Plasmonic antennas and zero mode waveguides to enhance single molecule fluorescence detection and fluorescence correlation spectroscopy towards physiological concentrations

Single-molecule approaches to biology offer a powerful new vision to elucidate the mechanisms that underpin the functioning of living cells. However, conventional optical single molecule spectroscopy techniques such as F\"orster fluorescence resonance energy transfer (FRET) or fluorescence correlation spectroscopy (FCS) are limited by diffraction to the nanomolar concentration range, far below the physiological micromolar concentration range where most biological reaction occur. To breach the diffraction limit, zero mode waveguides and plasmonic antennas exploit the surface plasmon resonances to confine and enhance light down to the nanometre scale. The ability of plasmonics to achieve extreme light concentration unlocks an enormous potential to enhance fluorescence detection, FRET and FCS. Single molecule spectroscopy techniques greatly benefit from zero mode waveguides and plasmonic antennas to enter a new dimension of molecular concentration reaching physiological conditions. The application of nano-optics to biological problems with FRET and FCS is an emerging and exciting field, and is promising to reveal new insights on biological functions and dynamics.Comment: WIREs Nanomed Nanobiotechnol 201

Quantum Yield Limits for the Detection of Single-Molecule Fluorescence Enhancement by a Gold Nanorod

Biological and Soft Matter Physic

Plasmonic Band Structure Controls Single-Molecule Fluorescence

A chieving a complete manipulation of the generally weak optical signal from a single quantum emitter is a key objective in nanophotonics. To this end, two major routes have been investigated: plasmonic metal nanostructures 1À11 and dielectric photonic crystals. 12À21 Both routes have demonstrated breakthrough results in tailoring the photoluminescence intensity, spectrum, or directionality of single emitters. The plasmonic approach has put the most emphasis on the nanoscale antenna element to control single-emitter radiation 1,2,22À24 via the strong electromagnetic enhancement in the near field of metals. In contrast, the photonic crystal approach centers on the use of coherent scattering to boost the interaction strength of intrinsically weakly scattering building blocks. State-of-the-art structures use thin highindex membranes perforated by nanoapertures, in which the guided modes fold into a complex band structure. Spontaneous emission control then revolves around the targeted coupling of an emitter to select Bloch modes, with well-controlled outcoupling characteristics. Very recently, interest has emerged in the interplay between these two approaches, implying the use of a coherent array of plasmonic resonators to shape the luminescence emission properties. Two key examples are provided on one hand by the use of diffractive modes in 2D arrays of plasmon particles to shape emission of thin emissive layers 10,11,25À27 and on the other hand by the demonstration of YagiÀUda antennas with a single quantum dot emitter in the optical regime, 3 where coherent near -field coupling between scattering nanoparticles is determinant to achieve directional emission. 6 Here, we investigate the emergence of coherent antenna array effects to shape the fluorescence emission of single molecules in finite-sized bidimensional arrays of apertures milled into a metal film that supports surface plasmon guided modes. Transmission properties of quasi-infinite aperture arrays and single holes have been thoroughly investigated in the framework of extraordinary optical transmission. Henzie. Received for review June 28, 2013 and accepted September 10, 2013. Published online 10.1021/nn4033008 ABSTRACT Plasmonics and photonic crystals are two complementary approaches to tailor singleemitter fluorescence, using strong local field enhancements near metals on one hand and spatially extended photonic band structure effects on the other hand. Here, we explore the emergence of spontaneous emission control by finite-sized hexagonal arrays of nanoapertures milled in gold film. We demonstrate that already small lattices enable highly directional and enhanced emission from single fluorescent molecules in the central aperture. Even for clusters just four unit cells across, the directionality is set by the plasmonic crystal band structure, as confirmed by full-wave numerical simulations. This realization of plasmonic phase array antennas driven by single quantum emitters opens a flexible toolbox to engineer fluorescence and its detection

Antennes optiques pour la détection de molécules fluorescentes individuelles à concentrations physiologiques

Optical nanoantennas provide a rich control over light at nanoscale to achieve high field enhancement and localization with a large absorption cross-sections. Considering the need for these virtues in broad range of fields the possible applications of these nanoantennas span into the fields of spectroscopy, photovoltaics, single photon sources, biological sensing. This thesis work mainly focuses on characterizing and manipulating optical antenna to detect single molecule fluorescence signal at high concentration of micromolar regime. At such high concentration we need to get the detection volume reduced at least three orders of magnitude beyond diffraction limits. Also the fluorescence signal enhancement is needed to have better value in order to have a single molecule stand out from the background. Chapter 1 deals with the motivation of the thesis by discussing about the well established strategies already applied to tackle the issues of volume reduction and fluorescence rate enhancement and how to go beyond the limitations of these methods. In Chapter 2 we discuss the local surface plasmonic properties of optical nanoantennas responsible for the local field enhancement and give an overview of the applications of optical antennas. Chapter 3 gives the detailed idea of the experimental techniques (Fluorescence Correlation Spectroscopy and Time correlated Single Photon Counting) that have been used to characterize the influence of Optical nanoantenna. Chapter 4 introduces the novel "antenna-in-box" platform, based on a gap-antenna inside a nanoaperture, which combines both enhancement and background screening, offering high single molecule sensitivity at micromolar concentrations. We demonstrate gap-antenna detection volumes of zeptoliter dimensions, corresponding to a 10,000-volume reduction compared to diffraction-limited optics, fluorescence enhancement up to 1100-fold and microsecond transit time. In the last Chapter 5 we show the experimental results on single gold nanoparticles with various diameters giving the idea that with 80 nm gold nanoparticle we can achieve detection volumes down to 270 zeptoliters (three orders of magnitude beyond the diffraction barrier) together with 60-fold enhancement of the fluorescence brightness per molecule. This chapter also includes results on dimers and trimers of 80 nm gold nanoparticles showing light confinement comparable to the "antenna-in-box” platform. The results in this thesis demonstrates the potential of optical antennas, fabricated by top-down ("antenna-in-box” platform) and bottom-up approach (colloidal synthesis of antennas using gold nanoparticles), to confine light and detect single molecule fluorescence at biologically relevant high concentrations regime.Les nanoantennes optiques offrent un contrôle riche sur la lumière à l’échelle nanométrique pour réaliser la mise en valeur de champ élevé et localisation avec une grande sections efficaces d’absorption. Considérant la nécessité pour ces vertus dans des domaines très divers les applications possibles de ces nanoantennes s’étendent dans les domaines de la spectroscopie, photovoltaïque, sources de photons uniques, détection biologique. Ce travail de thèse se concentre principalement sur la caractérisation et la manipulation antenne optique pour détecter seul signal de fluorescence de molécules à forte concentration de régime micromoles. Lors de cette forte concentration, nous devons obtenir le volume de détection réduite d’au moins trois ordres de grandeur au-delà des limites de diffraction. Aussi l’amélioration du signal de fluorescence est nécessaire d’avoir un meilleur rapport signal sur bruit afin d’avoir une seule molécule de se démarquer de l’arrière-plan. Chapitre 1 traite de la motivation de la thèse en discutant sur les stratégies bien établies déjà appliquées pour aborder les questions de la réduction du volume et l’amélioration du taux de fluorescence et comment aller au-delà des limites de ces méthodes. Dans le chapitre 2, nous discutons des propriétés de surface plasmoniques locaux de nanoantennes optiques responsables de la mise en valeur de champ local et donnons un aperçu des applications d’antennes optiques. Chapitre 3 donne l’idée détaillée des techniques expérimentales (corrélation de fluorescence de spectroscopie et Temps corrélation comptage de photons) qui ont été utilisées pour caractériser l’influence de la nano-antenne optique. Le chapitre 4 présente "antenne-in-box" plate-forme, basée sur un écart-antenne à l’intérieur d’un nanotrou, qui combine à la fois la mise en valeur et la vérification des antécédents, offrant une haute sensibilité de la molécule unique à des concentrations micromolaires. Nous démontrons volumes de détection écart-antenne de dimensions zeptoliter, correspondant à une réduction de 10,000-volume rapport à l’optique de diffraction limitée, l’amélioration de la fluorescence jusqu’à 1100 fois et le transit de la micro- seconde temps. Dans le dernier chapitre 5, nous montrons les résultats expérimentaux sur des nanoparticules d’or individuelles avec différents diamètres donnant l’idée que, avec 80 nm nanoparticules d’or, nous pouvons atteindre des volumes de détection jusqu’à 270 zeptoliters (trois ordres de grandeur au-delà de la barrière de diffraction) avec 60× l’amélioration de l’intensité de fluorescence par molécule. Ce chapitre comprend également les résultats actuels sur les dimères et trimères de 80 nm nanoparticules d’or montrant la lumière confinement comparable à la Plate-forme "antenne-in-box". Les résultats de cette thèse démontre le potentiel des antennes optiques, fabriqué par top-down ("antenne-in-box" plate-forme) et l’approche bottom-up(synthèse colloïdale d’antennes utilisant des nanoparticules d’or), pour confiner la lumière et de détecter la fluorescence d’une seule molécule au régime des concentrations élevées d’intérêt biologique

Single gold nanoparticles to enhance the detection of single fluorescent molecules at micromolar concentration using fluorescence correlation spectroscopy

International audienc

Plasmonic Band Structure Controls Single-Molecule Fluorescence

International audienc

Gold nanoparticles for enhanced single molecule fluorescence analysis at micromolar concentration

International audienc

Nanosecond time scale transient optoplasmonic detection of single proteins

Optical detection of individual proteins with high bandwidth holds great promise for understanding important biological processes on the nanoscale and for high-throughput fingerprinting applications. As fluorescent labels impose restrictions on detection bandwidth and require time-intensive and invasive processes, label-free optical techniques are highly desirable. Here, we read out changes in the resonantly scattered field of individual gold nanorods interferometrically and use photothermal spectroscopy to optimize the experiment's parameters. This interferometric plasmonic scattering enables the observation of single proteins as they traverse plasmonic near fields of gold nanorods with unprecedented temporal resolution in the nanosecond-to-microsecond range.Biological and Soft Matter Physic

Plasmonic Band Structure Controls Single-Molecule Fluorescence

Plasmonics and photonic crystals are two complementary approaches to tailor single-emitter fluorescence, using strong local field enhancements near metals on one hand and spatially extended photonic band structure effects on the other hand. Here, we explore the emergence of spontaneous emission control by finite-sized hexagonal arrays of nanoapertures milled in gold film. We demonstrate that already small lattices enable highly directional and enhanced emission from single fluorescent molecules in the central aperture. Even for clusters just four unit cells across, the directionality is set by the plasmonic crystal band structure, as confirmed by full-wave numerical simulations. This realization of plasmonic phase array antennas driven by single quantum emitters opens a flexible toolbox to engineer fluorescence and its detection