Active infrared tuning of metal-insulator-metal resonances by VO thin film.

VO is a promising phase change material offering a large contrast of electric, thermal, and optical properties when transitioning from semiconductor to metallic phase. Here we show that a hybrid metamaterial obtained by proper combination of a VO layer and a nanodisk gold array provides a tunable plasmonic gap resonance in the infrared range. Specifically, we have designed and fabricated a metal-insulator-metal gap resonance by inserting sub-wavelength VO film between a flat gold layer and a gold nanodisk resonator array.

Surprising Eutectics: Enhanced Properties of ZnO-ZnWO from Visible to MIR.

Zinc oxide-zinc tungstate (ZnO-ZnWO ) is a self-organized eutectic composite consisting of parallel ZnO thin layers (lamellae) embedded in a dielectric ZnWO matrix. The electromagnetic behavior of composite materials is affected not only by the properties of single constituent materials but also by their reciprocal geometrical micro-/nano-structurization, as in the case of ZnO-ZnWO . The light interacting with microscopic structural features in the composite material provides new optical properties, which overcome the possibilities offered by the constituent materials.

Free-standing plasmonic nanoarrays for leaky optical waveguiding and sensing.

Flat optics nanogratings supported on thin free-standing membranes offer the opportunity to combine narrowband waveguided modes and Rayleigh anomalies for sensitive and tunable biosensing. At the surface of high-refractive index SiN membranes we engineered lithographic nanogratings based on plasmonic nanostripes, demonstrating the excitation of sharp waveguided modes and lattice resonances. We achieved fine tuning of these optical modes over a broadband Visible and Near-Infrared spectrum, in full agreement with numerical calculations.

Tuning and hybridization of surface phonon polaritons in α-MoO based metamaterials.

We propose an effective medium approach to tune and control surface phonon polariton dispersion relations along the three main crystallographic directions of α-phase molybdenum trioxide. We show that a metamaterial consisting of subwavelength air inclusions into the α-MoO matrix displays new absorption modes producing a split of the Reststrahlen bands of the crystal and creating new branches of phonon polaritons. In particular, we report hybridization of bulk and surface polariton modes by tailoring metamaterials' structural parameters.

Tuning of Optical Phonons in α-MoO-VO Multilayers.

Merging the properties of VO and van der Waals (vdW) materials has given rise to novel tunable photonic devices. Despite recent studies on the effect of the phase change of VO on tuning near-field optical response of phonon polaritons in the infrared range, active tuning of optical phonons (OPhs) using far-field techniques has been scarce. Here, we investigate the tunability of OPhs of α-MoO in a multilayer structure with VO.

Effect of heating/cooling dynamics in the hysteresis loop and tunable IR emissivity of VO thin films.

We experimentally investigate the semiconductor-to-metal transition (SMT) in vanadium dioxide thin films using an infrared thermographic technique. During the semiconductor to metal phase change process, VO optical properties dynamically change and infrared emission undergoes a hysteresis loop due to differences between heating and cooling stages. The shape of the hysteresis loop was accurately monitored under different dynamic heating/cooling rates.

Hybrid thermal Yagi-Uda nanoantennas for directional and narrow band long-wavelength IR radiation sources.

We investigate the possibility of spatially and spectrally controlling the thermal infrared emission by exploitation of the Yagi-Uda antenna design. Hybrid antennas composed of both SiC and Au rods are considered and the contributions of emission from all the elements, at a given equilibrium temperature, are taken into account. We show that the detrimental effect due to thermal emission from the not ideal parasitic elements drastically affect the performances of conventional thermal Au antennas in the 12 µm wavelength range.

Adaptive tuning of infrared emission using VO thin films.

Phase-transition materials provide exciting opportunities for controlling optical properties of photonic devices dynamically. Here, we systematically investigate the infrared emission from a thin film of vanadium dioxide (VO). We experimentally demonstrate that such thin films are promising candidates to tune and control the thermal radiation of an underlying hot body with different emissivity features.

New Technologies in Rice Derivatives.

In this research the incapsulation of ferulic acid (FA) in advanced systems of protection with the aim of improving its stability and photostability was studied. Lipoparticles and polymeric microparticles as incapsulation systems were prepared and characterized. Lipoparticles were completely of natural origin, while microparticles were obtained using chitosan as natural polymer.

Chiral near-field manipulation in Au-GaAs hybrid hexagonal nanowires.

We demonstrate the control of enhanced chiral field distribution at the surface of hybrid metallo-dielectric nanostructures composed of self-assembled vertical hexagonal GaAs-based nanowires having three of the six sidewalls covered with Au. We show that weakly-guided modes of vertical GaAs nanowires can generate regions of high optical chirality that are further enhanced by the break of the symmetry introduced by the gold layer. Changing the angle of incidence of a linearly polarized plane wave it is possible to tailor and optimize the maps of the optical chirality in proximity of the gold plated walls.

Photo-acoustic spectroscopy revealing resonant absorption of self-assembled GaAs-based nanowires.

III-V semiconductors nanowires (NW) have recently attracted a significant interest for their potential application in the development of high efficiency, highly-integrated photonic devices and in particular for the possibility to integrate direct bandgap materials with silicon-based devices. Here we report the absorbance properties of GaAs-AlGaAs-GaAs core-shell-supershell NWs using photo-acoustic spectroscopy (PAS) measurements in the spectral range from 300 nm to 1100 nm wavelengths. The NWs were fabricated by self-catalyzed growth on Si substrates and their dimensions (length ~5 μm, diameter ~140-150 nm) allow for the coupling of the incident light to the guided modes in near-infrared (IR) part of the spectrum.

Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal.

Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation.

Chiral light intrinsically couples to extrinsic/pseudo-chiral metasurfaces made of tilted gold nanowires.

Extrinsic or pseudo-chiral (meta)surfaces have an achiral structure, yet they can give rise to circular dichroism when the experiment itself becomes chiral. Although these surfaces are known to yield differences in reflected and transmitted circularly polarized light, the exact mechanism of the interaction has never been directly demonstrated. Here we present a comprehensive linear and nonlinear optical investigation of a metasurface composed of tilted gold nanowires.

Second harmonic generation on self-assembled tilted gold nanowires.

Here we present measurements on a metasurface composed by tilted gold nanowires. The metasurface can induce an optical chiral response of the whole sample when the light impinges on the sample out of the normal incidence angle. In order to investigate the symmetry breaking induced by the geometry, we measured the second harmonic generation (SHG) signal generated by circular polarized pulsed light.

Thermal mud maturation: organic matter and biological activity.

Objective: Many of the therapeutic and cosmetic treatments offered in spas are centred on mud therapy, to moisturize the skin and prevent skin ageing and rheumatic diseases. Thermal mud is a complex matrix composed of organic and inorganic elements which contribute to its functions. It is a natural product derived from the long mixing of clay and thermal water.

Polarization insensitive infrared absorbing behaviour of one-dimensional multilayer stack: a fractal approach.

The control and tailoring of infrared absorbance/emittance is a crucial task for all those applications involving thermal radiation management and detection. We theoretically investigated the peculiar absorbing/emitting behaviour of pre-fractal Cantor multilayers, in order to design a polarization-insensitive multilayer stack absorbing over a wide angular lobe in the mid wavelength infrared range (8-10 μm). Using transfer matrix method, we explored the spectral properties arising from both the material and the geometrical dispersion.

4-Methylbenzylidene camphor microspheres: reconstituted epidermis (Skinethic®) permeation and distribution.

Objective: The UV filter 3(4-methylbenzylidene) camphor (4-MBC) is a common ingredient in sunscreen cosmetic products. However, different 'in vitro' and 'in vivo' studies suggest that 4-MBC can cause endocrine disrupting effects. Therefore, there is a need for new systems able to minimize the skin penetration of this UV filter.

Improving photoprotection: 4-methylbenzylidene camphor microspheres.

We propose a new approach for photoprotection. 4-Methylbenzylidene camphor (4-MBC), one of the most widely used UV filters, was encapsulated in microspheres, with a view to overcoming problems (percutaneous absorption, photodegradation and lack of lasting effect) arising with organic sunscreens, and to achieve safe photoprotection. We focused on this filter in the light of the Cosmetics Europe opinion concerning its possible effects on the thyroid gland.

Nanostripe length dependence of plasmon-induced material deformations.

Following the impact of a single femtosecond light pulse on nickel nanostripes, material deformations-or "nanobumps"-are created. We have studied the dependence of these nanobumps on the length of nanostripes and verified the link with plasmons. More specifically, local electric currents can melt the nanostructures in the hotspots, where hydrodynamic processes give rise to nanobumps.

GC-MS profiling of the phytochemical constituents of the oleoresin from Copaifera langsdorffii Desf. and a preliminary in vivo evaluation of its antipsoriatic effect.

Copaiba is the oleoresin (OR) obtained from Copaifera (Fabaceae), a neotropical tree which grows in Amazon regions. The balsam, constituted by an essential oil and a resinous fraction is used as folkloristic remedy in the treatment of several inflammatory diseases and for its antioxidant and antibacterial properties. Aim of this work was (a) to carry out a characterization by GC-MS of the volatile and nonvolatile constituents of Copaifera langsdorffii Desf.

Second harmonic generation from 3D nanoantennas: on the surface and bulk contributions by far-field pattern analysis.

We numerically study second harmonic generation from dipole gold nanoantennas by analyzing the different contributions of bulk and surface nonlinear terms. We focus our attention to the properties of the emitted field related to the different functional expressions of the two terms. The second harmonic field exhibits different far and near field patterns if both nonlinear contributions are taken into account or if only one of them is considered.

Circular dichroism in the optical second-harmonic emission of curved gold metal nanowires.

Here we report the experimental observation of circular dichroism in the second-harmonic field (800-400 nm conversion) generated by self-organized gold nanowire arrays with subwavelength periodicity (160 nm). Such circular dichroism, raised by a nonlinear optical extrinsic chirality, is the evident signature of the sample morphology. It arises from the curvature of the self-assembled wires, producing a lack of symmetry at oblique incidence.

New multifunctional surfactants from natural phenolic acids.

Several new multifunctional molecules derived from natural sources such as amino acids and hydroxycinnamic acids were synthesized. They exhibit various activities such as emulsifying, UV-protecting, and radical scavenging, thereby conforming to the latest requirements for cosmetic ingredients. The synthesis comprises only a few steps: (i) the amino acid, the acid groups of which are protected by esterification, is coupled with ferulic or caffeic acid; (ii) the p-hydroxyl group of the cinnamic derivative reacts with dodecyl bromide in the presence of potassium carbonate (the resulting compounds are highly lipophilic and tested as water/oil (W/O) emulsifiers); (iii) these molecules, by deprotonating the acid groups of the amino acids, with successive salification, are more hydrophilic, with stronger O/W emulsifying properties.

The human olfactory receptor 17-40: requisites for fitting into the binding pocket.

To gain structural insight on the interactions between odorants and the human olfactory receptor, we did homology modelling of the receptor structure, followed by molecular docking simulation with ligands. Molecular dynamics simulation on the structures resulting from docking served to estimate the binding free energy of the various odorant families. A correlation with the odorous properties of the ligands is proposed.