We study the anisotropic electronic properties of two-dimensional (2D) SnS, an analogue of phosphorene, grown by physical vapor transport. With transmission electron microscopy and polarized Raman spectroscopy, we identify the zigzag and armchair directions of the as-grown 2D crystals. The 2D SnS field-effect transistors with a cross-Hall-bar structure are fabricated. They show heavily hole-doped (∼10 cm) conductivity with strong in-plane anisotropy. At room temperature, the mobility along the zigzag direction exceeds 20 cm V s, which can be up to 1.7 times that in the armchair direction. This strong anisotropy is then explained by the effective mass ratio along the two directions and agrees well with previous theoretical predictions. Temperature-dependent carrier density determined the acceptor energy level to be ∼45 meV above the valence band maximum. This value matches a calculated defect level of 42 meV for Sn vacancies, indicating that Sn deficiency is the main cause of the p-type conductivity.

high photostability, and ease of preparation, [1,2] which render them attractive for applications in bioimaging, [3][4][5] sensor, [6] photocatalysis, [7] energy storage, [8,9] and optoelectronic devices. [10][11][12] Luminescence properties of CDots are still under intensive investigations, both to reveal their origin and to optimize them for lighting applications. [13][14][15][16] In terms of the emission mechanisms, apart from the recently evolving evidences on the molecular fluorophore formation during the synthesis of CDots and their contribution to the strong emission of the resulting samples in the blue spectral region, [17][18][19] intrinsic (bandgap related) emission from the CDots core originating from the conjugated sp 2 -domains [20,21] is most promising for their development and applications. [22] Theoretical calculations [23] and experimental studies [24] pointed out that the intrinsic emissions of CDots can be tuned by modulating the dimension of conjugated sp 2 -domains. However, it is still lack of experimental method to achieve full color emissions through tuning the sizes of sp 2 -domains in CDots. Several groups also showed that the emission of CDots can be tuned toward green and red through surface modification. [25,26] Ding et al. prepared a series of CDots with emission tunable from 440 to 625 nm, which has been ascribed to the varying degree of their surface oxidation. [27] Similarly, Bao et al. reported a wet chemical method toward CDots with emission tunable from 430 to 610 nm by surface oxidation. [28] Several other recent studies suggested some strategies to achieve higher photoluminescence quantum yields (PLQYs) in the full-color range by using different precursors. [29] To the best of our knowledge, there is no experimental evidence to achieve full-color emissive CDots in the same precursors and method, which is very important for fundamental understanding and realizing full-color intrinsic emissive CDots.Apart from their promising biological applications, CDotbased solid state luminescent composites, as emerging environmentally friendly phosphors, have received increasing attentions for carbon-based light emitting diodes (LEDs), and particularly white LEDs (WLEDs). [30,31] However, in realizing efficient CDot-based phosphors, the quenching of emission in the solid state constitutes a severe issue. [32,33] It is important to exploit suitable matrices, surface functionalizing agents and methods to produce well dispersed, environmentally protected, Light-emitting carbon dots (CDots) are widely investigated due to their distinct merits. However, it is still a challenge to modulate their bandgap emissions and conquer their aggregation-induced luminescence quenching to achieve full-color highly emissive CDot-based phosphors. Herein, this study proposes an approach toward realization of full-color emissive CDots from two common precursors, citric acid and urea, through employing three different solvents (water, glycerol, and dimethylformamide) and their combinations in a solvothermal synth...

A new layered oxide semiconductor (Bi2O2Se) is found with excellent electronic properties for promising applications.

Recently, VIB-group layered transition metal dichalcogenides (TMDs), MX 2 (M = Mo, W; X = S, Se, Te), attracted extensive attention due to rich physiochemical properties, ranging from catalysis, [1][2][3] topological states, [4][5][6][7][8][9][10][11][12][13][14][15][16] valley polarization, [17][18][19][20][21][22] even to superconductivity. [23][24][25][26][27][28] These multiple electronic properties essentially originate from varied crystal structures of TMD materials. The typical crystal structure in TMD materials is the 2H-type structure with [X-M-X] atoms in ABA stacking in each monolayer (Figure S1a, Supporting Information). Usually, 2H MX 2 materials are semiconducting, such as, 2H MoS 2 , where the valley polarization was widely studied. [17][18][19] Also, Ising superconductivity was observed when the TMD materials are reduced down to a few or even oneRecently the metastable 1T′-type VIB-group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS 2 dubbed "2M" WS 2 , is constructed from 1T′ WS 2 monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system. Intrinsic superconductivity is observed in 2M WS 2 with a transition temperature T c of 8.8 K, which is the highest among TMDs not subject to any fine-tuning process. Furthermore, the electronic structure of 2M WS 2 is found by Shubnikov-de Haas oscillations and first-principles calculations to have a strong anisotropy. In addition, topological surface states with a single Dirac cone, protected by topological invariant Z 2 , are predicted through first-principles calculations. These findings reveal that the new 2M WS 2 might be an interesting topological superconductor candidate from the VIB-group transition metal dichalcogenides.

Thermal‐treatment controlled room temperature phosphorescence is realized by embedding either originally synthesized carbon dots (CDs) or 200 °C thermal‐treated CDs into a polyvinylalcohol (PVA) matrix through post‐synthetic thermal annealing at 200 or 150 °C. The thermal‐treatment controlled phosphorescence is attributed to the transfer of photoexcitation from the excited singlet state to the triplet state through intersystem crossing, followed by radiative transition to the ground state, which is due to decrease of quenchers (oxygen) in the CDs and suppression of the vibrational dissipations through the chemical bonding of CDs in the PVA matrix. Multilevel fluorescence/phosphorescence data encryption is demonstrated based on the thermal‐treatment controlled phosphorescence from CD@PVA composites.

Quantum confined materials have been extensively studied for photoluminescent applications. Due to intrinsic limitations of low biocompatibility and challenging modulation, the utilization of conventional inorganic quantum confined photoluminescent materials in bio-imaging and bio-machine interface faces critical restrictions. Here, we present aromatic cyclo-dipeptides that dimerize into quantum dots, which serve as building blocks to further self-assemble into quantum confined supramolecular structures with diverse morphologies and photoluminescence properties. Especially, the emission can be tuned from the visible region to the near-infrared region (420 nm to 820 nm) by modulating the self-assembly process. Moreover, no obvious cytotoxic effect is observed for these nanostructures, and their utilization for in vivo imaging and as phosphors for light-emitting diodes is demonstrated. The data reveal that the morphologies and optical properties of the aromatic cyclo-dipeptide self-assemblies can be tuned, making them potential candidates for supramolecular quantum confined materials providing biocompatible alternatives for broad biomedical and opto-electric applications.

Exchange bias is a physical phenomenon whereby the spins of a ferromagnet are pinned by those of an antiferromagnet, and this phenomenon has played an undisputed role in magnetic data storage. Over the past few decades, this effect has been observed in a variety of antiferromagnet/ferromagnet systems. New aspects of this phenomenon are being discovered. With the increasing interest in van der Waals (vdW) magnets, we address the question whether the effect can exist in magnetic vdW heterostructures. Here, we report exchange-bias fields of over 50 mT in mechanically exfoliated CrCl3/Fe3GeTe2 heterostructures at 2.5 K, the value of which is highly tunable by the field-cooling process and the heterostructure thickness. We postulate an intuitive picture explaining how the effect arises in this vdW heterostructure, as well as explaining the practical difficulty associated with capturing the effect. This work opens up new routes toward designing spintronic devices made of atomically thin vdW magnets.

Recent precise measurements of cosmic ray spectra revealed an anomalous hardening at ∼200 GV, observed by the ATIC, CREAM, PAMELA, and AMS02 experiments. Particularly, the latest observation of the