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See detailHyperbolic dispersion metasurfaces for molecular biosensing
Palermo, Giovanna; Sreekanth, Kandammathe Valiyaveedu; Maccaferri, Nicolò UL et al

in Nanophotonics (in press)

Sensor technology has become increasingly crucial in medical research and clinical diagnostics to directly detect small numbers of low-molecular-weight biomolecules relevant for lethal diseases. In recent ... [more ▼]

Sensor technology has become increasingly crucial in medical research and clinical diagnostics to directly detect small numbers of low-molecular-weight biomolecules relevant for lethal diseases. In recent years, various technologies have been developed, a number of them becoming core label-free technologies for detection of cancer biomarkers and viruses. However, to radically improve early disease diagnostics, tracking of disease progression and evaluation of treatments, today’s biosensing techniques still require a radical innovation to deliver high sensitivity, specificity, diffusion-limited transport, and accuracy for both nucleic acids and proteins. In this review, we discuss both scientific and technological aspects of hyperbolic dispersion metasurfaces for molecular biosensing. Optical metasurfaces have offered the tantalizing opportunity to engineer wavefronts while its intrinsic nanoscale patterns promote tremendous molecular interactions and selective binding. Hyperbolic dispersion metasurfaces support high-k modes that proved to be extremely sensitive to minute concentrations of ultralow-molecular-weight proteins and nucleic acids. [less ▲]

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See detailSpeeding up nanoscience and nanotechnology with ultrafast plasmonics
Maccaferri, Nicolò UL; Meuret, Sophie; Kornienko, Nikolay et al

in Nano Letters (2020)

Surface plasmons are collective oscillations of free electrons at the interface between a conducting material and the dielectric environment. These excitations support the formation of strongly enhanced ... [more ▼]

Surface plasmons are collective oscillations of free electrons at the interface between a conducting material and the dielectric environment. These excitations support the formation of strongly enhanced and confined electromagnetic fields. As well, they display fast dynamics lasting tens of femtoseconds and can lead to a strong nonlinear optical response at the nanoscale. Thus, they represent the perfect tool to drive and control fast optical processes, such as ultrafast optical switching, single photon emission, as well as strong coupling interactions to explore and tailor photochemical reactions. In this Virtual Issue, we gather several important papers published in Nano Letters in the past decade reporting studies on the ultrafast dynamics of surface plasmons. [less ▲]

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See detailMachine learning in nanoscience: big data at small scales
Brown, Keith A.; Brittman, Sarah; Maccaferri, Nicolò UL et al

in Nano Letters (2020), 20(1), 2-10

Recent advances in machine learning (ML) offer new tools to extract new insights from large data sets and to acquire small data sets more effectively. Researchers in nanoscience are experimenting with ... [more ▼]

Recent advances in machine learning (ML) offer new tools to extract new insights from large data sets and to acquire small data sets more effectively. Researchers in nanoscience are experimenting with these tools to tackle challenges in many fields. In addition to ML’s advancement of nanoscience, nanoscience provides the foundation for neuromorphic computing hardware to expand the implementation of ML algorithms. In this mini-review, which is not able to be comprehensive, we highlight some recent efforts to connect the ML and nanoscience communities focusing on three types of interaction: (1) using ML to analyze and extract new information from large nanoscience data sets, (2) applying ML to accelerate materials discovery, including the use of active learning to guide experimental design, and (3) the nanoscience of memristive devices to realize hardware tailored for ML. We conclude with a discussion of challenges and opportunities for future interactions between nanoscience and ML researchers. [less ▲]

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See detailParticle trapping and beaming using a 3D nanotip excited with a plasmonic vortex
Liu, Kai; Maccaferri, Nicolò UL; Shen, Yuefeng et al

in Optics Letters (2020), 45(4), 823-826

Recent advances in nanotechnology have prompted the need for tools to accurately and non-invasively manipulate individual nano-objects. Among the possible strategies, optical forces have been widely used ... [more ▼]

Recent advances in nanotechnology have prompted the need for tools to accurately and non-invasively manipulate individual nano-objects. Among the possible strategies, optical forces have been widely used to enable nano-optical tweezers capable of trapping or moving a specimen with unprecedented accuracy. Here, we propose an architecture consisting of a nanotip excited with a plasmonic vortex enabling effective dynamic control of nanoparticles in three dimensions. The structure illuminated by a beam with angular momentum can generate an optical field which can be used to manipulate single dielectric nanoparticles. We demonstrate that it’s possible to stably trap or push the particle from specific points, thus enabling a new platform for nanoparticle manipulation. [less ▲]

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See detailIntracellular recording of human cardiac action potentials on market-available multielectrode array platforms
Melle, Giovanni; Bruno, Giulia; Maccaferri, Nicolò UL et al

in Frontiers in Bioengineering and Biotechnology (2020), 8

High quality attenuated intracellular action potentials from large cell networks can be recorded on multi-electrode arrays by means of 3D vertical nanopillars using electrical pulses. However,most of the ... [more ▼]

High quality attenuated intracellular action potentials from large cell networks can be recorded on multi-electrode arrays by means of 3D vertical nanopillars using electrical pulses. However,most of the techniques require complex 3D nanostructures that prevent the straightforward translation into marketable products and the wide adoption in the scientific community. Moreover, 3D nanostructures are often delicate objects that cannot sustain several harsh use/cleaning cycles. On the contrary, laser optoacoustic poration allows the recording of action potentials on planar nanoporous electrodes made of noble metals. However, these constraints of the electrode material and morphology may also hinder the full exploitation of this methodology. Here, we show that optoacoustic poration is also very effective for porating cells on a large family of MEA electrode configurations, including robust electrodes made of nanoporous titanium nitride or disordered fractal-like gold nanostructures. This enables the recording of high quality cardiac action potentials in combination with optoacoustic poration, providing thus attenuated intracellular recordings on various already commercial devices used by a significant part of the research and industrial communities. [less ▲]

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See detailEnhanced magnetic modulation of light polarization exploiting hybridization with multipolar dark plasmons in magnetoplasmonic nanocavities
Lopez-Ortega, Alberto; Zapata-Herrera, Mario; Maccaferri, Nicolò UL et al

in Light: Science and Applications (2020), 9

Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. Here, we disclose a so far ... [more ▼]

Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. Here, we disclose a so far unexplored approach that exploits hybridization with multipolar dark modes in specially designed magnetoplasmonic nanocavities to achieve a large enhancement of the magneto-optically induced modulation of light polarization. The broken geometrical symmetry of the design enables coupling with free-space light and hybridization of multipolar dark modes of a plasmonic ring nanoresonator with the dipolar localized plasmon resonance of the ferromagnetic disk placed inside the ring. Such hybridization results in a low-radiant multipolar Fano resonance that drives a strongly enhanced magneto-optically induced localized plasmon. The large amplification of the magneto-optical response of the nanocavity is the result of the large magneto-optically induced change of light polarization produced by the strongly enhanced radiant magneto-optical dipole, which is achieved avoiding the simultaneous enhancement of re-emitted light with the incident polarization by the driving multipolar Fano resonance. The partial compensation of the magneto-optically induced polarization change caused by the large re-emission of light with the original polarization is a critical limitation of magnetoplasmonic designs explored so far. [less ▲]

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See detailDesigner Bloch plasmon polariton dispersion in grating-coupled hyperbolic metamaterials
Maccaferri, Nicolò UL; Isoniemi, Tommi; Hinczewski, Michael et al

in APL Photonics (2020), 5

Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. How- ever, it is challenging to tailor and excite these modes at optical ... [more ▼]

Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. How- ever, it is challenging to tailor and excite these modes at optical frequencies by prism coupling because of the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we report on the mechanism of excitation of high-index Bloch plasmon polariton modes with sub-diffraction spatial confinement using a meta-grating, which is a combined structure of a metallic diffraction grating and a type II HMM. We show how a one-dimensional plasmonic grating without any mode in the infrared spectral range, if coupled to an HMM supporting high-index modes, can efficiently enable the excitation of these modes via coupling to far- field radiation. Our theoretical predictions are confirmed by experimental reflection measurements as a function of angle of incidence and excitation wavelength. We introduce design principles to achieve a full control of high-index modes in meta-gratings, thus enabling a better understanding of light–matter interaction in this type of hybrid structure. The exploitation of the spectral response of these modes can find applications in bio-chemical sensing, integrated optics, and optical sub-wavelength imaging. [less ▲]

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See detailUltrafast all-optical switching enabled by epsilon-near-zero-tailored absorption in metal-insulator nanocavities
Kuttruff, Joel; Garoli, Denis; Allerbeck, Jonas et al

in Communications Physics (2020), 3

Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature ... [more ▼]

Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature switching speeds that are extremely low with respect to the time scales at which it is possible to control light. Here, we exploit the artificial epsilon-near-zero (ENZ) modes of a metal-insulator-metal nanocavity to tailor the linear photon absorption of our system and realize a nondegenerate all-optical ultrafast modulation of the reflectance at a specific wavelength. Optical pumping of the system at its high energy ENZ mode leads to a strong redshift of the low energy mode because of the transient increase of the local dielectric function, which leads to a sub-3-ps control of the reflectance at a specific wavelength with a relative modulation depth approaching 120%. [less ▲]

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See detailPlasmon Hybridization in Compressible Metal-Insulator-Metal Nano-Cavities: an Optical Approach for Sensing Deep Sub-Wavelength Deformation
Carrara, Angelica; Maccaferri, Nicolò UL; Cerea, Andrea et al

in Advanced Optical Materials (2020), 8(18), 2000609

We present a pressure-induced deformation-sensitive device based on 2D matrices of plasmonic gold nanodisks coupled to a metal thin layer through a compressible dielectric spacer, namely a deformable ... [more ▼]

We present a pressure-induced deformation-sensitive device based on 2D matrices of plasmonic gold nanodisks coupled to a metal thin layer through a compressible dielectric spacer, namely a deformable metal-insulator-metal (MIM) nanocavity, to report deep sub-wavelength size variations (< λ/200). The system is characterized by two hybrid branches, which are resonant in the visible/near infrared spectral region. The fundamental mode, owing to the near-field interaction between the plasmonic nanostructures and the metal film, exhibits a remarkable sensitivity to the gap size, exceeding that of a planar “macroscopic” optical cavity and extending its operational domain to the sub-wavelength range, where excellent opportunities towards truly multiscale MIMs-based pressure sensors can be envisioned. Concurrently, its intrinsic plasmonic nature synergistically combines into a single platform multi-purpose functionalities, such as ultrasensitive detection, remote temperature readout etc., with practical perspectives in ultra-compact inspection tools for structural and functional information at the nanoscale. [less ▲]

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See detailElectron Energy Loss Spectroscopy of Bright and Dark Modes in Hyperbolic Metamaterial Nanostructures
Isoniemi, Tommi; Maccaferri, Nicolò UL; Ramasse, Quentin M. et al

in Advanced Optical Materials (2020), 8(13), 2000277

Layered metal/dielectric hyperbolic metamaterials (HMMs) support a wide landscape of plasmon polariton excitations. In addition to surface plasmon polaritons, coupled Bloch-like gap-plasmon polaritons ... [more ▼]

Layered metal/dielectric hyperbolic metamaterials (HMMs) support a wide landscape of plasmon polariton excitations. In addition to surface plasmon polaritons, coupled Bloch-like gap-plasmon polaritons with high modal confinement inside the multilayer are supported. Photons can excite only a subset of these polaritonic modes, typically with a limited energy and momentum range in respect to the wide set of high-K modes supported by hyperbolic dispersion media, and coupling with gratings or local excitation is necessary. Strikingly, electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope allows nm-scale local excitation and mapping of the spatial field distribution of all the modes supported by a photonic or plasmonic structure, both bright and dark, and also all other inelastic interactions of the beam, including phonons and interband transitions. Herein, experimental evidence of the spatial distribution of plasmon polaritons in multilayered type II HMM nanostructures is acquired with an aloof electron beam adjacent to structures of current interest. HMM pillars are useful for their separation and adjustability of optical scattering and absorption, while HMM slot cavities can be used as waveguides with high field confinement. The nature of the modes is confirmed with corresponding simulations of EEL and optical spectra and near-field intensities. [less ▲]

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See detailTwo-state switchable plasmonic tweezers for dynamic manipulation of nano-objects
Messina, Gabriele; Zambrana-Puyalto, Xavier; Maccaferri, Nicolò UL et al

in Nanoscale (2020), 12

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer ... [more ▼]

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer wall of a vertical gold nanochannel, can be activated by varying the focusing position of the excitation laser along the main axis of the nanotube. We show that the switching of the trapping site is induced by changes in the distribution of the electromagnetic field and of the trapping force. The “inner” and “outer” trapping states are characterized by a static and a dynamic behavior respectively, and their stiffness is measured by analyzing the positions of the trapped specimens as a function of time. In addition, we demonstrate that the stiffness of the static state is high enough to trap particles with diameter as small as 40 nm. These results show a simple, controllable way to generate a switchable two-state trapping regime, which could be used as a model for the study of dynamic trapping or as a mechanism for the development of nanofluidic devices. [less ▲]

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See detailNanoscale magnetophotonics
Maccaferri, Nicolò UL; Zubritskaya, Irina; Razdolski, Ilya et al

in Journal of Applied Physics (2020), 127(8), 080903

This Perspective surveys the state-of-the-art and future prospects of science and technology employing nanoconfined light (nanophotonics and nanoplasmonics) in combination with magnetism. We denote this ... [more ▼]

This Perspective surveys the state-of-the-art and future prospects of science and technology employing nanoconfined light (nanophotonics and nanoplasmonics) in combination with magnetism. We denote this field broadly as nanoscale magnetophotonics. We include a general introduction to the field and describe the emerging magneto-optical effects in magnetoplasmonic and magnetophotonic nanostructures supporting localized and propagating plasmons. Special attention is given to magnetoplasmonic crystals with transverse magnetization and the associated nanophotonic non-reciprocal effects and to magneto-optical effects in periodic arrays of nanostructures. We also give an overview of the applications of these systems in biological and chemical sensing, as well as in light polarization and phase control. We further review the area of nonlinear magnetophotonics, the semiconductor spin-plasmonics, and the general principles and applications of opto-magnetism and nano-optical ultrafast control of magnetism and spintronics. [less ▲]

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See detailBio-assisted tailored synthesis of plasmonic silver nanorings and site-selective deposition on graphene arrays
Giovannini, Giorgia; Ardini, Matteo; Maccaferri, Nicolò UL et al

in Advanced Optical Materials (2020), 8(4), 1901583

The spontaneous interaction between noble metals and biological scaffolds enables simple and cost‐effective synthesis of nanomaterials with unique features. Here, plasmonic silver nanorings are ... [more ▼]

The spontaneous interaction between noble metals and biological scaffolds enables simple and cost‐effective synthesis of nanomaterials with unique features. Here, plasmonic silver nanorings are synthesized on a ring‐like protein, i.e., a peroxiredoxin (PRX), and used to assemble large arrays of functional nanostructures. The PRX drives the seeding growth of metal silver under wet reducing conditions, yielding nanorings with outer and inner diameters down to 28 and 3 nm, respectively. The obtained hybrid nanostructures are selectively deposited onto a solid‐state 2D membrane made of graphene in order to prepare plasmonic nanopores. In particular, the interaction between the graphene and the PRX allows for the simple preparation of ordered arrays of plasmonic nanorings on a 2D‐material membrane. This fabrication process can be finalized by drilling a nanometer scale pore in the middle of the ring. Fluorescence spectroscopic measurements in combination with numerical simulations demonstrate the plasmonic effects induced in the metallic nanoring cavity. The prepared nanopores represent one of the first examples of hybrid plasmonic nanopore structures integrated on a 2D‐material membrane. The diameter of the nanopore and the atomically thick substrate make this proof‐of‐concept approach particularly interesting for nanopore‐based technologies and applications such as next‐generation sequencing and single‐molecule detection. [less ▲]

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See detailλ-DNA Through porous materials – Surface Enhanced Raman Scattering in a simple plasmonic nanopore
Hubarevich, Aliaksandr; Huang, Jian-An; Giovannini, Giorgia et al

in Journal of Physical Chemistry C (2020), 124(41), 22663-22670

Engineered electromagnetic fields in plasmonic nanopores enable enhanced optical detection for single molecule sensing and sequencing. Here, a plasmonic nanopore prepared in a thick nanoporous film is ... [more ▼]

Engineered electromagnetic fields in plasmonic nanopores enable enhanced optical detection for single molecule sensing and sequencing. Here, a plasmonic nanopore prepared in a thick nanoporous film is used to investigate, by means of surface enhanced Raman spectroscopy, the interaction between the metallic surface of the pore and a long-chain double strand DNA molecule free to diffuse through the pore. We discuss how the matrix of the porous material can interact with the molecule thanks to: i) transient aspecific interactions between the porous surface and DNA; ii) diffusion; iii) thermal and optical forces exerted by the localized field in a metallic nanostructure on the DNA molecule. An interaction time up to tens of milliseconds enables to collect high signal-to-noise Raman signatures, allowing an easy label-free reading of information from the DNA molecule. Moreover, to increase the rate of detection, we tested a polymeric porous hydrogel placed beneath the solid-state membrane. The hydrogel enables a slowdown of the molecule diffusion time, thus increasing the number of detected interaction events by a factor 20. The analysis of the observed Raman peaks and their relative intensities, combined with theoretical simulations, allow to get further information on the process of translocation and on the folding state and orientation of the translocating molecule. Our results demonstrate temporary adsorption of the DNA molecule on the porous material during the translocation due to the diffusion force. Finally, we provide a qualitative evaluation of the nucleotides’ contents in the different groups of collected signal. The proposed approach can find interesting applications not only in DNA sensing and sequencing, but also on generic nanopore spectroscopy. [less ▲]

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See detailCoupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications
Maccaferri, Nicolò UL

in Journal of the Optical Society of America B (2019), 36(7), 112-131

We review both the fundamental aspects and the applications of functional magneto-optic and opto-magnetic metamaterials displaying collective and coupling effects on the nanoscale, where the concepts of ... [more ▼]

We review both the fundamental aspects and the applications of functional magneto-optic and opto-magnetic metamaterials displaying collective and coupling effects on the nanoscale, where the concepts of optics and magnetism merge to produce unconventional phenomena. The use of magnetic materials instead of the usual noble metals allows for an additional degree of freedom for the control of electromagnetic field properties, as well as it allows light to interact with the spins of the electrons and to actively manipulate the magnetic properties of such nanomaterials. In this context, we explore the concepts of near-field coupling of plasmon modes in magnetic meta-molecules, as well as the effect of excitation of surface lattice resonances in magneto-plasmonic crystals. Moreover, we discuss how these coupling effects can be exploited to artificially enhance optical magnetism in plasmonic meta-molecules and crystals. Finally, we highlight some of the present challenges and provide a perspective on future directions of the research towards photon-driven fast and efficient nanotechnologies bridging magnetism and optics beyond current limits. [less ▲]

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See detailTime-Resolved Investigations and Biotechnological Applications of Plasmonic Nanostructures
Maccaferri, Nicolò UL

in Proceedings (2019), 26(1), 24

Plasmonics exploits the collective motion of conduction electrons in metals (plasmons), thus enabling light to couple with nanoscale objects, with the consequent generation of a plenty of novel and ... [more ▼]

Plasmonics exploits the collective motion of conduction electrons in metals (plasmons), thus enabling light to couple with nanoscale objects, with the consequent generation of a plenty of novel and unexpected optical effects and functionalities. Plasmonic nanostructures have been deeply studied in the last decade due to their crucial impact on several areas of nanoscience and nanotechnology. Their unrivalled capability to squeeze light well beyond its diffraction limit, leading to extremely confined and enhanced electromagnetic fields on the nanoscale at optical frequencies, is of great interest for the prospect of real-life applications, such as energy harvesting and photovoltaics, wave-guiding and lasing, optoelectronics, fluorescence emission enhancement, plasmon-assisted biointerfaces and nanomedicine. In this framework, traditional studies of the resonant behavior of plasmonic nanoantennas rely on standard intensity detection schemes. Up to date, the temporal dynamics of plasmonic nanoantennas remains challenging. In the first part of the talk we will show that, by combining femtosecond time-domain spectroscopy and high-resolution confocal microscopy, it is possible to measure full time- and field-resolved response of single plasmonic nanoantennas [1]. In the second part of the talk, we will then show practical applications of plasmonic nanostructures to single-molecule detection [2–4], enhanced spectroscopy on single-cells [5–7], optical trapping [8,9], enhanced Raman scattering [10–12] and resonant energy transfer [13]. [less ▲]

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See detailChasing plasmons in flatland
Celano, Umberto; Maccaferri, Nicolò UL

in Nano Letters (2019), 19(11), 7549-7552

Two-dimensional layered crystals, including graphene and transition metal dichalcogenides, represent an interesting avenue for studying light-matter interactions at the nanoscale in confined geometries ... [more ▼]

Two-dimensional layered crystals, including graphene and transition metal dichalcogenides, represent an interesting avenue for studying light-matter interactions at the nanoscale in confined geometries. They offer several attractive properties, such as large exciton binding energies, strong excitonic resonances, and tunable bandgaps from the visible to the near-IR along with large spin–orbit coupling, direct band gap transitions, and valley-selective responses. [less ▲]

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See detailPlasmonic nanopores for single-molecule detection and manipulation: towards sequencing applications
Garoli, Denis; Yamazaki, Hirohito; Maccaferri, Nicolò UL et al

in Nano Letters (2019), 19(11), 7553-7562

Solid-state nanopore-based sensors are promising platforms for next-generation sequencing technologies, featuring label-free single-molecule sensitivity, rapid detection, and low-cost manufacturing. In ... [more ▼]

Solid-state nanopore-based sensors are promising platforms for next-generation sequencing technologies, featuring label-free single-molecule sensitivity, rapid detection, and low-cost manufacturing. In recent years, solid-state nanopores have been explored due to their miscellaneous fabrication methods and their use in a wide range of sensing applications. Here, we highlight a novel family of solid-state nanopores which have recently appeared, namely plasmonic nanopores. The use of plasmonic nanopores to engineer electromagnetic fields around a nanopore sensor allows for enhanced optical spectroscopies, local control over temperature, thermophoresis of molecules and ions to/from the sensor, and trapping of entities. This Mini Review offers a comprehensive understanding of the current state-of-the-art plasmonic nanopores for single-molecule detection and biomolecular sequencing applications and discusses the latest advances and future perspectives on plasmonic nanopore-based technologies. [less ▲]

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See detailFRET Characterization of Hollow Plasmonic Nanoantennas
Maccaferri, Nicolò UL; Ponzellini, Paolo; Giovannini, Giorgia et al

in Proceedings of SPIE : The International Society for Optical Engineering (2019), 10894

We fabricated hollow nanoantennas with varying inner channels sizes on a gold-covered silicon nitride membrane. Our fabrication technique allowed us to narrow the size of the inner channels down to 15nm ... [more ▼]

We fabricated hollow nanoantennas with varying inner channels sizes on a gold-covered silicon nitride membrane. Our fabrication technique allowed us to narrow the size of the inner channels down to 15nm. We managed to exclusively decorate the tips of the antennas with thiol-conjugated dyes by creating a concentration gradient through the nanoantennas. Finally, we characterized the antennas in terms of their effect on the lifetime of dyes. We used Atto 520 and Atto 590 for the experiments. We carried out experiments with the antennas decorated with Atto 520, with Atto 590 as well as with the two Atto dyes at the same time. The experiments carried out with the antennas decorated with Atto 520 only and Atto 590 only yielded a lifetime reduction with respect to the confocal case. Interestingly, their lifetime reductions were significantly different. Then, we decorated the antennas with the two dyes at the same time. Even though we could not control the distance between the two dyes, FRET effects were clearly observed. The FRET effects were found to be dependent on the size of the inner channel. We believe that our tip decorated hollow nanoantennas could find application in FRET-based single molecule nanopore technologies. [less ▲]

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See detailTunable magnetoplasmonics in lattices of Ni/SiO2/Au dimers
Pourjamal, Sara; Kataja, Mikko; Maccaferri, Nicolò UL et al

in Scientific Reports (2019), 9

We present a systematic study on the optical and magneto-optical properties of Ni/SiO2/Au dimer lattices. By consideringthe excitation of orthogonal dipoles in the Ni and Au nanodisks, we analytically ... [more ▼]

We present a systematic study on the optical and magneto-optical properties of Ni/SiO2/Au dimer lattices. By consideringthe excitation of orthogonal dipoles in the Ni and Au nanodisks, we analytically demonstrate that the magnetoplasmonicresponse of dimer lattices is governed by a complex interplay of near- and far-field interactions. Near-field coupling betweendipoles in Ni and low-loss Au enhances the polarizabilty of single dimers compared to that of isolated Ni nanodisks. Far-fielddiffractive coupling in periodic lattices of these two particle types enlarges the difference in effective polarizability further.This effect is explained by an inverse relationship between the damping of collective surface lattice resonances and theimaginary polarizability of individual scatterers. Optical reflectance measurements, magneto-optical Kerr effect spectra, andfinite-difference time-domain simulations confirm the analytical results. Hybrid dimer arrays supporting intense plasmonexcitations are a promising candidate for active magnetoplasmonic devices. [less ▲]

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