Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

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Plasmonics: Fundamentals and Applications

We demonstrate logic circuits with field-effect transistors based on single carbon nanotubes. Our device layout features local gates that provide excellent capacitive coupling between the gate and nanotube, enabling strong electrostatic doping of the nanotube from p-doping to n-doping and the study of the nonconventional long-range screening of charge along the one-dimensional nanotubes. The transistors show favorable device characteristics such as high gain (>10), a large on-off ratio (>10(5)), and room-temperature operation. Importantly, the local-gate layout allows for integration of multiple devices on a single chip. Indeed, we demonstrate one-, two-, and three-transistor circuits that exhibit a range of digital logic operations, such as an inverter, a logic NOR, a static random-access memory cell, and an ac ring oscillator.

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Logic circuits with carbon nanotube transistors

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

Elastic scattering measurements show that isolated nanometric holes in optically thin Au films exhibit a localized surface plasmon resonance in the red to near-infrared region. The hole plasmon red shifts with increasing hole diameter or increasing refractive index of the surrounding medium, analogous to a dipolar particle plasmon. A pronounced blue shift is observed when the distance between holes is decreased, indicating an enhanced coupling between holes mediated by surface plasmon polaritons of the intervening flat film surface.

Optical Spectroscopy of Nanometric Holes in Thin Gold Films

We present a sensitive and easily regenerated nano-optical sensor based on immobilization of avidin-coated colloidal gold particles on a biotin-modified planar lipid bilayer supported on the walls of a quartz cuvette. The so constructed sensing template, being specific for capturing of biotinylated biomacromolecules, is analyzed using optical spectroscopy combined with Mie theory calculations for quantification of the colorimetric changes induced by biorecognition events in the interfacial region of the particles. By further utilizing de Feiter's formalism, which correlates changes in effective refractive index and thickness with adsorbed mass, a good agreement between the Mie theory and experiments is demonstrated. Furthermore, the template is proven sensitive enough to follow the hybridization kinetics of 15-mer fully complementary DNA strands without the introduction of labels or secondary signal amplification.

Surface-Based Gold-Nanoparticle Sensor for Specific and Quantitative DNA Hybridization Detection

A single-electron tunneling transistor was made by capturing a chemically synthesized gold cluster between two gold electrodes. The transistor had a quasiperiodic modulation of the current–voltage characteristics as a function of a gate voltage applied to an oxidized aluminum electrode at 4.2 K. The Coulomb blockade voltage for this device was 50 mV observed at 4.2 K and room temperature. The maximum observed blockade voltage was 200 mV for devices without gate.

A self-assembled single-electron tunneling transistor

Single electron tunneling devices were made by combiningstandard electron beam lithography and the self-assembly ofchemically synthesized gold clusters. These clusters, withdiameters from 2 to 5 nm, were captured in a 5–10 nm gapbetween two gold electrodes. The gold particles as well as theelectrodes were covered with self-assembled monolayers (SAM)of organic molecules which served as tunnel barriers.Operating devices show a suppressed current due to the Coulombblockade of tunneling at room temperature. When cooled to4.2 K, a Coulomb staircase was observed. By applying a voltageto an oxidized aluminum gate beneath the electrodes and thetrapped gold cluster the current voltage characteristics weremodulated. Anomalous effects are observed such as constantcurrent plateaus whose positions are gate-voltage dependent.An electrodeposition method for gold has been used tofabricate gaps between electrodes smaller than 2 nm. A self-assembled monolayer was used successfully on the electrodes inorder to prevent the gold atoms from migrating on the surfacebetween the electrodes and thereby short-circuiting thejunction. The conductance of such a tunnel junction has beenmeasured and compared to the theory with good agreement. Fromthis comparison the capacitance of the junction was estimated,and we could use that value to calculate a rough estimation ofthe distance between the electrodes.

Nanofabrication of Self-assembled Molecular-scale Electronics

Single-electron tunneling devices were made by self-assembly of colloidal ligand-stabilized gold clusters in the small gap between two gold electrodes, which were covered with a self-assembled monolayer of 1,8-octanedithiol. With this method we control the size of the active part of the device which is smaller than the traditional lithographic resolution, with chemical methods and use self-positioning of the particle by weak forces between the substrate and the particle. The current voltage characteristic of the devices exhibit a Coulomb staircase and gate effect at 4.2 K, and a prominent Coulomb blockade at room temperature.

Linda Olofsson

Papers

Optical Spectroscopy of Nanometric Holes in Thin Gold Films

Surface-Based Gold-Nanoparticle Sensor for Specific and Quantitative DNA Hybridization Detection

A self-assembled single-electron tunneling transistor

Nanofabrication of Self-assembled Molecular-scale Electronics

A Self-Assembled Single-Electron Tunneling Device