We have demonstrated that the electronic and magnetic properties of graphene sheet can be delicately tuned by surface modification. Applying an external electric field to a fully hydrogenated graphene sheet can unload hydrogen atoms on one side, while keeping the hydrogen atoms on the other side, thus forming a half-hydrogenated graphene sheet, where the unpaired electrons in the unsaturated C sites give rise to magnetic moments, coupled through extended p-p interactions. Furthermore, the electronic structure of the resulting half-hydrogenated graphene sheet can be further tuned by introducing F atoms on the other side, making a nonmagnetic semiconductor with a direct band gap.
Hybrid halide perovskite solar cells (PSCs) giving over 22 % power conversion efficiencies (PCEs) have attracted considerable attention. Although perovskite plays a significant role in the operation of PSCs, the fundamental theories associated with perovskites have not been resolved in spite of the increase in research. In this Minireview, we assess the current understanding, based on the first-principles calculations, of structural and electronic properties, defects, ionic diffusion, and shift current for CH NH PbI perovskite, and the effect of ionic transport on the hysteresis of current-voltage curves in PSCs. The shift current connected to the possible presence of ferroelectricity is also discussed. The current state-of-the-art and some open questions regarding PSCs are also highlighted, and the benefits, challenges, and potentials of perovskite for use in PSCs are stressed.
Single Mo center supported on N-doped black phosphorus is predicted to be a compelling highly efficient and durable catalyst for electrochemical N2 fixation by density functional theory calculations.
Thermal responses in terms of geometry and crystalline phase evolution of ultrathin hexagonal gold nanoribbons (4H Au NRBs) were studied by in situ TEM. Under moderate electron beam-induced heating below 400 K, ''Rayleigh instability'' occurred with an obvious geometric effect, but the 4H phase remained stable. However, phase transition from 4H to face-centered cubic phase occurred when heating temperature approached 800 K by a dedicated MEMS chip, which agrees well with the molecular dynamics simulation results.
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