Excitons and Electron-Hole Liquid State in 2D gamma-Phase Group-IV Monochalcogenides

Different dispersion near the electronic band edge of a semiconductor can have great influence on its transport, thermoelectric, and optical properties. Using first‐principles calculations, it is demonstrated that a new phase of group‐IV monochalcogenides (γ‐MX, M = Ge, Sn; X = S, Se, or Te) can be stabilized in monolayer limit. γ‐MXs are shown to possess a unique band dispersion—that is, camel's back like structure—in the top valence band.

A monolayer transition-metal dichalcogenide as a topological excitonic insulator

Monolayer transition-metal dichalcogenides in the T′ phase could enable the realization of the quantum spin Hall effect at room temperature, because they exhibit a prominent spin–orbit gap between inverted bands in the bulk. Here we show that the binding energy of electron–hole pairs excited through this gap is larger than the gap itself in the paradigmatic case of monolayer T′ MoS2 , which we investigate from first principles using many-body perturbation theory.

Single-Facet Dominant Anatase TiO2 (101) and (001) Model Catalysts to Elucidate the Active Sites for Alkanol Dehydration

Alkanol dehydration on Lewis acid–base pairs of transition metal oxide catalysts is a reaction of importance in oxygen removal from biomass-derived feedstocks and their conversion to chemicals in general. However, catalysts with a high degree of structural heterogeneity, such as commercial TiO2 powders, are not well-suited to establish rigorous structure–function relationships at an atomic level. Here, we provide compelling evidence for the effects of surface orientation of TiO2 catalyst on elimination reactions of alcohols.

Massive Dirac Fermion Behavior in a Low Bandgap Graphene Nanoribbon Near a Topological Phase Boundary

Graphene nanoribbons (GNRs) have attracted much interest due to their largely modifiable electronic properties. Manifestation of these properties requires atomically precise GNRs which can be achieved through a bottom–up synthesis approach. This has recently been applied to the synthesis of width‐modulated GNRs hosting topological electronic quantum phases, with valence electronic properties that are well captured by the Su–Schrieffer–Heeger (SSH) model describing a 1D chain of interacting dimers.

Band Depopulation of Graphene Nanoribbons Induced by Chemical Gating with Amino Groups

The electronic properties of graphene nanoribbons (GNRs) can be precisely tuned by chemical doping. Here we demonstrate that amino (NH2) functional groups attached at the edges of chiral GNRs (chGNRs) can efficiently gate the chGNRs and lead to the valence band (VB) depopulation on a metallic surface. The NH2-doped chGNRs are grown by on-surface synthesis on Au(111) using functionalized bianthracene precursors.

Single-Atom Pt-N-3 Sites on the Stable Covalent Triazine Framework Nanosheets for Photocatalytic N-2 Fixation

The commercial Haber-Bosch process for NH3 production not only requires large amounts of energy and hydrogen supply but also generates tremendous greenhouse CO2 emission. To mitigate energy and environmental challenges, renewable ammonia production technologies based on electrochemical and photochemical methods, in particular, photocatalytic nitrogen fixation in aqueous phase for ammonia production is highly desired.

Probing the Magnetism of Topological End States in 5-Armchair Graphene Nanoribbons

We extensively characterize the electronic structure of ultranarrow graphene nanoribbons (GNRs) with armchair edges and zigzag termini that have five carbon atoms across their width (5-AGNRs), as synthesized on Au(111). Scanning tunneling spectroscopy measurements on the ribbons, recorded on both the metallic substrate and a decoupling NaCl layer, show well-defined dispersive bands and in-gap states. In combination with theoretical calculations, we show how these in-gap states are topological in nature and localized at the zigzag termini of the nanoribbons.

NEXT Automated in Silico Design of Homogeneous Catalysts

Catalyst discovery is increasingly relying on computational chemistry, and many of the computational tools are currently being automated. The state of this automation and the degree to which it may contribute to speeding up development of catalysts are the subject of this Perspective.

Perfluorinated Self-Assembled Monolayers Enhance the Stability and Efficiency of Inverted Perovskite Solar Cells

Perovskite solar cells are among the most exciting photovoltaic systems as they combine low recombination losses, ease of fabrication, and high spectral tunability. The Achilles heel of this technology is the device stability due to the ionic nature of the perovskite crystal, rendering it highly hygroscopic, and the extensive diffusion of ions especially at increased temperatures.