First-principles calculations are performed to study the electronic and magnetic properties of VX(2) monolayers (X = S, Se). Our results unveil that VX(2) monolayers exhibit exciting ferromagnetic behavior, offering evidence of the existence of magnetic behavior in pristine 2D monolayers. Furthermore, interestingly, both the magnetic moments and strength of magnetic coupling increase rapidly with increasing isotropic strain from -5% to 5% for VX(2) monolayers. It is proposed that the strain-dependent magnetic moment is related to the strong ionic-covalent bonds, while both the ferromagnetism and the variation in strength of magnetic coupling with strain arise from the combined effects of both through-bond and through-space interactions. These findings suggest a new route to facilitate the design of nanoelectronic devices for complementing graphene.

Conventional TiO 2 photocatalyst possesses excellent activities and stabilities, but requires near-ultraviolet (UV) irradiation (about 4% of the solar spectrum) for effective photocatalysis, thereby severely limiting its practical application. It is highly desirable to develop a photocatalyst that can use visible light in high efficiency under sunlight irradiation. In this work, we prepare new visible-light-driven plasmonic photocatalyst Ag/ AgCl/TiO 2 nanotube arrays (NTs) by depositing AgCl nanoparticles (NPs) into the self-organized TiO 2 NTs, and then reducing partial Ag + ions in the surface region of the AgCl particles to Ag 0 species under xenon lamp irradiation. The prepared metal-semiconductor nanocomposite plasmonic photocatalyst exhibits a highly visible-light photocatalytic activity for photocatalytic degradation of methyl orange in water and stability. A new plasmonic photocatalytic mechanism, which is proposed on the basis of the fact that the Ag NPs are photoexcited due to plasmon resonance and charge separation, is accomplished by the transfer of photoexcited electrons from the Ag NPs to the TiO 2 conduction band and the simultaneous transfer of compensative electrons from a donor (Cl -) to the Ag NPs. The proposed mechanism is further confirmed by the experiments of hydroxyl radical and transient photocurrent response. The prepared photocatalysts are also of great interest in solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology. This study may provide new insight into the design and preparation of advanced visible-light photocatalytic materials.

The geometric and electronic structures of graphene adsorption on MoS(2) monolayer have been studied by using density functional theory. It is found that graphene is bound to MoS(2) with an interlayer spacing of 3.32 Å and with a binding energy of -23 meV per C atom irrespective of adsorption arrangement, indicating a weak interaction between graphene and MoS(2). A detailed analysis of the electronic structure indicates that the nearly linear band dispersion relation of graphene can be preserved in MoS(2)/graphene hybrid accompanied by a small band-gap (2 meV) opening due to the variation of on-site energy induced by MoS(2). These findings are useful complement to experimental studies of this new synthesize system and suggest a new route to facilitate the design of devices where both finite band-gap and high carrier mobility are needed.

A facile and efficient photoreduction method is employed to synthesize the composite of methylammonium lead iodide perovskite (MAPbI ) with reduced graphene oxide (rGO). This MAPbI /rGO composite is shown to be an outstanding visible-light photocatalyst for H evolution in aqueous HI solution saturated with MAPbI . Powder samples of MAPbI /rGO (100 mg) show a H evolution rate of 93.9 µmol h , which is 67 times faster than that of pristine MAPbI , under 120 mW cm visible-light (λ ≥ 420 nm) illumination, and the composite is highly stable showing no significant decrease in the catalytic activity after 200 h (i.e., 20 cycles) of repeated H evolution experiments. The electrochemiluminescence performance of MAPbI is investigated to explore the charge transfer process, to find that the photogenerated electrons in MAPbI are transferred to the rGO sites, where protons are reduced to H .