Enhanced optical, magnetic and hydrogen evolution reaction properties of Mo1-x Ni x S2 nanoflakes.

Due to exceptional electronic, optoelectronic and catalytic properties, MoS2 has attracted extensive research interest in various applications. In the present scenario, the exploitation of noble-metal-free catalysts for hydrogen evolution is of great interest. Herein, we report the structural, optical, magnetic and electrocatalytic properties of pure and nickel-substituted MoS2 nanostructures synthesized by the hydrothermal method. X-ray diffraction (XRD) analysis reveals that all samples exhibit the hexagonal structure of MoS2 and the formation of NiS2 at higher concentrations of nickel. Vibrating sample magnetometer (VSM) measurements of the Mo1-x Ni x S2 nanostructures show a hysteresis loop at room temperature with a higher saturation magnetization for 1% Ni-substituted MoS2 nanostructures, confirming the ferromagnetic behaviour of the sample. The indirect-to-direct band gap transition of few-layered nanostructures was confirmed by the optical absorption spectrum showing bands in the 600-700 nm and 350-450 nm regions. This study also highlights the excitation wavelength-dependent down- and up-conversion photoluminescence of the as-synthesized samples, providing new horizons for the design of MoS2-based optical and spintronic devices. The electrocatalytic effect of 3% Ni-substituted MoS2 nanostructures has been found to be higher than that of other deposit concentrations as it corresponds to the efficient hydrogen evolution reaction (HER).

MoS2-ZnO nanocomposites as highly functional agents for anti-angiogenic and anti-cancer theranostics.

Due to its excellent properties, 2D-MoS2 finds potential applications in the fields of electronics, optoelectronics, energy storage and conversion, biomedicine, etc. This work deals with the incorporation of ZnO into 2D-MoS2, its structural, morphological, optical, and magnetic studies and its application as an efficient cancer therapeutic agent. The MoS2-ZnO nanocomposite exhibits remarkable excitation wavelength dependent down-conversion and up-conversion photoluminescence. The observation of wasp-waisted magnetism in the MoS2-ZnO nanocomposite indicates the coupling of ZnO and MoS2 materials inducing multimodal population. The MoS2-ZnO nanocomposite showed cytotoxic properties with a safety index reaching up to ∼2. An in ovo xenograft assay revealed that the MoS2-ZnO nanocomposite retards tumor growth by specifically activating caspase-3 and thereby inducing cellular apoptosis. Moreover, the treatment of xenografts with the MoS2-ZnO nanocomposite down regulated the expression of major pro-angiogenic genes such as VEGF, VEGFR2 etc. thereby curtailing vascularization into the tumor intima. Treatment of tumor xenografts with the MoS2-ZnO nanocomposite caused reduced expression of mesenchymal specific genes and elevated expression of epithelial specific genes, implying a role of the MoS2-ZnO nanocomposite in retarding the process of epithelial to mesenchymal transition (EMT). This study highlights that the introduction of ZnO into MoS2 nanostructures offers a unique idea to design efficient MoS2-based multifunctional nanocomposites that provide opportunities in advanced biomedical and optoelectronic applications.

Observation of Room Temperature Photoluminescence from Asymmetric CuGaO2/ZnO/ZnMgO Multiple Quantum Well Structures.

Asymmetric (CuGaO2/ZnO/ZnMgO) and symmetric (ZnMgO/ZnO/ZnMgO) multiple quantum well (MQW) structures were successfully fabricated using pulsed laser deposition (PLD) and their comparison were made. Efficient room temperature photoluminescent (PL) emission was observed from these MQWs and temperature dependent luminescence of asymmetric and symmetric MQWs can be explained using the existing theories. A systematic blue shift was observed in both MQWs with decrease in the confinement layer thickness which could be attributed to the quantum confinement effects. The PL emission from asymmetric and symmetric MQW structures were blue shifted compared to 150 nm thick ZnO thin film grown by PLD due to quantum confinement effects.