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.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright \copyright American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b03015, Nano Letters 201

An alternative to MINFLUX that enables nanometer resolution in a confocal microscope

Localization of single fluorescent emitters is key for physicochemical and biophysical measurements at the nanoscale and beyond ensemble averaging. Examples include single-molecule tracking and super-resolution imaging by single-molecule localization microscopy. Among the numerous localization methods available, MINFLUX outstands for achieving a ~10-fold improvement in resolution over wide-field camera-based approaches, reaching the molecular scale at moderate photon counts. Widespread application of MINFLUX and related methods has been hindered by the technical complexity of the setups. Here, we present RASTMIN, a single-molecule localization method based on raster scanning a light pattern comprising a minimum of intensity. RASTMIN delivers ~1–2 nm localization precision with usual fluorophores and is easily implementable on a standard confocal microscope with few modifications. We demonstrate the performance of RASTMIN in localization of single molecules and super-resolution imaging of DNA origami structures.Fil: Masullo, Luciano Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Szalai, Alan Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Lopez, Lucía Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Pilo Pais, Mauricio. Universite de Fribourg;Fil: Acuna, Guillermo P.. Universite de Fribourg;Fil: Stefani, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentin

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

Directing single-molecule emission with dna origami-assembled optical antennas

We demonstrate the capability of DNA self-assembled optical antennas to direct the emission of an individual fluorophore, which is free to rotate. DNA origami is used to fabricate optical antennas composed of two colloidal gold nanoparticles separated by a predefined gap and to place a single Cy5 fluorophore near the gap center. Although the fluorophore is able to rotate, its excitation and far-field emission is mediated by the antenna, with the emission directionality following a dipolar pattern according to the antenna main resonant mode. This work is intended to set out the basis for manipulating the emission pattern of single molecules with self-assembled optical antennas based on colloidal nanoparticles

DNA origami assembled nanoantennas for manipulating single-molecule spectral emission

Optical nanoantennas can affect the decay rates of nearby emitters by modifying the local density of photonic states around them. In the weak-coupling limit, and according to the Fermi's Golden Rule, the emission spectrum of a dye is given by the energy of all the possible radiative transitions weighted by the probability of each of them to occur. By engineering the resonance of a nanoantenna, one can selectively enhance specific vibronic transitions of a dye molecule, thus shaping its emission spectrum. Since interactions between emitters and nanoantennas are known to be position dependent, we make here use of DNA origami to precisely place an individual dye at different positions around a gold nanorod. We show how this relative position between the nanorod and the emitter affects the emission spectrum of the latter. In particular, we observe the appearance of a second fluorescence peak whose wavelength and intensity are correlated with the fundamental plasmonic resonance of the nanorod, which we extract from its photoluminescence spectrum. This second peak results from the selective enhancement of transitions to different vibrational levels of the excitonic ground state, whose energies are in resonance with the plasmonic one. Furthermore, we argue that the drastic alteration of the fluorescence spectrum in some of our samples cannot be accounted for with Kasha's rule, which indicates that radiative and vibrational relaxation dye lifetimes can become comparable through the coupling to the gold nanorods

DNA‐mediated self‐assembly of plasmonic antennas with a single quantum dot in the hot spot

DNA self‐assembly is a powerful tool to arrange optically active components with high accuracy in a large parallel manner. A facile approach to assemble plasmonic antennas consisting of two metallic nanoparticles (40 nm) with a single colloidal quantum dot positioned at the hot spot is presented here. The design approach is based on DNA complementarity, stoichiometry, and steric hindrance principles. Since no intermediate molecules other than short DNA strands are required, the structures possess a very small gap (≈ 5 nm) which is desired to achieve high Purcell factors and plasmonic enhancement. As a proof‐of‐concept, the fluorescence emission from antennas assembled with both conventional and ultrasmooth spherical gold particles is measured. An increase in fluorescence is obtained, up to ≈30‐fold, compared to quantum dots without antenna

In situ photothermal response of single gold nanoparticles through hyperspectral imaging anti-stokes thermometry

Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task for both modeling and experimental measurements. Here, we present an 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, potentially 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.Fil: Barella, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Violi, Ianina Lucila. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Gargiulo, Julian. Ludwig Maximilians Universitat; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martínez, Luciana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Goschin, Florian. Ludwig Maximilians Universitat; AlemaniaFil: Guglielmotti, Victoria. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pallarola, Diego Andres. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schlücker, Sebastian. Universitat Essen; AlemaniaFil: Pilo Pais, Mauricio. University Of Fribourg; SuizaFil: Acuna, Guillermo P.. University Of Fribourg; SuizaFil: Maier, Stefan A.. Ludwig Maximilians Universitat; Alemania. Imperial College London; Reino UnidoFil: Cortés, Emiliano. Ludwig Maximilians Universitat; AlemaniaFil: Stefani, Fernando Daniel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentin

Metallic Nanostructures Based on Self-Assembling DNA Templates for Studying Optical Phenomena

<p>DNA origami is a novel self-assembly technique that can be used to form various </p><p>2D and 3D objects, and to position matter with nanometer accuracy. It has been </p><p>used to coordinate the placement of nanoscale objects, both organic and inorganic, to make molecular motor and walkers; and to create optically active nanostructures. In this dissertation, DNA origami templates are used to assemble plasmonic structures. Specifically, engineered Surface Enhanced Raman Scattering (SERS) substrates were fabricated. Gold nanoparticles were selectively placed on the corners of rectangular origami and subsequently enlarged via solution-based metal deposition. The resulting assemblies exhibited "hot spots" of enhanced electromagnetic field between the nanoparticles. These hot spots significantly enhanced the Raman signal from Raman molecules covalently attached to the assemblies. Control samples with only one nanoparticle per DNA template, which therefore lacked inter-particle hot spots, did not exhibit strong enhancement. Furthermore, Raman molecules were used to map out the hot spots' distribution, as the molecules are photo-damaged when experiencing a threshold electric field. This method opens up the prospect of using DNA origami to rationally engineer and assemble plasmonic structures for molecular spectroscopy.</p>Dissertatio