Molecular interfaces for plasmonic hot electron photovoltaics

The use of self-assembled monolayers (SAMs) to improve and tailor the photovoltaic performance of plasmonic hot-electron Schottky solar cells is presented. SAMs allow the simultaneous control of open-circuit voltage, hot-electron injection and short-circuit current. To that end, a plurality of molecule structural parameters can be adjusted: SAM molecule's length can be adjusted to control plasmonic hot electron injection. Modifying SAMs dipole moment allows for a precise tuning of the open-circuit voltage. The functionalization of the SAM can also be selected to modify short-circuit current. This allows the simultaneous achievement of high open-circuit voltages (0.56 V) and fill-factors (0.58), IPCE above 5% at the plasmon resonance and maximum power-conversion efficiencies of 0.11%, record for this class of devices.Peer ReviewedPostprint (published version

Vapor swellable colloidal photonic crystals with pressure tunability

Polyferrocenylsilane gel photonic crystals have been reversibly swollen using solvent vapors, and exhibit precise pressure tunability over a wavelength range of greater than 100 nmGeneralitat Valenciana CTDIA/2002/2

Surface resonant modes in colloidal photonic crystals

Herein we report an experimental and theoretical optical analysis of the effect of growing a dielectric slab on the surface of photonic colloidal crystals. Optical spectroscopy shows an enhancement of the transmitted intensity for certain frequencies within the photonic pseudogap. Simulations based on a scalar wave approximation fairly reproduce the experimental results and provide a description of the interplay between the features arising from the presence of the surface slab and the finite size of the photonic crystal. The experimental observations are explained by the excitation of photon resonant states at the crystal boundary. Our work demonstrates that the amplitude of light waves penetrating the crystal with frequencies lying within the pseudogap range can be greatly modified by rather simple means

Large-Area Plasmonic-Crystal−Hot-Electron-Based Photodetectors

In view of their exciting optoelectronic light− matter interaction properties, plasmonic−hot-electron devices have attracted significant attention during the last few years as a novel route for photodetection and light-energy harvesting. Herein we report the use of quasi-3D large-area plasmonic crystals (PC) for hot-electron photodetection, with a tunable response across the visible and near-infrared. The strong interplay between the different PC modes gives access to intense electric fields and hot-carrier generation confined to the metal− semiconductor interface, maximizing injection efficiencies with responsivities up to 70 mA/W. Our approach, compatible with large-scale manufacturing, paves the way for the practical implementation of plasmonic−hot-electron optoelectronic devices.Peer ReviewedPostprint (published version

Magneto-ionic suppression of magnetic vortices

Magneto-ionics refers to the non-volatile control of the magnetic properties of materials by voltage-driven ion migration. This phenomenon constitutes one of the most important magnetoelectric mechanisms and, so far, it has been employed to modify the magnetic easy axis of thin films, their coercivity or their net magnetization. Herein, a novel magneto-ionic effect is demonstrated: the transition from vortex to coherent rotation states, caused by voltage-induced ion motion, in arrays of patterned nanopillars. Electrolyte-gated Co/GdOx bilayered nanopillars are chosen as a model system. Electron microscopy observations reveal that, upon voltage application, oxygen ions diffuse from GdOx to Co, resulting in the development of paramagnetic oxide phases (CoOx) along sporadic diffusion channels. This breaks up the initial magnetization configuration of the ferromagnetic pillars (i.e. vortex states) and leads to the formation of small ferromagnetic nanoclusters, embedded in the CoOx matrix, which behave as single-domain nanoparticles. As a result, a decrease in the net magnetic moment is observed, together with a drastic change in the shape of the hysteresis loop. Micromagnetic simulations are used to interpret these findings. These results pave the way towards a new potential application of magnetoelectricity: the magneto-ionic control of magnetic vortex states

Geometric frustration in ordered lattices of plasmonic nanoelements

Inspired by geometrically frustrated magnetic systems, we present the optical response of three cases of hexagonal lattices of plasmonic nanoelements. All of them were designed using a metal-insulator-metal configuration to enhance absorption of light, with elements in close proximity to exploit near-field coupling, and with triangular symmetry to induce frustration of the dipolar polarization in the gaps between neighboring structures. Both simulations and experimental results demonstrate that these systems behave as perfect absorbers in the visible and/or the near infrared. Besides, the numerical study of the time evolution shows that they exhibit a relatively extended time response over which the system fluctuates between localized and collective modes. It is of particular interest the echoed excitation of surface lattice resonance modes, which are still present at long times because of the geometric frustration inherent to the triangular lattice. It is worth noting that the excitation of collective modes is also enhanced in other types of arrays where dipolar excitations of the nanoelements are hampered by the symmetry of the array. However, we would like to emphasize that the enhancement in triangular arrays can be significantly larger because of the inherent geometric incompatibility of dipolar excitations and three-fold symmetry axes

Multiplex SERS Detection of Metabolic Alterations in Tumor Extracellular Media

The composition and intercellular interactions of tumor cells in the tissues dictate the biochemical and metabolic properties of the tumor microenvironment. The metabolic rewiring has a profound impact on the properties of the microenvironment, to an extent that monitoring such perturbations could harbor diagnostic and therapeutic relevance. A growing interest in these phenomena has inspired the development of novel technologies with sufficient sensitivity and resolution to monitor metabolic alterations in the tumor microenvironment. In this context, surface-enhanced Raman scattering (SERS) can be used for the label-free detection and imaging of diverse molecules of interest among extracellular components. Herein, the application of nanostructured plasmonic substrates comprising Au nanoparticles, self-assembled as ordered superlattices, to the precise SERS detection of selected tumor metabolites, is presented. The potential of this technology is first demonstrated through the analysis of kynurenine, a secreted immunomodulatory derivative of the tumor metabolism and the related molecules tryptophan and purine derivatives. SERS facilitates the unambiguous identification of trace metabolites and allows the multiplex detection of their characteristic fingerprints under different conditions. Finally, the effective plasmonic SERS substrate is combined with a hydrogel-based three-dimensional cancer model, which recreates the tumor microenvironment, for the real-time imaging of metabolite alterations and cytotoxic effects on tumor cells.J.P. acknowledges an FPU fellowship from the Spanish Ministry of Science, Innovation and Universities. L.M.L.-M. acknowledges funding from the European Research Council (ERC AdG 787510, 4DbioSERS) and the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency (Grant No. MDM-2017-0720). C.G.-A. acknowledges a Juan de la Cierva Fellowship from the Spanish Ministry of Science, Innovation and Universities (FJCI-2016-28887). The authors thank Dr. J. Calvo and Dr. D. Otaegui at CIC biomaGUNE for support with LC/ESI-HRMS measurements. The work of A.C. was supported by the Basque Department of Industry, Tourism and Trade (Elkartek), and the department of education (IKERTALDE IT1106-16, also participated by A. Gomez-Munoz), the BBVA foundation, the MINECO (SAF2016-79381-R (FEDER/EU); Severo Ochoa Excellence Program SEV-2016-0644-18-1; Excellence Networks SAF2016-81975-REDT), European Training Networks Project (H2020-MSCA-ITN-308 2016 721532), the AECC (IDEAS175CARR, GCTRA18006CARR), La Caixa Foundation (HR17-00094), and the European Research Council (starting Grant 336343, PoC 754627). CIBERONC was co-funded with FEDER funds and funded by ISCIII. A.M. acknowledges funding from the European Research Council (Consolidator Grant 819242) and the Spanish Ministry of Science, Innovation and Universities for the excellence program SEV-2015-049