discharge and charge. These problems cause early cell death, poor Coulombic efficiency (CE), rapid cycling capacity decay, and catastrophic thermal runaway. [9][10][11][12] To overcome the above thorny issues, extensive endeavors have been revived and a number of strategies have been proposed and practiced. For example, strengthening the solid electrolyte interphase (SEI) films by engineering liquid electrolytes with functional additives (LiNO 3 , Cs + , LiF, etc.) or employing solid electrolytes to prevent the Li dendrites. [13][14][15][16][17][18][19] However, these efforts cannot accommodate the infinite volume changes of Li metal during lithium stripping/plating, which can damage the contact interfaces between the electrolytes and Li anodes for continuous charge/discharge cycling. Porous and conductive scaffolds are expected to simultaneously suppress the Li dendrite growth and minimize the volume changes of Li metal electrodes. [20][21][22][23][24][25][26] Such host materials with a large specific surface area not only lower the local effective current density to form a uniform Li-ion flux but also provide an ample space to accommodate Li. Multifarious porous metal foams, such as 3D porous Cu foils and Cu-Ni core-shell nanowire networks, have behaved as effective hosts of Li. [23,27,28] However, the high mass density of these porous metals dramatically reduces the overall energy density of the composite electrodes, and dissipates the advantages of Li-metal anodes in specific capacity and energy density. In this respect, it is highly desirable to develop lightweight, flexible, conductive, and porous host materials with a lower interfacial energy with lithium.Lightweight porous carbon materials, including carbon nanotube and graphene exhibit distinct advantages over porous metals. [10,[29][30][31][32][33] The appealing characteristics of low mass density, excellent electrical conductivity, and chemical stability render them as promising host materials of Li anodes. [34][35][36][37][38][39][40][41] However, these carbon skeletons are usually lithium-phobic and require Li seed growth or additional lithiophilic surface modification to load Li. [42][43][44][45][46][47] Additionally, conventional porous carbon hosts with relatively large pore size (>10 µm) cannot efficiently dissipate large current densities due to limited surface areas, deteriorating the high rate performance of Limetal anodes. [29,31,36] Technically, it is difficult to efficiently pack 1D carbon nanotube and 2D graphene sheets into a 3D porous structure that can simultaneously achieve high porosity, largeThe key bottlenecks hindering the practical implementations of lithiummetal anodes in high-energy-density rechargeable batteries are the uncontrolled dendrite growth and infinite volume changes during charging and discharging, which lead to short lifespan and catastrophic safety hazards. In principle, these problems can be mitigated or even solved by loading lithium into a high-surface-area, conductive, and lithiophilic porous scaffold. However, ...

Scanning tunneling spectroscopic studies revealed the quantum-confinement effects in Ge nanocrystals formed with ultrahigh density (>1012cm−2) by Ge deposition on ultrathin Si oxide films. With decreasing crystal size, the conduction band maximum upshifted and the valence band minimum downshifted. The energy shift in both cases was about 0.7 eV with the size change from 7 to 2 nm. This shows that the energy band gaps of Ge nanocrystals increased to ∼1.4eV with decreasing size. This size dependence can be explained by the quantum-confinement effect in Ge nanocrystals.

Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan–French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.

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State-of-the-art carbonaceous anodes are approaching their achievable performance limit in Li-ion batteries (LIBs). Silicon has been recognized as one of the most promising anodes for next-generation LIBs because of its advantageous specific capacity and secure working potential. However, the practical implementation of silicon anodes needs to overcome the challenges of substantial volume changes, intrinsic low conductivity, and unstable solid electrolyte interphase (SEI) films. Here, we report an inventive design of a sandwich N-doped graphene@Si@hybrid silicate anode with bicontinuous porous nanoarchitecture, which is expected to simultaneously conquer all these critical issues. In the ingeniously designed hybrid Si anode, the nanoporous N-doped graphene acts as a flexible and conductive support and the amorphous hybrid silicate coating enhances the robustness and suppleness of the electrode and facilitates the formation of stable SEI films. This binder-free and stackable hybrid electrode achieves excellent rate capability and cycling performance (817 mAh/g at 5 C for 10 000 cycles). Paired with LiFePO4 cathodes, more than 100 stable cycles can be readily realized in full batteries.

GaAs/GaAsBi coaxial multishell nanowires were grown by molecular beam epitaxy. Introducing Bi results in a characteristic nanowire surface morphology with strong roughening. Elemental mappings clearly show the formation of the GaAsBi shell with inhomogeneous Bi distributions within the layer surrounded by the outermost GaAs, having a strong structural disorder at the wire surface. The nanowire exhibits a predominantly ZB structure from the bottom to the middle part. The polytipic WZ structure creates denser twin defects in the upper part than in the bottom and middle parts of the nanowire. We observe room temperature cathodoluminescence from the GaAsBi nanowires with a broad spectral line shape between 1.1 and 1.5 eV, accompanied by multiple peaks. A distinct energy peak at 1.24 eV agrees well with the energy of the reduced GaAsBi alloy band gap by the introduction of 2% Bi. The existence of localized states energetically and spatially dispersed throughout the NW are indicated from the low temperature cathodoluminescence spectra and images, resulting in the observed luminescence spectra characterized by large line widths at low temperatures as well as by the appearance of multiple peaks at high temperatures and for high excitation powers.

We report the electric conductivity of three-dimensional (3D) nanoporous gold at low temperatures and in strong magnetic fields. It was found that topologically disordered 3D nanoporosity leads to extremely low magnetoresistance and anomalous temperature dependence as the characteristic length of nanoporous gold is tuned to be approximately 14 nm. This study underscores the importance of 3D topology of a nanostructure on electronic transport properties and has implications in manipulating electron transport by tailoring 3D nanostructures.

Heavy chemical doping and high electrical conductivity are two key factors for metal-free graphene electrocatalysts to realize superior catalytic performance toward hydrogen evolution. However, heavy chemical doping usually leads to the reduction of electrical conductivity because the catalytically active dopants give rise to additional electron scattering and hence increased electrical resistance. A hierarchical nanoporous graphene, which is comprised of heavily chemical doped domains and a highly conductive pure graphene substrate, is reported. The hierarchical nanoporous graphene can host a remarkably high concentration of N and S dopants up to 9.0 at % without sacrificing the excellent electrical conductivity of graphene. The combination of heavy chemical doping and high conductivity results in high catalytic activity toward electrochemical hydrogen production. This study has an important implication in developing multi-functional electrocatalysts by 3D nanoarchitecture design.