Probing the plasmonic near-field by one- and two-photon excited surface enhanced Raman scattering

• Katrin Kneipp and
• Harald Kneipp

Beilstein J. Nanotechnol. 2013, 4, 834–842, doi:10.3762/bjnano.4.94

• hottest spots can be enhanced by three orders of magnitudes. Nanoaggregates of 100 nm dimensions provide one hot spot on this highest enhancement level where the enhancement is confined within less than 1nm dimension. The near-field enhancement in the hottest spots increases with decreasing photon energy

• molecules reside exclusively in the hottest hot spots provided in the near-field. We employ surface-enhanced pumped anti-Stokes Raman scattering (SEPARS) and one- and two-photon excited surface enhanced Raman (SERS) and hyper Raman (SEHRS) signals, respectively for estimating the maximum field enhancement

• provide extremely high near-field enhancement levels, which are suitable for single-molecule SERS under non-resonant conditions. The silver structures were prepared by a standard citrate reduction procedure [37]. In this study, SERS experiments are carried out in solutions of silver nanoaggregates under

Controlling the near-field excitation of nano-antennas with phase-change materials

• Tsung Sheng Kao,
• Yi Guo Chen and
• Ming Hui Hong

Beilstein J. Nanotechnol. 2013, 4, 632–637, doi:10.3762/bjnano.4.70

• one at a corresponding gap g of 12, 14, 14, 16, and 20 nm, respectively. These different choices in the lengths and gaps of antennas are made in order to have a comparable field enhancement on one excited nano-antenna, whereas the others remain completely unexcited. The width w and thickness h of all

• of the antenna. By adjusting the proportion value m of crystallized phase-change molecules, the GST crystalline level with different dielectric properties is gradually changed and the excitation wavelength at the field enhancement peak of each nano-antenna can be tuned as the spectral shift shown in

• hybridized plasmonic nanosystem. Figure 4a and b show that the arrays of nano-antennas with the same geometric parameters are placed on a GST phase-change thin film, but spatially separated with different centre-to-centre spacing d, while Figure 4c and d show that the calculated near-field field enhancement

k-space imaging of the eigenmodes of sharp gold tapers for scanning near-field optical microscopy

• Martin Esmann,
• Simon F. Becker,
• Bernard B. da Cunha,
• Jens H. Brauer,
• Ralf Vogelgesang,
• Petra Groß and
• Christoph Lienau

Beilstein J. Nanotechnol. 2013, 4, 603–610, doi:10.3762/bjnano.4.67

• ion beam milling of the grating couplers. Field enhancement at the taper apex was much more pronounced for the tip shown in panel a). Propagation constants kz of the three lowest eigenmodes of an infinitely long gold wire as a function of wire radius R. Displayed are the real (solid blue lines) and

Mapping of plasmonic resonances in nanotriangles

• Simon Dickreuter,
• Julia Gleixner,
• Andreas Kolloch,
• Johannes Boneberg,
• Elke Scheer and
• Paul Leiderer

Beilstein J. Nanotechnol. 2013, 4, 588–602, doi:10.3762/bjnano.4.66

• a wavelength of 800 nm, which excited higher order plasmon modes in these triangles. The ablation distribution as well as the local melting of small parts of the nanostructures reflect the regions of large near-field enhancement. The observed patterns are reproduced in great detail by FDTD

• for the field enhancement are typically somewhat smaller than the calculated ones. The results demonstrate the caveats for FDTD simulations and the potential and the limitations of “near field photography” by local ablation and melting for the mapping of complex plasmon fields and their applications

• . Keywords: ablation; FDTD simulations; field enhancement; nanotriangles; near field; surface plasmons; Introduction Considering classical optics, light cannot be focused to a scale much smaller than half its wavelength. This phenomenon, commonly known as “diffraction limit”, represents a major obstacle in

3D nano-structures for laser nano-manipulation

• Gediminas Seniutinas,
• Lorenzo Rosa,
• Gediminas Gervinskas,
• Etienne Brasselet and
• Saulius Juodkazis

Beilstein J. Nanotechnol. 2013, 4, 534–541, doi:10.3762/bjnano.4.62

• trapping effect. The light intensity distributions in the top-illuminated substrates reveals the configuration of the trapping field: while the field enhancement is not very strong (less than 10) in water, as shown in Figure 4a and Figure 4b, we see the formation of large spots hovering above the nano-well

Apertureless scanning near-field optical microscopy of sparsely labeled tobacco mosaic viruses and the intermediate filament desmin

• Alexander Harder,
• Mareike Dieding,
• Volker Walhorn,
• Sven Degenhard,
• Andreas Brodehl,
• Christina Wege,
• Hendrik Milting and
• Dario Anselmetti

Beilstein J. Nanotechnol. 2013, 4, 510–516, doi:10.3762/bjnano.4.60

• topography and fluorescence imaging. Commonly, among the various (apertureless) SNOM approaches metallic or metallized probes are used. Here, we report on our custom-built aSNOM setup, which uses commercially available monolithic silicon AFM cantilevers. The field enhancement confined to the tip apex

• , apertureless SNOM probes appear favorable [3][4][5][6][7]. Commonly, metallic and metallized probes expose a strong field enhancement and dipolar coupling between fluorophore and tip, which result in a remarkable increase of the observable fluorescence emission. However, the interaction between dye and tip

• ]. Silicon probes expose only a moderate field enhancement and the dipolar coupling between probe and dye is less pronounced [4]. Even though, silicon tips can quench the fluorescence emission at close proximity [14]. Moreover, the elaborate probe design of custom-made tips demand complex fabrication

Femtosecond-resolved ablation dynamics of Si in the near field of a small dielectric particle

• Paul Kühler,
• Daniel Puerto,
• Mario Mosbacher,
• Paul Leiderer,
• Francisco Javier Garcia de Abajo,
• Jan Siegel and
• Javier Solis

Beilstein J. Nanotechnol. 2013, 4, 501–509, doi:10.3762/bjnano.4.59

• after excitation. Keywords: crystalline Si; fs-resolved microscopy; laser ablation; near-field enhancement; ultrafast dynamics; Introduction The term “near field optics” is used to describe the phenomena associated to non-propagating and highly localized electromagnetic fields and their interaction

• consequence, the electric field can be enhanced by several orders of magnitude which is particularly useful for exciting optical non-linearities (Kerr, Raman, … [3][4]) in the vicinity of metal particles. For dielectric particles, Mie scattering can similarly lead to strong field enhancement effects [5][6

• which allows us to conclude that our calculation of the maximum field enhancement expected (≈40) on the Si substrate for the particle size and irradiation geometry considered is quite accurate. When a pulsed laser of moderate fluence illuminates the surface, the local fluence close to the particle can

A nano-graphite cold cathode for an energy-efficient cathodoluminescent light source

• Alexander N. Obraztsov,
• Victor I. Kleshch and
• Elena A. Smolnikova

Beilstein J. Nanotechnol. 2013, 4, 493–500, doi:10.3762/bjnano.4.58

• , radius of emission area r, L is the distance between two emission sites which is supposed to be in the same order as the height h, and β is the so-called field enhancement factor which may be estimated as the aspect ratio r/h. Thus, the expected range for the averaged emission current density of a

Near-field effects and energy transfer in hybrid metal-oxide nanostructures

• Ulrich Herr,
• Barat Achinuq,
• Cahit Benel,
• Giorgos Papageorgiou,
• Manuel Goncalves,
• Johannes Boneberg,
• Paul Leiderer,
• Paul Ziemann,
• Peter Marek and
• Horst Hahn

Beilstein J. Nanotechnol. 2013, 4, 306–317, doi:10.3762/bjnano.4.34

• applications such as the generation of hydrogen by photocatalytic splitting of water molecules. We use high-resolution techniques such as confocal fluorescence microscopy for the investigation of energy-transfer processes. The experiments are supported by simulations of the electromagnetic field enhancement in

• the vicinity of well-defined nanoantennas. The results show that the presence of the nanoparticle layer can modify the field enhancement significantly. In addition, we find that the fluorescent intensities observed in the experiments are affected by agglomeration of the nanoparticles. In order to

• Eu fluorescence can be suppressed by covering the nanoantennas with a 10 nm thick SiOx layer. Keywords: confocal microscopy; energy transfer; field enhancement; light harvesting; luminescence; nano-antennas; nanosphere lithography; nanostructures; plasmonics; simulation; TiO2 nanoparticles

Plasmonic oligomers in cylindrical vector light beams

• Mario Hentschel,
• Jens Dorfmüller,
• Harald Giessen,
• Sebastian Jäger,
• Andreas M. Kern,
• Kai Braun,
• Dai Zhang and
• Alfred J. Meixner

Beilstein J. Nanotechnol. 2013, 4, 57–65, doi:10.3762/bjnano.4.6

• a plasmonic oligomer under radial and azimuthal excitation. The upper row of Figure 9 depicts the near-field intensity distribution within the symmetry plane of the cluster; the lower row shows a 3-D plot of the same data. In both excitation geometries we observe a strong near-field enhancement

• . The field enhancement for azimuthal excitation is significantly stronger as it perfectly matches the nanoscale gaps at the circumference of the cluster. The field is mostly concentrated within these gaps, whereas nearly no field localization is associated with the center particle. This behavior is in

Assessing the plasmonics of gold nano-triangles with higher order laser modes

• Laura E. Hennemann,
• Andreas Kolloch,
• Andreas Kern,
• Josip Mihaljevic,
• Johannes Boneberg,
• Paul Leiderer,
• Alfred J. Meixner and
• Dai Zhang

Beilstein J. Nanotechnol. 2012, 3, 674–683, doi:10.3762/bjnano.3.77

• plasmonic excitability at the centre of the nano-triangle by means of a plasmonic centre mode and additional excitability at the triangle edges by an edge mode [5]. These eigenmodes of plasmonic enhancement are dubbed according to the spots of strong field enhancement. This near field radiates into the far

The morphology of silver nanoparticles prepared by enzyme-induced reduction

• Henrik Schneidewind,
• Thomas Schüler,
• Katharina K. Strelau,
• Karina Weber,
• Dana Cialla,
• Marco Diegel,
• Roland Mattheis,
• Andreas Berger,
• Robert Möller and
• Jürgen Popp

Beilstein J. Nanotechnol. 2012, 3, 404–414, doi:10.3762/bjnano.3.47

• for large particle sizes above 0.5 µm. These special nanostructures, composed of different intertwined plates, show sharp and spiky features, thus comprising areas which are characterized by a strong electromagnetic-field enhancement due to the interaction of light with plasmonically active structures

Distance dependence of near-field fluorescence enhancement and quenching of single quantum dots

• Volker Walhorn,
• Jan Paskarbeit,
• Heinrich Gotthard Frey,
• Alexander Harder and
• Dario Anselmetti

Beilstein J. Nanotechnol. 2011, 2, 645–652, doi:10.3762/bjnano.2.68

• experimental data. Moreover, we revealed and quantified the influence of interfering processes such as field enhancement confined at interface boundaries, mirror dipoles and (resonant) dipolar coupling. Keywords: AFM; fluorescence energy transfer; multiple multipole simulation; quantum dots; Introduction

• dipolar coupling between the incident light and the gold tip leads to a field enhancement confined at the tip apex. Secondly, we have to consider the dipolar coupling between the fluorophore and the tip, which either leads to fluorescence enhancement due to resonant coupling or fluorescence quenching as a

• evanescent field and the AFM cantilever tip (Figure 3a). At small tip distances a strong field enhancement is observed that rapidly decreases with growing gap size. This strong distance dependence is characteristic of dipole–dipole coupling effects. Upon further retraction from the surface Γexc exhibits a

Distinction of nucleobases – a tip-enhanced Raman approach

• Regina Treffer,
• Xiumei Lin,
• Elena Bailo,
• Tanja Deckert-Gaudig and
• Volker Deckert

Beilstein J. Nanotechnol. 2011, 2, 628–637, doi:10.3762/bjnano.2.66

• the respective nucleobases is possible, and this eventually led to successful TERS measurements on a single RNA strand of a cytosine homopolymer [19]. The dependency of the electromagnetic field enhancement of TERS on the composition of the substrate, amongst other parameters, was shown in three

• -dimensional finite-difference time domain (3D-FDTD) simulations [20]. A metal substrate such as gold provides an additional field enhancement as it produces a large electromagnetic (EM) coupling with the tip, which is often called a “gap mode”. In contrast, dielectric materials cannot couple as effectively

• strands. First of all a reproducible immobilization of DNA and RNA strands on different substrates could be achieved. The successful TERS measurement on a uracil homopolymer immobilized on a gold nanoplate substrate is of particular interest regarding the additional field enhancement and field confinement

Towards multiple readout application of plasmonic arrays

• Dana Cialla,
• Karina Weber,
• René Böhme,
• Uwe Hübner,
• Henrik Schneidewind,
• Matthias Zeisberger,
• Roland Mattheis,
• Robert Möller and
• Jürgen Popp

Beilstein J. Nanotechnol. 2011, 2, 501–508, doi:10.3762/bjnano.2.54

• achieved for molecules directly adsorbed on the metallic surface due to the strong field enhancement, but where, however, the fluorescence is quenched most efficiently. Furthermore, the fluorescence can be enhanced efficiently by careful adjustment of the optical behavior of the plasmonic arrays. In this

• sections by applying SERS is based on the strong plasmonic field enhancement at rough metallic surfaces. Since SERS combines the unique fingerprint specificity of Raman with trace level sensitivity, it is a very active topic in (bio)analytics [4][5][6][7][8][9][10][11][12][13]. In order to exploit the

• evanescent decay on the metal surface. This strong field enhancement by the evanescent field can be employed for an effective enhancement of the weak Raman cross section (surface-enhanced Raman spectroscopy – SERS) [25] and also of the fluorescence signal (surface-enhanced fluorescence – SEF) [26]. However

Plasmonic nanostructures fabricated using nanosphere-lithography, soft-lithography and plasma etching

• Manuel R. Gonçalves,
• Taron Makaryan,
• Fabian Enderle,
• Stefan Wiedemann,
• Alfred Plettl,
• Othmar Marti and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 448–458, doi:10.3762/bjnano.2.49

• can be utilized in experiments requiring light confinement. Keywords: nanosphere-lithography; near-field enhancement; plasma etching; soft-lithography; surface plasmons; Introduction Classical electromagnetic theories describing optical transmission through small apertures [1][2] do not take into