77 research outputs found
Magneto-optical methods for magnetoplasmonics in noble metal nanostructures
No full textThe use of magneto-optical techniques to tune the plasmonic response of nanostructures—magnetoplasmonics—is a hot topic in active plasmonics, with fascinating implications for several plasmon-based applications and devices. In this exciting field, plasmonic nanomaterials with strong optical response to magnetic fields are desired, which is generally challenging to achieve with pure noble metals. To overcome this issue, several efforts have been carried out to design and tailor the magneto-optical response of metal nanostructures, mainly by combining plasmonic and magnetic materials or using ferromagnetic materials able to sustain a plasmonic response. However, despite their weak magneto-optical response, noble metals are a valuable model system allowing an accurate rationalization of magnetoplasmonic effects based on the interaction of magnetic fields with charge carriers. In addition, the emerging class of non-magnetic plasmonic heavily doped semiconductors is showing great potential for high performance magnetoplasmonics in the infrared range. In this Tutorial, the most common magneto-optical experimental methods employed to measure these effects are introduced, followed by a review of the major experimental observations that are discussed within the framework of an analytical model developed for the rationalization of magnetoplasmonic effects. Different materials are discussed, from noble metals to heavily doped semiconductors
XAS and XMCD of Single Molecule Magnets
No full textMolecular magnetism is here presented with emphasis concerning the single molecule magnets (SMMs). The architecture of SMMs is reviewed as well as the various ingredients promoting magnetic anisotropy and the relation between magnetic anisotropy and the dynamics of magnetization. Then it is shown how XAS and XMCD can be unique tools to unravel the magnetic properties of SMM submonolayers grafted on clean surfaces. We bring a special attention to the spectral features associated with the magnetic anisotropy and magnetization dynamics
Intermetallic Au3LixM1-x (M = Fe, Ni or Co) nanoalloys: Effect of synthetic conditions on the composition and order-disorder transition
No full textModulation of the magnetic properties of gold-spinel ferrite heterostructured nanocrystals
No full textThe rational design of complex nanostructures is of paramount importance to gain control over their chemical and physical properties. Recently, magnetic-plasmonic heterostructured nanocrystals have been recognized as key players in nanomedicine as multifunctional therapeutic-diagnostic tools and in catalysis. Here we show how the properties of gold-iron oxide heterostructured nanocrystals can be tuned by chemical doping of the magnetic subunit. The divalent cations in the iron oxide were substituted with cobalt and manganese to obtain a general formula Au-MFe2O4 (M = Fe, Co, Mn). Magnetic properties of the heterostructures could be tuned, while maintaining well-defined plasmon resonance signatures, confirming the dual magnetic-plasmonic functional capability of these nanostructures. [Figure not available: see fulltext.]
Magnetoplasmonics beyond Metals: Ultrahigh Sensing Performance in Transparent Conductive Oxide Nanocrystals
No full textActive modulation of the plasmonic response is at the forefront of today's research in nano-optics. For a fast and reversible modulation, external magnetic fields are among the most promising approaches. However, fundamental limitations of metals hamper the applicability of magnetoplasmonics in real-life active devices. While improved magnetic modulation is achievable using ferromagnetic or ferromagnetic-noble metal hybrid nanostructures, these suffer from severely broadened plasmonic response, ultimately decreasing their performance. Here we propose a paradigm shift in the choice of materials, demonstrating for the first time the outstanding magnetoplasmonic performance of transparent conductive oxide nanocrystals with plasmon resonance in the near-infrared. We report the highest magneto-optical response for a nonmagnetic plasmonic material employing F- and In-codoped CdO nanocrystals, due to the low carrier effective mass and the reduced plasmon line width. The performance of state-of-the-art ferromagnetic nanostructures in magnetoplasmonic refractometric sensing experiments are exceeded, challenging current best-in-class localized plasmon-based approaches
Synthesis and Structural Characterization of Non-Homoleptic Carbamato Complexes of V(V) and W(VI) and Their Facile Implantation onto Silica Surfaces
No full textThe vanadium(V) amido-carbamato derivatives VO(NR2)(O2CNR2)2 (R = Me, 1; Et, 2) were obtained by reaction of VOCl3 with preformed carbamato species (ammonium or sodium carbamates). The synthesis of an ionic ammonium chlorido-amide of W(VI), 3, was performed using WOCl4 and diethylamine as precursors. Moreover, reactivity of 3 with CO2 was investigated. Mixed W(VI) chlorido-carbamato compounds, 4-5, were obtained by reaction of WOCl4 with stoichiometric amounts of sodium diethylcarbamate. All the products were characterized by analytical and spectroscopic methods (IR, multinuclear NMR), and by X-ray diffraction in the cases of 3 and 4. DFT calculations were useful to elucidate the structures of the compounds and to give insight into the various reaction pathways. The combination of 2 or 5 with amorphous silica gave solid materials which were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Energy Dispersive X-ray Spectroscopy (EDS) coupled to Scanning Electron Microscopy (SEM)
EDS, HRTEM/STEM, and X-ray absorption spectroscopy studies of co-substituted maghemite nanoparticles
No full textA detailed study of the composition and structure of Co-doped maghemite nanoparticles with systematically varying composition has been carried out by transmission electron microscopy (TEM) techniques, such as high-resolution TEM, scanning TEM, and energy-dispersive X-ray spectrometry, and by X-ray absorption spectroscopy at the Fe and Co K-edges, analyzing both the extended X-ray absorption fine structure and the X-ray absorption near-edge structure regions. The latter techniques, in particular, allow us to determine the degree of inversion of divalent and trivalent metal ions among the octahedral and tetrahedral sites in the spinel structure of the nanoparticles and give detailed information on atomic distances. The samples consist of single-crystal nanoparticles with a composition corresponding to the Fe/Co ratio used in the synthesis. The degree of inversion is quite similar for all samples and close to the value found in a pure cobalt ferrite bulk sample. © 2013 American Chemical Society
Magnetic, optical and relaxometric properties of organically coated gold-magnetite (Au-Fe 3O 4) hybrid nanoparticles for potential use in biomedical applications
No full textWe present the magnetic, optical and relaxometric properties of multifunctional Au-Fe 3O 4 hybrid nanoparticles (HNPs), as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The HNPs have been synthesized by wet chemical methods in heterodimer and core-shell geometries and capped with oleylamine. Structural characterization of the samples have been made by X-ray diffraction and transmission electron microscopy, while magnetic properties have been investigated by means of Superconducting Quantum Interference Device-SQUID magnetometry experiments. As required for MRI applications using negative CAs, the samples resulted superparamagnetic at room temperature and well above their blocking temperatures. Optical properties have been investigated by analyzing the optical absorbtion spectra collected in UV-visible region. Relaxometric measurements have been performed on organic suspensions of HNPs and Nuclear Magnetic Resonance (NMR) dispersion curves have been obtained by measuring the longitudinal 1/T 1 and transverse 1/T 2 relaxation rates of solvent protons in the range 10 kHz/300 MHz at room temperature. NMR relaxivities r 1 and r 2 have been compared with ENDOREM ®, one of the commercial superparamagnetic iron oxide based MRI contrast agents. MRI contrast enhancement efficiencies have been investigated also by examining T 2-weighted MR images of suspensions. The experimental results suggest that the nanoparticles suspensions are good candidates as negative CAs. © 2012 Elsevier B.V. All rights reserved
Perspective: plasmon antennas for nanoscale chiral chemistry
No full textPlasmon nanoantennas are extensively used with molecular systems for chemical and biological ultra-sensing, for boosting the molecular emissive and energy transfer properties, for nanoscale catalysis, and for building advanced hybrid nanoarchitectures. In this perspective, we focus on the latest developments of using plasmon nanoantennas for nanoscale chiral chemistry and for advancing molecular magnetism. We overview the decisive role nanoplasmonics and nano-optics can play in achieving chirally selective molecular synthesis and separation and the way such processes might be precisely controlled by potentially merging chirality and magnetism at the molecular scale. We give our view on how these insights might lead to the emergence of exciting new fundamental concepts in nanoscale materials science
- …
