Pengfei Gao

Could Borophene Be Used as a Promising Anode Material for High-Performance Lithium Ion Battery?

The rapid development of electronic products has inspired scientists to design and explore novel electrode materials with an ultrahigh rate of charging/discharging capability, such as two-dimensional (2-D) nanostructures of graphene and MoS2. In this study, another 2-D nanosheet, that is a borophene layer, has been predicted to be utilized as a promising anode material for high-performance Li ion battery based on density functional theory calculations. Our study has revealed that Li atom can combine strongly with borophene surface strongly and easily, and exist as a pure Li(+) state. A rather small energy barrier (0.007 eV) of Li diffusion leads to an ultrahigh diffusivity along an uncorrugated direction of borophene, which is estimated to be 10(4) (10(5)) times faster than that on MoS2 (graphene) at room temperature. A high Li storage capacity of 1239 mA·h/g can be achieved when Li content reaches 0.5. A low average operating voltage of 0.466 V and metallic properties result in that the borophene can be used as a possible anode material. Moreover, the properties of Li adsorption and diffusion on the borophene affected by Ag (111) substrate have been studied. It has been found that the influence of Ag (111) substrate is very weak. Li atom can still bind on the borophene with a strong binding energy of -2.648 eV. A small energy barrier of 0.033 eV can be retained for Li diffusion along the uncorrugated direction, which can give rise to a high Li diffusivity. Besides, the performances of borophene-based Na ion battery have been explored. Our results suggest that an extremely high rate capability could be expected in borophene-based Li ion battery.

Graphdiyne as a promising material for detecting amino acids

The adsorption of glycine, glutamic acid, histidine and phenylalanine on single-layer graphdiyne/ graphene is investigated by ab initio calculations. The results show that for each amino acid molecule, the adsorption energy on graphdiyne is larger than the adsorption energy on graphene and dispersion interactions predominate in the adsorption. Molecular dynamics simulations reveal that at room temperature the amino acid molecules keep migrating and rotating on graphdiyne surface and induce fluctuation in graphdiyne bandgap. Additionally, the photon absorption spectra of graphdiyne-amino-acid systems are investigated. We uncover that the presence of amino acid molecules makes the photon absorption peaks of graphdiyne significantly depressed and shifted. Finally, quantum electronic transport properties of graphdiyne-amino-acid systems are compared with the transport properties of pure graphdiyne. We reveal that the amino acid molecules induce distinct changes in the electronic conductivity of graphdiyne. The results in this paper reveal that graphdiyne is a promising two-dimensional material for sensitively detecting amino acids and may potentially be used in biosensors.

Width-dependent structural stability and magnetic properties of monolayer zigzag MoS2 nanoribbons

First-principles study based on density functional theory has been employed to investigate width-dependent structural stability and magnetic properties of monolayer zigzag MoS2 nanoribbons (ZZ-MoS2 NRs). The width N = 4–6 (the numbers of zigzag Mo–S chains along the ribbon length) are considered. The results show that all studied ZZ-MoS2 NRs are less stable than two-dimensional MoS2 monolayer, exhibiting that a broader width ribbon behaves better structural stability and an inversely proportional relationship between the structural stability (or the ribbon with) and boundary S–Mo interaction. Electronic states imply that all ZZ-MoS2 NRs exhibit magnetic properties, regardless of their widths. Total magnetic moment increases with the increasing width N, which is mainly ascribed to the decreasing S–Mo interaction of the two zigzag edges. In order to confirm this reason, a uniaxial tension strain is applied to ZZ-MoS2 NRs. It has been found that, with the increasing tension strain, the bond length of boundary S–Mo increases, at the same time, the magnetic moment increases also. Our results suggest the rational applications of ZZ-MoS2 NRs in nanoelectronics and spintronics.

Enhanced visible light absorption in ZnO/GaN heterostructured nanofilms

Abstract First-principles calculations have been employed to investigate structural stability and electronic properties of non-polar ( 1 1 ¯ 00 ) and ( 11 2 ¯ 0 ) ZnO/GaN heterostructured nanofilms. The effects of nanofilm thickness and GaN ratio are considered. It has been found that all studied heterostructured nanofilms are less stable than the corresponding pure ZnO film but more stable than pure GaN one, exhibiting a much thicker film with better stability. Electronic band structures display that both two types of heterostructured nanofilms are semiconductors with their band gaps strongly depending on the GaN ratios as well as the thicknesses. Of particular interest is that the band gaps decrease firstly, and then increase with the increasing GaN ratio, showing flexibly tunable band gaps that cover a wide range of the solar spectrum. Furthermore, spatial charge distribution to the valence band maximum and the conduction band minimum has been studied. By calculating the complex dielectric function, the properties of optical absorption has been explored to exploit their potential application in the solar energy harvesting.

Strain-tunable electronic and optical properties of BC3 monolayer

Two-dimensional layered nanostructures with unique electronic and optical properties may hold great potential in nanoelectronics and optoelectronics applications. In this work, structural stability, elastic, electronic, and optical properties of BC3 monolayers have been investigated using a first-principles study. The BC3 monolayer can be regarded as a series of hexagonal C rings with the connections of B atoms, which has been tested to be highly dynamically stable. The in-plane stiffness is 316.2 N cm−1, potentially rivalling graphene. A screened hybrid density functional HSE06 is used to calculate the electronic and optical properties. It is found that the BC3 monolayer is an indirect band gap semiconductor with a moderate gap energy of 1.839 eV. Spatial charge distribution to the valence band maximum and the conduction band minimum is analyzed to explore the origin of indirect band gap features. By calculating the complex dielectric function, optical properties considered as excitonic effects are discussed. Besides, the effects of various in-plane strains on electronic and optical properties are explored. Our results of good structural stability, moderate and tunable band gap, and strain-controllable optical properties suggest that the BC3 monolayer holds great promise in the applications of nanoelectronic and optoelectronic devices.