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1.
Chemistry ; 18(29): 8925-8, 2012 Jul 16.
Artículo en Inglés | MEDLINE | ID: mdl-22706791

RESUMEN

The future's wheel: A new class of wheels, based on subphthalocyanine fragments, for future incorporation in functional nanovehicles is reported (see figure). The syntheses of a symmetric wheel, a nitrogen-tagged wheel, and their ethynyl-bridged homodimers are presented. Theoretical calculations and STM imaging demonstrate the advantage of a bowl-shaped structure and the efficiency of the tag for STM imaging.


Asunto(s)
Boro/química , Indoles/química , Indoles/síntesis química , Compuestos de Boro , Isoindoles , Microscopía de Túnel de Rastreo , Modelos Moleculares , Estructura Molecular
2.
Chemphyschem ; 11(16): 3522-8, 2010 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-20872393

RESUMEN

The adsorption of individual [11]anthrahelicene molecules and their self-assembly into monolayer islands on an InSb(001) c(8×2) reconstructed surface is studied with low-temperature scanning probe microscopy. A racemic mixture is deposited on atomically flat terraces of InSb at room temperature. At lower coverage, the molecules tend to decorate atomic step edges of the substrate. At higher coverage, [11]anthrahelicene molecules form 2D islands. A quasi-hexagonal ordering of molecules within the layer is identified. Furthermore, it is shown that molecules adsorb with the helical axis almost perpendicular to the substrate. Interference between tunneling through the molecular layer and directly through space is reported. Finally, experimental results are compared to those of theoretical calculations.

3.
Nat Commun ; 6: 7397, 2015 Jul 06.
Artículo en Inglés | MEDLINE | ID: mdl-26145188

RESUMEN

Molecular-scale electronics is mainly concerned by understanding charge transport through individual molecules. A key issue here is the charge transport capability through a single--typically linear--molecule, characterized by the current decay with increasing length. To improve the conductance of individual polymers, molecular design often either involves the use of rigid ribbon/ladder-type structures, thereby sacrificing for flexibility of the molecular wire, or a zero band gap, typically associated with chemical instability. Here we show that a conjugated polymer composed of alternating donor and acceptor repeat units, synthesized directly by an on-surface polymerization, exhibits a very high conductance while maintaining both its flexible structure and a finite band gap. Importantly, electronic delocalization along the wire does not seem to be necessary as proven by spatial mapping of the electronic states along individual molecular wires. Our approach should facilitate the realization of flexible 'soft' molecular-scale circuitry, for example, on bendable substrates.

5.
Nat Nanotechnol ; 7(11): 713-7, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23064554

RESUMEN

Graphene nanoribbons could potentially be used to create molecular wires with tailored conductance properties. However, understanding charge transport through a single molecule requires length-dependent conductance measurements and a systematic variation of the electrode potentials relative to the electronic states of the molecule. Here, we show that the conductance properties of a single molecule can be correlated with its electronic states. Using a scanning tunnelling microscope, the electronic structure of a long and narrow graphene nanoribbon, which is adsorbed on a Au(111) surface, is spatially mapped and its conductance then measured by lifting the molecule off the surface with the tip of the microscope. The tunnelling decay length is measured over a wide range of bias voltages, from the localized Tamm states over the gap up to the delocalized occupied and unoccupied electronic states of the nanoribbon. We also show how the conductance depends on the precise atomic structure and bending of the molecule in the junction, illustrating the importance of the edge states and a planar geometry.


Asunto(s)
Grafito/química , Nanotubos de Carbono/química , Conductividad Eléctrica , Electrones , Modelos Moleculares , Nanotubos de Carbono/ultraestructura , Propiedades de Superficie
6.
J Phys Condens Matter ; 24(9): 095011, 2012 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-22329961

RESUMEN

Atomic-scale Boolean logic gates (LGs) with two inputs and one output (i.e. OR, NOR, AND, NAND) were designed on a Si(100)-(2 × 1)-H surface and connected to the macroscopic scale by metallic nano-pads physisorbed on the Si(100)-(2 × 1)-H surface. The logic inputs are provided by saturating and unsaturating two surface Si dangling bonds, which can, for example, be achieved by adding and extracting two hydrogen atoms per input. Quantum circuit design rules together with semi-empirical elastic-scattering quantum chemistry transport calculations were used to determine the output current intensity of the proposed switches and LGs when they are interconnected to the metallic nano-pads by surface atomic-scale wires. Our calculations demonstrate that the proposed devices can reach ON/OFF ratios of up to 2000 for a running current in the 10 µA range.


Asunto(s)
Hidrógeno/química , Lógica , Silicio/química , Modelos Moleculares , Conformación Molecular , Propiedades de Superficie
7.
J Phys Condens Matter ; 24(40): 404001, 2012 Oct 10.
Artículo en Inglés | MEDLINE | ID: mdl-22968915

RESUMEN

A new class of double-wheel molecules is manipulated on a Au(111) surface by the tip of a scanning tunneling microscope (STM) at low temperature. The double-wheel molecule consists of two subphthalocyanine wheels connected by a central rotation carbon axis. Each of the subphthalocyanine wheels has a nitrogen tag to monitor its intramolecular rolling during an STM manipulation sequence. The position of the tag can be followed by STM, allowing us to distinguish between the different lateral movements of the molecule on the surface when manipulated by the STM tip.


Asunto(s)
Oro/química , Indoles/química , Micromanipulación/métodos , Microscopía de Túnel de Rastreo/métodos , Nanopartículas/química , Nanopartículas/ultraestructura , Isoindoles , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Tamaño de la Partícula , Propiedades de Superficie
8.
ACS Nano ; 5(2): 1436-40, 2011 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-21291281

RESUMEN

Quantum states of a trinaphthylene molecule were manipulated by putting its naphthyl branches in contact with single Au atoms. One Au atom carries 1-bit of classical information input that is converted into quantum information throughout the molecule. The Au-trinaphthylene electronic interactions give rise to measurable energy shifts of the molecular electronic states demonstrating a NOR logic gate functionality. The NOR truth table of the single molecule logic gate was characterized by means of scanning tunnelling spectroscopy.

9.
Nano Lett ; 9(1): 144-7, 2009 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19090685

RESUMEN

Decoupling the electronic properties of a molecule from a substrate is of crucial importance for the development of single-molecule electronics. This is achieved here by adsorbing pentacene molecules at low temperature on a hydrogenated Si(100) surface (12 K). The low temperature (5 K) scanning tunneling microscope (STM) topography of the single pentacene molecule at the energy of the highest occupied molecular orbital (HOMO) tunnel resonance clearly resembles the native HOMO of the free molecule. The negligible electronic coupling between the molecule and the substrate is confirmed by theoretical STM topography and diffusion barrier energy calculations.


Asunto(s)
Electroquímica/métodos , Aumento de la Imagen/métodos , Microscopía de Túnel de Rastreo/métodos , Técnicas de Sonda Molecular , Nanoestructuras/química , Nanoestructuras/ultraestructura , Nanotecnología/métodos , Ensayo de Materiales/métodos , Tamaño de la Partícula , Semiconductores
10.
Science ; 323(5918): 1193-7, 2009 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-19251624

RESUMEN

The development of electronic devices at the single-molecule scale requires detailed understanding of charge transport through individual molecular wires. To characterize the electrical conductance, it is necessary to vary the length of a single molecular wire, contacted to two electrodes, in a controlled way. Such studies usually determine the conductance of a certain molecular species with one specific length. We measure the conductance and mechanical characteristics of a single polyfluorene wire by pulling it up from a Au(111) surface with the tip of a scanning tunneling microscope, thus continuously changing its length up to more than 20 nanometers. The conductance curves show not only an exponential decay but also characteristic oscillations as one molecular unit after another is detached from the surface during stretching.

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