74 research outputs found
Magnetoplasmonics in confined geometries : current challenges and future opportunities
No full textPlasmonics represents a unique approach to confine and enhance electromagnetic radiation well below the diffraction limit, bringing a huge potential for novel applications, for instance, in energy harvesting, optoelectronics, and nanoscale biochemistry. To achieve novel functionalities, the combination of plasmonic properties with other material functions has become increasingly attractive. In this Perspective, we review the current state of the art, challenges, and future opportunities within the field of magnetoplasmonics in confined geometries, an emerging area aiming to merge magnetism and plasmonics to either control localized plasmons, confined electromagnetic-induced collective electronic excitations, using magnetic properties, or vice versa. We begin by highlighting the cornerstones of the history and principles of this research field. We then provide our vision of its future development by showcasing raising research directions in hybrid magnetoplasmonic systems to overcome radiation losses and novel materials for magnetoplasmonics, such as transparent conductive oxides and hyperbolic metamaterials. Finally, we provide an overview of recent developments in plasmon-driven magnetization dynamics, nanoscale opto-magnetism, and acousto-magnetoplasmonics. We conclude by giving our personal vision of the future of this thriving research fiel
Probing temperature changes using nonradiative processes in hyperbolic meta-antennas
No full textMultilayered metal-dielectric nanostructures display both a strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and nonradiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities toward the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control of light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation. Nevertheless, the temperature dependence of the optical properties of these multilayered systems has never been investigated. In this work, we study how radiative and nonradiative processes in hyperbolic meta-antennas can probe temperature changes of the surrounding medium. We show that, while radiative processes are essentially not affected by a change in the external temperature, the nonradiative ones are strongly affected by a temperature variation. By combining experiments and temperature-dependent effective medium theory, we find that this behavior is connected to enhanced damping effects due to electron-phonon scattering. Contrary to standard plasmonic systems, a red-shift of the nonradiative mode occurs for small variations of the environment temperature. Our study shows that, to probe temperature changes, it is essential to exploit nonradiative processes in systems supporting plasmonic excitations, which can be used as very sensitive thermometers via linear absorption spectroscopy
Synthesis of brightly luminescent colloidal formamidinium lead bromide perovskite FAPbBr
No full textHybrid halide perovskites are semicondoctor materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology. They have size-tunable emissions due to quantum size effects. In this work, the Formamidinium Lead Bromide perovskite CH(NH2)2PbBr3 nanoplatelets (NPLs) were successfully synthesized by ligand-assisted reprecipitation method under room condition, in which the emission color-tunability was realized via quantum size effect without anion–halide mixing, by varying the oleylamine to oleic acid volume ratio as surfactants, while the total amount of oleic acid remained unchanged. We are able to adjust the optical proprieties of FAPbBr3 NPLs and, consequently, their structural properties. The obtained colloidal solutions of FAPbBr3 nanoplatelets with uniform size exhibited different photoluminescence wavelengths covering the spectral region from 440 to 525 nm. The maximum absolute PL quantum yield (PLQY) of the green emission was measured to be as high as 80% at room temperature. The size of FAPbBr3 NPLs could be effectively tuned from 15.5 to 38.1 nm with an increase in the oleylamine and oleic acid ligands ratio
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
Metal N,N-dialkylcarbamates as easily available catalytic precursors for the carbon dioxide/propylene oxide coupling under ambient conditions
No full textA series of previously reported homoleptic and non-homoleptic N,N-dialkylcarbamates of a range of non precious metals and N,N-dialkylcarbamate of Al(III) were investigated as easily available and inexpensive catalysts in the solventless synthesis of propylene carbonate (PC) from propylene oxide (PO) and CO2. By operating at atmospheric CO2 pressure at ambient temperature, excellent results were achieved using Ti(O2CNEt2)4, Al(O2CNR2)3 (R = Et, iPr), Cu(O2CNEt2)2 and Sn(O2CNEt2)4, in combination with NBu4X (X = Br or Cl) as a co-catalyst. The reactions of MCl2(O2CNEt2)2 (M = Ti, Zr) with amorphous silica were straightforward through partial release of both chlorido and carbamato ligands, and readily afforded solid materials which were characterized by ICP-OES and EDS analyses, coupled to SEM. These heterogeneous catalytic systems revealed less efficient than the homogeneous counterparts
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)
Low temperature synthesis of ultra-green luminescent colloidal FAPbBr3 perovskite nanocrystals
No full textAccording to the updated recommendation for displays standard (Rec. 2020), ultrapure green emitters with a narrow emission (below 25 nm) in the 525-535 nm spectral range are desired. However, finding an emitter material that can meet such requirements, is still challenging. To this purpose, organic-inorganic halide perovskites nanocrystals have been considered as promising high-color purity light emitters at a lower cost, that overcome the issues associated with conventional emitters. Herein, to reach these standards simultaneously, we have synthesized Formamidinium lead bromide perovskite nanocrystals (NCs) at room temperature by ligand-assisted reprecipitation (LARP). The obtained FAPbBr(3) NCs coated with oleic acid and oleylamine show an average size of about 20 nm. FAPbBr(3) NCs dispersions in hexane exhibited bright photoluminescence with a high quantum yield (74%). The color coordinates on CIE 1931 are (0.2, 0.75), with a corresponding strong green emission at 533 nm. The emission is characterized by an ultranarrow full width at half-maximum (FWHM = 22 nm), and long radiative lifetimes (approximate to 82 ns). The synthesized FAPbBr(3) NCs present ideal features toward solution-processable ultrapure green emitters. Copyright (C) 2022 Elsevier Ltd. All rights reserved
Magnetic Circular Dichroism Elucidates Molecular Interactions in Aggregated Chiral Organic Materials
No full textChiral materials formed by aggregated organic compounds play a fundamental role in chiral optoelectronics, photonics and spintronics. Nonetheless, a precise understanding of the molecular interactions involved remains an open problem. Here we introduce magnetic circular dichroism (MCD) as a new tool to elucidate molecular interactions and structural parameters of a supramolecular system. A detailed analysis of MCD together with electronic circular dichroism spectra combined to ab initio calculations unveils essential information on the geometry and energy levels of a self-assembled thin film made of a carbazole di-bithiophene chiral molecule. This approach can be extended to a generality of chiral organic materials and can help rationalizing the fundamental interactions leading to supramolecular order. This in turn could enable a better understanding of structure-property relationships, resulting in a more efficient material design.Magnetic circular dichroism gives access to the geometry and interactions leading to the supramolecular structure of a thin film of an organic chiral molecule. The technique presented here may be applied to elucidate the structures of aggregates of organic compounds.+imag
Exploring magneto-optical properties in plasmonic and magnetoplasmonic nanostructures
No full textPlasmonic nanostructures are intriguing materials for applications in optical sensing and enhanced spectroscopies. To further improve their performances, one of the most appealing strategies is the active modulation of the plasmonic response by means of an external magnetic field, i.e.magnetoplasmonics. To reach such a controlled magnetic modulation, the accurate design of the nanostructures in terms of architecture and material choice is crucial. Indeed, conventional plasmonic materials typically display poor magnetic field response, while the insertion of magnetic materials usually damps the plasmonic resonance in hybrid systems.
In this thesis, Magnetic Circular Dichroism is employed as a characterization tool to assess the magnitude of the magnetic modulation of the plasmonic resonance in properly designed nanostructures, and some of the key aspects involved in the enhancement of the modulation are highlighted. Colloidal chemistry approaches are almost exclusively exploited to prepare such nanostructures. The investigation covers a wide range of materials and architectures, from purely plasmonic nanomaterials (noble metals and degenerately doped semiconductors) to complex hybrid nanostructures with different degree of interaction between the plasmonic and the magnetic material (mainly core@shell and nanoalloys)
Magnetic Circular Dichroism Elucidates Molecular Interactions in Aggregated Chiral Organic Materials
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