Display omitted
•A comprehensive review of recent research progress on the magnetic properties of ligand-free clusters and endohedral metallofullerenes.•A detailed survey of elemental metal clusters, ...alloy clusters, metal-doped semiconductor clusters, magnetic superatom clusters.•Both experimental and theoretical studies have been carefully discussed.•Fascinating properties and potential applications.
Magnetic clusters are aggregates of a few to thousands of atoms or molecules that exhibit magnetism. Understanding the evolution of magnetism from individual atom to bulk solid is fundamentally important, and combining different types and number of atoms would lead to many opportunities in tuning magnetic properties of an alloy cluster. The magnetic behaviors of a cluster can be measured by the Stern–Gerlach deflections or the X-ray magnetic circular dichroism spectroscopy in a molecular beam and calculated by ab initio methods. Herein we present a comprehensive review on the experimental and theoretical progresses on the magnetic properties of the ligand-free gas-phase clusters up to a few hundred atoms, including elemental metal clusters, alloy clusters, metal-doped semiconductor clusters, magnetic superatom clusters. Endohedral metallofullerenes, a special kind of magnetic clusters, are also briefly illustrated.
Metallic carbon has received long-standing attentions for its fascinating applications in superconductivity, electronic devices and high-performance anode materials. Here we design two types of ...metallic carbon phases, namely O-type and T-type carbon, using self-assembling diamond nanostripes as building block and CC bond as linkers. These O-type and T-type allotropes are energetically more favorable than most previously identified three-dimensional (3D) metallic carbon allotropies, while their stability is confirmed by a series of first-principles calculations. Excitingly, these all-carbon crystals not only exhibit ultrahigh Fermi velocity and anisotropic electrical conductivity, but also belong to superhard materials with good mechanical properties. By simulating the X-ray diffraction patterns, we propose that O-type and T-type carbon would be one of the unidentified carbon phases observed in recent detonation experiments or shock-compression of tetracyanoethylene (TCE) powder. The good electrical conductivity, high mechanical strength, tunable electronic properties might find applications in electromechanical systems and nanoelectronic devices.
Display omitted
Site levels of VBM and CBM for OH:O=1 and OH:O=2 graphene oxide with different coverage rate: (a), (b), (c), (d), and (e) represented C36O8H4, C24O8H4, and C24O12H6 with OH:O=1, C20O6H4 and C16O6H4 ...with OH:O=2, respectively. The dot lines are standard water redox potentials. The reference potential is the vacuum level.
Our results not only explain the recent experimental observations that graphene oxide is a promising two-dimensional material for visible-light photocatalysis but can be very helpful in designing the optimal composition for higher performance. Display omitted
► Show GO is a promising material for visible-light-driven photocatalyst. ► Explain recent observations. ► Helpful in designing GO.
To elucidate the usage of graphene oxide (GO) as a photocatalysis material, we have studied the effect of epoxy and hydroxyl functionalization on the electronic structure, work function, CBM/VBM position, and optical absorption spectra of GO using density functional theory calculations. By varying the coverage and relative ratio of the surface epoxy (O) and hydroxyl (OH) groups, both band gap and work function of the GO materials can be tuned to meet the requirement of photocatalyst. Interestingly, the electronic structures of GO materials with 40–50% (33–67%) coverage and OH:O ratio of 2:1 (1:1) are suitable for both reduction and oxidation reactions for water splitting. Among of these systems, the GO composition with 50% coverage and OH:O (1:1) ratio can be very promising materials for visible-light-driven photocatalyst. Our results not only explain the recent experimental observations about 2-D graphene oxide as promising visible-light-driven photocatalyst materials but can also be very helpful in designing the optimal composition for higher performance.
In vacuum, the bare zigzag (zz) edge of graphene is reconstructed into a line of pentagon–heptagon pairs, while the pristine armchair (ac) edge is retained. Our first-principle explorations of ...graphene edges on three metal surfaces Cu(111), Co(111), and Ni(111) indicate an opposite tendency, that is, the pristine zz edge is energetically favorable and the reconstructed ac edge with dangling C atoms is highly stable on Co(111) and Ni(111) surfaces. Insightful analysis shows that passivation of the graphene edge by metal surfaces is responsible for the dramatic differences. Beyond this, the unique edge configuration has a significant impact on the graphene CVD growth behavior.
The transmission rate seasonality is an important index for transmission dynamics in many childhood infections, and has been widely studied in industrialized countries. However, it has been neglected ...in the study of pathogens in China.
To understand the transmission dynamics of hand, foot and mouth disease (HFMD), we examined the transmission rate seasonality of HFMD in three provinces, Henan, Anhui and Chongqing, in China, using a dynamical stochastic SIR model. We investigated potential driving factors, including school terms, the Chinese Spring Festival period, meteorological factors and population flux for their effects on the HFMD transmission seasonality using multiple regression models.
The transmission rate of HFMD had complex seasonality with one large major peak in March and one small peak in autumn. School terms, the Chinese Spring Festival period, population flux and meteorological factors had combined effects on the HFMD transmission seasonality in mainland China. The school terms reflects the seasonal contact rate in Children, while the population flux and the Chinese Spring Festival period reflect the seasonal contact rate in population. They drove HFMD transmission rate seasonality in different time periods of the year in China. Contact rate seasonality in population dominated effects on HFMD transmission in February and March. The dramatic increase in transmission rate during February coincides with the Chinese Spring Festival period and high population flux in this month. The contact rate seasonality in children dominated effects on the transmission in the other months of the year in Chongqing. Meteorological factors can not solely explain the seasonality in HFMD transmission in mainland China; however, they may have combined effects with school terms and the highway passenger traffic on the transmission rate in Anhui during the fall semester.
The transmission rate of HFMD in three provinces in China had complex seasonality. The Chinese Spring Festival period, population flux and (or) school terms explained the majority of the transmission rate seasonality of HFMD, and they drove HFMD transmission rate seasonality in different time periods of the year. The Chinese Spring Festival period dominantly caused the dramatic increase of the HFMD transmission rate during February.
The nucleation of graphene on a transition metal surface, either on a terrace or near a step edge, is systematically explored using density functional theory calculations and applying the ...two-dimensional (2D) crystal nucleation theory. Careful optimization of the supported carbon clusters, C N (with size N ranging from 1 to 24), on the Ni(111) surface indicates a ground state structure transformation from a one-dimensional C chain to a 2D sp2 C network at N ≈ 10−12. Furthermore, the crucial parameters controlling graphene growth on the metal surface, nucleation barrier, nucleus size, and nucleation rate on a terrace or near a step edge are calculated. In agreement with numerous experimental observations, our analysis shows that graphene nucleation near a metal step edge is superior to that on a terrace. On the basis of our analysis, we propose the use of graphene seeds to synthesize high-quality graphene in large area.
Two-dimensional MA2Z4 (M = Mo, W, V, Nb, Ta, Ti, Zr, Hf, or Cr; A = Si or Ge; Z = N, P, or As) is a new lead in the 2D family, because it exhibits versatile properties by tuning the components M, A ...and Z. However, theoretical studies on MA2Z4 are quite limited, and electronic properties are mainly studied by standard DFT levels, which seriously underestimates the band gap. Here, we systematically investigated the electronic properties and nonlinear optical response of MA2Z4 using a hybrid HSE06 functional. It was found that replacing component Z changes the lattice constant most, while the lattice influence by component M substitution is only slight. We showed that the gap difference between PBE and HSE06 is generally about 30% but can be up to 101%. (MIV = Hf, Ti, or Zr)Si2N4 possesses multi-valley characteristics. Furthermore, the second-harmonic generation (SHG) responses of various MA2Z4 composites were also calculated. Three non-zero elements of second order non-linear susceptibilities are revealed for MA2Z4 with the relationship: d16 = d21 = d22, indicating that MA2Z4 belongs to the D3H1 space group. HfSi2N4 possesses a multi-valley characteristic, and exhibits the largest susceptibility under broad wavelengths and the value of d21 reaches 3697.04 pm V-1 at band gap resonance energy. Intriguingly, the non-linear coefficients of MoSi2P4 and MoSi2As4 in the IR region are two orders of magnitude larger than those of other well-known non-linear crystals, such as LiGaS2 and BaAl4S7. We further explored the anisotropic SHG response by the polar plot of intensity under different incident light into MA2Z4. Our work provides theoretical guidelines for further experimental explorations of MA2Z4 and paves the way for its utilization in non-linear optic devices.
SnS2 with high theoretical capacity has been impeded from practical applications as the anode of lithium-ion (Li-ion) batteries due to its large volume expansion and fast capacity decay. A ...nanostructure of the SnS2 semifilled carbon nanotube (SnS2@CNT) has been realized by plasma-assisted fabrication of Sn semifilled CNT (Sn@CNT) followed by post-sulfurization. When serving as the anode of a Li-ion battery, SnS2@CNT delivers an initial discharge capacity of 1258 mAh g–1 at 0.3 A g–1. Instead of capacity fading, SnS2@CNT shows inverse capacity growth to 2733 mAh g–1 after 470 cycles. The high-resolution transmission electron microscopy images show that the void in CNTs, after cycling, is fully filled with pulverized SnS2 grains which have a shortened Li-ion diffusion path and enhanced surface area for interfacial redox reactions. In addition, the CNTs, like a pocket, confine the pulverized SnS2, maintain the electric contact and structural integrity, and thus allow the electrodes to work safely under long cyclic loadings and extreme temperature conditions.
PDF
