Two-Dimensional Anisotropic C10 Carbon Allotrope with Mechanically Tunable Band Gap.

A high band gap, two-dimensional (2D) twisted octagonal (TO-)C10 allotrope of carbon is proposed. This dynamically and mechanically stable structure shows thermal stability up to 500 K and shows one of the largest Young's modulus of 306.4 GPa nm (close to graphene) among 2D carbon derivatives. TO-C10 also possesses one of the highest 2.94 eV (3.97 eV by HSE06) indirect band gap among reported 2D allotropes of carbon. Owing to structural anisotropy with respect to the basal plane and strong directional sp3 bonding, the band gap of the structure is tuned with high strain endurance along with variation in the band gap subject to applied direction of strain. The nature of the band gap also changes between indirect and direct on account of variation in the valence band states, dominantly governed by carbon atoms in the less symmetrically bonded ladder sites. Further, the band gap can be tuned with doping of Si and Ge and also by forming one-directional nanoribbons. Owing to structural inhomogeneity and inherent high band gap, the proposed 2D TO-C10 can be a potential candidate for future applications.

Electronic Structure of Visible Light-Driven Photocatalyst δ-Bi11VO19 Nanoparticles Synthesized by Thermal Plasma.

Size confinement for tailoring of electronic structures can in principle be explored for enhancement of photocatalytic properties. In the present work, vanadium-doped bismuth oxide nanoparticles, with an average particle size of 36 nm, are synthesized for the first time, using the thermal plasma method, in large scale with high yield to explore for photocatalytic applications. The electronic and crystallographic structures of the sample are studied experimentally and theoretically. Systematic investigations of the electronic structure of the fluorite type cubic phase of Bi11VO19 nanoparticles are reported for the first time. Enhancement is observed in the photocatalytic activity as compared to other delta phases of bismuth vanadate. The valence band is found to comprise mainly of O 2p states, whereas the conduction band arises from V 3d states giving rise to a band gap value of 2.26 eV. Absence of excess O in δ-Bi2O3 results in shrinking of the band gap because of O 2p, Bi 6s and 6p states from the surrounding atoms at doping sites. Bi11VO19 nanoparticles show an efficient visible light absorption and exhibit excellent photodegradation properties of methylene blue solution under visible light irradiation.