Theoretical Study of Gold Nanoparticles Randomly Dispersed on a Dielectric/Gold Substrate.

We theoretically study random arrangements of cylindrical gold nanoparticles (NPs) deposited on a dielectric/gold substrate. We use two methods, namely the Finite Element Method (FEM) and the Coupled Dipole Approximation (CDA) method. The FEM is increasingly used to analyze the optical properties of NPs, but calculations for arrangements containing a large number of NPs have a high computational cost.

Phononic Crystal Made of Silicon Ridges on a Membrane for Liquid Sensing.

We propose the design of a phononic crystal to sense the acoustic properties of a liquid that is constituted by an array of silicon ridges on a membrane. In contrast to other concepts, the ridges are immersed in the liquid. The introduction of a suitable cavity in the periodic array gives rise to a confined defect mode with high localization in the cavity region and strong solid-liquid interaction, which make it sensitive to the acoustic properties of the liquid.

Emerging topics in nanophononics and elastic, acoustic, and mechanical metamaterials: an overview.

This broad review summarizes recent advances and "hot" research topics in nanophononics and elastic, acoustic, and mechanical metamaterials based on results presented by the authors at the EUROMECH 610 Colloquium held on April 25-27, 2022 in Benicássim, Spain. The key goal of the colloquium was to highlight important developments in these areas, particularly new results that emerged during the last two years. This work thus presents a "snapshot" of the state-of-the-art of different nanophononics- and metamaterial-related topics rather than a historical view on these subjects, in contrast to a conventional review article.

Physics of surface vibrational resonances: pillared phononic crystals, metamaterials, and metasurfaces.

The introduction of engineered resonance phenomena on surfaces has opened a new frontier in surface science and technology. Pillared phononic crystals, metamaterials, and metasurfaces are an emerging class of artificial structured media, featuring surfaces that consist of pillars-or branching substructures-standing on a plate or a substrate. A pillared phononic crystal exhibits Bragg band gaps, while a pillared metamaterial may feature both Bragg band gaps and local resonance hybridization band gaps.

Impact of SiO Particles in Polyethylene Textile Membrane for Indoor Personal Heating.

Keeping the human body in a thermal comfort state inside a room has become a challenge in recent years. While the most common strategy is to heat buildings, it requires a lot of energy. Reducing this energy consumption will have positive impacts, both economically and environmentally.

Polymer photonic crystal membrane for thermo-regulating textile.

We study numerically the absorption and scattering properties of a polymer photonic membrane to thermoregulate the human body microclimate which corresponds to the area between the skin and a textile. We first show that the structuration of the absorbing photonic membrane with air holes leads to a modulation of the optical spectrum in the Mid-Infrared range. Indeed, we show that the membrane is able to modulate the transmission amplitude by 28% in benefit or deficit of both the absorption and reflection.

Elastic stubbed metamaterial plate with torsional resonances.

We report on a new mechanism involving the torsional resonance of stubs to achieve the negative effective shear modulus of an elastic metamaterial plate. Combined with a mechanism to create a negative mass density, we develop a general method to set up and enlarge a shear-horizontal-polarized double-negative branch in the elastic metamaterial plate with stubs on both sides. We explore the capabilities of this structure for polarization filtering, mode conversion and abnormal refraction.

Spatiotemporal Imaging of the Acoustic Field Emitted by a Single Copper Nanowire.

The monochromatic and geometrically anisotropic acoustic field generated by 400 and 120 nm diameter copper nanowires simply dropped on a 10 μm silicon membrane is investigated in transmission using three-dimensional time-resolved femtosecond pump-probe experiments. Two pump-probe time-resolved experiments are carried out at the same time on both sides of the silicon substrate. In reflection, the first radial breathing mode of the nanowire is excited and detected.

Gradient Index Devices for the Full Control of Elastic Waves in Plates.

In this work, we present a method for the design of gradient index devices for elastic waves in plates. The method allows the design of devices to control the three fundamental modes, despite the fact that their dispersion relation is managed by different elastic constants. It is shown that by means of complex graded phononic crystals and thickness variations it is possible to independently design the three refractive indexes of these waves, allowing therefore their simultaneous control.

Simultaneous bandgaps in LiNbO3 phoxonic crystal slab.

We study simultaneous photonic and phononic crystal slabs created in Z-cut lithium niobate membranes. Bandgaps for guided waves are identified using the three-dimensional finite element method (FEM). Three lattices are considered: the square, the hexagonal, and the honeycomb lattices.

Phonons in slow motion: dispersion relations in ultrathin Si membranes.

We report the changes in dispersion relations of hypersonic acoustic phonons in free-standing silicon membranes as thin as ∼8 nm. We observe a reduction of the phase and group velocities of the fundamental flexural mode by more than 1 order of magnitude compared to bulk values. The modification of the dispersion relation in nanostructures has important consequences for noise control in nano- and microelectromechanical systems (MEMS/NEMS) as well as opto-mechanical devices.

Coverage-dependent adsorption geometry of octithiophene on Au(111).

The adsorption behavior of α-octithiophene (8T) on the Au(111) surface as a function of 8T coverage has been studied with low-temperature scanning tunneling microscopy, high resolution electron energy loss spectroscopy as well as with angle-resolved two-photon photoemission and ultraviolet photoemission spectroscopy. In the sub-monolayer regime 8T adopts a flat-lying adsorption geometry. Upon reaching the monolayer coverage the orientation of 8T molecules changes towards a tilted configuration, with the long molecular axis parallel to the surface plane, facilitating attractive intermolecular π-π-interactions.

Simultaneous guidance of slow photons and slow acoustic phonons in silicon phoxonic crystal slabs.

We demonstrate theoretically that photons and acoustic phonons can be simultaneously guided and slowed down in specially designed nanostructures. Phoxonic crystal waveguides presenting simultaneous phononic and photonic band gaps were designed in perforated silicon membranes that can be conveniently obtained using silicon-on-insulator technology. Geometrical parameters for simultaneous photonic and phononic band gaps were first chosen for optical wavelengths around 1550 nm, based on the finite element analysis of a perfect phoxonic crystal of circular holes.

Plasmonic properties of silver nanostructures coated with an amorphous silicon-carbon alloy and their applications for sensitive sensing of DNA hybridization.

The use of an amorphous silicon-carbon alloy overcoating on silver nanostructures in a localized surface plasmon resonance (LSPR) sensing platform allows for decreasing the detection limit by an order of magnitude as compared to sensors based on gold nanostructures deposited on glass. In addition, silver based multilayer structures show a distinct plasmonic behaviour as compared to gold based nanostructures, which provides the sensor with an increased short-range sensitivity and a decreased long-range sensitivity.

Effects of rituximab therapy on quality of life in patients with primary Sjögren's syndrome.

Objectives: To assess the efficacy of the anti-CD20 antibody rituximab in improving physical function and health-related quality of life (HRQoL) in patients with active primary Sjögren's syndrome (pSS), as well as the duration and sources of HRQoL improvements.

Methods: Sixteen patients with pSS received rituximab infusions (375 mg/m2) at weeks 0 and 1 and were followed up for 36 weeks. All patients fulfilled 2002 American-European Consensus Group criteria for pSS and had active disease defined as scores >50 mm on two of four 100-mm visual analogue scales (VAS) evaluating global disease activity, fatigue, pain, and dryness.

Tuning and switching the hypersonic phononic properties of elastic impedance contrast nanocomposites.

Anodic aluminum oxide (AAO) containing arrays of aligned cylindrical nanopores infiltrated with polymers is a well-defined model system for the study of hypersound propagation in polymer nanocomposites. Hypersonic phononic properties of AAO/polymer nanocomposites such as phonon localization and anisotropic sound propagation can be tailored by adjusting elastic contrast and density contrast between the components. Changes in density and elastic properties of the component located in the nanopores induced by phase transitions allow reversible modification of the phononic band structure and mode switching.

Visualizing the frontier orbitals of a conformationally adapted metalloporphyrin.

We present a molecular-level study of the geometric and electronic properties of Co(II) tetraphenylporphyrin molecules adsorbed on the Cu(111) surface. A combination of low-temperature scanning tunneling microscopy and near-edge X-ray absorption fine structure observations reveals how the metal substrate induces a conformational adaptation into a distorted saddle-shaped geometry. By scanning tunneling spectroscopy we identified the discrete energy levels of the molecule and mapped their spatial electron-density distributions.

Conformational adaptation and selective adatom capturing of tetrapyridyl-porphyrin molecules on a copper (111) surface.

We present a combined low-temperature scanning tunneling microscopy and near-edge X-ray adsorption fine structure study on the interaction of tetrapyridyl-porphyrin (TPyP) molecules with a Cu(111) surface. A novel approach using data from complementary experimental techniques and charge density calculations allows us to determine the adsorption geometry of TPyP on Cu(111). The molecules are centered on "bridge" sites of the substrate lattice and exhibit a strong deformation involving a saddle-shaped macrocycle distortion as well as considerable rotation and tilting of the meso-substituents.

Zwitterionic self-assembly of L-methionine nanogratings on the Ag(111) surface.

The engineering of complex architectures from functional molecules on surfaces provides new pathways to control matter at the nanoscale. In this article, we present a combined study addressing the self-assembly of the amino acid L-methionine on Ag(111). Scanning tunneling microscopy data reveal spontaneous ordering in extended molecular chains oriented along high-symmetry substrate directions.