Molybdenum disulphide is a layered transition metal dichalcogenide that has recently raised considerable interest due to its unique semiconducting and opto-electronic properties. Although several theoretical studies have suggested an electronic phase transition in molybdenum disulphide, there has been a lack of experimental evidence. Here we report comprehensive studies on the pressure-dependent electronic, vibrational, optical and structural properties of multilayered molybdenum disulphide up to 35 GPa. Our experimental results reveal a structural lattice distortion followed by an electronic transition from a semiconducting to metallic state at B19 GPa, which is confirmed by ab initio calculations. The metallization arises from the overlap of the valance and conduction bands owing to sulphur-sulphur interactions as the interlayer spacing reduces. The electronic transition affords modulation of the opto-electronic gain in molybdenum disulphide. This pressuretuned behaviour can enable the development of novel devices with multiple phenomena involving the strong coupling of the mechanical, electrical and optical properties of layered nanomaterials.

Controlling the band gap by tuning the lattice structure through pressure engineering is a relatively new route for tailoring the optoelectronic properties of two-dimensional (2D) materials. Here, we investigate the electronic structure and lattice vibrational dynamics of the distorted monolayer 1T-MoS2 (1T') and the monolayer 2H-MoS2 via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS2 increases by 11.7% from 1.85 to 2.08 eV, which is the highest reported for a 2D transition metal dichalcogenide (TMD) material. DFT calculations reveal a subsequent decrease in the band gap with eventual metallization of the monolayer 2H-MoS2, an overall complex structure-property relation due to the rich band structure of MoS2. Remarkably, the metastable 1T'-MoS2 metallic state remains invariant with pressure, with the J2, A1g, and E2g modes becoming dominant at high pressures. This substantial reversible tunability of the electronic and vibrational properties of the MoS2 family can be extended to other 2D TMDs. These results present an important advance toward controlling the band structure and optoelectronic properties of monolayer MoS2 via pressure, which has vital implications for enhanced device applications.

Individual ribbons of graphene show orientation-dependent electronic properties of great interest, yet to ensure their perfect geometry and integrity or to assemble free ribbons into a device remains a daunting task. Here we explore, using density functional theory, an alternative possibility of "nanoroads" of pristine graphene being carved in the electrically insulating matrix of fully hydrogenated carbon sheet (graphane). Such one-dimensional entities show individual characteristics and, depending upon zigzag (and their magnetic state) or armchair orientation, can be metallic or semiconducting. Furthermore, the wide enough zigzag roads become magnetic with energetically similar ferro- and antiferromagnetic states. Designing magnetic, metallic, and semiconducting elements within the same mechanically intact sheet of graphene presents a new opportunity for applications.

The high entropy alloy (HEA) nanoparticles have been prepared using cast cum cryo-milling process. In which, the Au, Ag, Pd, Pt and Cu (99.9 at. % pure, Alfa Aesar, USA) melted under argon environment to synthesize cast HEAs and afterwardcast HEA have been milled in cryomill for 6 hours. The detailed synthesis process can be found elsewhere. 1 The cryomilled powder (HEA nanoparticles) has been characterizedin order tothe crystalline phase, size, chemical homogeneity, composition, and catalyst activity. The X-ray diffraction recorded using Panalytical empyrean ( max =1.54056 A),and size of nanoparticles have been estimated using Transmission electron microscope (FEI, Technai G 2 , UT 20 operated at 200

SnO 2 is widely used as a transparent conductor and sensor material. Better understanding and control of its conductivity would enhance its performance in existing applications and enable new ones, such as in light emitters. Using density functional theory, we show that the conventional attribution of n-type conductivity to intrinsic point defects is incorrect. Unintentional incorporation of hydrogen provides a consistent explanation of experimental observations. Most importantly, we find that SnO 2 offers excellent prospects for p-type doping by incorporation of acceptors on the Sn site. Specific strategies for optimizing acceptor incorporation are presented.