Sharma S. R. K. C. Yamijala

A hexanuclear Cu(I) cluster supported by cuprophilic interaction: effects of aromatics on luminescence properties

A hexanuclear Cu(I) cluster {Cu3(L)2}2 (1) based on a novel tripodal linker (L) has been synthesized. 1 shows intense emission (λmax = 560 nm) with lifetime 〈τ〉 = 224 μs and quantum yield = 27.6%. The emission is highly sensitive towards different electron rich and electron deficient aromatics. DFT calculations were performed to understand the origin of emission and sensing properties.

Clean WS2 and MoS2 Nanoribbons Generated by Laser‐Induced Unzipping of the Nanotubes

The preparation of 1D WS(2) and MoS(2) flexible nanoribbons by laser-induced unzipping of the nanotubes is reported. The nanoribbons are of high quality, uniform width, and devoid of surface contamination. The zig-zag edges in WS(2) nanoribbons give rise to ferromagnetism at room temperature.

Pressure induced structural, electronic topological, and semiconductor to metal transition in AgBiSe2

We report the effect of strong spin orbit coupling inducing electronic topological and semiconductor to metal transitions on the thermoelectric material AgBiSe2 at high pressures. The synchrotron X-ray diffraction and the Raman scattering measurement provide evidence for a pressure induced structural transition from hexagonal (α-AgBiSe2) to rhombohedral (β-AgBiSe2) at a relatively very low pressure of around 0.7 GPa. The sudden drop in the electrical resistivity and clear anomalous changes in the Raman line width of the A1g and Eg(1) modes around 2.8 GPa was observed suggesting a pressure induced electronic topological transition. On further increasing the pressure, anomalous pressure dependence of phonon (A1g and Eg(1)) frequencies and line widths along with the observed temperature dependent electrical resistivity show a pressure induced semiconductor to metal transition above 7.0 GPa in β-AgBiSe2. First principles theoretical calculations reveal that the metallic character of β-AgBiSe2 is induced mainl...

Nitrogen-Doped Graphene Quantum Dots as Possible Substrates to Stabilize Planar Conformer of Au20 over Its Tetrahedral Conformer: A Systematic DFT Study

Utilizing the strengths of nitrogen-doped graphene quantum dot (N-GQD) as a substrate, herein, we have shown that one can stabilize the catalytically more active planar Au20 (P-Au20) compared with the thermodynamically more stable tetrahedral structure (T-Au20) on an N-GQD. Clearly, this simple route avoids the usage of traditional transition-metal oxide substrates, which have been suggested and used for stabilizing the planar structure for a long time. Considering the experimental success in the synthesis of N-GQDs and in the stabilization of Au nanoparticles on N-doped graphene, we expect our proposed method to stabilize planar structure will be realized experimentally and will be useful for industrial level applications.

Effects of edge passivations on the electronic and magnetic properties of zigzag boron-nitride nanoribbons with even and odd-line stone–wales (5–7 pair) defects

First-principles spin-polarized calculations have been performed on passivated boron-nitride nanoribbons (BNNRs) with pentagon–heptagon line-defects (PHLDs), also called as Stone–Wales line-defects. Two kinds of PHLDs, namely, even-line and odd-line PHLDs, have been added either at one edge or at both edges of BNNRs. Single-edge (with all its different possibilities, for example, for a BNNR with 2-line PHLD at single-edge there are eight possibilities) as well as both-edge passivations have been considered for all the ribbons in this study by passivating each edge atom with hydrogen atom. Density of states (DOS) and projected-DOS analysis have been accomplished to understand the underlying reason for various properties. We find that passivation lead to different effects on the electronic and magnetic properties of a system, and the effects are mainly based on the line-defect introduced and/or on the atoms which are present at the passivated edge. In general, we find that, passivation can play a key role in tuning the properties of a system only when it has a zigzag edge.

Alpha Lead Oxide (α-PbO): A New 2D Material with Visible Light Sensitivity

Even though transition metal dichalcogenides (TMDCs) are deemed to be novel photonic and optoelectronic 2D materials, the visible band gap being often limited to monolayer, hampers their potential in niche applications due to fabrication challenges. Uncontrollable defects and degraded functionalities at elevated temperature and under extreme environments further restrict their prospects. To address such limitations, the discovery of a new 2D material, α-PbO is reported. Micromechanical as well as sonochemical exfoliation of 2D atomic sheets of α-PbO are demonstrated and its optical behavior is investigated. Spectroscopic investigations indicate layer dependent band gaps. In particular, even multilayered PbO sheets exhibit visible band gap > 2 eV (direct) which is rare among semiconducting 2D materials. The emission lifetime of multilayer PbO atomic sheets is 7 ns (dim light) as compared to the monolayer which gives 2.5 ns lifetime and an intense light. Density functional theory calculations of layer dependent band structure of α-PbO matches well with experimental results. Experimental findings suggest that PbO atomic sheets exhibit hydrophobic nature, thermal robustness, microwave stability, anti-corrosive behaviour and acid resistance. This new low-cost, abundant and robust 2D material is expected to find many applications in the fields of electronics, optoelectronics, sensors, photocatalysis and energy storage.