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International audience; Over the last three decades, photonic crystals (PhCs) have attracted intense interests thanks to their broad potential applications in optics and photonics. Generally, these structures can be fabricated via either ‘‘top-down’’ lithographic or ‘‘bottom-up’’ self-assembly approaches. The self-assembly approaches have attracted particular attention due to their low cost, simple fabrication processes, relative convenience of scaling up, and the ease of creating complex structures with nanometer precision. The self-assembled colloidal crystals (CCs), which are good candidates for PhCs, have offered unprecedented opportunities for photonics, optics, optoelectronics, sensing, energy harvesting, environmental remediation, pigments, and many other applications. The creation of high-quality CCs and their mass fabrication over large areas are the critical limiting factors for real-world applications. This paper reviews the state-of-the-art techniques in the self-assembly of colloidal particles for the fabrication of large-area high-quality CCs and CCs with unique symmetries. The first part of this review summarizes the types of defects commonly encountered in the fabrication process and their effects on the optical properties of the resultant CCs. Next, the mechanisms of the formation of cracks/defects are discussed, and a range of versatile fabrication methods to create large-area crack/defect-free twodimensional and three-dimensional CCs are described. Meanwhile, we also shed light on both the advantages and limitations of these advanced approaches developed to fabricate high-quality CCs. The self-assembly routes and achievements in the fabrication of CCs with the ability to open a complete photonic bandgap, such as cubic diamond and pyrochlore structure CCs, are discussed as well. Then emerging applications of large-area high-quality CCs and unique photonic structures enabled by the advanced self-assembly methods are illustrated. At the end of this review, we outlook the future approaches in the fabrication of perfect CCs and highlight their novel real-world applications.

International audience; Electrified interfaces play a central role in energy technologies, from batteries and capacitors to heterogeneous electrocatalysis. The structural complexity and the presence of the electrochemical potential present significant challenges to the atomistic understanding and modeling of these interfaces. In particular, including the electrochemical potential explicitly in the quantum mechanical simulations is equivalent to simulating systems with a surface charge (typically grand-canonical DFT). For realistic relationships between the potential and the surface charge (i.e., the capacity), the solvent and counter charge need to be treated carefully. Either solvent molecules and ions are included explicitly or implicit solvent-electrolyte descriptions are adopted. The first option is computationally too demanding to achieve a representative phase-space sampling, while the second is far from the realistic structuring of the interface. Both approaches suffer from a lack of validation against directly comparable experimental data. Furthermore, the limitations of density functional theory in terms of accuracy are critical for these metal/liquid interfaces. Nevertheless, even the imperfect models allow atomistic insights in electrocatalytic interfaces with unprecedented details. MoS2 as a catalyst for HER will be our example to illustrate the insights provided by grand-canonical DFT. We will present a detailed mechanistic study of hydrogen evolution over the single sulfur vacancy (Vs) on the MoS2 basal plane, including the potential-dependent Vomer, Tafel and Heyrovsky transition states for the various possible reaction steps.

We report a method for the fabrication of relatively uniform sandwich-like core-interlayer-shell nanostructures by using γ-Fe2O3 as the inner core, SiO2 as the interlayer, and relatively uniform gold (Au) as the outer shell. The resulting novel hybrid nanoparticle combines the intense local fields of nanorods with the highly tunable plasmon resonances of nanoshells. The length and diameter of the resulting nanoparticles can be tuned by the aspect ratio of α-Fe2O3, the interlayer of SiO2 and the outer layer of Au. After calcination under H2 and then exposure to air, α-Fe2O3 was transformed into γ-Fe2O3, which provides the hybrid particle magnetic tunability. This metal oxide (γ-Fe2O3) dielectric core, the SiO2 interlayer and the Au shell spindle nanoparticle resemble a grain of Au nanorice (γ-Fe2O3@SiO2@Au ellipsoids). The core-interlayer-shell geometry possesses greater structural and magnetic tunability than a nanorod or a nanoshell. The plasmon resonance of this novel γ-Fe2O3@SiO2@Au geometry is believed to arise from a hybridization of the primitive plasmons of an ellipsoidal cavity inside a continuous Au shell. The unique magnetoplasmonic properties of this γ-Fe2O3@SiO2@Au nanostructure are highly attractive for applications such as surface plasmon resonance sensing because of the dipole resonance of the resultant nanostructure and recyclable catalysts arising from the outer Au layer and the inner magnetic γ-Fe2O3 core.