Qunxiang Li

Surface Structure-Dependent Molecular Oxygen Activation of BiOCl Single-Crystalline Nanosheets

We demonstrate that BiOCl single-crystalline nanosheets possess surface structure-dependent molecular oxygen activation properties under UV light. The (001) surface of BiOCl prefers to reduce O2 to ·O2(-) through one-electron transfer, while the (010) surface favors the formation of O2(2-) via two-electron transfer, which is cogoverned by the surface atom exposure and the situ generated oxygen vacancy characteristics of the (001) and (010) surfaces under UV light irradiation.

Graphene nanoribbon as a negative differential resistance device

We present a theoretical study on electronic structure and elastic transport properties of armchair graphene nanoribbon based junctions by using density functional theory calculations and nonequili ...

Electronic structures of SiC nanoribbons

Electronic structures of SiC nanoribbons have been studied by spin-polarized first-principles calculations. The armchair nanoribbons are nonmagnetic semiconductors, while the zigzag nanoribbons are magnetic metals. The spin polarization in the zigzag SiC nanoribbons is originated from the unpaired electrons localized on the ribbon edges. Interestingly, the zigzag nanoribbons narrower than approximately 4 nm present half-metallic behavior. Without the aid of external field or chemical modification, the metal-free half-metallicity predicted for narrow SiC zigzag nanoribbons opens a facile way for nanomaterial-based spintronics applications.

Strain effect on electronic structures of graphene nanoribbons: A first-principles study

We report a first-principles study on the electronic structures of deformed graphene nanoribbons (GNRs). Our theoretical results show that the electronic properties of zigzag GNRs are not sensitive to uniaxial strain, while the energy gap modification of armchair GNRs (AGNRs) as a function of uniaxial strain displays a nonmonotonic relationship with a zigzag pattern. The subband spacings and spatial distributions of the AGNRs can be tuned by applying an external strain. Scanning tunneling microscopy dI/dV maps can be used to characterize the nature of the strain states, compressive or tensile, of AGNRs. In addition, we find that the nearest neighbor hopping integrals between pi-orbitals of carbon atoms are responsible for energy gap modification under uniaxial strain based on our tight binding approximation simulations.

Enhanced photocatalytic mechanism for the hybrid g-C3N4/MoS2 nanocomposite

Here, we explore the enhanced photocatalytic mechanism for the hybrid g-C3N4/MoS2 nanocomposites for the first time by performing extensive density functional theory calculations. The calculated band alignment between the g-C3N4 monolayer and MoS2 sheets clearly reveals that the conduction band minimum and valence band maximum of the g-C3N4 monolayer are higher by about 0.83 eV and 0.15 eV respectively than those of the MoS2 sheet. This predicted type-II band alignment ensures the photogenerated electrons easily migrate from the g-C3N4 monolayer to the MoS2 sheet, and leads to the high hydrogen-evolution reaction activity. The charge transfer between MoS2 and g-C3N4 results in a polarized field within the interface region, which will benefit the separation of photogenerated carriers. The calculated optical absorption curves verify that this proposed layered nanocomposite is a good light-harvesting semiconductor. Moreover, a g-C3N4 bilayer covering a MoS2 sheet also displays desirable properties. These findings indicate that the MoS2 sheet is a promising candidate as a non-noble metal co-catalyst for g-C3N4 photocatalysts, and also provide useful information for understanding the observed enhanced photocatalytic mechanism in experiments.

Tuning the electronic structure of graphene nanoribbons through chemical edge modification : a theoretical study

We report combined first-principle and tight-binding (TB) calculations to simulate the effects of chemical edge modifications on structural and electronic properties. The C-C bond lengths and bond angles near the GNR edge have considerable changes when edge carbon atoms are bounded to different atoms. By introducing a phenomenological hopping parameter

Z-shaped graphene nanoribbon quantum dot device

t_{1}

Co3O4 Hexagonal Platelets with Controllable Facets Enabling Highly Efficient Visible-Light Photocatalytic Reduction of CO2

for nearest-neighboring hopping to represent various chemical edge modifications, we investigated the electronic structural changes of nanoribbons with different widths based on the tight-binding scheme. Theoretical results show that addends can change the band structures of armchair GNRs and even result in observable metal-to-insulator transition.

Chiral selective tunneling induced negative differential resistance in zigzag graphene nanoribbon: A theoretical study

Stimulated by recent advances in isolating graphene, we discovered that quantum dot can be trapped in Z-shaped graphene nanoribbon junciton. The topological structure of the junction can confine electronic states completely. By varying junction length, we can alter the spatial confinement and the number of discrete levels within the junction. In addition, quantum dot can be realized regardless of substrate induced static disorder or irregular edges of the junction. This device can be used to easily design quantum dot devices. This platform can also be used to design zero-dimensional functional nanoscale electronic devices using graphene ribbons.Stimulated by recent advances in isolating graphene, the authors discovered that a quantum dot can be trapped in a Z-shaped graphene nanoribbon junction. The topological structure of the junction can completely confine electronic states. By varying the junction length, the authors can alter the spatial confinement and the number of discrete levels within the junction. In addition, a quantum dot can be realized regardless of substrate induced static disorder or irregularities on the edges of the junction. The method can be used to easily design quantum dot devices. The authors also provide a platform to design zero-dimensional functional nanoscale electronic devices using graphene ribbons.

Electronic and magnetic properties of V-doped anatase TiO2 from first principles

A heterogeneous catalyst made of well-defined Co3 O4 hexagonal platelets with varied exposed facets is coupled with [Ru(bpy)3 ]Cl2 photosensitizers to effectively and efficiently reduce CO2 under visible-light irradiation. Systematic investigation based on both experiment and theory discloses that the exposed {112} facets are crucial for activating CO2 molecules, giving rise to significant enhancement of photocatalytic CO2 reduction efficiency.