Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

In 1982, the Belgian Pilots' Guild raised the question of what effect exposure to radar radiation--for example, that encountered in passing a pilot launch's radar--might have on the human body. Recapitulating investigations of this question, this article states that in 25 years of experience with radar, there have been no known incidents of pilots being affected by radar waves. In the future, however, involvement by some pilots with Vessel Traffic Service shore-based radar could affect pilots somewhat differently from limited exposure to pilot launch radar. Pilots who find themselves in new working conditions close to an emitting source should exercise care all times.

About heat waves

What are Marine Diatoms

Heterogeneous catalysis involves solid-state catalysts, among which metal nanoparticles occupy an important position. Unfortunately, no two nanoparticles from conventional synthesis are the same at the atomic level, though such regular nanoparticles can be highly uniform at the nanometer level (e.g., size distribution ∼5%). In the long pursuit of well-defined nanocatalysts, a recent success is the synthesis of atomically precise metal nanoclusters protected by ligands in the size range from tens to hundreds of metal atoms (equivalently 1-3 nm in core diameter). More importantly, such nanoclusters have been crystallographically characterized, just like the protein structures in enzyme catalysis. Such atomically precise metal nanoclusters merge the features of well-defined homogeneous catalysts (e.g., ligand-protected metal centers) and enzymes (e.g., protein-encapsulated metal clusters of a few atoms bridged by ligands). The well-defined nanoclusters with their total structures available constitute a new class of model catalysts and hold great promise in fundamental catalysis research, including the atomically precise size dependent activity, control of catalytic selectivity by metal structure and surface ligands, structure-property relationships at the atomic-level, insights into molecular activation and catalytic mechanisms, and the identification of active sites on nanocatalysts. This Review summarizes the progress in the utilization of atomically precise metal nanoclusters for catalysis. These nanocluster-based model catalysts have enabled heterogeneous catalysis research at the single-atom and single-electron levels. Future efforts are expected to achieve more exciting progress in fundamental understanding of the catalytic mechanisms, the tailoring of active sites at the atomic level, and the design of new catalysts with high selectivity and activity under mild conditions.

Toward Active-Site Tailoring in Heterogeneous Catalysis by Atomically Precise Metal Nanoclusters with Crystallographic Structures.

Many-body physics aims to understand emergent properties of systems made of many interacting objects. This article reviews recent progress on the topic of radiative heat transfer in many-body systems consisting of thermal emitters interacting in the near-field regime. Near-field radiative heat transfer is a rapidly emerging field of research in which the cooperative behavior of emitters gives rise to peculiar effects which can be exploited to control heat flow at the nanoscale. Using an extension of the standard Polder and van Hove stochastic formalism to deal with thermally generated fields in $N$-body systems, along with their mutual interactions through multiple scattering, a generalized Landauer-like theory is derived to describe heat exchange mediated by thermal photons in arbitrary reciprocal and non-reciprocal multi-terminal systems. In this review, we use this formalism to address both transport and dynamics in these systems from a unified perspective. Our discussion covers: (i) the description of non-additivity of heat flux and its related effects, including fundamental limits as well as the role of nanostructuring and material choice, (ii) the study of equilibrium states and multistable states, (iii) the relaxation dynamics (thermalization) toward local and global equilibria, (iv) the analysis of heat transport regimes in ordered and disordered systems comprised of a large number of objects, density and range of interactions, and (v) the description of thermomagnetic effects in magneto-optical systems and heat transport mechanisms in non-Hermitian many-body systems. We conclude this review by listing outstanding challenges and promising future research directions.

Near-field radiative heat transfer in many-body systems

The near-field energy transfer between dielectric nanoparticles by considering the full coupling between all the thermal electric fields is studied theoretically for the case of a dimer and a trimer. We show that coupled modes between nanoparticles open channels through which energy may be transferred, increasing the power exchanged more than one order of magnitude as compared with existing models. We discuss how the contribution from coupled modes changes as parameters of the system are varied for the case of a two- and three-particle system. It is done by developing a spectral representation formalism for the near field, where fluctuating multipolar moments are fully incorporated, allowing identification of the contribution of energy transfer of each coupled mode. This information can be used to understand and control the energy flux among nanoparticles.

Near-field energy transfer between nanoparticles modulated by coupled multipolar modes

A systematic study of the adsorption of a methylthio on different sites of silver nanoparticles of 13, 55, 147, and 309 atoms with icosahedral symmetry as well as on the (111) surface is performed using density functional theory. Ab initio molecular dynamics were used to obtain the adsorption energies, atomic positions, and electronic properties of the lowest-energy configurations. Different adsorption sites and orientations of the molecule were tested. The electronic density of states also shows a size dependence, in which a transition from discrete to more band-like structure is found. Adsorption of a second methylthio is also studied. It was observed that final structures, adsorption energies, and electronic density of states strongly depended on the nanoparticle size and thus on the atomic coordination number, where bridge configurations had the lowest total energy and the highest adsorption energy for all sizes except Ag13.

Adsorption of a Methylthio Radical on Silver Nanoparticles: Size Dependence

Honeycomb plasmonic lattices are paradigmatic examples of non-Bravais lattices. We experimentally measure surface lattice resonances in effectively free-standing honeycomb lattices composed of silver nanospheres. By combining numerical simulations with analytical methods, we analyze the dispersion relation and the near-field properties of these modes along high symmetry trajectories. We find that our results can be interpreted in terms of dipole-only interactions between the two non-equivalent triangular sublattices, which naturally lead to an asymmetric near-field distribution around the nanospheres. We generalize the interaction between the two sublattices to the case of variable adjacent interparticle distance within the unit cell, highlighting symmetry changes and diffraction degeneracy lifting associated to the transition between Bravais and non-Bravais lattices.

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Diffractive dipolar coupling in non-Bravais plasmonic lattices

XV. Check-list of marine diatoms from the Caribbean Sea

A method to manipulate the multipolar plasmonic response of a nanostructure in the quasi-static limit is introduced. The theoretical method puts on the same footing geometry, dielectric properties, and incident field and proceeds in two steps: it optimizes the geometry of the nanostructure to maximize the intensity of the scattering cross-section spectrum. This is done by calculating the coupling strengths of the different modes of the system to the external field, which the method naturally provides. Then, it exploits the symmetry of the incident electromagnetic field to enhance or suppress specific orders, which, in turn, tunes the field enhancement. We demonstrate the method by using a plasmonic dimer of nanospheres.

David Becerril

Papers

Near-field energy transfer between nanoparticles modulated by coupled multipolar modes

Adsorption of a Methylthio Radical on Silver Nanoparticles: Size Dependence

Diffractive dipolar coupling in non-Bravais plasmonic lattices

XV. Check-list of marine diatoms from the Caribbean Sea

Efficient Coupling to Plasmonic Multipole Resonances by Using a Multipolar Incident Field