Gold Nanoparticle Networks Research Articles

Vapor Sensitivity of Networked Gold Nanoparticle Chemiresistors: Importance of Flexibility and Resistivity of the Interlinkage

In this study we investigated the response behavior of chemiresistors made from differently interlinked networks of gold nanoparticles. Our results show that the degree of flexibility and conductivity of the interlinkage between the nanoparticles has a profound impact on the response characteristics of such sensors. 1,12-Dodecanedithiol was used as a hydrophobic, flexible linker compound. For comparison, [4]-staffane-3,3‘ ‘‘-dithiol provided a rigid, rodlike linkage, and 4,4‘-terphenyldithiol was used as a rigid linker with enhanced conductivity due to its delocalized aromatic moieties. As determined by AFM, all three sensor coatings had similar thicknesses (∼30 nm), but the degree of interlinkage, as measured by XPS, was significantly higher in the case of the flexible network. All three materials showed linear current−voltage characteristics. The vapor sensitivity was tested by dosing the sensors with toluene, 1-propanol, 4-methyl-2-pentanone, and water in the concentration range 100−5000 ppm at 0% rela...

Construction of a two-dimensional molecule-nanoparticle network using iron(II) bis(terpyridine) complex formation for molecular-device applications

We report a novel method to construct a two-dimensional network of gold nanoparticles and metal complex molecules. Terpyridine derivatives having a thiol group are adsorbed on a gold nanoparticle surface through formation of a gold–sulfur bond. A monolayer of nanoparticles is then formed on the water surface, then transferred onto a Si/SiO2 substrate. The introduction of Fe2+ from a Fe(BF4)2 solution forms an iron(II) bis(terpyridine) complex, which simultaneously forms a network where the complex molecules interlink adjacent nanoparticles. The conductivity of the network, formed by the conjugated terpyridine derivative, is 4 or 5 orders of magnitude higher than that of non-conjugated derivatives. Conductivity is modulated by gate voltage when a conjugated derivative is used but not when a non-conjugated derivative is used. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Aerogel-like Three-dimensional Gold Nanoparticle Network via Sublimation of Volatile Organic Crystals Decorated with Gold Nanoparticles

Abstract We demonstrate novel strategy to create the three-dimensional networks of the gold nanoparticle from organic crystals decorated by the gold nanoparticles via slow removal of the crystals by sublimation.

Networks of gold nanoparticles and bacteriophage as biological sensors and cell-targeting agents.

Biological molecular assemblies are excellent models for the development of nanoengineered systems with desirable biomedical properties. Here we report an approach for fabrication of spontaneous, biologically active molecular networks consisting of bacteriophage (phage) directly assembled with gold (Au) nanoparticles (termed Au-phage). We show that when the phage are engineered so that each phage particle displays a peptide, such networks preserve the cell surface receptor binding and internalization attributes of the displayed peptide. The spontaneous organization of these targeted networks can be manipulated further by incorporation of imidazole (Au-phage-imid), which induces changes in fractal structure and near-infrared optical properties. The networks can be used as labels for enhanced fluorescence and dark-field microscopy, surface-enhanced Raman scattering detection, and near-infrared photon-to-heat conversion. Together, the physical and biological features within these targeted networks offer convenient multifunctional integration within a single entity with potential for nanotechnology-based biomedical applications.

Electron transport in networks of gold nanoparticles connected by oligothiophene molecular wires

Network structures made of π-conjugated molecular wires of oligothiophene 3mer, or 9mer carrying thiol groups at α,ω-positions, and gold nanoparticles with average diameter of 4 nm were prepared on interdigitated gold electrodes. Observation of the resultant assemblies by means of FE-SEM and TEM revealed that the gold nanoparticles were connected by π-molecular wires to form a network. The networks exhibited thermally activated electron transport at room temperature with activation energies of 21and 45 meV for 3mer- and 9mer-networks, respectively, and these values were almost the same as those of networks connected with non-conjugated molecules having similar lengths. However, the activation energy became very small (∼0.1 meV) at temperatures lower than 30 K and non-linear current–voltage characteristics (I ∝ V3) appeared in π-conjugated networks at 4.2 K. These results suggest that the gold nanoparticles in the networks work as Coulomb islands and the temperature-independent behavior at lower temperatures can be interpreted in terms of a co-tunneling mechanism.

Monte Carlo simulation of gold nano-colloids aggregation morphologies on a heterogeneous surface

After one hour immersion (adsorption) in nano-colloidal suspensions, mesoscopic (μm scale) aggregation networks of gold nanoparticles (25 nm) are formed on a methyl/amine terminated surface (CH 3/NH 2) and followed by the substrate drying. A Monte Carlo simulation is then performed to model these patterns in microscopic scale. It is revealed that a two-state Pott-like model allows to reproduce these structures if some inactive sites are introduced at the interface between (CH 3/NH 2) and Au nano-colloids. The purpose of this study is to estimate the number of inactive sites by an inverse method based on an original multi-fractal formalism. Multi-fractal measures are defined like the quantity of information contained at different scales in surface morphology. After, parameters are estimated to minimise the norm between the experimental multi-fractal and simulated spectra. The robustness of this multi-scale analysis is tested by a statistical bootstrap protocol that gives computing confidence intervals of the physical coefficients.

Gold Nanoparticle Networks with Photoresponsive Interparticle Spacings

Photoresponsive gold nanoparticle networks were prepared by functionalizing them with azobenzene derivatives. A network can be formed when a linker molecule constituting the azobenzene moiety suitably derivatized on either side with gold surface sensitive groups such as thiols and amines is added to the nanoparticle solution. It is shown that the interparticle spacing in the networks could be controlled by the reversible trans-cis isomerization of the azobenzene moiety induced by UV and visible light, respectively. The photoinduced variation in the interparticle spacings is inferred by the changes in the optical spectra of the gold nanoparticles which display a red or blue shift in the surface plasmon resonance peak depending on a decrease or increase in the interparticle spacing, respectively. Transmission electron microscopy images are in consonance with the evidence from the optical spectra.

The Structural Characterization of Oligonucleotide-Modified Gold Nanoparticle Networks Formed by DNA Hybridization

The structural properties of DNA-linked gold nanoparticle materials were examined using synchrotron small-angle X-ray scattering. The materials are composed of 12 or 19 nm diameter gold particles modified with 3‘ or 5‘ alkylthiol-capped 12-base oligonucleotides and linked with complementary oligonucleotides. Structure factors were derived from scattering intensities, and nearest-neighbor distances were determined from the primary peak in the pair distance distribution functions. The separation between particles was found to increase linearly with DNA linker length for 24, 48, and 72 base pair linkers. For assemblies formed in 0.3 M NaCl, 10 mM phosphate buffer solution, the increment in the interparticle distance was found to be 2.5 Å per base pair. Particle separations in assemblies at lower electrolyte concentration were larger, indicating that dielectric screening modulates the interactions. The effect of DNA sequence was studied with poly-adenine or poly-thymine spacer sequences incorporated between the alkylthiol and recognition sequences. The assemblies with poly-adenine spacer sequences showed significantly shorter particle separations than the assemblies involving poly-thymine spacers, a consequence of their different affinities for the gold surface. While the scattering data do not display evidence of long-range order, pair distance distribution functions indicate the presence of short-range order.

Phase transition of DNA-linked gold nanoparticles

Melting and hybridization of DNA-capped gold nanoparticle networks are investigated with optical absorption spectroscopy. Single-stranded, 12-base DNA-capped gold nanoparticles are linked with complementary, single-stranded, 24-base linker DNA to form particle networks. Compared to free DNA, a sharp melting transition is seen in these networked DNA-nanoparticle systems. The sharpness is explained by percolation transition phenomena.

3D Hybrid Nanonetworks from Gold-Functionalized Nanoparticles

Highly ordered 3D hybrid networks of gold nanoparticles assemble after in-situ generation of linkers between particles, achieved by amide-bond formation. Unlike their counterparts obtained by linking Au nanoparticles with 1,ω-dithiols, which are amorphous, these networks show a regular hexagonal array (see Figure).

Electrochemical Organization of Gold Nanoclusters in Three Dimensions as Thin Films from an Aminosilicate-Stabilized Gold Sol and Their Characterization

Electrochemical organization of a thin film of gold nanoparticles from an aminosilicate-stabilized gold sol on an indium tin oxide coated glass is demonstrated. Films are semitransparent to reflectivity depending on the thickness and have three-dimensional conductivity. Characterization of the films using UV−visible spectroscopy, IR spectroscopy, atomic force microscopy, and cyclic voltammetry has shown that they are made of a network of gold nanoparticles that are interconnected by aminosilicate moieties. This methodology is successfully extended to codeposited glucose oxidase enzyme, based on which a glucose biosensor is demonstrated.

Room Temperature Single Electron Charging in Gold Nanoparticle Networks Formed on Biopolymer Templates

ABSTRACTWe report the current-voltage characteristics of gold nanoparticle – biopolymer networks at room temperature. Above a threshold voltage the current-voltage relationship is almost linear. From the current-voltage scaling above threshold we argue that one-dimensional regions of the network dominate the transport. Periodic features in the conductance are found in many samples. Both the threshold voltage and the conductance features occur at voltages much greater than expected for the capacitance of the nanoparticles. Possible explanations for the structure are considered.