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Spurred by outstanding optical properties, chemical stability, and facile bioconjugation, plasmonic metals have become the first-choice materials for optical signal transducers in biosensing. While the design rules for surface-based plasmonic sensors are well-established and commercialized, there is limited knowledge of the design of sensors based on nanoparticle aggregation. The reason is the lack of control over the interparticle distances, number of nanoparticles per cluster, or multiple mutual orientations during aggregation events, blurring the threshold between positive and negative readout. Here we identify the geometrical parameters (size, shape, and interparticle distance) that allow for maximizing the color difference upon nanoparticle clustering. Finding the optimal structural parameters will provide a fast and reliable means of readout, including unaided eye inspection or computer vision. J.L.M.-P., N.Z., and J.A. acknowledge financial support from Spanish MICIN/AE/DOI 10.13039/501100004837, Reg. No. PID2019-107432GB-I00 and from the Department of Education of the Basque Government under Project IT1526-22. M.G. acknowledges Euskampus Foundation for financial support (Resilience COVID19). This work received computational support from DIPC's HPC cluster ATLAS, operated by DIPC Supercomputing Center.

The ultrafast concentration of electromagnetic energy in nanoscale volumes is one of the key features of optical nanoantennas illuminated at their surface plasmon resonances. Here, we drive the insulator to metal phase transition in vanadium dioxide (VO2) using a laser-induced pumping effect obtained by positioning a single gold nanoantenna in proximity to a VO2 thermochromic material. We explore how the geometry of the single nanoantenna affects the size and permittivity of the nanometer-scale VO2 regions featuring phase transition under different pumping conditions. The results reveal that a higher VO2 phase transition effect is obtained for pumping of the longitudinal or transversal localized surface plasmon depending on the antenna length. This characterization is of paramount importance since the single nanoantennas are the building blocks of many plasmonic nanosystems. Finally, we demonstrate the picosecond dynamics of the VO2 phase transition characterizing this system, useful for the realization of fast nano-switches. Our work shows that it is possible to miniaturize the hybrid plasmonic-VO2 system down to the single-antenna level, still maintaining a controllable behavior, fast picosecond dynamics, and the features characterizing its optical and thermal response., LB, NZ, and JA acknowledge financial support from Spanish MICIN (DOI 10.13039/501100004837) through Project Ref. No. PID2019-107432GB-I00, from the Department of Education of the Basque Government under project IT1164-19 and the Department of Industry of the Basque Government under Elkartek project KK-2018/0000. OM and BC acknowledge support from EPSRC (DOI 10.13039/501100000266) through grants EP/J016918/1 and EP/M009122/1.

We show that the magnetic-modulation of the optical response induced by an external magnetic field in giant-magneto-resistance rod-slit arrays is more sensitive to the presence of a molecular vibration than the direct optical response.

We present experimental and theoretical results of the molecular sensing performance of a novel platform based on magnetic modulation of surface-enhanced infrared absorption spectroscopy. For this, we study the effect that molecular infrared vibrations of a PMMA layer have on the optical and magneto-refractive response of spintronic antennas. Specifically, a periodic array of rods is fabricated from giant-magneto-resistance Au/Ni81Fe19 metallic multilayers, and the effect of depositing a layer of PMMA on top of the array is investigated from both experimental and theoretical points of view. We find that the relative changes induced by the infrared vibrations of PMMA on the magneto-refractive signal are larger than the relative changes induced on the optical transmission. This result indicates that the magneto-refractive response is more sensitive to the excitation of molecular vibrations than the optical response and fosters the development of a novel type of an infrared sensing technique based on spintronic antennas: Magneto-Refractive Surface-Enhanced Infrared Absorption (SEIRA) Spectroscopy., We acknowledge financial support from MINECO through projects AMES (No. MAT 2014-58860-P), Quantum Spin Plasmonics (No. FIS2015-72035-EXP), and MIRRAS (No. MAT2017-84009-R) and Comunidad de Madrid (CM) through project SINOXPHOS-CM (No. S2018/BAA-4403). We acknowledge the service from the MiNa Laboratory at IMN and funding from MINECO under Project No. CSIC13-4E-1794 and from CM under Project No. S2013/ICE-2822 (Space-Tec), both with support from EU (FEDER, FSE). L.B., N.Z., and J.A. acknowledge support from the Department of Education, Research and Universities of the Basque Government through Project Ref. No. IT-1164-19, the Department of Industry of the Basque Government through Project No. KK-2018/00001, and the Spanish MICIN through Project Ref. No. PID2019-107432GB-I00.

"Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM", El objetivo principal de este documento internacional de consenso sobre apnea obstructiva del sue˜no esproporcionar unas directrices que permitan a los profesionales sanitarios tomar las mejores decisionesen la asistencia de los pacientes adultos con esta enfermedad según un resumen crítico de la literaturamás actualizada. El grupo de trabajo de expertos se ha constituido principalmente por 17 sociedadescientíficas y 56 especialistas con amplia representación geográfica (con la participación de 4 sociedadesinternacionales), además de un metodólogo experto y un documentalista del Centro Cochrane Iberoame-ricano. El documento consta de un manuscrito principal, con las novedades más relevantes, y una seriede manuscritos online que recogen las búsquedas bibliográficas sistemáticas de cada uno de los aparta-dos del documento internacional de consenso. Este documento no cubre la edad pediátrica ni el manejodel paciente en ventilación mecánica crónica no invasiva (que se publicarán en sendos documentos deconsenso aparte)., The main aim of this international consensus document on obstructive sleep apnea is to provide guidelines based on a critical analysis of the latest literature to help health professionals make the best decisions in the care of adult patients with this disease. The expert working group was formed primarily of 17 scientific societies and 56 specialists from a wide geographical area (including the participation of 4 international societies), an expert in methodology, and a documentalist from the Iberoamerican Cochrane Center. The document consists of a main section containing the most significant innovations and a series of online manuscripts that report the systematic literature searches performed for each section of the international consensus document. This document does not discuss pediatric patients or the management of patients receiving chronic non-invasive mechanical ventilation (these topics will be addressed in separate consensus documents).

Complementary metasurfaces composed of randomly-placed arrays of aligned rods or slits are fabricated out of giant magnetoresistance Ni81Fe19/Au multilayers (MLs), a material whose optical properties change under the application of an external static magnetic field. The two metasurfaces are studied from both the experimental and theoretical viewpoints. The induced magnetic modulation (MM) of both the far-field signal and the resonant near field, at the rod/slit localized surface plasmon frequency, are found to obey the Babinet’s principle. Furthermore, the near-field MM is found to be higher than the far-field counterpart. At resonance, both arrays show spots with high values of the magnetic modulated intensity of the electric near field (MM hot-spots). We show that this high magnetic modulation of the near-field intensity is very promising for the future development of high sensitivity molecular sensing platforms in the Mid- and Far-IR, using Magnetic-Modulation of Surface-Enhanced Infrared Absorption (MM-SEIRA) spectroscopy, Ministerio de Economía y Competitividad (AMES (MAT 2014-58860-P), CSIC13-4E-1794, MIRRAS(MAT2017-84009-R), PID2019-107432GB-I00, Quantum Spin Plasmonics (FIS2015-72035-EXP)); Ekonomiaren Garapen eta Lehiakortasun Saila, Eusko Jaurlaritza (KK-2018/00001); Hezkuntza, Hizkuntza Politika Eta Kultura Saila, Eusko Jaurlaritza (No. IT-1164-19); Comunidad de Madrid (S2013/ICE- 2822 (Space-Tec), SINOXPHOS-CM (S2018/BAA-4403)).

The dynamic restructuring of metal nanoparticle surfaces is known to greatly influence their catalytic, electronic transport, and chemical binding functionalities. Here we show for the first time that non-equilibrium atomic-scale lattice defects can be detected in nanoparticles by purely optical means. These fluctuating states determine interface electronic transport for molecular electronics but because such rearrangements are low energy, measuring their rapid dynamics on single nanostructures by X-rays, electron beams, or tunnelling microscopies, is invasive and damaging. We utilise nano-optics at the sub-5nm scale to reveal rapid (on the millisecond timescale) evolution of defect morphologies on facets of gold nanoparticles on a mirror. Besides dynamic structural information, this highlights fundamental questions about defining bulk plasma frequencies for metals probed at the nanoscale., Dynamic restructuring of metal nanoparticle surfaces greatly influences their catalytic, electronic transport, and chemical binding functionalities. Here, the authors show that non-equilibrium atomic-scale lattice defects can be detected in nanoparticles by using nano-optics at the sub-5nm scale.

In this work, we experimentally demonstrate magnetic modulation of mid-infrared (mid-IR) plasmon resonances in microantenna and hole-array metamaterial platforms made of Ni81Fe19/Au multilayers. The responsible mechanism is the magnetorefractive effect linked to the giant magnetoresistance (GMR) present in this system. Ni81Fe19/Au multilayers experience a modification in the electrical resistivity upon the application of a small magnetic field. This directly translates into a change in the optical constants of the multilayer, making it possible to magnetically modulate the plasmon resonances. Because GMR acts on conduction electrons, the optical modulation occurs in the low energy, mid-IR range, even being possible to extend it to the THz range. Electrodynamical calculations confirm the experimental observations. This approach improves by up to 2 orders of magnitude previous attempts for mid-IR magnetic modulation, is potentially ultrafast due to the characteristic spintronics dynamics, and establishes a roadmap for spintronically controlled devices in the whole mid-IR to THz band., We acknowledge financial support from MINECO through project AMES (MAT 2014-58860-P), Quantum Spin Plasmonics (FIS2015-72035-EXP), PlasmoQuanta (FIS2016-80174-P), and MIRRAS (MAT2017-84009-R). L.B., N.Z., and J.A. acknowledge support from the Basque Department of Education and the UPV-EHU (Grant IT-756-13). A.M. acknowledges support from the Spanish Ministry of Economy and Competiveness (MINECO) under grant TEC2014-51902-C2-1-R. We acknowledge the service from the MiNa Laboratory at IMN and funding from MINECO under project CSIC13-4E-1794 and from CM under project S2013/ICE-2822 (Space-Tec), both with support from EU (FEDER, FSE).

The non-physical effects on the transverse momentum transfer from fast electrons to gold nanoparticles associated to the use of non-causal dielectric functions are studied. A direct test of the causality based on the surface Kramers–Kronig relations is presented. This test is applied to the different dielectric function used to describe gold nanostructures in electron microscopy., A.R-C. acknowledges financial support from DGAPA/PAPIIT-UNAM project IA105917. R.E-S. acknowledges financial support from DGAPA/PAPIIT-UNAM project IN110916. N. Z. and A. R. acknowledge financial support from MINECO (FIS2016-80174-P) and Basque Government grant of UPV/EHU Grupos Consolidados IT-756-13.

The αv β3 integrin receptor plays an important role in tumor metastasis and tumor-induced angiogenesis. The inhibition of this receptor with diverse ligands, antibodies, or cyclic peptides is a promising research field for the treatment of a variety of tumors. The replacement of Phe-(Me)Val dipeptide by a β-lactam ring in Cilengitide has led to new products that show higher inhibitory activity than the parent cyclopeptide. In particular, substitution of a peptide bond β-lactam-NH-Asp linkage by a β-lactam-O-Asp ester linkage increases the activity of the new cyclodepsipeptide. In the same way it has been found that open-chain compounds of the form Asp-β-lactam-Arg can interact with the receptor and inhibit its activity moderately. The integrin inhibitory activity of the synthesized compounds has been established by using the CGH array, a method that appears to be a more reliable trial than the classical adhesion test.

We present magnetic field induced modulation of the optical response of slit plasmonic metasurfaces fabricated out of giant magnetoresistance/spintronic materials in the 2–17 μm spectral range of the spectrum. The modulation of the slit plasmonic modes is due to the modification of the electrical resistivity (and, in turn, of the optical constants) induced by the application of an external magnetic field. This modulation is found to continuously increase both with the slit concentration and with the slit resonance wavelength, with a prospective further increase for wavelengths of up to 60–80 μm. The direct fabrication and implementation of the modulation setup opens a competitive route for the development of active plasmonic metasurfaces in a wide spectral range., We acknowledge financial support from MINECO through projects AMES (MAT2014-58860-P), Quantum Spin Plasmonics (FIS2015-72035-EXP), PlasmoQuanta (FIS2016-80174-P), MIRRAS (MAT2017-84009-R), and Comunidad de Madrid through project SINOXPHOSCM (S2018/BAA-4403). LB, NZ, and JA acknowledge support from the Department of Education of the Basque Government under project IT1164-19, and the Department of Industry of the Basque Government under Elkartek project KK-2018/00001. We acknowledge the service from the MiNa Laboratory at IMN and funding from MINECO under project CSIC13-4E-1794 and from CM under project S2018/NMT-4291 TEC2SPACE, both with support from EU (FEDER, FSE).

This work is supported by Eusko Jaurlaritza under Grants No. IT-1005-16 and No. IT-756-13 and by Spanish Ministry of Economy and Competitiveness under Grant No. MAT2015- 65165-C2-R (MINECO/FEDER). I. Unzueta also wants to acknowledge Eusko Jaurlaritza for Grant No. PRE-2014-214.

Single-nanoantenna has intrigued vast interest due to its exceptional properties such as light harvesting and field enhancement, which provide the opportunities for strengthening light-matter interaction and efficient photon manipulation in nano-scale, as well as boosting nonlinear response. On the other hand, materials with structural or electronic phase transition have been employed to achieve large optical modulation contrast and order-unity switching, making them promising building blocks for high-performance optical circuits and devices with ultra-small footprint. In this context we demonstrate nano-scale all-optical modulation with single Au antennas fabricated on phase-transition material vanadium dioxide (VO2) substrate. VO2 films are deposited on boroaluminosilicate glass coated with a 30-nm layer of fluorine-doped tin oxide. The inclusion of this intermediate layer allows the production of VO2 films with low surface roughness and suitable thermochromic transition temperature. Then the nanoantennas are fabricated by e-beam lithography and subsequent 45-nm-thick gold deposition on the VO2 substrate. A 5-nm-thick Ti layer is used to improve the adhesion of the gold to the VO2. We use a pump-probe spectroscopy to characterize the modulation feature of the antenna/VO2. The pump beam at 1060 nm wavelength is used to introduce a local heating for VO2's phase transition and the probe beam from 1100 nm to 2000 nm wavelength is for readout of the modulated local transmission of antenna/VO2 hybrid owing to the dielectric environment change. A spatial modulation technique is also used to extract the differential transmission (ΔT/T) around the antennas. As a result, with pump pulse energy increasing to less than 1 nJ, the measured ΔT/T of single-antenna//VO2 hybrid exhibits substantial change that crossing the zero line and significant blue shift. As reported the ΔT/T obtained from spatial modulation spectroscopy is supposed to be proportional to the antenna’s extinction cross section. However, with the obtained negative values which lead to unphysical extinction cross sections less than 0, we believe the VO2 substrate beneath the antennas is highly involved as its optical property has been modified considerately. In addition, we observe that the pump-modulated differential transmission of the antenna/VO2 hybrid evidently depends on the polarisation of the pump when it is below a certain level. In this regime, the parallel pumping excites the longitudinal resonant mode while the perpendicular one only induces non-resonant absorption of antenna’s transverse mode. Going beyond this regime, the stronger pump transits the VO2 substrate from insulating phase into metallic phase completely, which dominates the dielectric environment change of the antenna, leading to nearly polarisation-independent modulation. The time for fully switch-on obtained from the pump-probe measurement is less than 50 ps. We also investigate the time response of the differential transmission dependent on the pulse repetition rate and substrate temperature, respectively. Less modulation depth with repetition rate over 2 MHz or base temperature higher than 40 °C suggest that the heat accumulation from adjacent pulses and thermal equilibrium time plays important roles in the achievable modulation speed. The single-antenna/VO2 structure may find applications in nano-scale optoelectronics for multiple functionalities including modulation, memory and so on.

We analyze the full relativistic force experienced by swift electrons moving close to planar films for the experimental conditions commonly used in electron energy loss spectroscopy in STEM. In metals the main effects derive from the dispersion of the surface plasmons, which are clearly observed in the EEL spectra. In insulators we explore the role played by the Cherenkov radiation (CR) emitted in the energy gap window. The focus is placed on the transverse force and different factors which may turn this force into repulsive, as reported in recent experimental and theoretical works., This project was supported by the ETORTEK project NANOIKER from the Basque Government (BG), project FIS2010-19609-C02-01 from the Spanish Ministry of Science and Innovation and Grant IT-75613 from BG-UPV/EHU.

Plasmonic gaps are known to produce nanoscale localization and enhancement of optical fields, providing small effective mode volumes of about a few hundred nm. Atomistic quantum calculations based on time-dependent density functional theory reveal the effect of subnanometric localization of electromagnetic fields due to the presence of atomic-scale features at the interfaces of plasmonic gaps. Using a classical model, we explain this as a nonresonant lightning rod effect at the atomic scale that produces an extra enhancement over that of the plasmonic background. The near-field distribution of atomic-scale hot spots around atomic features is robust against dynamical screening and spill-out effects and follows the potential landscape determined by the electron density around the atomic sites. A detailed comparison of the field distribution around atomic hot spots from full quantum atomistic calculations and from the local classical approach considering the geometrical profile of the atoms' electronic density validates the use of a classical framework to determine the effective mode volume in these extreme subnanometric optical cavities. This finding is of practical importance for the community of surface-enhanced molecular spectroscopy and quantum nanophotonics, as it provides an adequate description of the local electromagnetic fields around atomic-scale features with use of simplified classical methods., Financial support from Project No. FIS2016-80174-P and MAT2016-78293-C6-4-R of MINECO, grant of Consolidated Groups at UPV/EHU (IT-756-13) of the Basque Government, and project 70NANB15H32 from U.S. Department of Commerce, National Institute of Standards and Technology, is acknowledged. M.U. acknowledges support from the University of the Basque Country through a Ph.D. grant, as well as DIPC and CFM at the initial stages of this work. M.B. acknowledges support from the Departamento de Educacion of the Basque Government through a Ph.D. grant, as well as from Euskampus and the DIPC at the initial stages of this work. P.K. acknowledges financial support from the Fellows Gipuzkoa program of the Gipuzkoako Foru Aldundia through the FEDER funding scheme of the European Union, “Una manera de hacer Europa”.

The goal of the research presented in this paper is to design and incorporate new technologies into railway bogie-mounted sensors. It is often impossible to connect the mounted systems to physical wires due to their location in an inaccessible position or the distance to the energy source. Therefore, another power source must be used to solve this problem. Energy harvesting technology is an increasingly popular solution that extracts energy from the ambient environment and transforms it into electrical energy. Using piezoelectric transducers, it is possible to transform the vibrations experienced by the bogie into energy that can be used to power the sensors. A prototype with multiple piezoelectric transducers has been designed, built and subjected to tests to validate the technology. The experimental results for all of the different configurations tested and levels of energy collected are presented.

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Angiogenesis, the sprouting of new blood vessels from pre-existing vessels, is a remarkable feature of tumours growth and metastasis. The in vivo inhibition of this receptor by cyclic peptides containing RGD sequence may be used to selectively suppress these disease1. Our research group has developed a new methodology2 for the evaluation of new antiangiogenic compounds, based in the genetic expression analysis using CGH array system. The RGD mimetics activity can be modified by the presence of ester-bond3, Therefore, we decided to prepare some depsipeptides analogous to the RGD-β-lactam compounds and evaluate their activity performing a genetic expression analysis. We also have evaluated the activity of open-chain compounds without RGD formal structure. The cyclic depsipeptides have demonstrated a very effective inhibitory activity. In the other hand the open-chain compounds have a surprising behavior, demonstrating a similar gene activation. This way, we call into question the essential need of RGD sequence to have an interaction between ligand and the receptor of the integrin4, 5. da Ressurreicao, A. S. M.; Vidu, A.; Civera M.; Belvisi L.; Potenza, D.; Manzoni, L.; Ongeri, S.; Gennari, C.; Piarulli, U.; Eur. 2009, 15, 12184. Aizpurua, J. M.; Ganboa, J. I.; Palomo, C.; Loinaz, I.; Oyarbide, J.; Fernandez, X.; Belentova, E.; Fratila, R. M.; Jimenez A.; Miranda, J. I.; Laso, A.; Avila, S.; Castrillo, J. L.; ChemBioChem, 2001, 11, 401. Cupido, T.; Spengler, J.; Ruiz-Rodriguez, J.; Adan, J.; Mitjans, F.; Puilats, J.; Albericio, F.; Chem. Int. Ed., 2010, 49, 2732. Xiong, J. P.; Stehle, T.; Zhang, R.; Joachimiak, A.; Frech, M.; Goodman, S. L.; Arnaout, M. A.; Science, 2002, 296, 151. Craig, D.; Gao, M.; Schulten, K.; Vogel, V.; Structure, 2004, 12, 2049.

Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits. Materials exhibiting a structural or electronic phase transition offer a large modulation contrast with multi-level optical switching and memory functionalities. In addition, plasmonic nanoantennas can provide an efficient enhancement mechanism for both the optically induced excitation and the readout of materials strategically positioned in their local environment. Here, we demonstrate picosecond all-optical switching of the local phase transition in plasmonic antenna-vanadium dioxide (VO2) hybrids, exploiting strong resonant field enhancement and selective optical pumping in plasmonic hotspots. Polarization- and wavelength-dependent pump–probe spectroscopy of multifrequency crossed antenna arrays shows that nanoscale optical switching in plasmonic hotspots does not affect neighboring antennas placed within 100 nm of the excited antennas. The antenna-assisted pumping mechanism is confirmed by numerical model calculations of the resonant, antenna-mediated local heating on a picosecond time scale. The hybrid, nanoscale excitation mechanism results in 20 times reduced switching energies and 5 times faster recovery times than a VO2 film without antennas, enabling fully reversible switching at over two million cycles per second and at local switching energies in the picojoule range. The hybrid solution of antennas and VO2 provides a conceptual framework to merge the field localization and phase-transition response, enabling precise, nanoscale optical memory functionalities.

We demonstrate ultrafast all-optical switching of local phase-change in plasmonic gold antenna-VO 2 hybrids exploting the strong resonant Near-Field enhancement on localized nanoscale regions.

By synergically combining experiments and simulations, we show how the excitation of lattice surface modes in ordered arrays of magnetic and optically-anisotropic nanoantennas leads to a highly enhanced and tunable Fano-like modulation of the magnetoplasmonic response.

Electron energy loss spectroscopy (EELS) induced by fast electrons in electron microscopes are used to probe photonic structures. Some of the loss features are shown to be associated to the excitation of radiative modes in the samples (Cherenkov radiation), from where information on photonic bands is extracted. The case of a 1D crystal is qualitatively discussed to explain the physics behind Cherenkov radiation in photonic crystals. For an electron beam collimated on one of the pores of 2D crystal consisting of a porous alumina film with 100-nm lattice constant, theory predicts a Cherenkov feature at around 6–9 eV, which is in excellent agreement with experiment. Finally, the features of the loss spectra are shown to be strongly correlated with the density of photonic states, suggesting the potential application of this technique to probe the quality and actual performance of photonic crystals., The authors acknowledge support from the Basque Departamento de Educación, Universidades e Investigación, the University of the Basque Country UPV/EHU (contract no. 00206.215-13639/2001), and Spanish Ministerio de Ciencia y Tecnologa (contract no. MAT2001-0946 and MAT2002-04087-C02-01).

Swift electron energy losses have been investigated in nanoporous alumina, taking into account retardation effects. A simple analytical expression is obtained for the energy loss probability. The electron energy loss spectra observed with the Scanning transmission electron microscope are reasonably well reproduced using a simple model consisting of a cylindrical shell of alumina surrounded by an effective porous medium. The Cherenkov radiation is responsible for energy losses below 8 eV. These losses are very sensitive to the shape of the nanostructures, up to distances much larger than the adiabatic length v/ω., Support from the Basque Government and the Basque Country University is gratefully acknowledged.

Following an adapted three-step seed-mediated method, we synthesize colloidal Au thin and long (L > 100 nm) nanorods (NRs) and characterize the metallic nanostructures evolving from the initial Au nanoparticle (NPs) seeds to thiolate-functionalized NRs, using HRTEM and ultraviolet, visible, and near-infrared absorption spectroscopy (UV-vis-NIR). For the long NRs we analyze the role of several solvents and rod concentration on the spectral features of the assembled products, which are further studied with simulated spectra. Superimposed to a broad resonance in the range 700-900 nm, which corresponds to short (L < 100 nm) interacting nanorods, the growth of long nanorods is clearly identified with the emergence of a robust resonance at 960 nm, linked to the three half-wavelength antenna plasmon mode. This mode is enhanced when the nanorod concentration decreases and splits into two peaks when the thiolate coverage chemically modifies the rod surface by a thin layer of nanometer size. This behavior is explained with a dielectric model based on ab initio calculations of thiolate-gold cluster surfaces., We gratefully acknowledge the support of the Basque Departamento de Educacion and the UPV/EHU (Grant No.IT-366-07) and Spanish Ministry of Economy and Competitiveness MINECO (FIS2013-48286-C2-1-P and FIS2013-41184-P) and the ETORTEK research program funded by the Basque Departamento de Industria and the Diputacion Foral de Guipuzcoa (nanoGUNE 2014). F.J. Recio thanks a Fondecyt 3130538 Postdoctoral Grant.

In the framework of the classical dielectric theory, the role of the image potential in electron energy loss spectroscopy (EELS) of fast electrons commonly used in scanning transmission electron microscopy travelling near a surface is studied. Relativistic and dispersive corrections are evaluated to establish the range of validity of this theory. The spatial resolution of the EELS technique is discussed for valence and core electron excitations. The effect of the quantal nature of the probe is also discussed. Finally, several problems involving planar surfaces, small particles, cylinders and truncated targets of interest in nanotechnology are studied., The authors thank the Basque Government for financial support (PI-1997-39).

The ground-state electronic structures of cylindrical quantum wires are studied within the stabilized jellium model and using the spin-dependent density-functional theory. The subband structure is shown to affect the cohesive properties, causing an oscillating structure in the force needed to elongate the wire. Because the steps in the quantized conductance reflect also the subband structure a correlation between the force oscillations and conductance steps is established. The model also predicts magnetic solutions commensurate with the subband structure and consequently additional steps in the conductance., N. Z. acknowledges the financial support of the Spanish Ministry of Education DGES, Project Reference PR95-591.

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence., The full retarded electromagnetic force experienced by swift electrons moving parallel to planar boundaries is revisited, for both metallic and dielectric targets, with special emphasis on the consequences in electron microscopy experiments. The focus is placed on the sign of the transverse force experienced by the electron beam as a function of the impact parameter. For point probes, the force is found to be always attractive. The contribution of the induced magnetic field and the causality requirements of the target dielectric response, given by the Kramers-Kronig (K-K) relations, prove to be crucial issues at small impact parameters. For spatially extended probes, repulsive forces are predicted for close trajectories, in agreement with previous works. The force experienced by the target is also explored, with the finding that in insulators, the momentum associated to Cherenkov radiation (CR) is relevant at large impact parameters. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft., This project was supported by the ETORTEK project NANOIKER from the Basque Government (BG), project FIS2010-19609-C02-01 from the Spanish Ministry of Science and Innovation, and grant IT-75613 from BG-UPV/EHU.

We present a theoretical study of a metal-molecular aggregate hybrid system consisting of a strongly coupled dimer connected by molecules characterized by an excitonic transition. The plasmonic resonances of the metallic dimer interact with the molecular excitations giving rise to coupled plasmon-exciton states, so called plexcitons. We compare the differences in the optical response when the excitonic material is placed only as a linker in the plasmonic gap of the dimer and when the material is distributed as an aggregate layer covering the dimer entirely. We also explore the efficiency of plexcitons for localized surface plamon resonance (LSPR) sensing in both situations. The ordinary shift-based sensing is more efficient for dimers connected through molecular linkers, whereas intensity-based sensing is more effective when the molecular aggregate covers the entire nanostructure. These results can serve to design the chemistry of excitons around metallic nanoparticles. © 2014 IOP Publishing Ltd., This project was supported by the Etortek project Nanoiker from the Basque Government (BG), project FIS2010-19609-C02-01 from the Spanish Ministry of Science and Innovation and grant IT-75613 from BG-UPV/EHU. OPG acknowledges financial support from Vicerrectorado de Investigación of the University of the Basque Country (Ayudas Especialización Doctores).

The energy-loss experienced by swift scanning transmisson electron microscopy electrons is calculated for a target constituted by two spherical particles in the framework of dielectric theory, using bispherical coordinates. Deviations from the behavior of the isolated sphere are investigated. The coupling between close particles and its effects on the energy-loss spectrum is found to depend significantly on the electron trajectory and target situation ~particle size and interparticle distance !. Excitations above the planar surface plasmon energy are found to be the dominant contribution to the loss spectrum for trajectories between the two spheres, while low-energy excitations, under those of the isolated sphere, appear for trajectories out of that region. The different possibilities are analyzed and compared with experimental results for aluminum particles and provisions of recent effective medium theories. The inelastic part of the induced electric field around the spheres is also studied showing a very important localization of the excitation in the space between both particles, even for trajectories outside that region. The expressions obtained are available for any local dielectric function. @S0163-1829~97!04435-4#

We present a theoretical study of the optical properties of a strongly coupled metallic dimer when an ensemble of molecules is placed in the inter-particle cavity. The linking molecules are characterized by an excitonic transition which couples to the Bonding Dimer Plasmon (BDP) and the Bonding Quadrupolar Plasmon (BQP) resonances, arising from the hybridization of the dipolar and quadrupolar modes of the individual nanoparticles, respectively. As a consequence, both modes split into two coupled plasmon-exciton modes, so called plexcitons. The Charge Transfer Plasmon (CTP) resonance, involving plasmonic oscillations of the dimer as a whole, arises when the conductance of the excitonic junction is above a threshold value. The possibility of exploiting plexcitonic resonances for sensing is explored in detail. We find high sensitivity to the environment when different dielectric embedding media are considered. Contrary to standard methods, we propose a new framework for effective sensing based on the relative intensity of plexcitonic peaks. © 2013 Optical Society of America., This project was supported by the Etortek project nanoiker from the Basque Government (BG), project FIS2010-19609-C02-01 from the Spanish Ministry of Science and Innovation and grant IT-366-07 from BG-UPV/EHU. O.P.G. acknowledges financial support from Vicerrectorado de Investigación of the University of the Basque Country (Ayudas Especialización Doctores). Computational resources were provided by DIPC (UPV/EHU, MICINN, BG, ESF).

We study theoretically the quantum well states (QWSs) localized in Pb overlayers on Cu(111) surface. Particular emphasis is given to the states with energies close to the vacuum level. Inclusion of the long-range image potential tail into the model potential description of the system allows us to show the effect of hybridization between QWSs and image potential states (ISs). The particle-in-a-box energy sequence characteristic for QWSs evolves into the Rydberg series converging towards the vacuum level. The electron density of the corresponding states is partially moved from inside the metal overlayer into the vacuum. The decay rates due to the inelastic electron-electron scattering decrease with increasing energy, opposite to >conventional> QWSs and similar to the ISs. Many-body and wave packet propagation calculations of the inelastic decay rates are supplemented by simple analysis based on the phase accumulation model and wave-function penetration approximation. This allows an analytical description of the dependence of the QWS/ISs hybridization on different parameters and, in particular, on the overlayer thickness. © 2012 American Physical Society., This work was partially funded by MCINN(FIS2010-19609-C02-01) and G.V-UPV/EHU(IT- 366-07).

We present a theoretical study of the constant current scanning tunneling spectroscopy of quantum well states localized in Pb(111) overlayers on Cu(111) surfaces. The distance-voltage characteristic of the tunneling junction is obtained with a mixed approach. The wave packet propagation technique is applied to describe electron tunneling from the tip into the sample, and the density functional calculations provide the necessary inputs for the one-dimensional model potential representation of the system. The excited-state population decay mechanisms via inelastic electron-electron and electron-phonon interactions are taken into account with a bias-dependent absorbing potential introduced in the metal. Our results are in good agreement with recent experimental studies over the energy range where the free-electron description of the Pb overlayer used here applies. We find that at high bias the quantum well states experience a Stark energy shift and partially acquire a character of field emission resonances. The present model study also sheds light at the experimentally observed departure of the energies of the quantum well states from the particle-in-a-box prediction for the bias above 4 eV. The measured trend can be consistently explained as due to the departure of the realistic Pb band structure in the Γ-L direction from free-electron parabola when the electron momentum approaches the Γ point. © 2011 American Physical Society.

10 páginas, 6 figuras, 3 tablas.-- PACS number(s): 73.40.Jn, 73.23.Ad, 73.63.Nm, 73.63.Rt, We study the conductance during the elongation and breakage of Na nanowires described with the ultimate jellium model. A combined approach is used where the nanowire breakage is simulated self-consistently within the density-functional theory, and the wave packet propagation technique is applied for ballistic electron transport. For certain conditions the breakage of the nanowire is preceded by formation of clusters of magic size in the break junction. This affects the conductance G, in particular the shape of the G=3G0 to G=G0 (=2e2/h) step upon elongation. The observed trends can be explained as due to the transient trapping of ballistic electrons inside the cluster, leading to a resonant character of the electron transport through the break junction. The cluster-derived resonances appear as peak structures in the differential conductance which may serve as an experimental signature of clustering., This work has been funded partially by the University of theBasque Country UPV/EHU (Grant No.GIC07IT36607), the Departamento de Educación del Gobierno Vasco, and the Spanish Ministerio de Ciencia y Technología (MCyT) (Grant No. FIS2007-66711-C02-01). The SGI/IZO-SGIker UPV/EHU (supported by the National Program for the Promotion of Human Resources within the National Plan of Scientific Research, Development and Innovation - Fondo Social Europeo, MCyT and Basque Government) as well as the Academy of Finland through its Centers of Excellence Program are gratefully acknowledged.

1 página, 1 figura.-- PACS numbers: 68.37.Ef, 68.65.Fg, 73.21.Fg, This work was partially funded by MCINN(FIS2010- 19609-C02-01) and G.V-UPV/EHU(IT-366-07).

We present a theoretical study of the optical properties of nanoparticle dimers connected by conductive gap linkers. The geometrical and conductive properties of the linker modify strongly the optical response of the linked metallic cavity. Two plasmonic modes are responsible for the main spectral features of the cavity: a bonding dimer plasmon (BDP) and a charge transfer plasmon (CTP). We first explore how these two modes are modified as a function of the geometry and the conductance through the cavity, identifying the spatial distribution of the linking current densities. Furthermore, we introduce a resonant feature in the conductivity of the linker, where we observe a complex splitting of the plasmon modes. We also study the capabilities of the BDP and CTP modes in localized surface plasmon resonance (LSPR) sensing. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Event: SPIE NanoScience + Engineering, 2011, San Diego, California, United States., In this work we study how plasmon modes of gold dimers are affected by a molecular bridge connecting both particles. Different models for the linker are considered to envisage the relation between the spectral changes observed in the extinction spectra and the electronic transport through the molecules. Depending on the size and nature of the molecular linker two different modes, known as BDP (Bonding Dimer Plasmon) and CTP (Charge Transfer Plasmon), are excited. Furthermore, when the molecular linker has an excitonic resonance, new spectral features emerge due to the plasmon-exciton coupling., This project was supported by the Etortek project inanoGUNE from the Basque Government (BG), project FIS2010-19609-C02-01 from the Spanish Ministry of Science and Innovation, grant IT-366-07 from BG-UPV/EHU and project CUBIHOLE EUI2008-03816 from European Union. Computational resources were provided by IZOSGIker (UPV/EHU, MICINN, BG, ESF).

The optical properties of a nanoparticle dimer bridged by a conductive junction depend strongly on the junction conductivity. As the conductivity increases, the bonding dimer plasmon blueshifts and broadens. For large conductance, a low energy charge transfer plasmon also appears in the spectra with a line width that decreases with increasing conductance. A simple physical model for the understanding of the spectral feature is presented. Our finding of a strong influence of junction conductivity on the optical spectrum suggests that plasmonic cavities might serve as probes of molecular conductance at elevated frequencies not accessible through electrical measurements., This project was supported by the Robert A. Welch Foundation, Grants C-1220 and C-1222(P.N., N.J.H.), Etortek project inanoGUNE from the Basque Government (BG), Project FIS2007-066711-C02-00 from the Spanish MICINN, Grant IT-366-07 from BG-UPV/EHU and Project EUI2008-03816 CUBiHOLE from the internationalization national plan of the Spanish MICINN within the EU ERA-NET projects (J.A., N.Z., O.P.G.). Computational resources were provided by IZO-SGIker (UPV/EHU, MICINN, BG, ESF).

A standard many-body method, based on the spherical-harmonics representation of the Bethe-Salpeter ladder solution for the two-particle scattering amplitude in two-dimensional jellium electron gases, is applied to determine a pair formation temperature Tp from the pole of the pairing vertex. In this method, pairing may occur due to attractive spherical harmonics in the input interparticle interaction. The comparative study was performed with parametrized models for this interaction obtained by considering the real-space aspects of screening holes around moving electrons. The theoretical, maximal pair formation temperatures are in the ∼100K range and appear at small values of the density of the jellium system., The work of I.N. was supported partly by the Hungarian OTKA -Grant No. T049571 and that of N.Z. and P.M.E. by the University of Basque Country and the Basque Unibertsitate eta Ikerketa Saila GV-UPV/EHU s/n Grant No. IT-366-07 and the Spanish MCyT Grant No. FIS2007-66711-C02-01

If the bare interaction between two electrons is dressed in the two-dimensional (2D) electron gas by the many-body environment, pairing may occur. Here, we study numerically the existence and character of bound states in cases where the basic dressing is described by superimposing normalized holes centered around both electrons. Beyond this modeling, a possible modification of the interaction energy at short range is considered by a repulsive potential term. The effect of the ionic polarizability on pair interaction is approximated by a static dielectric constant. A many-body analysis of pairing, employing the spherical harmonics representation of the Bethe–Salpeter ladder-solution for the two-particle scattering amplitude in 2D, is given as well. Pairing occurs due to attractive spherical harmonics in our interparticle potential., The work of IN has been supported partly by the Hungarian OTKA (Grant No. T049571), that of NZ and PME by the University of the Basque Country and the Basque Unibertsitate eta Ikerketa Saila (GV-UPV/EHU (s/n) IT-366-07) and the Spanish MCyT (FIS2007-66711-C02-01).

11 páginas, 8 figuras, 1 tabla.-- PACS number(s): 73.21.Fg, 73.50.Gr, 73.20.At, 78.47.-p.-- Trabajo presentado al "DIPC10 : Passion for Knowledge" celebrado en Donostia (España) del 27 de septiembre al 1 de octubre de 2010., We present results of calculations of the lifetimes of excited electrons (holes) in quantum well states and quantum well resonances in Pb overlayers supported on Cu(111). Many-body decay via inelastic energy relaxation and one-electron decay via energy-conserving one-electron transfer into the substrate are considered. One-electron energies and wave functions have been computed for different coverages of the Pb overlayer (from 1 to 18 monolayers) by using a one-dimensional pseudopotential for the entire overlayer-substrate system in the framework of density functional theory within the local density approximation. The elastic (energy-conserving resonant electron transfer) contribution to the total lifetime broadening of quantum well resonances has been calculated within the wave packet propagation method. The inelastic electron-electron (many-body) contribution to the lifetime broadening of both occupied and unoccupied quantum well states has been evaluated using GW approximation. The decay mechanisms of both quantum well states and quantum well resonances in thick overlayers are discussed., This work has been funded partially by the University of the Basque Country UPV/EHU (Grant No. GIC07IT36607), the Departamento de Educación del Gobierno Vasco, and the Spanish Ministerio de Ciencía y Technología (MCyT) (Grant No. FIS2007-66711-C02-01).

Surface plasmon energies of single and oxidized spheres half-embedded on a planar support are calculated in the framework of the classical dielectric theory. Simple analytic expressions are obtained. New resonances appear related to the coupling between both media. The main difference between a supported sphere and an isolated sphere is the splitting of the multipolar energy modes, according to their parity. The support effect on EELS spectra is analyzed for some cases of experimental interest in electron microscopy., The authors thank Gipuzkoako Foru Aldundia for financial support.

8 pages, 7 figures.-- Printed version published on Aug 6, 2008., The role of quantum well states (QWSs) and quantum well resonances (QWRs) in the stability of metallic overlayers is studied. When the substrate presents a confining gap, as it is the case of Cu(111), the stability is determined by QWSs and there is experimental evidence of the existence of magic thicknesses. For overlayers which do not have QWSs, as those grown on Al(111), we explore the existence of thicknesses of enhanced stability due to QWRs by comparing the strength of the oscillations in the surface energy., We acknowledge partial support by the University of the Basque Country and the Basque Hezkuntza Unibertsitate eta Ikerkuntza Saila (Grant No. IT-366-07), and Spanish MEC (FIS2007-65711-C02-01 and MAT2006-12743). The SGI/IZO-SGIker UPV/EHU (supported by the National Program for the Promotion of Human Resources within the National Plan of Scientific Research, Development and Innovation—Fondo Social Europeo, MCyT and Basque Government) is gratefully acknowledged for generous allocation of computational resources. This work was also partially supported by the Academy of Finland through its Centre of Excellence Program.

Electronic states of one monolayer high Na nanoislands on the Cu(111) surface are studied as a function of the nanoisland size. Properties of nanoislands such as one-electron states, the electron density, and the associated potential are obtained self-consistently within the density-functional formalism using a one-dimensional pseudopotential for the Cu(111) substrate and the jellium model for Na. A wave packet propagation method is used to study the energies and lifetimes of quasistationary states localized at Na islands. For very large islands, island-localized states merge into the two-dimensional continuum of the Na quantum well state. Thus, we assign the quasistationary states studied as arising from the quantization of the two-dimensional quantum well continuum due to the finite island size. The scattering at the island boundaries results in the energy-conserving resonant electron transfer into the continuum of the substrate states broadening the island-localized states into resonances.

Abnormally large stability of Pb nanostructures grown on metallic or semiconductor substrates has been observed even for heights of about 30 monolayers. Using both density-functional theory calculations and analytical models, we demonstrate that the stability at even higher coverages (N>30 ML) is supported by an extra second quantum beat pattern in the energetics of the metal film as a function of the number of atomic layers. This pattern is triggered by the butterflylike shape of the Fermi surface of lead in the (111) direction and supports the detection of stable magic islands of higher heights than measured up to now., This work was supported by the ETORTEK -NANOMAT program of the Basque government, Spanish Ministerio de Ciencia y Tecnología -MCyT of Spain -Grant No. Fis 2004-06490-CO3-00, the European Network of Excellence NANOQUANTA -NM4-CT-2004-500198 and the Intramural Special Project -Ref. 2006601242. The SGI/IZOSGIker UPV/EHU supported by the National Program for the Promotion of Human Resources within the National Plan of Scientific Research, Development and Innovation-Fondo Social Europeo, MCyT and Basque Government is gratefully acknowledged for allocation of computational resources.