Francisco González

Francisco González
Universidad de Cantabria | UNICAN · Department of Applied Physics

PhD

About

209
Publications
31,542
Reads
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3,044
Citations
Citations since 2016
51 Research Items
1806 Citations
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300

Publications

Publications (209)
Article
Full-text available
Developing a simple, fast, and label-free method for discrimination between live cancer cells and normal cells in biological samples still remains a challenge. Here, a system is described that fulfills these features to analyze individual living cells. The system consists of a gold nanohole array biosensor plus a microscope optical design to isolat...
Article
Full-text available
Photoinduced hyperthermia is a cancer therapy technique that induces death to cancerous cells via heat generated by plasmonic nanoparticles. While previous studies have shown that some nanoparticles can be effective at killing cancer cells under certain conditions, there is still a necessity (or the need) to improve its heating efficiency. In this...
Conference Paper
Resonances with nanostructured metals due to the excitation of plasmons has shown to be a relevant effect for enhancing surface electromagnetic fields and localize their energy at the nanoscale level. A wide gamut of applications has showed up, from communications, memory storage, etc. to biomedical and health purposes. Coinage metals, like gold, h...
Article
Full-text available
Structural color emerges from the interaction of light with structured matter when its dimension is comparable to the incident wavelength. The reflected color can be switched by controlling such interaction with materials whose properties can be changed through external stimuli such as electrical, optical, or thermal excitation. In this research, a...
Article
Discrete dipole approximation (DDA) is a computational method broadly used to solve light scattering problems. In this work, we propose an extension of DDA that we call Chiral-DDA (CDDA), to study light-chiral matter interactions with the capability of describing the underlying physics behind. Here, CDDA is used to solve and analyze the interaction...
Article
Full-text available
High refractive index dielectric (HRID) nanoparticles are a clear alternative to metals in nanophotonic applications due to their low losses and directional scattering properties. It has been demonstrated that HRID dimers are more efficient scattering units than single nanoparticles in redirecting the incident radiation towards the forward directio...
Preprint
Full-text available
Photoinduced hyperthermia is a cancer therapy technique that induces death to cancerous cells via heat generated by plasmonic nanoparticles. While previous studies have shown that some nanoparticles are somewhat effective at killing cancer cells there is still room for improvement in terms of heating efficiency where a detailed and realistic thermo...
Article
Full-text available
Active materials which show phase transitions, usually known as Phase Change Materials (PCM), have paved the way to a new generation of reconfigurable plasmonic platforms. Tunable color devices have experienced a great development in the recent years. In particular, reflective color filters can take advantage from sunlight to select and reflect a s...
Article
Optical biosensing is currently an intensively active research area, with an increasing demand of highly selective, sensitivity-enhanced and low-cost devices where different plasmonic approaches have been developed. In this work we propose a tunable optimized grating-based gold metasurface that can act both as a high sensitivity sensor device (up t...
Article
Color prediction in dyed wood is a difficult task since it involves the analysis of light propagation through a complex media where scattering and absorption processes are present. Kubelka-Munk-based models are usually proposed to make those predictions. Here, an oak wood color prediction tool is presented with the Kubelka-Munk theory and self-lear...
Article
Full-text available
Low-loss dielectric nanomaterials are being extensively studied as novel platforms for enhanced light-matter interactions. Dielectric materials are more versatile than metals when nanostructured as they are able to generate simultaneously electric-and magnetic-type resonances. This unique property gives rise to a wide gamut of new phenomena not obs...
Article
Sulfur hexafluoride (SF6) is one of the most harmful greenhouse gases producing environmental risks. Therefore, developing ways of degrading SF6 without forming hazard products is increasingly important. Herein we demonstrate for the first time the plasmon-catalytic heterogeneous degradation of SF6 into non-hazardous MgF2 and MgSO4 products by non-...
Article
Localized surface plasmon resonances (LSPRs) optically excited in metallic nanoparticles (NPs) produce beneficial thermal and non-thermal effects. Non-thermal effects, such as enhancing and localizing fields on subwavelength scales and photo-generating hot carriers, have been extensively exploited, while interest in highly localized photothermal he...
Article
Full-text available
In order to exploit gallium’s (Ga) rich polymorphism in the design of phase-change plasmonic systems, accurate understanding of the dielectric function of the different Ga-phases is crucial. The dielectric dispersion profiles of those phases appearing at atmospheric pressure have been reported in the literature, but there is no information on the d...
Article
Full-text available
Rhodium (Rh) nanoparticles have attracted a lot of attention due to their strong and ambient-stable UV plasmonic response. Very recently, the synthesis of Rh tetrahedra with and without concave defect-rich surfaces serving in plasmon assisted photocatalytic energy conversion has been reported. In this work, we perform a systematic numerical study o...
Article
Metallic nanohole arrays have shown their potential as sensing tools. Important research supported by sophisticated laboratory experiments have been recently carried out, that may help to develop practical devices to be implemented in the real life. To get this goal, the gap between industry and technology at the nanoscale level must be overcome. O...
Article
Full-text available
The possibility of using light to drive chemical reactions has highlighted the role of photocatalysis as a key tool to address the environmental and energy issues faced by today’s society. Plasmonic photocatalysis, proposed to circumvent some of the problems of conventional semiconductor catalysis, uses hetero-nanostructures composed by plasmonic m...
Article
High Refractive Index Dielectric nanoparticles have been proposed as an alternative to metallic ones due to their low losses and their directionality properties. In particular, at the Zero-Backward condition (near Zero-Forward condition), incident radiation is forward (backward) scattered being null (almost null) in the backward (forward) direction...
Article
Interest in gallium (Ga) is growing rapidly, thanks in part to its wide spectral tunability and its intriguing temperature‐dependent polymorphism. In order to exploit and control phase‐change plasmonics in the liquid and solid phases of Ga, an accurate understanding of the dielectric functions for each Ga phase is needed. A comprehensive analysis o...
Article
Nanoparticles made of High Refractive Index dielectric materials have been proposed as an alternative to metals driven by their low-losses and magnetic response. The coherent effects between the electric and magnetic resonances are responsible for their exceptional directionality properties that make them attractive in applications where enhancing...
Article
Full-text available
Due to the complexity of the radiative transfer equation, light transport problems are commonly solved using either models under restrictive assumptions, e.g., N-flux models where infinite lateral extension is assumed, or numerical methods. While the latter can be applied to more general cases, it is difficult to relate their parameters to the phys...
Preprint
Full-text available
Metallic nanohole arrays have shown their potential as sensing tools. Important research supported by sophisticated laboratory experiments have been recently carried out, that may help to develop practical devices to be implemented in the real life. To get this goal, the gap between industry and technology at the nanoscale level must be overcome. O...
Article
Full-text available
Nanostructured High Refractive Index (HRI) dielectric materials, when acting as nanoantennas or metasurfaces in the near-infrared (NIR) and visible (VIS) spectral ranges, can interact with light and show interesting scattering directionality properties. Also, HRI dielectric materials with low absorption in these spectral ranges show very low heat r...
Article
Full-text available
Low-losses and directionality effects exhibited by High Refractive Index Dielectric particles make them attractive for applications where radiation direction control is relevant. For instance, isolated metallo-dielectric core-shell particles or aggregates (dimers) of High Refractive Index Dielectric particles have been proposed for building operati...
Article
Full-text available
In this research, we investigate the electromagnetic behavior of a metallic thin-film with a periodic array of subwavelength apertures when dielectric objects are located on it. The influence of size, geometry and optical properties of the objects on the transmission spectra is numerically analyzed. We study the sensitivity of this system to change...
Conference Paper
Subwavelength metallic nanoparticles have been proposed for optimizing efficiency of current solar cells. However, their inherent ohmic losses limit their performance. High Refractive Index dielectric particles have been suggested as an alternative to metallic ones due to their low-losses in the visible and near infrared spectral regions and also t...
Article
Full-text available
Ultraviolet plasmonics (UV) has become an active topic of research due to the new challenges arising in fields such as biosensing, chemistry or spectroscopy. Recent studies have pointed out aluminum, gallium, magnesium and rhodium as promising candidates for plasmonics in the UV range. Aluminum and magnesium present a high oxidation tendency that h...
Conference Paper
UV nanoplasmonics and scattering directionality properties of High Refractive Index Dielectrics (HRID) launches this research in materials with HRID character in the UV: Photocatalysis and solar energy harvesting applications are the target.
Article
Full-text available
For applications of surface-enhanced spectroscopy and photocatalysis, the ultraviolet (UV) plasmonic behavior and charge distribution within rhodium nanocubes is explored by a detailed numerical analysis. The strongest plasmonic hot-spots and charge concentrations are located at the corners and edges of the nanocubes, exactly where they are the mos...
Article
Full-text available
High Refractive Index (HRI) dielectric nanoparticles have been proposed as an alternative to metallic ones due to their low absorption and magnetodielectric response in the VIS and NIR ranges. For the latter, important scattering directionality effects can be obtained. Also, systems constituted by dimers of HRI dielectric nanoparticles have shown t...
Article
Full-text available
Current effective medium theories for nano-shells are reviewed. A new method for calculating the effective dielectric function of a core-shell nanoparticle is presented and compared with existing theories showing clear advantages in most conditions. It consists of introducing radiating effects in the polariz- ability of the effective sphere, and co...
Article
Full-text available
High Refractive Index (HRI) dielectric particles smaller than the wavelength, isolated or forming a designed ensemble are ideal candidates as new multifunctional elements for building optical devices. Their directionality effects are traditionally analyzed through forward and backward measurements, even if these directions are not suitable for prac...
Data
Supplementary Figures, Supplementary Notes, Supplementary Methods and Supplementary References
Article
In this work we review and—to some extent—upgrade one of the main theories of light flux through homogeneous isotropic media, namely, the Kubelka–Munk (K–M) theory, and in particular the later expansion made by Kubelka to obtain the reflectance of a specimen when a substrate lies underneath. We have completed this solution by calculating the transv...
Article
The ultraviolet (UV) range presents new challenges for plasmonics, with interesting applications ranging from engineering to biology. In previous research, gallium, aluminum, and magnesium were found to be very promising UV plasmonic metals. However, a native oxide shell surrounds nanostructures of these metals that affects their plasmonic response...
Article
The influence of increasing the core size of Ag–Si core–shell nanoparticles has been investigated by using the values of the linear polarization degree at a right-angle scattering configuration, . Changes in dipolar resonances and scattering directionality conditions as a function of the core radius (R int) for a fixed shell size ( nm) have been an...
Conference Paper
We analyze the effect of contaminants on the quadrupolar magnetic, dipolar electric and dipolar magnetic resonances of silicon nanoparticles (NPs) by considering the spectral evolution of the linear polarization degree at right angle scattering configuration, PL(90°). From an optical point of view, a decrease in the purity of silicon nanoparticles...
Conference Paper
Plasmonics in the UV-range constitutes a new challenge due to the increasing demand to detect, identify and destroy biological toxins, enhance biological imaging, and characterize semiconductor devices at the nanometer scale. Silver and aluminum have an efficient plasmonic performance in the near UV region, but oxidation reduces its performance in...
Article
Full-text available
The ability to infer near-field scattering properties from far-field measurements is of paramount importance in nano-optics. Recently we derived an approximate formula for predicting the frequency shift between near- and far-field intensity peaks in the case of a dielectric sphere. In this work we demonstrate that almost an identical formula can be...
Conference Paper
The spectral evolution of the degree of linear polarization (P L) at a scattering angle of 90º is studied numerically for high refractive index (HRI) dielectric spherical nanoparticles. The behaviour of P L (90º) is analyzed as a function of the refractive index of the surrounding medium and the particle radius. We focus on the spectral region wher...
Conference Paper
Recent studies show that the spectral behaviour of localized surface plasmon resonances (LPSRs) in metallic nanoparticles suffer from both a redshift and a broadening in the transition from the far-to the near-field regimes. An interpretation of this effect was given in terms of the evanescent and propagating components of the angular spectrum repr...
Article
Polydisperse rhodium nanoparticles have recently shown promise for ultraviolet (UV) plasmonics, but controlling the size and morphology of metal nanoparticles is essential for tuning surface plasmon resonances. Here we report the use of slow-injection polyol methods to synthesize monodisperse Rh nanocubes with unprecedentedly large sizes and slight...
Article
Full-text available
The near-field electromagnetic scattering intensity resonances are redshifted in frequency with respect to their far-field counterparts. We derive simple, approximate, analytical formulas for this shift in the case of a plane wave interacting with a dielectric sphere. Numerical results comparing the approximate formulas to the numerically exact sol...
Article
Local field enhancements produced by metal nanoparticles have been widely investigated in the visible range for common metals like gold and silver, but recent interest in ultraviolet plasmonics has required consideration of alternate metals. Aluminum and gallium are particularly attractive, but the native oxide that forms on them consumes the metal...
Article
Full-text available
The spectral evolution of the degree of linear polarization (PL) at a scattering angle of 90° is studied numerically for high refractive index (HRI) dielectric spherical nanoparticles. The behaviour of PL(90°) is analysed as a function of the refractive index of the surrounding medium and the particle radius, and it is compared with the more conven...
Article
The non-oxidizing catalytic noble metal rhodium is introduced for ultraviolet plasmonics. Planar tripods of 8 nm Rh nanoparticles, synthesized by a modified polyol reduction method, have a calculated local surface plasmon resonance near 330 nm. By attaching p-aminothiophenol, local field-enhanced Raman spectra and accelerated photo-damage were obse...
Article
Full-text available
The influence of the degree of purity of a silicon nanoparticle on its resonances, either electric or magnetic, is assessed by using Mie theory as well as finite-element simulations. In particular, it is shown that the main effect of the increase of absorption due to the pollutants is observed in the magnetic resonances. Concerning Kerker’s conditi...
Conference Paper
Full-text available
Electromagnetic enhancement of metallic nanoparticles on substrates is assessed by an exhaustive numerical analysis. The potential of each technologically promising metal for UV-plasmonic applications may be ascertained.