization changes them into MoS 2 nanoribbons. These findings provide a facile approach to MoS 2 nanoribbons and enrich the horizon of the preparation of nanostructured transition metal dichalcogenides.
A method has been developed for controlled epitaxial growth on cubic nanocrystals by selectively activating their surface via etching. For example, it produces Pd concave nanocubes via seeding growth on their corners and edges, and in turn, formulates highly active sites for catalysis. This method offers a better capability of preventing atomic addition on undesired locations and maintaining particle size in the seeding process, as compared with the previous technique. With the particle size well maintained, the products fully exhibit superior electrocatalytic performance enabled by active sites and high-index facets in formic acid oxidation. Another contribution of this work is to enable the growth of a noble metal with high catalytic activities on another type of cheaper metal, which greatly reduces the usage of expensive materials while retaining high catalytic activity. In this article, we have demonstrated the deposition of a very limited amount of Pt (only 3.3 wt%) on Pd nanocrystals towards high electrocatalytic activities in an oxygen reduction reaction. Preliminary studies demonstrate that the synthetic strategy can be also applied to the controllable deposition of a different material on the faces of a nanocrystal by simply altering surface conditions.
2D nonlayered materials have attracted more and more attention due to their novel properties and special surface structures. However, due to isotropic chemical bonds within the crystal, the synthesis of ultrathin 2D nonlayered materials is an urgent challenge. Herein, α -Fe 2 O 3 2D nanosheets as thin as ≈8.2 nm on different substrates using self-designed ultralow concentration precursors combined with Gibbs free energy and Se catalysts design are successfully synthesized. The thickness-dependent growth mechanism is systematically studied, demonstrating the thermodynamic and kinetic controlling factors. The as-grown α -Fe 2 O 3 nanosheets are demonstrated with single-crystal structures without any other elements doping. The α -Fe 2 O 3 nanosheets photodetectors show the reasonable response performance with the positive photoconductive mechanism. This improved chemical vapor deposition method provides a promising idea for the synthesis of ultrathin 2D nonlayered materials.
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