Suchergebnisse

We developed a nanostructure to enhance the photoluminescence intensity of two-dimensional monolayers of transition metal dichalcogenides based on plasmonic supercrystal arrays. These plasmonic supercrystal arrays are deposited on top the monolayers by means of a template-assisted assembly of gold nanospheres with patterned polydimethylsiloxane molds [1]. These supercrystals arrays consist on square arrays of hexagonally packed gold nanoparticles (50 nm of diameter) which exhibit well-defined surface lattice resonance modes that can be tuned from the visible through the near-infrared by simple variation of the lattice parameter. This tunability can be used to enhance the photoluminescence emission of different transition metal dichalcogenides monolayers. So, as proof of concept, the photoluminescence signal of the monolayer MoS2 and MoSe2 can be significantly enhanced up to 5-6-fold coupling the frequency of the surface lattice resonance of the plasmonic supercrystal to the frequency emission of the transition metal dichalcogenides monolayer. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 840064

Ordered arrays of metal nanoparticles offer new opportunities to engineer light–matter interactions through the hybridization of Rayleigh anomalies and localized surface plasmons. The generated surface lattice resonances exhibit much higher quality factors compared to those observed in isolated metal nanostructures. Template-induced colloidal self-assembly has already shown a great potential for the scalable fabrication of 2D plasmonic meta-molecule arrays, but the experimental challenge of controlling optical losses within the repeating units has so far prevented this approach to compete with more standard fabrication methods in the production of high-quality factor resonances. In this manuscript, the optical properties of plasmonic arrays are investigated by varying the lattice parameter (between 200 and 600 nm) as well as the diameter of the gold colloidal building-blocks (between 11 ± 1 and 98 ± 6 nm). It is systematically studied how the internal architecture of the repeating gold-nanoparticle meta-molecules influences the optical response of the plasmonic supercrystals. Combining both experimental measurements and simulations, it is demonstrated how, reducing the size of the gold nanoparticles it is possible to switch from strong near-field plasmonic architectures to high-quality factors (>60) for lattice plasmon resonances located in the visible spectral range. ; P.M. and N.P. contributed equally to this work. This project had received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 637116, ENLIGHTMENT) and the Spanish Ministerio de Ciencia e Innovación through grant, PID2019-106860GB-I00 and FUNFUTURE (CEX2019-000917-S), in the framework of the Spanish Severo Ochoa Centre of Excellence program. L.S. research was supported by the Marie Sklodowska-Curie Actions SHINE (H2020- MSCA-IF-2019, grant agreement no. 894847) and the 2020 Post-doctoral Junior Leader-Incoming Fellowship by "la Caixa" Foundation (ID 100010434, fellow-ship code LCF/BQ/PI20/11760028). L.A.P. thanks the Marie Sklodowska-Curie Actions (H2020-MSCA-IF-2018) for grant agreement no. 839402, PLASMIONICO. P.M. acknowledges financial support from an FPI contract (2017) of the MICINN (Spain) cofounded by the ESF and the UAB under the auspices of the UAB material science doctoral program. ; Peer reviewed

Colloidal anisotropic gold nanocrystals play a central role in the field of plasmonics owing to their tunable optical activity across a wide spectral range. However, achieving sufficient optical quality for practical implementation requires advanced synthetic protocols yielding gold nanocrystals with the desired morphology and plasmonic properties. This Minireview focuses on a fundamental step during the growth of anisotropic nanocrystals, namely symmetry breaking. In connection with thermodynamic and kinetic control of nanocrystal growth, we discuss the complex interplay between the role of seed morphology and that of surfactants, shape‐directing additives and reducing agents. We revisit some iconic syntheses of anisotropic gold nanoparticles, including nanorods, nanotriangles, and nanobipyramids. Finally, we analyze the use of co‐surfactants as an emerging strategy to disconnect the symmetry breaking event from the anisotropic growth process, overcoming current limitations in the synthesis of anisotropic gold nanocrystals. ; G. González‐Rubio gratefully acknowledges the Alexander von Humboldt Foundation for financial support. This work has been funded by the Spanish Ministry of Science, Innovation and Universities (grants RTI2018‐095844‐B‐I00, MAT2017‐86659‐R) and the Madrid Regional Government (grant P2018/NMT‐4389). This work was performed under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency – Grant No. MDM‐2017‐0720. ; Peer reviewed

Gold nanorod supercrystals have been widely employed for the detection of relevant bioanalytes with detection limits ranging from nano- to picomolar levels, confirming the promising nature of these structures for biosensing. Even though a relationship between the height of the supercrystal (i.e., the number of stacked nanorod layers) and the enhancement factor has been proposed, no systematic study has been reported. In order to tackle this problem, we prepared gold nanorod supercrystals with varying numbers of stacked layers and analyzed them extensively by atomic force microscopy, electron microscopy and surface enhanced Raman scattering. The experimental results were compared to numerical simulations performed on real-size supercrystals composed of thousands of nanorod building blocks. Analysis of the hot spot distribution in the simulated supercrystals showed the presence of standing waves that were distributed at different depths, depending on the number of layers in each supercrystal. On the basis of these theoretical results, we interpreted the experimental data in terms of analyte penetration into the topmost layer only, which indicates that diffusion to the interior of the supercrystals would be crucial if the complete field enhancement produced by the stacked nanorods is to be exploited. We propose that our conclusions will be of high relevance in the design of next generation plasmonic devices. ; This work was supported by the European Research Council (ERC Advanced Grant #267867 Plasmaquo and ERC Starting Grant #335078 Colouratom) and the Spanish Ministerio de Economía y Competitividad (MAT2013-46101-R). D.M.S., J.M.T., and F.O. acknowledge funding from the European Regional Development Fund (ERDF) and the Spanish Ministerio de Economía y Competitividad (MAT2014-58201-C2-1-R, MAT2014-58201-C2-2-R, project TACTICA), from the ERDF and the Galician Regional Government under Projects CN2012/279 and CN2012/260 (AtlantTIC), and the Plan I2C (2011-2015), and from the ERDF and the Extremadura Regional ...