We report high magnetic field scanning tunneling microscopy and Landau level spectroscopy of twisted graphene layers grown by chemical vapor deposition. For twist angles exceeding ~3° the low energy carriers exhibit Landau level spectra characteristic of massless Dirac fermions. Above 20° the layers effectively decouple and the electronic properties are indistinguishable from those in single-layer graphene, while for smaller angles we observe a slowdown of the carrier velocity which is strongly angle dependent. At the smallest angles the spectra are dominated by twist-induced van Hove singularities and the Dirac fermions eventually become localized. An unexpected electron-hole asymmetry is observed which is substantially larger than the asymmetry in either single or untwisted bilayer graphene.

Single-Layer Behavior and Its Breakdown in Twisted Graphene Layers

Two main innovations are presented in this article. (1) The first reproducible synthesis of silicon carbide nanotubes of different internal and external diameters. The method used, the shape memory synthesis, is based on the gas‐solid reaction between a vapor of SiO and nanotubes of carbon for the high diameters, and nanofibers of carbon for the small diameters. (2) A significant increase in the rate of a catalytic reaction (oxidation of H2S in S) probably due to a microscopic increase of the partial pressure of H2S inside the nanotubes, produced by condensation and microcapillarity, while the macroscopic partial pressure outside the tubes remains unchanged. This phenomenon could be extended to many other reactions, with polar gaseous reactants which are prone to condensation by capillarity at the usual temperatures of catalytic reaction, or with liquid phase reaction by an overconcentration of one of the reactants inside the tubes. c ∞ 2001 Academic Press

RESEARCH NOTE The First Preparation of Silicon Carbide Nanotubes by Shape Memory Synthesis and Their Catalytic Potential

Volumes in this widely revered series present comprehensive reviews of drug substances and additional materials, with critical review chapters that summarize information related to the characterization of drug substances and excipients. This organizational structure meets the needs of the pharmaceutical community and allows for the development of a timely vehicle for publishing review materials on this topic. The scope of the Profiles series encompasses review articles and database compilations that fall within one of the following six broad categories: Physical profiles of drug substances and excipients; Analytical profiles of drug substances and excipients; Drug metabolism and pharmacokinetic profiles of drug substances and excipients; Methodology related to the characterization of drug substances and excipients; Methods of chemical synthesis; and Reviews of the uses and applications for individual drug substances, classes of drug substances, or excipients. * Contributions from leading authorities * Informs and updates on all the latest developments in the field

Profiles of Drug Substances, Excipients, and Related Methodology

Synthesis of novel inhibitors of α-glucosidase based on the benzothiazole skeleton containing benzohydrazide moiety and their molecular docking studies

Isatin based Schiff bases as inhibitors of α-glucosidase: Synthesis, characterization, in vitro evaluation and molecular docking studies.

Giant NLO response and deep ultraviolet transparency of dual (alkali/alkaline earth) metals doped C6O6Li6 electrides

Synthesis of pyridine and furan based arylated ketones through palladium catalyst with DFT study of their static and frequency dependent NLO response

Reversible H_2 Storage Capacity of Ni Functionalized Carbyne (C_10) Complex

Bio-oils obtained from biomass contain heteroatoms compounds, like oxolane and thiolane. It is quite difficult for industrialist to purify such refractory bio-oils. One of the efficient strategies for the elimination of heteroatoms is hydrogenolysis process, which results in the formation of H2O and H2S residues as by-products. In this work, quantum chemical studies have been used to analyse the reaction mechanism for the removal of hetero atoms (S and O) as H2O and H2S. We selected B3LYP functional of DFT with Pople's basis set 6-311G(d,p) for computing the hydrogenolysis steps without catalyst. LANL2DZ basis set, is used for studying hydrogenolysis steps involving AlCl3 and WS3H3+ as catalysts. All the reactions are analysed at the temperature of 600 K and pressure of 40 bars. Structural, thermodynamic, kinetic properties have been employed to study this process. The analysis of variations parameters during the hydrogenolysis process reveals that these two organic biomass compounds undergo sequential ring opening at C-X (X = O, S) bonds. Butanol and Butanethiol are obtained as a result of first hydrogenolysis process, and these compounds are converted to butane during second catalytic process while eliminating heteroatoms. 

Quantum chemical hydrogenolysis strategy for elimination of heteroatoms in biomass homologous organic compounds based on oxolane and thiolane.

Materials having nonlinear optical (NLO) properties are the demand of optics and optoelectronics fields because of their widespread applications. Keeping in view the applications of NLO materials, some new superalkalis doped C6O6Li6 complexes are introduced in this study having remarkable NLO response. Thermodynamic stability of nonlinear optical materials (NLO) is prime requirement of experimentalists for practical applications. All the considered complexes have high thermodynamic stability. Furthermore, these superalkali doped complexes reveal fabulous electronic properties. Superalkalis shift their outer shell electrons towards the C6O6Li6 nanocluster, which act as diffuse excess electrons. The HOMO-LUMO gaps (H-L Egap) of superalkali doped complexes are effectively reduced due to shifting of electrons that reveals their conducting properties. NBO charge analysis confirmed electron charge transfer from superalkalis to C6O6Li6 surface. Linear and NLO properties of these complexes are estimated from first order polarizability (α o) and hyperpolarizability (β o) parameters. Among all complexes, C6O6Li6.K3O has the highest first hyperpolarizability (β o = 6.02 × 105 au). TD-DFT analysis confirmed the ultraviolet transparency of doped complexes. Two level model is used to rationalize the trend of first hyperpolarizability and the internal factors responsible for the enhancement of NLO response.

Naveen Kosar

Papers

Giant NLO response and deep ultraviolet transparency of dual (alkali/alkaline earth) metals doped C6O6Li6 electrides

Synthesis of pyridine and furan based arylated ketones through palladium catalyst with DFT study of their static and frequency dependent NLO response

Reversible H_2 Storage Capacity of Ni Functionalized Carbyne (C_10) Complex

Quantum chemical hydrogenolysis strategy for elimination of heteroatoms in biomass homologous organic compounds based on oxolane and thiolane.

Giant NLO response and ultraviolet transparency of superalakalis decorated C6O6Li6 complexes; a DFT perspective