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Quasi one-dimensional (1D) vanadium tetrasulfide (VS4) nanowires (NWs) are synthetic semiconductors which combine with each other through van der Waals interactions to form bulk phases. However, the properties of these individual NWs remain unknown. Nevertheless, our calculations of their stability indicate that VS4 NWs can be separated from their bulk structures. Accordingly, we theoretically investigated the geometrical, electronic, and magnetic properties of bulk phase and isolated VS4 NWs. Our results indicate that both bulk phase and isolated VS4 NWs are semiconductors with band gaps of 2.24 and 2.65 eV, respectively, and that they prefer the antiferromagnetic (AFM) ground state based on DFT calculations. These calculations also suggested that isolated VS4 NWs show half-metallic antiferromagnetism upon electron and hole doping because carrier doping splits the spin degeneracy to induce local spin polarisation. As a result, spin polarisation currents in isolated VS4 NWs can be manipulated with locally applied gate voltage. Therefore, these 1D AFM materials have a high potential for advancing both fundamental research and spintronic applications because they are more resistant to magnetic perturbation than their 1D ferromagnetic counterparts. [ABSTRACT FROM AUTHOR]

Manipulation of the electronic properties of 2D materials with molecular adsorption has been widely reported in the past decade. However, the impact of adsorption of molecules on the magnetism of intrinsic 2D magnets is not yet sufficiently understood. Inspired by the recent discovery of intrinsic 2D ferromagnetism in atomically thin Cr2Ge2Te6 and CrI3 crystals, in this investigation, the adsorption of gas molecules including CO, CO2, H2O, N2, NH3, NO, NO2, O2 and SO2 on the basal plane of a Cr2Ge2Te6 (CGT) monolayer was systematically investigated by density functional theory. The structures, energy, charge transfer, work function, and electronic and magnetic properties of the gas molecule adsorbed Cr2Ge2Te6 monolayers were explored. It has been found that the adsorption of gas molecules significantly influences the electronic and magnetic properties of a CGT sheet. It was observed that the adsorption of molecules could effectively enhance the ferromagnetism and Curie temperature (TC) of the CGT sheet. Notably, a remarkable enhancement of ferromagnetism and TC by 38% and 32% was achieved by the adsorption of NO and NO2, respectively. Moreover, NO2 adsorbed CGT exhibits a semiconductor-to-metal transition. The enhanced ferromagnetism and tunable electronic structure could be ascribed to the considerable charge transfer as well as to the alignment of the frontier molecular orbital. The outcome of this study reveals not only exciting insights into the environmental effect on 2D magnets but also provides a new candidate as a NO2 gas sensor. [ABSTRACT FROM AUTHOR]

Thallium compounds have appeared as a new class of advanced thermoelectric (TE) materials owing to their extremely low lattice thermal conductivity. Using a first-principles approach and Boltzmann transport theories, we investigate the electronic and phonon transport properties of a ternary thallium telluride, TlInTe2. Unlike the Bi2Te3 and PbTe used in current TE devices, a multi-valley band structure with intrinsic degeneracy is obtained for TlInTe2, which contributes to its high Seebeck coefficient and relatively high power factor. Also, because of its weak bonding stiffness and strong phonon anharmonicity, TlInTe2 has an extremely low lattice thermal conductivity of about 0.37 W m−1 K−1 at room temperature, which is almost one third of the values for Bi2Te3 and PbTe. Consequently, competitive ZT values of 1.78 and 1.84 are obtained at 300 K for p- and n-doped TlInTe2, respectively, indicating that thallium compounds are promising TE materials for practical applications. [ABSTRACT FROM AUTHOR]

A phenanthrene-bridged photochromic diarylethene with two crown ethers as ion recognizing groups has been synthesized and characterized by single crystal X-ray diffraction. This material shows good photochromism and fatigue resistance. Only the closed form of this diarylethene derivative can form coordination complexes with Cu2+ and Hg2+ and at the same time, the combination of the photochromic material and metal ions would lead to the cycle opening of the closed photochromic unit and color bleaching processes. This special property can be applied in the visual detection of these two heavy metal ions not only in solution but also in solid state. The fluorescence of the diarylethene is sensitive to light, copper and mercury ions. As a result, a single molecular logic circuit was constructed using the absorbance and fluorescence intensity at a specific wavelength as outputs and appropriate combinational stimuli of UV/Vis light, Cu2+ and Hg2+ ions as inputs. Moreover, its fluorescence is sensitive to historical input signals. Based on this, a key pad lock using three codes to open was fabricated. [ABSTRACT FROM AUTHOR]