The quest for efficient ways of modulating localized surface plasmon resonance is one of the frontiers in current research in plasmonics; the use of a magnetic field as a source of modulation is among the most promising candidates for active plasmonics. Here we report the observation of magnetoplasmonic modes on colloidal gold nanoparticles detected by means of magnetic circular dichroism (MCD) spectroscopy and provide a model that is able to rationalize and reproduce the experiment with unprecedented qualitative and quantitative accuracy. We believe that the steep slope observed at the plasmon resonance in the MCD spectrum can be very efficient in detecting changes in the refractive index of the surrounding medium, and we give a simple proof of principle of its possible implementation for magnetoplasmonic refractometric sensing.

The [Dy(tta)3(L)] complex behaves as a single ion magnet both in its crystalline phase and in solution. Experimental and theoretical magnetic anisotropy axes perfectly match and lie along the most electro-negative atoms of the coordination sphere. Both VSM and MCD measurements highlight the robustness of the complex, with persistence of the memory effect even in solution up to 4 K.

A frontier topic in nanotechnology is the realization of multifunctional nanoparticles (NPs) via the appropriate combination of different elements of the periodic table. The coexistence of Fe and Ag in the same nanostructure, for instance, is interesting for nanophotonics, nanomedicine, and catalysis. However, alloying of Fe and Ag is inhibited for thermodynamic reasons. Here, we describe the synthesis of Fe-doped Ag NPs via laser ablation in liquid solution, bypassing thermodynamics constraints. These NPs have an innovative structure consisting of a scaffold of face-centered cubic metal Ag alternating with disordered Ag–Fe alloy domains, all arranged in a truffle-like morphology. The Fe–Ag NPs exhibit the plasmonic properties of Ag and the magnetic response of Fe-containing phases, and the surface of the Fe–Ag NPs can be functionalized in one step with thiolated molecules. Taking advantage of the multiple properties of Fe–Ag NPs, the magnetophoretic amplification of plasmonic properties is demonstrated with proof-of-concept surface-enhanced Raman scattering and photothermal heating experiments. The synthetic approach is of general applicability and virtually permits the preparation of a large variety of multi-element NPs in one step.[Figure not available: see fulltext.

We present a study of the structural, magnetic, and magneto-optical properties of a series of Co-substituted ferrite nanoparticles (NPs) prepared by thermal decomposition of metallo-organic precursors in high boiling solvents. The structural characterization, carried out by using several techniques (transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and magnetic circular dichroism measurements), showed all the samples are high crystalline, 5–6 nm spherical NPs with the cubic spinel structure typical of ferrites. The evolution of lattice parameters with cobalt content suggests that the material is Co-substituted maghemite, also confirmed by XAS and magneto optical (MO) characterizations. The investigation of the magnetic and magneto-optical properties displays peculiar trends with the cobalt content, the main features being the large increase of the saturation magnetization and the anomalous dependence of magnetic anisotropy which reaches its maximum values for intermediate compositions. The large tuneability of this material makes it possible to implement the performances of devices used in biomedical and sensing applications

In this study, a new simple, fast, and inexpensive technique for the preparation of free-standing nanocomposite ultrathin films based on the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and embedding iron oxide nanoparticles (NPs) is presented. These nanofilms were fabricated by a single step of spin-coated assisted deposition in conjunction with a release technique ("supporting layer technique") to detach them from the substrate. Free-standing nanofilms can be easily transferred onto several substrates due to their high conformability, preserving their functionalities. The effect of the addition of iron oxide nanoparticles on the structural and functional properties of the PEDOT:PSS nanofilms is investigated through topography, thickness, magnetic, magneto-optical activity, and conductivity characterizations. PEDOT:PSS and PEDOT:PSS/iron oxide NP nanofilms were tested as resistive humidity sensors. Their sensitivity to humidity was found to increase with increasing nanoparticle concentration. On the basis of these results, it is expected that these composites may furnish inexpensive and reliable means for relative humidity detection.

Terbium(iii) bis-phthalocyaninato neutral complex, a robust and evaporable Single Molecule Magnet (SMM) with a record height of the anisotropy barrier, has recently attracted a great interest as an active unit in single molecule electronics, but at the same time its magnetic hysteresis has been found to be strongly affected when the environment is different from the crystalline phase. Here we present a systematic investigation of the magnetization dynamics in different environments, obtained by magnetic dilution, thermal treatment and sublimation of the molecules, to shed some light on the origin of the evanescence of the hysteretic behavior of this unique SMM. © 2013 The Royal Society of Chemistry

The major development recently undergone by quantum cascade lasers has effectively extended frequency comb emission to longer-wavelength spectral regions, i.e. the mid and far infrared. Unlike classical pulsed frequency combs, their mode-locking mechanism relies on four-wave mixing nonlinear processes, with a temporal intensity profile different from conventional short-pulses trains. Measuring the absolute phase pattern of the modes in these combs enables a thorough characterization of the onset of mode-locking in absence of shortpulses emission, as well as of the coherence properties.Here, by combining dual-comb multi-heterodyne detection with Fourier-transform analysis, we show how to simultaneously acquire and monitor over a wide range of timescales the phase pattern of a generic frequency comb. The technique is applied to characterize a mid-infrared and a terahertz quantum cascade laser frequency comb, conclusively proving the high degree of coherence and the remarkable long-term stability of these sources. Moreover, the technique allows also the reconstruction of electric field, intensity profile and instantaneous frequency of the emission. IntroductionThe optical frequency comb (FC) is a peculiar multi-frequency coherent photonic state made of a series of evenly-spaced modes in the frequency domain, typically generated by frequency-stabilized and controlled femtoseconds mode-locked lasers [1][2][3][4]. In the visible and near infrared (IR) such technology is nowadays well established [5]. The miniaturization of these sources, together with the expansion of their operation range towards other spectral regions (e.g. mid and far IR), is crucial for broadening their application range.In this direction, the most interesting results have recently been achieved with quantum cascade lasers (QCLs), current-driven semiconductor lasers based on intersubband transitions in quantum wells, emitting high-power coherent radiation in the mid IR and terahertz (THz) [6][7][8][9][10][11]. In

Zinc substitution is often proposed as an efficient strategy to improve the performances of spinel ferrite nanoparticles, particularly related to their application as theranostic agents. In this work, a series of 8 nm spinel ferrite nanoparticles of formula Co x Zn y Fe 3−(x+y) O 4 is synthesized by thermal decomposition with the purpose of investigating the role of Zn 2+ ions in modifying the structural and magnetic properties. Contrary to most of the literature on this subject, where the sum of Co and Zn is kept constant (x + y = 1), here, the amount of Co is maintained at ca. x = 0.6, corresponding to the maximum of magnetic anisotropy of the Zn-undoped system, whereas the amount of Zn is progressively varied along the series from y = 0.05 to 0.4. This approach allows enlightening the effect of the Zn introduction on the magnetic and crystal structures and, particularly, on magnetic anisotropy, which is deeply investigated by several complementary techniques. A significant increase of the saturation magnetization, M S , upon the Zn content up to y = 0.4 is confirmed only at low temperature, whereas at room temperature, this effect is partially nullified by the weakening of the magnetic exchange coupling constants due to the increasing Zn substitution. Moreover, we demonstrate that the lattice modifications following the Zn introduction are responsible of a strong decrease of the particle magnetic anisotropy. Overall, these effects limit the use of Zn-substituted ferrites in biomedical applications like magnetic resonance imaging and magnetic fluid hyperthermia only to very low amount of Zn, as here confirmed by relaxometric and calorimetric measurements.