Single-layer transition-metal dichalcogenides (TMDs) receive significant attention due to their intriguing physical properties for both fundamental research and potential applications in electronics, optoelectronics, spintronics, catalysis, and so on. Here, we demonstrate the epitaxial growth of high-quality single-crystal, monolayer platinum diselenide (PtSe2), a new member of the layered TMDs family, by a single step of direct selenization of a Pt(111) substrate. A combination of atomic-resolution experimental characterizations and first-principle theoretic calculations reveals the atomic structure of the monolayer PtSe2/Pt(111). Angle-resolved photoemission spectroscopy measurements confirm for the first time the semiconducting electronic structure of monolayer PtSe2 (in contrast to its semimetallic bulk counterpart). The photocatalytic activity of monolayer PtSe2 film is evaluated by a methylene-blue photodegradation experiment, demonstrating its practical application as a promising photocatalyst. Moreover, circular polarization calculations predict that monolayer PtSe2 has also potential applications in valleytronics.

Synthesis and magnetic properties of gold coated iron oxide nanoparticles J. Appl. Phys. 105, 07B504 (2009); 10.1063/1.3059607 Synthesis of self-assembled monodisperse 3 nm FePd nanoparticles: Phase transition, magnetic study, and surface effectThe monodisperse Fe 3 O 4 nanocubes with controllable sizes from 6.5 to 30.0 nm have been synthesized in one pot. The shape-induced texture of the self-assembled nanocube superlattices has been deposited onto substrates by a convective assembly technique. The cubelike shapes affect the crystalline orientation of individual particles within the self-assembled superlattices compared with the nanoparticles with an isotropic spherical shape. The nanocubes with a size less than 25 nm show a typical superparamagnetic behavior at room temperature. Comparison of the hysteresis loop at 5 K of cubes with different sizes reveals a size-dependent behavior of saturation magnetization and coercivity.

Organic redox-active molecules are inborn electrodes to store large-radius potassium (K) ion. High-performance organic cathodes are important for practical usage of organic potassium-ion batteries (OPIBs). However, smallmolecule organic cathodes face serious dissolution problems against liquid electrolytes. A novel insoluble small-molecule organic cathode [N,N′-bis(2anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g −1 ) is initially designed for OPIBs. In half cells (1-3.8 V vs K + /K) using 1 m KPF 6 in dimethoxyethane (DME), PTCDI-DAQ delivers a highly stable specific capacity of 216 mAh g −1 and still holds the value of 133 mAh g −1 at an ultrahigh current density of 20 A g −1 (100 C). Using reduced potassium terephthalate (K 4 TP) as the organic anode, the resulting K 4 TP||PTCDI-DAQ OPIBs with the electrolyte 1 m KPF 6 in DME realize a high energy density of maximum 295 Wh kg −1 cathode (213 mAh g −1 cathode × 1.38 V) and power density of 13 800 W Kg −1 cathode (94 mAh g −1 × 1.38 V @ 10 A g −1 ) during the working voltage of 0.2-3.2 V. Meanwhile, K 4 TP||PTCDI-DAQ OPIBs fulfill the superlong lifespan with a stable discharge capacity of 62 mAh g −1 cathode after 10 000 cycles and 40 mAh g −1 cathode after 30 000 cycles (3 A g −1 ). The integrated performance of PTCDI-DAQ can currently defeat any cathode reported in K-ion half/full cells.

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