The liquid-phase exfoliation of tin(II) sulfide to produce SnS nanosheets in N-methyl-2-pyrrolidone is reported. The material is characterized by Raman spectroscopy, atomic force microscopy, lattice-resolution scanning transmission electron microscope imaging, and energy dispersive X-ray spectrum imaging. Quantum chemical calculations on the optoelectronic characteristics of bulk and 10-layer down to monolayer SnS have been performed using a quantum chemical density functional tight-binding approach. The optical properties of the SnS and centrifugally fractionated SnS nanosheet dispersions were compared to that predicted by theory. Through centrifugation, bilayer SnS nanosheets can be produced size-selectively. The scalable solution processing of semiconductor SnS nanosheets is the key to their commercial exploitation and is potentially an important step toward the realization of a future electronics industry based on two-dimensional materials.
Similar to carbon, several transition-metal chalcogenides
are able
to form tubular structures. Here, we present results from systematic
theoretical investigations of structural and mechanical properties
of MoS2 and TiS2 nanotubes in comparison to
each other, to carbon nanotubes, and to corresponding experimental
results. We have obtained the nanotube’s Young’s moduli
(Y), Poisson ratios (ν), and shear moduli (G) as functions of diameter and chirality, using a density-functional-based
tight-binding method. Additionally, we have simulated tensile tests
by Born–Oppenheimer molecular dynamics simulations. The influence
of structural defects on the investigated mechanical properties has
been studied as well. As a result of the simulated stretching experiments,
we found that TiS2 nanotubes can be stretched only half
as much as MoS2 nanotubes.
Two-dimensional semiconductor materials with puckered structure offer a novel playground to implement nanoscale thermoelectric, electronic, and optoelectronic devices with improved functionality. Using a combination of approaches to compute the electronic and phonon band structures with Green's function based transport techniques, we address the thermoelectric performance of phosphorene, arsenene, and SnS monolayers. In particular, we study the influence of anisotropy in the electronic and phononic transport properties and its impact on the thermoelectric figure of merit ZT. Our results show no strong electronic anisotropy, but a strong thermal one, the effect being most pronounced in the case of SnS monolayers. This material also displays the largest figure of merit at room temperature for both transport directions, zigzag (ZT ∼ 0.95) and armchair (ZT ∼ 1.6), thus hinting at the high potential of these new materials in thermoelectric applications.
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