The large tunability of band gaps and optical absorptions of armchair MoS2 nanoribbons of different widths under bending is studied using density functional theory and many-body perturbation GW and Bethe–Salpeter equation approaches. We find that there are three critical bending curvatures, and the non-edge and edge band gaps generally show a non-monotonic trend with bending. The non-degenerate edge gap splits show an oscillating feature with ribbon width n, with a period $$\Delta n=3$$ Δ n = 3 , due to quantum confinement effects. The complex strain patterns on the bent nanoribbons control the varying features of band structures and band gaps that result in varying exciton formations and optical properties. The binding energy and the spin singlet–triplet split of the exciton forming the lowest absorption peak generally decrease with bending curvatures. The large tunability of optical properties of bent MoS2 nanoribbons is promising and will find applications in tunable optoelectronic nanodevices.

A chromium triiodide (CrI3) monolayer has an interesting ferromagnetic ground state. In this work, we calculate band structures and magnetic moments of tensile-strained and bent zigzag CrI3 nanoribbons with density functional theory. The edge iodine atoms form flat low-lying conduction bands and couple with chromium atoms ferromagnetically, while the non-edge iodine atoms weakly couple antiferromagnetically. Narrow CrI3 nanoribbons have two locally stable magnetic moment orientations, namely, out-of-plane and in-plane (along the nanoribbon periodic direction) configurations. This enables four magnetization states in CrI3 nanoribbons, including two out-of-plane ones (up and down) and two in-plane ones (forward and backward along the nanoribbon periodical direction), increasing the operating controllability. Based on the one-dimensional Ising spin chain model, the spin correlation length of the narrow CrI3 nanoribbon is estimated to be about 10 Å at its estimated Curie temperature of 27 K, which is lower than the measured 45 K of the monolayer CrI3. The optical absorption and magneto-optical properties of CrI3 nanoribbons are investigated with many-body perturbation GW-BSE (Bethe–Salpeter equation), including magnetic dichroism and Faraday and magneto-optical Kerr effects. The low-energy dark excitons are mainly from transitions between electrons and holes with unlike spins and are non-Frenkel-like, while the bright excitons have mixed spin configurations. The intrinsic lifetime of excitons can be over one nanosecond, suitable for quantum information processes. Tensile strains and bending manifestly modulate the absorption spectra and magneto-optical properties of CrI3 nanoribbons within a technologically important photon energy range of ∼1.0–2.0 eV. The CrI3 nanoribbons can be used in 1D or 2D magnetic storage nanodevices, tunable magnetic optoelectronics, and spin-based quantum information controls.

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Visceral leishmaniasis is the most severe form of leishmaniasis, caused by the obligate intracellular protozoan parasites Leishmania donovani or L. infantum , transmitted by the bite of phlebotomine sand fly. Visceral leishmaniasis is a disease of lowlands and uncommon in highlands. We report a case of visceral leishmaniasis in 13‐year‐old female patient from a village of Arghakhanchi situated at an altitude of 1200 m.

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A WSe2 monolayer shows many interesting properties due to its spin-orbit coupling induced spin splitting in bands around the Fermi level and the spin-valley configuration. The orientation of the spin...