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

• . Keywords: near-field; plasmonics; silver nanoaggregates; single molecule; surface-enhanced Raman scattering (SERS); Introduction The resonance frequencies of collective oscillations of the electrons in the conduction band in metal nanostructures, which are called surface plasmons, fall in the optical

• spectroscopy performed in the near-field. SERS enables Raman measurements on a single molecule [3]. Vice versa, here we show that single molecules and their Raman signatures can be useful tools for probing plasmonic near-fields. The measurement of Raman signals from single molecules requires high optical field

• imaging of SERS on silver nanoaggregates has directly confirmed nanoparticle junctions to be responsible for single molecule SERS [11]. Computations show dramatic variations in near-field intensities within a few nanometers. Even sophisticated optical experiments cannot reveal these dramatic spatial

Spin relaxation in antiferromagnetic Fe–Fe dimers slowed down by anisotropic Dy^III ions

• Valeriu Mereacre,
• Frederik Klöwer,
• Yanhua Lan,
• Rodolphe Clérac,
• Juliusz A. Wolny,
• Volker Schünemann,
• Christopher E. Anson and
• Annie K. Powell

Beilstein J. Nanotechnol. 2013, 4, 807–814, doi:10.3762/bjnano.4.92

• side and ferromagnetically cooperating with each other. This gives rise to a total ground spin state which cannot be affected by external applied magnetic field. It is worth mentioning that compound 1 is a single molecule magnet. It displays an out-of-phase response to the blocking temperature 2.5 K

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

• apex can be manifold and depend crucially on the experimental setup and the sample. As a result the fluorescence emission rate can be both significantly enhanced or reduced at distances up to some 10 nm [6][8][9][10][11], and single-molecule images can show complex fluorescence patterns [3][12][13

• topography and fluorescence of complex higher level structures down to the single-molecule level. The achieved resolution allows the allocation of single molecular building blocks within these constructs. In the case of the intermediate filament desmin this enables a detailed analysis of the filament

Antiferromagnetic coupling of TbPc₂ molecules to ultrathin Ni and Co films

• David Klar,
• Svetlana Klyatskaya,
• Andrea Candini,
• Bernhard Krumme,
• Kurt Kummer,
• Philippe Ohresser,
• Valdis Corradini,
• Valentina de Renzi,
• Roberto Biagi,
• Loic Joly,
• Jean-Paul Kappler,
• Umberto del Pennino,
• Marco Affronte,
• Heiko Wende and
• Mario Ruben

Beilstein J. Nanotechnol. 2013, 4, 320–324, doi:10.3762/bjnano.4.36

• , CNRS UMP 7504, 23 Rue du Loess, 67034 Strasbourg Cedex 2, France 10.3762/bjnano.4.36 Abstract The magnetic and electronic properties of single-molecule magnets are studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. We study the magnetic coupling of ultrathin Co and Ni

• . On both substrates the TbPc2 molecules couple antiferromagnetically to the ferromagnetic films, which is possibly due to a superexchange interaction via the phthalocyanine ligand that contacts the magnetic surface. Keywords: magnetic anisotropy; magnetic coupling; single molecule magnets; X-ray

• intensively over the past few years. Single-molecule magnets (SMMs) meet the requirements because of their magnetic remanence at low temperature without the need for long-range ordering. While most of the well-known SMMs consist of several interacting metal ions [10][11][12][13], bis(phthalocyaninato) terbium

Influence of the solvent on the stability of bis(terpyridine) structures on graphite

• Daniela Künzel and
• Axel Groß

Beilstein J. Nanotechnol. 2013, 4, 269–277, doi:10.3762/bjnano.4.29

• adsorption enthalpy [2] of a single molecule and estimated values for the hydrogen bonding between the molecules, the sequence of observed structures as a function of concentration could be reproduced [2]. This sequence could also be reproduced based on adsorption energies obtained from force-field

Current–voltage characteristics of single-molecule diarylethene junctions measured with adjustable gold electrodes in solution

• Bernd M. Briechle,
• Youngsang Kim,
• Philipp Ehrenreich,
• Artur Erbe,
• Dmytro Sysoiev,
• Thomas Huhn,
• Ulrich Groth and
• Elke Scheer

Beilstein J. Nanotechnol. 2012, 3, 798–808, doi:10.3762/bjnano.3.89

• : diarylethene; mechanically controllable break-junction; molecular electronics; photoswitching; single-molecule junctions; Introduction Charge transport in single-molecule devices is actively investigated with the aim to realize functional electronic circuits [1][2][3][4], such as switches [5], transistors [4

• [30][31]. Recently, low-temperature measurements of the current–voltage characteristics of single-molecule diarylethene junctions have been reported [32]. By applying the resonant-level model, the level alignment and the coupling strength of the dominant current-carrying molecular orbital (frontier

• conductance level in both states. Naively, the π-conjugation through the entire molecule in the closed form is supposed to show higher conductance than the broken π-system. While this has been confirmed by measurements in molecular ensembles and arrays [18][21] and single-molecule junctions [5][26], the

Revealing thermal effects in the electronic transport through irradiated atomic metal point contacts

• Bastian Kopp,
• Zhiwei Yi,
• Daniel Benner,
• Fang-Qing Xie,
• Christian Obermair,
• Thomas Schimmel,
• Johannes Boneberg,
• Paul Leiderer and
• Elke Scheer

Beilstein J. Nanotechnol. 2012, 3, 703–711, doi:10.3762/bjnano.3.80

• two metallic tips both theoretically [4][5][6][7] and experimentally [4][8][9][10][11]. Furthermore the influence of the environment on the conductance of single-molecule junctions [12] has been revealed. In a next step towards molecular electronics, one would like to see such molecules exhibiting

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

• to study light-matter interaction at nanometre scale or single molecule level [32]. Different from fluorescence spectroscopy, Raman spectroscopy provides a unique fingerprint of the molecules and therefore does not require labelling of the samples. However, conventional Raman spectroscopy is an

Combining nanoscale manipulation with macroscale relocation of single quantum dots

• Francesca Paola Quacquarelli,
• Richard A. J. Woolley,
• Martin Humphry,
• Jasbiner Chauhan,
• Philip J. Moriarty and
• Ashley Cadby

Beilstein J. Nanotechnol. 2012, 3, 324–328, doi:10.3762/bjnano.3.36

• experiments on a single particle. Automated nanoparticle manipulation and imaging routines have been developed so as to facilitate the rapid assembly of specific nanoparticle arrangements. Keywords: automation; nanoscale manipulation; nanotechnology; quantum dots; single molecule spectroscopy; Introduction

• resolution comparable to the length scale of the system of interest, however, continues to present a challenge. A number of techniques have been developed to push the resolution of optical microscopy and spectroscopy to the single-molecule/particle limit. These include scanning near-field optical microscopy

• (SNOM) [1][2][3] and techniques based on adaptations of single-molecule spectroscopy [4], such as fluorescence imaging with one-nanometer accuracy (FIONA) [5], stochastic optical reconstruction microscopy (STORM) [6]. These techniques require the fluorophore under observation to be isolated by distances

Graphite, graphene on SiC, and graphene nanoribbons: Calculated images with a numerical FM-AFM

• Fabien Castanié,
• Laurent Nony,
• Sébastien Gauthier and
• Xavier Bouju

Beilstein J. Nanotechnol. 2012, 3, 301–311, doi:10.3762/bjnano.3.34

• ripples of a graphene sheet relaxed on a silicon carbide substrate, and (iii) a corrugated transition of a graphene nanoribbon supported by a SiC surface. Improvements remain to be made for the prospective study of single molecule imaging and/or manipulation processes and related physical problems, such

Dipole-driven self-organization of zwitterionic molecules on alkali halide surfaces

• Laurent Nony,
• Franck Bocquet,
• Franck Para,
• Frédéric Chérioux,
• Eric Duverger,
• Frank Palmino,
• Vincent Luzet and
• Christian Loppacher

Beilstein J. Nanotechnol. 2012, 3, 285–293, doi:10.3762/bjnano.3.32

• conformation of the molecule adsorbed on the surface, we compare the experimentally determined parameters with the possible molecular conformations (the so-called scorpion- or agraffe-like conformation obtained by numerical simulation of a single molecule in vacuum, see Figure 1). Note that the comparison

An NC-AFM and KPFM study of the adsorption of a triphenylene derivative on KBr(001)

• Antoine Hinaut,
• Adeline Pujol,
• Florian Chaumeton,
• David Martrou,
• André Gourdon and
• Sébastien Gauthier

Beilstein J. Nanotechnol. 2012, 3, 221–229, doi:10.3762/bjnano.3.25

• larger than a single molecule. A modulation with a period of ~4 nm appears along the rows. Because of the above-mentioned observation that the dark lines can cross a KBr atomic step without be perturbed, we tentatively interpret these observations as indicating that one row corresponds to a stack of

• adjacent K+ sites on nonpolar steps, as shown for truxene molecules [11]. The origin of the molecular aggregates observed in Figure 2 and Figure 3 is less clear. As indicated previously a single molecule diffuses at room temperature despite its six CN anchoring groups. A lower estimate of the distance that

• interactions to be strong enough to significantly affect the adsorption conformation of the single molecule. A tentative model of the MLh layer is shown in Figure 10. The unit cell vectors u and v have been chosen on the basis of the experimental values extracted from Figure 7b. They are given in terms of the

Transmission eigenvalue distributions in highly conductive molecular junctions

• Justin P. Bergfield,
• Joshua D. Barr and
• Charles A. Stafford

Beilstein J. Nanotechnol. 2012, 3, 40–51, doi:10.3762/bjnano.3.5

• through a quantum-scale device may be uniquely characterized by its transmission eigenvalues τn. Recently, highly conductive single-molecule junctions (SMJ) with multiple transport channels (i.e., several τn > 0) have been formed from benzene molecules between Pt electrodes. Transport through these

• ; multichannel; quantum transport; single-molecule junction; transmission eigenchannels; Introduction The number of transmission channels for a single-atom contact between two metallic electrodes is simply given by the chemical valence of the atom [1]. Recently, it was argued [2] that the number of dominant

• transmission channels in a single-molecule junction (SMJ) is determined by the degeneracy of the molecular orbital [3] closest to the metal Fermi level. In this article, we focus on ensembles of highly conductive Pt–benzene–Pt junctions [4] in which the lead and molecule are in direct contact. Going beyond the

When “small” terms matter: Coupled interference features in the transport properties of cross-conjugated molecules

• Gemma C. Solomon,
• Justin P. Bergfield,
• Charles A. Stafford and
• Mark A. Ratner

Beilstein J. Nanotechnol. 2011, 2, 862–871, doi:10.3762/bjnano.2.95

• Department of Chemistry, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA 10.3762/bjnano.2.95 Abstract Quantum interference effects offer opportunities to tune the electronic and thermoelectric response of a quantum-scale device over orders of magnitude. Here we focus on single-molecule

• . Here we investigate the effect of these small terms using different Hamiltonian models with Hückel, gDFTB and many-body theory to calculate the transport through several single-molecule junctions, finding that terms that are generally thought to only slightly perturb the transport instead produce

• electronics; quantum interference; thermoelectrics; topology; Introduction Destructive interference effects, such as nodes in the transmission function, are a signature of coherence and offer a possible avenue for tuning the transport properties of single-molecule junctions. While not present in all systems

Direct monitoring of opto-mechanical switching of self-assembled monolayer films containing the azobenzene group

• Einat Tirosh,
• Enrico Benassi,
• Silvio Pipolo,
• Marcel Mayor,
• Michal Valášek,
• Veronica Frydman,
• Stefano Corni and
• Sidney R. Cohen

Beilstein J. Nanotechnol. 2011, 2, 834–844, doi:10.3762/bjnano.2.93

• , which is governed by several effects including the stiffness of the molecular bond itself, as well as steric effects, electronic coupling, and film structure. Single-molecule force microscopy was used to monitor the mechanical and structural changes in the cis↔trans transition of individual azo

• -assemble into monomolecular layers (self-assembled monolayers, SAMs) provides an additional nanometer-scale mechanical system, combining the advantages of single-molecule properties with the coherence and template capabilities of macroscopic structures. These films enable such applications as sensors, and

• The investigation of the relative stiffness of the azobenzene SAM at the molecular level was also approached by computational modeling. The problem was modeled within two different schemes, one based on a quantum mechanical (QM) description of the single molecule, and the other on classical molecular

Effect of the environment on the electrical conductance of the single benzene-1,4-diamine molecule junction

• Shigeto Nakashima,
• Yuuta Takahashi and
• Manabu Kiguchi

Beilstein J. Nanotechnol. 2011, 2, 755–759, doi:10.3762/bjnano.2.83

• coverage of the BDA molecule at metal electrodes and atomic and molecular motion of the single-molecule junction. Keywords: benzene-1,4-diamine; electric conductance; single-molecule junction; solvent; Introduction The electron transport properties through a single molecule bridging metal electrodes

• (single-molecule junction) have attracted much attention toward the realization of molecular scale electronics [1][2]. Electrical conductance of the single-molecule junction was investigated by means of mechanically controllable break junction (MCBJ), scanning tunneling microscope (STM), and other

• techniques. In the simple tunneling model, the transmission (T(E)) of the single-molecule junction can be represented by where t, ρ, Crk and εk are the hopping integral between the metal and molecular orbitals (MO), the local density of states (LDOS) of the metals at the Fermi level (EF), the kth MO

Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

• Mikkel Strange and
• Kristian S. Thygesen

Beilstein J. Nanotechnol. 2011, 2, 746–754, doi:10.3762/bjnano.2.82

• electrostatic shift corresponding to the single-molecule limit. We find that the electrostatic energy shift when going from a 4 × 4 supercell to the single-molecule limit is indeed significant with a value around 1 eV. Transport calculations The transmission functions of the C2-, C4- and C6-alkanediamine

• results for comparison. The dashed lines show the best fits to the exponential form Gn = Gcexp(−βn). The values for β and Gc corresponding to the single-molecule limit (η = 0) and 4 × 4 Au atoms per molecule (η = 1/16) are reported in Table 3 together with the experimental values. We note that the contact

• = 2, n = 4 and n = 6 at a coverage of η = 1/16. Calculated conductance plotted as a function of the molecular length for a coverage corresponding to 4 × 4 Au atoms per molecule (η = 1/16) and extrapolated to the single-molecule limit (η = 0). Calculated HOMO and HOMO–2 energies aligned to the vacuum

Charge transport in a zinc–porphyrin single-molecule junction

• Mickael L. Perrin,
• Christian A. Martin,
• Ferry Prins,
• Ahson J. Shaikh,
• Rienk Eelkema,
• Jan H. van Esch,
• Jan M. van Ruitenbeek,
• Herre S. J. van der Zant and
• Diana Dulić

Beilstein J. Nanotechnol. 2011, 2, 714–719, doi:10.3762/bjnano.2.77

• allows us to characterize the transport in a molecular junction in detail. This complex molecule can form different junction configurations, having an observable effect on the trace histograms and the current–voltage (I(V)) measurements. Both methods show that multiple, stable single-molecule junction

• interpreted with care, and that the combination with I(V) spectroscopy represents an essential tool for a more detailed characterization of the charge transport in a single molecule. Keywords: mechanically controllable break junction; molecular conformation; molecular electronics; porphyrin; single-molecule

• [15][16][17]. Multiple conductance peaks are often attributed to the formation of multiple molecular bridges connected in parallel [15][24]. The strength of the molecule–metal chemical bond is considered to play a central role in determining the single-molecule conductance values. Our results on the

An MCBJ case study: The influence of π-conjugation on the single-molecule conductance at a solid/liquid interface

• Wenjing Hong,
• Hennie Valkenier,
• Gábor Mészáros,
• David Zsolt Manrique,
• Artem Mishchenko,
• Alexander Putz,
• Pavel Moreno García,
• Colin J. Lambert,
• Jan C. Hummelen and
• Thomas Wandlowski

Beilstein J. Nanotechnol. 2011, 2, 699–713, doi:10.3762/bjnano.2.76

• down to 10 fA. We report single-molecule conductance measurements of an anthracene-based linearly conjugated molecule (AC), of an anthraquinone-based cross-conjugated molecule (AQ), and of a dihydroanthracene-based molecule (AH) with a broken conjugation. The quantitative analysis of complementary

• current–distance and current–voltage measurements revealed details of the influence of π-conjugation on the single-molecule conductance. Keywords: anthraquinone; π-conjugation; mechanically controlled break junction; single-molecule conductance; Introduction Molecular electronics has expanded

• junctions, and has attracted great interest in organic synthesis [19][20], conductance measurements [1][3][8][9][10][16][21][22][23] as well as in theoretical calculations [1][24][25]. In particular, single-molecule conductance measurements provide direct access to unravel the influence of π-conjugation on

Interaction of spin and vibrations in transport through single-molecule magnets

• Falk May,
• Maarten R. Wegewijs and
• Walter Hofstetter

Beilstein J. Nanotechnol. 2011, 2, 693–698, doi:10.3762/bjnano.2.75

• Grünberg Institut and JARA - Fundamentals of Information Technology, Forschungszentrum Jülich, 52425 Jülich, Germany 10.3762/bjnano.2.75 Abstract We study electron transport through a single-molecule magnet (SMM) and the interplay of its anisotropic spin with quantized vibrational distortions of the

• arises for transport through magnetic atoms embedded in a molecular network on an insulating surface in an STM setup [4][5]. Such systems, which for simplicity we shall refer to as single-molecule magnets (SMM), constitute a single, large spin-moment with spin-anisotropy. The interplay with quantum

• , where similar spin-vibration effects as studied here could occur. Conclusion We have studied the interplay of spin and vibration on the conductance through a single-molecule magnet. Whereas longitudinal coupling to the vibration increases the zero-field splitting and suppresses the quantum spin

Transport through molecular junctions

• Jan M. van Ruitenbeek

Beilstein J. Nanotechnol. 2011, 2, 691–692, doi:10.3762/bjnano.2.74

• in nanotechnology. Several groups have recently demonstrated, for a limited set of molecules, clear single-molecule characteristics and fair agreement with computations. Now that attaching leads to individual molecules has been demonstrated we naturally enter into the next exciting phase of the

• (vibrons). This coupling is predicted to influence transport in dramatic ways as it may destroy the coherence of charge carriers on the molecules and can lead to strong nonequilibrium effects. Many exciting predictions have been discussed in the recent literature showing unique features of single-molecule

• problem and help build confidence in our interpretations. Apart from direct conductance measurements, one now measures properties such as thermopower, shot noise, Raman scattering, photo-induced switching, and gate-induced level shifts, all at the single-molecule level. Moreover, by systematic variation

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

• commonly performed in homogenous media, effects at the interface boundaries can be neglected. Nevertheless, the combination of such assays with single-molecule manipulation techniques such as atomic force microscopy (AFM) requires a detailed understanding of the influence of interfaces on dipolar coupling

• fluorescence resonance energy transfer (FRET) [1] between individual molecules, open up fascinating means to explore inter- or intramolecular distances [2], orientation [3], affinity and binding dynamics at the single-molecule level [4]. The combination of fluorescence with single-molecule manipulation

• profound knowledge of these effects plays a key role in the acquisition and interpretation of data obtained with combined single-molecule mechano-optical setups. Results and Discussion The distance dependence of the electrodynamical coupling between a single dipole emitter located near an air–glass

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

• single-molecule sensitivity. In the presented experiments, single stranded adenine and uracil homopolymers were immobilized on different kinds of substrates (mica and gold nanoplates) and TERS experiments were conducted, which demonstrated the reproducibility of the technique. To elucidate the signal

• first sequencing methods were published in 1977 by Maxam and Gilbert [1], and Sanger et al. [2]. Since then the sequencing technology has been refined and automated, and current advances show a tendency towards single-molecule sequencing, which eventually results in the development of sequencing systems

Terthiophene on Au(111): A scanning tunneling microscopy and spectroscopy study

• Berndt Koslowski,
• Anna Tschetschetkin,
• Norbert Maurer,
• Elena Mena-Osteritz,
• Peter Bäuerle and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 561–568, doi:10.3762/bjnano.2.60

• consequence, the information on detailed adsorption geometries of a single molecule and on the morphology of extended molecular structures, as well as insight into the electronic structure of molecules on metal surfaces and their dynamic properties are of fundamental interest. All these basic issues can be

• addressed by scanning tunneling microscopy (STM) on a single-molecule scale. Additionally, quantum chemical properties of a thiophene molecule acting as a single-molecular wire have been investigated [8]. In that specific work, however, the molecule was just weakly coupled to the metal through a thin

• the interaction of molecules with the substrate on a single-molecule level. Specifically, the topographic and morphological properties of the molecules as well as of their arrays were studied by STM and the corresponding electronic properties by scanning tunneling spectroscopy (STS), both at low

Self-organizing bioinspired oligothiophene–oligopeptide hybrids

• Alexey K. Shaytan,
• Eva-Kathrin Schillinger,
• Elena Mena-Osteritz,
• Sylvia Schmid,
• Pavel G. Khalatur,
• Peter Bäuerle and
• Alexei R. Khokhlov

Beilstein J. Nanotechnol. 2011, 2, 525–544, doi:10.3762/bjnano.2.57

• are needed to complete one loop of the helical structure resulting in an experimental pitch length of 20 ± 1 nm (see above). The length of a single molecule of 1' amounts to 10 nm, whereas the length of a dimer of 6' is approximately 12 nm. Thus, the greater pitch length of 6' (25 ± 2 nm) fits very