arXiv subjects

Mauricio Pilo-Pais

Publications and source records attributed to Mauricio Pilo-Pais.

7 recordsLinked to original sources

arXiv2024

Giant Purcell broadening and Lamb shift for DNA-assembled near-infrared quantum emitters

Controlling the light emitted by individual molecules is instrumental to a number of novel nanotechnologies ranging from super-resolution bio-imaging and molecular sensing to quantum nanophotonics. Molecular emission can be tailored by modifying the local photonic environment, for example by precisely placing a single molecule inside a plasmonic nanocavity with the help of DNA origami. Here, using this scalable approach, we show that commercial fluorophores experience giant Purcell factors and Lamb shifts, reaching values on par with those recently reported in scanning tip experiments. Engineering of plasmonic modes enables cavity-mediated fluorescence far detuned from the zero-phonon-line (ZPL) - at detunings that are up to two orders of magnitude larger than the fluorescence linewidth of the bare emitter and reach into the near-infrared. Our results evidence a regime where the emission linewidth is dominated by the excited state lifetime, as required for indistinguishable photon emission, baring relevance to the development of nanoscale, ultrafast quantum light sources and to the quest toward single-molecule cavity-QED. In the future, this approach may also allow to design efficient quantum emitters at infrared wavelengths, where standard organic sources have a reduced performance.

physics.optics↗

arXiv2022

Super-resolved FRET imaging by confocal fluorescence-lifetime single-molecule localization microscopy

FRET-based approaches are a unique tool for sensing the immediate surroundings and interactions of (bio)molecules. FRET imaging and FLIM (Fluorescence Lifetime Imaging Microscopy) enable the visualization of the spatial distribution of molecular interactions and functional states. However, conventional FLIM and FRET imaging provide average information over an ensemble of molecules within a diffraction-limited volume, which limits the spatial information, accuracy, and dynamic range of the observed signals. Here, we demonstrate an approach to obtain super-resolved FRET imaging based on single-molecule localization microscopy using an early prototype of a commercial time-resolved confocal microscope. DNA Points Accumulation for Imaging in Nanoscale Topography (DNA-PAINT) with fluorogenic probes provides a suitable combination of background reduction and blinking kinetics compatible with the scanning speed of usual confocal microscopes. A single laser is used to excite the donor, a broad detection band is employed to retrieve both donor and acceptor emission, and FRET events are detected from lifetime information.

physics.optics↗

arXiv2022

DNA self-assembly of single molecules with deterministic position and orientation

An ideal nanofabrication method should allow the organization of nanoparticles and molecules with nanometric positional precision, stoichiometric control and well-defined orientation. The DNA origami technique has evolved into a highly versatile bottom-up nanofabrication methodology that fulfils almost all of these features. It enables the nanometric positioning of molecules and nanoparticles with stoichiometric control, and even the orientation of asymmetrical nanoparticles along predefined directions. However, orienting individual molecules has been a standing challenge, mainly due to unspecific electrostatic interactions. Here, we show how single molecules, namely Cy5 and Cy3 fluorophores, can be incorporated in a DNA origami with controlled orientation by doubly linking them to oligonucleotide strands that are hybridized while leaving enough unpaired bases to induce a stretching force. Particularly, we explore the effects of leaving 0, 2, 4, 6, and 8 unpaired bases and find extreme orientations for 0 and 8 unpaired bases, corresponding to the molecules being perpendicular and parallel to the DNA double helix, respectively. We foresee that these results will expand the application field of DNA origami towards the fabrication of nanodevices involving a wide range of orientation-dependent molecular interactions, such as energy transfer, intermolecular electron transport, catalysis, exciton delocalization, or the electromagnetic coupling of a molecule to specific resonant nano-antennas modes.

cond-mat.soft↗

arXiv2022

Unidirectional ultracompact DNA-templated optical antennas

Optical nanoantennas are structures designed to manipulate light-matter interactions at the nanoscale by interfacing propagating light with localized optical fields. In recent years, a plethora of devices have been realized that are able to efficiently tailor the absorption and/or emission rates of fluorophores. By contrast, modifying the spatial characteristics of their radiation fields remains a challenge. Up to date, the designs providing directionality to fluorescence emission have required compound, complex geometries with overall dimensions comparable to the operating wavelength. Here, we present the fabrication and characterization of DNA-templated ultracompact optical antennas, with sub-wavelength sizes and capable of directing single-molecule fluorescence into predefined directions. Using the DNA origami methodology, two gold nanorods are assembled side-to-side with a separation gap of 5 nm. We show that a single fluorescent molecule placed at the tip of one of the nanorods drives the dimer antenna in anti-phase, leading to unidirectional emission.

physics.optics↗

arXiv2022

Optical ultracompact directional antenna based on a dimer nanorod structure

Controlling directionality of optical emitters is of utmost importance for their application in communication and biosensing devices. Metallic nanoantennas have been proven to affect both excitation and emission properties of nearby emitters, including directionality of their emission. In this regard, optical directional nanoantennas based on a Yagi-Uda design have been demonstrated in the visible range. Despite this impressive proof of concept, their overall size and considerable number of elements represent obstacles for the exploitation of these antennas in nanophotonic applications and for their incorporation onto photonic chips. In order to address these challenges, we investigate an alternative design. In particular, we numerically demonstrate unidirectionality of an ultracompact optical antenna based on two parallel gold nanorods (side-by-side dimer). Our results show that exciting the antiphase mode by an emitter placed in the near-field can lead to unidirectional emission. Furthermore, in order to verify the feasibility of this design, we study the effect on the directionality of several parameters such as shape of the nanorods, possible defects in dimer assembly, and different position and orientation of the emitter. We conclude that this design is robust to changes, making it experimentally achievable.

physics.optics↗

arXiv2021

In Situ Photothermal Response of Single Gold Nanoparticles Through Hyperspectral Imaging AntiStokes Thermometry

Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task both for modeling and experimental measurements. Here, we present a new implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual nanoparticles (NPs) from a single hyperspectral photoluminescence confocal image. The method is label-free, applicable to any NP with detectable anti-Stokes emission, and does not require any prior information about the NP itself or the surrounding media. With it, we first studied the photothermal response of spherical gold NPs of different sizes on glass substrates, immersed in water, and found that heat dissipation is mainly dominated by the water for NPs larger than 50 nm. Then, the role of the substrate was studied by comparing the photothermal response of 80 nm gold NPs on glass with sapphire and graphene, two materials with high thermal conductivity. For a given irradiance level, the NPs reach temperatures 18% lower on sapphire and 24% higher on graphene than on bare glass. The fact that the presence of a highly conductive material such as graphene leads to a poorer thermal dissipation demonstrates that interfacial thermal resistances play a very significant role in nanoscopic systems, and emphasize the need for in situ experimental thermometry techniques. The developed method will allow addressing several open questions about the role of temperature in plasmon-assisted applications, especially ones where NPs of arbitrary shapes are present in complex matrixes and environments.

physics.optics↗

arXiv2017

Plasmon-Exciton Coupling Using DNA Templates

Coherent energy exchange between plasmons and excitons is a phenomenon that arises in the strong coupling regime resulting in distinct hybrid states. The DNA-origami technique provides an ideal framework to custom-tune plasmon-exciton nanostructures. By employing this well controlled self-assembly process, we realized hybrid states by precisely positioning metallic nanoparticles in a defined spatial arrangement with fixed nanometer-sized interparticle spacing. Varying the nanoparticle diameter between 30 nm and 60 nm while keeping their separation distance constant allowed us to precisely adjust the plasmon resonance of the structure to accurately match the energy frequency of a J-aggregate exciton. With this system we obtained strong plasmon-exciton coupling and studied far-field scattering at the single-structure level. The individual structures displayed normal mode splitting up to 170 meV. The plasmon tunability and the strong field confinement attained with nanodimers on DNA-origami renders an ideal tool to bottom-up assembly plasmon-exciton systems operating at room temperature.

cond-mat.mes-hall↗