The ability to control exciton radiative recombination dynamics is a promising element for expanding applications of atomically thin two-dimensional (2D) materials. Here, we show that twist angle can be used to control the interlayer indirect exciton dynamics of transitionmetal dichalcogenide bilayers by changing the indirect band gaps in the two layers. Exciton radiative recombination lifetimes of twisted MoS 2 bilayers are monitored by fluorescence lifetime imaging microscopy (FLIM) technology. Interestingly, interlayer twists cause only a weak change of direct excitons, but greatly modify the indirect exciton recombination channel due to the repulsive steric effects. Thus, the indirect exciton radiative recombination lifetime first increases from 5.2 to 27.0 ns with twist angle (θ) changing from 0 to 30°(more than 5-fold), and then decreases to 8.3 ns with θ further increasing to 60°. Our work paves a new route for engineering exciton radiative recombination dynamics of 2D materials, which can improve the future applications of optoelectronic devices based on 2D materials.
The structure of the title compound, [Ni(NCS)2(C6H8N2)4], consists of isolated molecules of [Ni(NCS)2(Aim)4] (Aim = 1-allylimidazole), which contain a distorted octahedral NiN6 chromophore. The NCS− anions are trans and four N atoms from the 1-allylimidazole ligands define the equatorial plane. The mean Mn—N(Aim) and Mn—N(NCS) distances are 2.105 (2) and 2.098 (2) Å, respectively. Weak C—H⋯N interactions contribute to the crystal packing stability.
Samples of AISI 201 austenitic stainless steel were produced by plasma nitriding at 350[Formula: see text]C, 390[Formula: see text]C, 420[Formula: see text]C, 450[Formula: see text]C and 480[Formula: see text]C for 5[Formula: see text]h. Systematic characterization of the nitrided layer was carried out in terms of micrograph observations, phase identification, chemical composition depth profiling, surface microhardness measurements and electrochemical corrosion tests. The results show that the surface hardness and the layer thickness increased with increasing temperature. XRD indicated that a single S-phase layer was formed during low temperature ([Formula: see text][Formula: see text]420[Formula: see text]C), while Cr2N or CrN phase was formed besides S-phase when nitrided at 450[Formula: see text]C and 480[Formula: see text]C. The specimen treated at 390[Formula: see text]C presents a much enhanced corrosion resistance compared to the untreated substrate. The corrosion resistance deteriorated for samples treated above 450[Formula: see text]C due to the formation of chromium nitrides.
The title compound, [Ni(NCS)2(C9H8N2)4], crystallizes with two independent half-molecules in the asymmetric unit and the NiII ions situated on centres of symmetry. In both independent molecules, the NiII ion displays a compressed octahedral environment formed by four N atoms from the 1-phenyl-1H-imidazole ligands, which define the equatorial plane, with a mean Ni—N distance of 2.119 (11) Å, and two axial N atoms from two NCS− anions, with a mean Ni—N distance of 2.079 (7) Å. The crystal packing exhibits weak intermolecular S⋯S contacts of 3.411 (2) Å.
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