Challenges and Opportunities for Renewable Ammonia Production via Plasmon‐Assisted Photocatalysis

International audienc

Raman spectroscopy to unravel the magnetic properties of iron oxide nanocrystals for bio-related applications

Iron oxide nanocrystals have become a versatile tool in biomedicine because of their low cytotoxicity while offering a wide range of tuneable magnetic properties that may be implemented in magnetic separation, drug and heat delivery and bioimaging. These capabilities rely on the unique magnetic features obtained when combining different iron oxide phases, so that an important portfolio of magnetic properties can be attained by the rational design of multicomponent nanocrystals. In this context, Raman spectroscopy is an invaluable and fast-performance tool to gain insight into the different phases forming part of the nanocrystals to be used, allowing correlation of the magnetic properties with the envisaged bio-related applications.Xunta de Galicia | Ref. ED431C 2016-034Ministerio de Economía y Competitividad | Ref. CTM2017-84050-RXunta de Galicia | Ref. 2017ED481

Effect of a side reaction involving structural changes of the surfactants on the shape control of cobalt nanoparticles

International audienceCobalt nanoparticles with different sizes and morphologies including spheres, rods, disks, and hexagonal prisms have been synthesized through the decomposition of the olefinic precursor [Co(η3-C8H13)(η4-C8H12)] under dihydrogen, in the presence of hexadecylamine and different rhodamine derivatives, or aromatic carboxylic acids. UV–vis spectroscopy, X-ray diffraction, low and high resolution transmission electron microscopy, and electron tomography have been used to characterize the nanomaterials. Especially, the Co nanodisks formed present characteristics that make them ideal nanocrystals for applications such as magnetic data storage. Focusing on their growth process, we have evidenced that a reaction between hexadecylamine and rhodamine B occurs during the formation of these Co nanodisks. This reaction limits the amount of free acid and amine, usually at the origin of the formation of single crystal Co rods and wires, in the growth medium of the nanocrystals. As a consequence, a growth mechanism based on the structure of the preformed seeds rather than oriented attachment or template assisted growth is postulated to explain the formation of the nanodisks

Titanate Nanowires as One-Dimensional Hot Spot Generators for Broadband Au–TiO2 Photocatalysis

International audienceMetal–semiconductor nanocomposites have become interesting materials for the development of new photocatalytic hybrids. Along these lines, plasmonic nanoparticles have proven to be particularly efficient photosensitizers due to their ability to transfer plasmonic hot electrons onto large bandgap semiconductors such as TiO2, thus extending the activity of the latter into a broader range of the electromagnetic spectrum. The extent of this photosensitization process can be substantially enhanced in those geometries in which high electromagnetic fields are created at the metal–semiconductor interface. In this manner, the formation of plasmonic hot spots can be used as a versatile tool to engineer the photosensitization process in this family of hybrid materials. Herein, we introduce the use of titanate nanowires as ideal substrates for the assembly of Au nanorods and TiO2 nanoparticles, leading to the formation of robust hybrids with improved photocatalytic properties. Our approach shows that the correct choice of the individual units together with their rationa

Remote Activation of Hollow Nanoreactors for Heterogeneous Photocatalysis in Biorelevant Media

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Chiral Generation of Hot Carriers for Polarization-Sensitive Plasmonic Photocatalysis

International audienceMastering the manipulation of chirality at the nanoscale has long been a priority for chemists, physicists, and materials scientists, given its importance in the biochemical processes of the natural world and in the development of novel technologies. In this vein, the formation of novel metamaterials and sensing platforms resulting from the synergic combination of chirality and plasmonics has opened new avenues in nano-optics. Recently, the implementation of chiral plasmonic nanostructures in photocatalysis has been proposed theoretically as a means to drive polarization-dependent photochemistry. In the present work, we demonstrate that the use of inorganic nanometric chiral templates for the controlled assembly of Au and TiO 2 nanoparticles leads to the formation of plasmon-based photocatalysts with polarization-dependent reactivity. The formation of plasmonic assemblies with chiroptical activities induces the asymmetric formation of hot electrons and holes generated via electromagnetic excitation, opening the door to novel photocatalytic and optoelectronic features. More precisely, we demonstrate that the reaction yield can be improved when the helicity of the circularly polarized light used to activate the plasmonic component matches the handedness of the chiral substrate. Our approach may enable new applications in the fields of chirality and photocatalysis, particularly toward plasmon-induced chiral photochemistry

Surface-enhanced spectroscopy on plasmonic oligomers assembled by AFM nanoxerography

International audienceSurface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from individualplasmonic oligomers are investigated by confocal Raman micro-spectroscopy and time-resolved fluorescencemicroscopy coupled to steady state micro-spectroscopy. The nanoparticle (NP) oligomers aremade of either ligand protected Au or Au@SiO2 core–shell colloidal NPs, which were assembled into ordered arrays by atomic force microscopy (AFM) nanoxerography. A strong dependence of the SERS emission on the polarization of incident light relative to the specific geometry of the plasmonic oligomer was observed. The SEF studies, performed on a large collection of NP oligomers of various known configurations showed interesting fluorophore decay rate modification and red-shift of the emission spectra. The experimental results are analyzed theoretically by employing finite-difference time-domain (FDTD) simulations on equivalent realistic structures, within the local density of optical states (LDOS)framework. The presented results, together with the proven potential of the LDOS approach as a useful common tool for analyzing both SERS and SEF effects further the general understanding of plasmonrelatedphenomena in nanoparticle oligomers

Effect of a Side Reaction Involving Structural Changes of the Surfactants on the Shape Control of Cobalt Nanoparticles

International audienceCobalt nanoparticles with different sizes and morphologies including spheres, rods, disks, and hexagonal prisms have been synthesized through the decomposition of the olefinic precursor [Co(η3-C8H13)(η4-C8H12)] under dihydrogen, in the presence of hexadecylamine and different rhodamine derivatives, or aromatic carboxylic acids. UV–vis spectroscopy, X-ray diffraction, low and high resolution transmission electron microscopy, and electron tomography have been used to characterize the nanomaterials. Especially, the Co nanodisks formed present characteristics that make them ideal nanocrystals for applications such as magnetic data storage. Focusing on their growth process, we have evidenced that a reaction between hexadecylamine and rhodamine B occurs during the formation of these Co nanodisks. This reaction limits the amount of free acid and amine, usually at the origin of the formation of single crystal Co rods and wires, in the growth medium of the nanocrystals. As a consequence, a growth mechanism based on the structure of the preformed seeds rather than oriented attachment or template assisted growth is postulated to explain the formation of the nanodisks