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The first principles calculations of an oxidative cut of graphene which is realized by forming epoxy and then carbonyl pairs is reported. The proposed epoxy pairs might be related to some long puzzling experimental observations on graphene oxide.

A detailed study was performed to determine the electronic properties and relative stabilities of several edge-modified zigzag edge graphene nanoribbons (ZGNRs). The results suggested that half-metallic ZGNR based spintronic devices can be obtained by applying an external transverse electric field.

The nonlinear optical signal generated in phenol by three femtosecond pulses with wavevectors [k.sub.1], [k.sub.2] and [k.sub.3] in the phase-matching direction [k.sub.1] + [k.sub.2] - [k.sub.3] is simulated. The signal has vanished for uncorrelated electrons due to interference among quantum pathways, which is illustrated by the very different two-dimensional coherent spectroscopy (2DCS) signals.

Several first-principles studies are conducted to measure the ultraviolet absorption and circular dichroism (CD) of a cyclic dipeptide. The results show that the CD spectrum of the peptides exhibit amide, as well as aromatic units transitions.

The electron transport properties of dithiocarboxylate terminated molecular junctions are investigated computationally. The findings show that the peaks in the transmission spectra of 4'-thiolato-biphenyl-4-dithiocarboxylate junction respond differently to the applied voltage and depending on the origin of a transmission resonance in the orbital interaction picture, its energy could be shifted along with the chemical potential of the electrode to which the molecule is more strongly or more weakly coupled.

The role of dithiocarbamate anchoring group on transport properties of molecular wire junctions is explored computationally. The results show that the 4-(4'-pyridyl)-peridium-1-carbodithioate molecular wire junction rectifies the flowing electric current.

Density functional theory (DFT) study of inorganic electrides is reported. The inorganic electride has very active channel sites as a powerful reducing agent because of its relatively high Fermi energy and the delocalization of the donated-electron density.

Nearly free electron (NFE) states are widely existed on atomically smooth surfaces in two-dimensional materials. Since they are mainly distributed in free space, these states can in principle provide ideal electron transport channels without nuclear scattering. Unfortunately, NFE states are typically unoccupied, and electron doping is required to shift them toward the Fermi level and, thus, to be involved in electron transport. Instead of occupying these NFE states, it is more desirable to have intrinsic nucleus-free two-dimensional electron gas in free space (2DEG-FS) at the Fermi level without relying on doping. Inspired by a recently identified electride material, we suggest that Ca2N monolayer should possess such a 2DEG-FS state, which is then confirmed by our first-principles calculations. Phonon dispersion in Ca2N monolayer shows no imagery frequency indicating that the monolayer structure is stable. A mechanical analysis demonstrates that Ca2N bulk exfoliation is feasible to produce a freestanding monolayer. However, in real applications, the strong chemical activity of 2DEG-FS may become a practical issue. It is found that some ambient molecules can dissociatively adsorb on the Ca2N monolayer, accompanying with a significant charge transfer from the 2DEG-FS state to adsorbates. To protect the 2DEG-FS state from molecule adsorption, we predict that graphane can be used as an effective encapsulating material. A well-encapsulated intrinsic 2DEG-FS state is expected to play an important role in low-dimensional electronics by realizing nuclear scattering free transport. [ABSTRACT FROM AUTHOR]

The possible reaction mechanisms of stereoselective [4 + 2] cycloaddition of enals and chalcones catalyzed by N-heterocyclic carbene (NHC) have been investigated using density functional theory (DFT). The calculated results indicate that the most favorable reaction channel occurs through five steps. The first step is the nucleophilic attack on the enal by NHC. Then, there are two consecutive acid (AcOH)-assisted proton-transfer steps. Subsequently, the fourth step is the [4 + 2] cycloaddition process associated with the formation of two chiral centers, followed by dissociation of NHC and product. Our computational results demonstrate that the [4 + 2] cycloaddition is the rate-determining and stereoselectivity-determining step. The energy barrier for the SS configurational channel (17.62 kcal/mol) is the lowest one, indicating the SS configurational product should be the main product, which is in agreement with experiment. Moreover, the role of NHC catalyst in the [4 + 2] cycloaddition of enal and chalcone was explored by the analysis of global reactivity indexes. This work should be helpful for realizing the significant roles of catalyst NHC and the additive AcOH and thus provide valuable insights on the rational design of potential catalyst for this kind of reactions. [ABSTRACT FROM AUTHOR]

The article presents a study about the highly sensitive and stable humidity nanosensors based on Lithium Chloride (LiCl) doped Titanium Oxide (TiO2) electrospun nanofibers. These chemical sensors have been applied in various research fields due to their various practical and applications but mainly on their high surface to volume ratio and physical and chemical properties.