65 results found
Stefancu A, Lee S, Zhu L, et al., 2021, Fermi Level Equilibration at the Metal-Molecule Interface in Plasmonic Systems, NANO LETTERS, Vol: 21, Pages: 6592-6599, ISSN: 1530-6984
Zhu C, Fan C, Cortes E, et al., 2021, In situ surface-enhanced Raman spectroelectrochemistry reveals the molecular conformation of electrolyte additives in Li-ion batteries, JOURNAL OF MATERIALS CHEMISTRY A, ISSN: 2050-7488
Wang X, Liu C, Gao C, et al., 2021, Self-constructed multiple plasmonic hotspots on an individual fractal to amplify broadband hot electron generation., ACS Nano, Vol: 15, Pages: 10553-10564, ISSN: 1936-0851
Plasmonic nanoparticles are ideal candidates for hot-electron-assisted applications, but their narrow resonance region and limited hotspot number hindered the energy utilization of broadband solar energy. Inspired by tree branches, we designed and chemically synthesized silver fractals, which enable self-constructed hotspots and multiple plasmonic resonances, extending the broadband generation of hot electrons for better matching with the solar radiation spectrum. We directly revealed the plasmonic origin, the spatial distribution, and the decay dynamics of hot electrons on the single-particle level by using ab initio simulation, dark-field spectroscopy, pump-probe measurements, and electron energy loss spectroscopy. Our results show that fractals with acute tips and narrow gaps can support broadband resonances (400-1100 nm) and a large number of randomly distributed hotspots, which can provide unpolarized enhanced near field and promote hot electron generation. As a proof-of-concept, hot-electron-triggered dimerization of p-nitropthiophenol and hydrogen production are investigated under various irradiations, and the promoted hot electron generation on fractals was confirmed with significantly improved efficiency.
Hüttenhofer L, Tittl A, Kühner L, et al., 2021, Anapole-assisted absorption engineering in arrays of coupled amorphous gallium phosphide nanodisks, ACS Photonics, Vol: 8, Pages: 1469-1476, ISSN: 2330-4022
Broadband solar light harvesting plays a crucial role for efficient energy conversion. Anapole excitations and associated absorption engineering in dielectric nanoresonators are a focus of nanophotonic research due to the intricate combination of nonradiating modes and strong electromagnetic field confinement in the underlying material. The arising high field strengths are used for enhanced second-harmonic generation and photocatalysis, where devices require large areas with closely spaced nanoresonators for sizable photonic yields. However, most anapole studies have so far been carried out at the single-particle level, neglecting the influence of anapole–anapole interactions. Here, we present a systematic study of coupling mechanisms in rectangular arrays of amorphous GaP nanodisks that support anapole excitations at 600 nm, which is within the lossy spectral regime of the material. Our experimental findings show that maximum visible light extinction by the array and maximum absorption in the GaP are not achieved by the densest packing of resonators. Counterintuitively, increasing the array periodicities such that collective effects spectrally overlap with the anapole excitation of a single particle leads to an absorption enhancement of up to 300% compared to a single disk. An analysis of coupling in one- and two-dimensional arrays with polarization-dependent measurements and numerical simulations allows us to discriminate between coupling interactions parallel and perpendicular to the polarization axis and evaluate their strengths. Utilizing a multipolar decomposition of excitations in single nanodisks embedded in one-dimensional arrays, we can attribute the coupling to enhanced electric and toroidal dipoles under variation of the interparticle spacing. Our results provide a fundamental understanding of tailored light absorption in coupled anapole resonators and reveal important design guidelines for advanced metasurface approaches in a wide range of energy
Li H, Liu K, Fu J, et al., 2021, Paired Ru-O-Mo ensemble for efficient and stable alkaline hydrogen evolution reaction, NANO ENERGY, Vol: 82, ISSN: 2211-2855
Barella M, Violi IL, Gargiulo J, et al., 2021, In Situ Photothermal Response of Single Gold Nanoparticles through Hyperspectral Imaging Anti-Stokes Thermometry, ACS NANO, Vol: 15, Pages: 2458-2467, ISSN: 1936-0851
Lee JB, Walker H, Li Y, et al., 2020, Template Dissolution Interfacial Patterning of Single Colloids for Nanoelectrochemistry and Nanosensing, ACS NANO, Vol: 14, Pages: 17693-17703, ISSN: 1936-0851
Lee S, Hwang H, Lee W, et al., 2020, Core-Shell Bimetallic Nanoparticle Trimers for Efficient Light-to-Chemical Energy Conversion, ACS ENERGY LETTERS, Vol: 5, Pages: 3881-3890, ISSN: 2380-8195
Tilmann B, Grinblat G, Berte R, et al., 2020, Nanostructured amorphous gallium phosphide on silica for nonlinear and ultrafast nanophotonics, NANOSCALE HORIZONS, Vol: 5, Pages: 1500-1508, ISSN: 2055-6756
Poblet M, Li Y, Cortes E, et al., 2020, Direct Detection of Optical Forces of Magnetic Nature in Dielectric Nanoantennas, NANO LETTERS, Vol: 20, Pages: 7627-7634, ISSN: 1530-6984
Grinblat G, Zhang H, Nielsen MP, et al., 2020, Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation, SCIENCE ADVANCES, Vol: 6, ISSN: 2375-2548
Mancini A, Gubbin CR, Berte R, et al., 2020, Near-Field Spectroscopy of Cylindrical Phonon-Polariton Antennas, ACS NANO, Vol: 14, Pages: 8508-8517, ISSN: 1936-0851
Cortes E, Govorov AO, Misawa H, et al., 2020, Special topic on emerging directions in plasmonics, JOURNAL OF CHEMICAL PHYSICS, Vol: 153, ISSN: 0021-9606
Boggiano HD, Berte R, Scarpettini AF, et al., 2020, Determination of nanoscale mechanical properties of polymers via plasmonic nanoantennas, ACS Photonics, Vol: 7, Pages: 1403-1409, ISSN: 2330-4022
Nanotechnology and the consequent emergence of miniaturized devices are driving the need to improve our understanding of the mechanical properties of a myriad of materials. Here we focus on amorphous polymeric materials and introduce a new way to determine the nanoscale mechanical response of polymeric thin films in the GHz range, using ultrafast optical means. Coupling of the films to plasmonic nanoantennas excited at their vibrational eigenfrequencies allows the extraction of the values of the mechanical moduli as well as the estimation of the glass transition temperature via time-domain measurements, here demonstrated for PMMA films. This nanoscale method can be extended to the determination of mechanical and elastic properties of a wide range of spatially strongly confined materials.
Doiron B, Gusken NA, Lauri A, et al., 2020, Hot Carrier Optoelectronics with Titanium Nitride, Lasers and Electro-Optics Society Annual Meeting-LEOS, ISSN: 1092-8081
© 2020 OSA. Titanium oxynitride enables a range of plasmonic and optoelectronic functionality using long-lived photo-generated hot carriers. We explore the time scale of hot carriers in TiN and their use in photochemical reduction and Schottky detectors.
Bell SEJ, Charron G, Cortés E, et al., 2020, Auf dem Weg zur verlässlichen und quantitativen SERS‐Spektroskopie: von Schlüsselparametern zur guten analytischen Praxis, Angewandte Chemie, Vol: 132, Pages: 5496-5505, ISSN: 0044-8249
Bell SEJ, Charron G, Cortes E, et al., 2020, Towards Reliable and Quantitative Surface-Enhanced Raman Scattering (SERS): From Key Parameters to Good Analytical Practice, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 5454-5462, ISSN: 1433-7851
Hüttenhofer L, Eckmann F, Lauri A, et al., 2020, Anapole excitations in oxygen vacancy-rich TiO2-x nanoresonators: tuning the absorption for photocatalysis in the visible., ACS Nano, Vol: 14, Pages: 2456-2464, ISSN: 1936-0851
Research on optically resonant dielectric nanostructures has accelerated the development of photonic applications, driven by their ability to strongly confine light on the nanoscale. However, since dielectric resonators are typically operated below their bandgap to minimize optical losses, the usage of dielectric nanoantenna concepts for absorption enhancement has largely remained unexplored. In this work, we realize engineered nanoantennas composed of photocatalytic dielectrics and demonstrate their increased light harvesting capabilities in otherwise weakly absorptive spectral regions. In particular, we employ anapole excitations, which are known for their strong light confinement, in nanodisks of oxygen-vacancy-rich TiO2-x, a prominent photocatalyst that provides a powerful platform for exploring concepts in absorption enhancement in tunable nanostructures. We show that by varying the nanodisk geometry, we can shift the anapole wavelength into resonance with optical transitions associated with the sub-bandgap oxygen vacancy (VO) states and thereby increase visible light absorption. The arising photocatalytic effect is monitored on the single particle level using the well-established photocatalytic silver reduction reaction on TiO2. With the freedom of changing the optical properties of TiO2 through tuning the abundance of VO-states we discuss the interplay between cavity damping and the anapole-assisted field confinement for absorption enhancement. This concept is general and can be extended to other catalytic materials with higher refractive indices.
Glass D, Cortes E, Peveler WJ, et al., 2020, Enhancing hybrid metal-semiconductor systems beyond SERS with PIERS (Photo-induced enhanced Raman scattering) for trace analyte detection, Conference on Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI held at SPIE Defense + Commercial Sensing Conference, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Glass D, Cortes E, Ben-Jaber S, et al., 2019, Dynamics of Photo-Induced Surface Oxygen Vacancies in Metal-Oxide Semiconductors Studied Under Ambient Conditions, ADVANCED SCIENCE, Vol: 6
Lee S, Kim J, Yang H, et al., 2019, Particle-in-a-Frame Nanostructures with Interior Nanogaps, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 15890-15894, ISSN: 1433-7851
In recent years, the possibility to induce chemical transformations by using tunable plasmonic modes has opened the question of whether we can control or create chemical hot spots in these systems. This can be rationalized as the reactive analogue of the well-established concept of optical hot spots, which have drawn a great deal of attention to plasmonic nanostructures for their ability to circumvent the far-field diffraction limit of conventional optical elements.Although optical hot spots can be mainly defined by the geometry and permittivity of the nanostructures, the degrees of freedom influencing their photocatalytic properties appear to be much more numerous. In fact, the reactivity of plasmonic systems are deeply influenced by the dynamics and interplay of photons, plasmon-polaritons, carriers, phonons, and molecular states. These degrees of freedom can affect the reaction rates, the product selectivity, or the spatial localization of a chemical reaction. In this Account, we discuss the oportunities to control chemical hot spots by tuning the cascade of events that follows the excitation and decay of plasmonic modes in nanostructures.We discuss a series of techniques to spatially map and image plasmonic nanoscale reactivity at the single photocatalyst level. We show how to optimize the reactivity of carriers by manipulating their excitation and decay mechanisms in plasmonic nanoparticles. In addition, the tailored generation of non-thermal phonons in metallic nanostructures and their dissipation is shown as a promise to understand and exploit thermal photocatalysis at the nanoscale. Understanding and controlling these processes is essential for the rational design of solar nanometric photocatalysts.Nevertheless, the ultimate capability of a plasmonic photocatalyst to trigger a chemical reaction is correlated to its ability to navigate through, or even modify, the potential energy surface of a given chemical reaction. Here we reunite both worlds, the plasmoni
Guerra Hernandez LA, Huidobro PA, Cortes E, et al., 2019, Resonant Far- to Near-Field Channeling in Synergetic Multiscale Antennas, ACS PHOTONICS, Vol: 6, Pages: 1466-1473, ISSN: 2330-4022
Aizpurua J, Ashfold M, Baletto F, et al., 2019, Dynamics of hot electron generation in metallic nanostructures: general discussion., Faraday Discuss, Vol: 214, Pages: 123-146
Simoncelli S, Pensa EL, Brick T, et al., 2019, Monitoring plasmonic hot-carrier chemical reactions at the single particle level, Faraday Discussions, Vol: 214, Pages: 73-87, ISSN: 1359-6640
Plasmon excitation in metal nanoparticles triggers the generation of highly energetic charge carriers that, when properly manipulated and exploited, can mediate chemical reactions. Single-particle techniques are key to unearthing the underlying mechanisms of hot-carrier generation, transport and injection, as well as to disentangling the role of the temperature increase and the enhanced near-field at the nanoparticle-molecule interface. Gaining nanoscopic insight into these processes and their interplay could aid in the rational design of plasmonic photocatalysts. Here, we present three different approaches to monitor hot-carrier reactivity at the single-particle level. We use a combination of dark-field microscopy and photoelectrochemistry to track a hot-hole driven reaction on a single Au nanoparticle. We image hot-electron reactivity with sub-particle spatial resolution using nanoscopy techniques. Finally, we push the limits by looking for a hot-electron induced chemical reaction that generates a fluorescent product, which should enable imaging plasmonic photocatalysis at the single-particle and single-molecule levels.
Zaza C, Violi IL, Gargiulo J, et al., 2019, Size-selective optical printing of silicon nanoparticles through their dipolar magnetic resonance, ACS Photonics, Vol: 6, Pages: 815-822, ISSN: 2330-4022
Silicon nanoparticles possess unique size-dependent optical properties due to their strong electric and magnetic resonances in the visible range. However, their widespread application has been limited, in comparison with other (e.g., metallic) nanoparticles, because their preparation on monodisperse colloids remains challenging. Exploiting the unique properties of Si nanoparticles in nano- A nd microdevices calls for methods able to sort and organize them from a colloidal suspension onto specific positions of solid substrates with nanometric precision. We demonstrate that surfactant-free silicon nanoparticles of a predefined and narrow (σ < 10 nm) size range can be selectively immobilized on a substrate by optical printing from a polydisperse colloidal suspension. The size selectivity is based on differential optical forces that can be applied on nanoparticles of different sizes by tuning the light wavelength to the size-dependent magnetic dipolar resonance of the nanoparticles.
Pensa E, Gargiulo J, Lauri A, et al., 2019, Spectral screening of the energy of hot holes over a particle plasmon resonance, Nano Letters, Vol: 19, Pages: 1867-1874, ISSN: 1530-6984
Plasmonic hot carriers have been recently identified as key elements for photocatalysis at visible wavelengths. The possibility to transfer energy between metal plasmonic nanoparticles and nearby molecules depends not only on carrier generation and collection efficiencies but also on their energy at the metal-molecule interface. Here an energy screening study was performed by monitoring the aniline electro-polymerization reaction via an illuminated 80 nm gold nanoparticle. Our results show that plasmon excitation reduces the energy required to start the polymerization reaction as much as 0.24 eV. Three possible photocatalytic mechanisms were explored: the enhanced near field of the illuminated particle, the temperature increase at the metal-liquid interface, and the excited electron-hole pairs. This last phenomenon is found to be the one contributing most prominently to the observed energy reduction.
Berte R, Della Picca F, Poblet M, et al., 2018, Acoustic far-field hypersonic surface wave detection with single plasmonic nanoantennas, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The optical properties of small metallic particles allow us to bridge the gap between the myriad of subdiffraction local phenomena and macroscopic optical elements. The optomechanical coupling between mechanical vibrations of Au nanoparticles and their optical response due to collective electronic oscillations leads to the emission and the detection of surface acoustic waves (SAWs) by single metallic nanoantennas. We take two Au nanoparticles, one acting as a source and the other as a receptor of SAWs and, even though these antennas are separated by distances orders of magnitude larger than the characteristic subnanometric displacements of vibrations, we probe the frequency content, wave speed, and amplitude decay of SAWs originating from the damping of coherent mechanical modes of the source. Two-color pump-probe experiments and numerical methods reveal the characteristic Rayleigh wave behavior of emitted SAWs, and show that the SAW-induced optical modulation of the receptor antenna allows us to accurately probe the frequency of the source, even when the eigenmodes of source and receptor are detuned.
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