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[en] The initial reactant concentration and the substrate play an important role on the nucleation and growth of MoS2 nanostructures during hydrothermal growth. In this work, MoS2 nanoflakes are grown on FTO and TiO2 nanorod arrays (NRs) substrates. The morphology, optical and photoelectric properties of MoS2 nanoflakes are affected by the initial reactant concentration. Compared with the FTO substrate, MoS2 nanoflakes tend to grow on TiO2 NRs substrates due to less mismatch between TiO2 and MoS2. The large surface roughness and the presence of surface states of the TiO2 NRs facilitate the nucleation and growth of MoS2 nanoflakes. The photoelectric characteristics of MoS2/TiO2 NRs compositions have been investigated. The MoS2/TiO2 NRs compositions prepared using the initial reactant concentration with 4 mM S atom concentration exhibit the higher photoresponse behavior, which is attributed to the better heterojunction contact interface between MoS2 nanoflakes and TiO2 NRs. MoS2 nanoflakes can not completely cover the TiO2 NRs under low initial reactant concentration, resulting in the small area of the contact interface. On the other hand, MoS2 nanoflakes tend to form the self-assembly nanoflowers under high initial reactant concentration, which induces the carriers recombination in MoS2, the poor transport properties of MoS2 and the detrimental effects on the photogenerated current.
[en] A ripples structure is observed in the photoluminescence (PL) spectra of MoS2 adsorbed on the surface of single polymethyl methacrylate (PMMA) microspheres in contrast to the broad spectra of nanosheets. Theoretical simulations and photonic nanojet technique have been used to identify the ripple structures. Part of these structures has been found to be due to the whispering gallery modes (WGMs) of the microcavity. The Raman modes of MoS2 and PMMA, on the other hand, are identified by the photonic nanojet induced enhancement. This work helps applications in photonics and sensing technique which require clean systems with well characterized spectral lines.
[en] Highlights: • We investigate the ballistic conduction of MoS2 in a spatially modulated magnetic field. • The chemical-potential-dependent conductance exhibits step behavior. • The sharp peak and rectangular structures of the conductance are stretched out as temperature rises. We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.
[en] A design for a high-sensitivity photodetector with a single layer of MoS2 transition-metal dichalcogenide used as the basic functional element is proposed and the process of its fabrication is presented step by step. Quality evaluation and the selection of functional MoS2 flakes is based on the results of combined optical characterization. The main operating characteristics of the fabricated device are investigated and a photosensitivity of 1.4 mA/W is demonstrated. A difference of this device in comparison with existing analogues is its high photosensitivity at low operating voltages (in the range of ±3 V).
[en] Highlights: • We perform first-principle studies on electron transport through four-terminal MoS2 nanoribbons. • Insulating bands exist in the spectra of linear conductance in the straight channels. • Finite transports are allowed to take place in the insulating-band region in the curved channels. • These results provide useful information for manipulating transport through MoS2 nanoribbons. - Abstract: We perform the first-principle studies on electron transport through four-terminal MoS2 nanoribbons. It is found that in such structures, insulating bands exist in the linear-conductance spectra of the nanoribbons with straight channels, which are related to the band gaps of the MoS2 nanoribbons. However, nonzero transports are allowed to take place in the insulating-band region in the geometries with curved channels. This phenomenon can be attributed to the formation of edge states in the curved-channel structures. We believe that these results provide useful information for the manipulation of electron transport through MoS2 nanoribbons.
[en] Monitoring the uptake, micro-environment and fate of micro or nano scaled particulate materials in cells is of paramount importance for the emerging fields of toxicology and medicine. Such particulate materials are known to interfere with colorimetric assays and many such assays record only a single end-point. Therefore, there is a need for a label-free, cost effective technique with little or no inference from the particulate materials. Raman micro-spectroscopy was used to simultaneously interrogate the integrity of few-layer MoS2 submicrometric plates in human macrophage-like cells, in vitro, as well as the biochemical characteristics of the local micro-environment in which they are encompassed. Firstly, the degradation profile of MoS2 plates induced by hydrogen peroxidase was established using UV–vis absorption and Raman micro-spectroscopy. Raman micro-spectroscopic maps interrogated all aspects of the cell, including the nucleus, cytoplasm and perinuclear region, and the location/distribution of MoS2 was monitored as a function of time (4, 24 and 72 h). Whereas only pristine MoS2 was detectable after 4 and 72 periods, degradation in vitro was confirmed following a 24 h incubation. Analysis of the MoS2 micro-environments revealed the presence of both phosphatidyl lipidic vesicles and enzymatic regions containing lysozyme, the former being most associated with the MoS2 degradation. There was an increase and saturation of cytosolic neutral lipids detected following a 24 h incubation with MoS2, which reduces following a prolonged incubation of 72 h. This study reveals that macrophage-like cells perform degradation of the material in vitro within lipidic vesicles subsequent to phagocytosis, which manifest as an increase in the production of lipid bodies as a mechanism of defense following exposure to industrial grade MoS2. (paper)
[en] Highlights: • Introduction of Graphite oxide and molybdenum disulfide composite for efficient hydrogen evolution reaction. • Overpotential of −0.47 V of the composite was two and three times lower than those of MoS2 and GO. • High stability of the composite was shown after 500 cycles. • High catalytic activity and excellent stability of the Go-MoS2 composite compared to MoS2 and GO. Graphite oxide and molybdenum disulfide (GO-MoS2) composite is prepared through a wet process by using hydrolysis of ammonium tetrathiomolybdate, and it exhibits excellent catalytic activity of the hydrogen evolution reaction (HER) with a low overpotential of −0.47 V, which is almost two and three times lower than those of precursor MoS2 and GO. The high performance of HER of the composite attributes to the reduced GO supporting MoS2, providing a conducting network for fast electron transport from MoS2 to electrodes. The composite also shows high stability after 500 cycles, demonstrating a synergistic effect of MoS2 and GO for efficient HER.
[en] Highlights: • The branched MoS2 nanowires were facile synthesized. • The PVP played an important role in forming the branched MoS2 nanowires. • The growth mechanism of branched MoS2 nanowires was proposed. - Abstract: In this work, the branched MoS2 nanowires are synthesized by a facile and feasible reflux method. It is clearly that the MoS2 nanowires interconnect with each other, forming regular branched network. In this fabrication, the polyvinyl pyrrolidone (PVP) is used as surfactant which is critical for the formation of branched MoS2 wires. Without the PVP, only MoS2 nanoparticles can be obtained.