Chemical synthesis of gold nanowires in acidic solutions

High aspect ratio gold nanowires with single crystalline surface have long been a missing piece in the toolbox of plasmonics metal nanostructures. Such wires are now made with a room temperature, surfactant assisted chemical synthesis in acidic aqueous solution. The diameters and lengths of the multiply twinned gold nanowires can be tuned by varying the amount of seed particles and acid in the growth solution. Nanowires with diameters around 35 nm and lengths up to 10 micron were made with a low seed concentration in pH approximately 1 solution.     

Comparative study of electrically conductive cotton fabric prepared through the in situ synthesis of different conductive materials

Cellulose - The electrical conductivity of cotton fabrics was enhanced using an in situ synthesis of graphene or polymerization of conductive polymer. The impact of conductive materials...     

Reliability of flexible electrically conductive adhesives

Based on our previous work about electrically conductive adhesives (ECAs), a flexibilizer named 1,3‐propanediol bis (4‐aminobenzoate) was used to fabricate flexible ECAs (FECAs). ECAs, FECAs, and electronic devices connected by them were carried out the hot and humid aging test under constant humidity level of 85% relative humidity at 85 °C for 600 h. After aging, the bulk resistance change of ECAs was about 26%, that of FECAs was a little higher, about 29%. The contact resistance change of devices connected by ECAs and FECAs was very great, about 450% and 410%, respectively. The bonding area at connection interface between colloids and devices had delamination, even cracks. The delamination of ECAs was calculated about 60%, the average shear strength of ECAs was reduced about 45%, and those of FECAs were about 50% and 30%, respectively, so FECAs had a higher bonding stability in hot and humid environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Simple, one-step synthesis of gold nanowires in aqueous solution

A simple procedure to synthesize gold nanowires based on the reduction of hydrogen tetrachloroaurate by 2-mercaptosuccinic acid in aqueous solution is presented. This procedure requires no additional capping or reduction agent and produces wires with an apparent curly morphology several micrometers in length with diameters as thin as 15 nm. Some of the wires produced end in a ribbonlike structure, finally terminated by a flat triangular prism. Investigations by scanning electron microscopy, transmission electron microscopy (bright and dark field), scanning transmission electron microscopy, and atomic force microscopy as well as conductivity measurements indicate fully connected, polycrystalline gold objects.     

Starfruit-shaped gold nanorods and nanowires: synthesis and SERS characterization

Recently, branched and star-shaped gold nanoparticles have received significant attention for their unique optical and electronic properties, but most examples of such nanoparticles have a zero-dimensional shape with varying numbers of branches coming from a quasi-spherical core. This report details the first examples of higher-order penta-branched gold particles including rod-, wire-, and platelike particles which contain a uniquely periodic starfruitlike morphology. These nanoparticles are synthesized in the presence of silver ions by a seed-mediated approach based on utilizing highly purified pentahedrally twinned gold nanorods and nanowires as seed particles. The extent of the growth can be varied, leading to shifts in the plasmon resonances of the particles. In addition, the application of the starfruit rods for surface-enhanced Raman spectroscopy (SERS) is demonstrated.     

Microwave synthesis of core-shell gold/palladium bimetallic nanoparticles

The microwave-assisted polyol reduction method was applied to the synthesis of core-shell gold/palladium bimetallic nanoparticles by the simultaneous reduction of the AuIII and PdII ions. The thickness of the palladium shell was calculated to be approximately 3 nm, and the gold core diameter is 9 nm. The structure and composition of the bimetallic particles were characterized by high-resolution transmission electron microscopy equipped with a nanoarea energy-dispersive X-ray spectroscopy attachment, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy.     

CO oxidation on electrically charged gold nanotips

We report a study of the oxidation of CO on a gold nanotip in the presence of high electrostatic fields. With the binding energies obtained using density functional theory as a function of the electric field, a simple field-dependent kinetic model based on the Langmuir-Hinshelwood mechanism is set up. We show that the dissociative adsorption of oxygen on gold happens only below a negative critical value of the electric field while the binding of CO on gold is enhanced for positive values. We explain the propagation of a wave observed in field ion microscopy experiments and predict that the oxidation of CO occurs on negatively charged gold clusters.     

Preparation of helical gold nanowires on surfactant tubules

Electroless gold nanoplating of various forms of surfactant tubules yielded mono-, double- and multi-helical gold nanowires and their yarns in solution.     

Characterization of electrically conductive vanadate glass containing tungsten oxide

New conductive glass with a composition of 20BaO·10Fe₂O₃·xWO₃·(70 ? x)V₂O₅ (x = 10–50) was investigated by means of Mössbauer spectroscopy. A marked decrease in quadrupole splitting (Δ) was observed after the isothermal annealing at 500 °C for 1,000 min, due to the structural relaxation of 3D-network composed of FeO₄, VO₄, and VO₅ units. After the isothermal annealing, a marked increase in the electrical conductivity (σ) was observed from 1.7 × 10^?5 to 1.0 × 10^?1 S cm^?1 when “x” was 10, whereas comparable σ values of 1.1 × 10^?4 and 2.0 × 10^?4 S cm^?1 were observed when “x” was 40. These results evidently show that structural relaxation of 3D-network structure involved with a marked increase in σ is intrinsic of “vanadate glass”. XRD pattern indicated several weak peaks due to needle-like BaFe₂O₄ and α-Fe₂O₃ when the glass sample with “x” of 20 was annealed at 500 °C for 1,000 min. SEM study proved the formation of needle-like BaFe₂O₄ just on the surface of the sample, whereas hexagonal BaFe₁₂O₁₉ were observed in the annealed sample with “x” of 40. Chemical durability of WO₃-containing vanadate glass was investigated by immersing each glass sample into 20 %-HCl solution for 72 h.     

Alpha-helix-inducing dimerization of synthetic polypeptide scaffolds on gold

Designed, synthetic polypeptides that assemble into four-helix bundles upon dimerization in solution were studied with respect to folding on planar gold surfaces. A model system with controllable dimerization properties was employed, consisting of negatively and positively charged peptides. Circular dichroism spectroscopy and surface plasmon resonance based measurements showed that at neutral pH, the peptides were able to form heterodimers in solution, but unfavorable electrostatic interactions prevented the formation of homodimers. The dimerization propensity was found to be both pH- and buffer-dependent. A series of infrared absorption-reflection spectroscopy experiments of the polypeptides attached to planar gold surfaces revealed that if the negatively charged peptide was immobilized from a loading solution where it was folded, its structure was retained on the surface provided it had a cysteine residue available for anchoring to gold. If it was immobilized as random coil, it remained unstructured on the surface but was able to fold through heterodimerization if subsequently exposed to a positively charged polypeptide. When the positively charged peptide was immobilized as random coil, heterodimerization could not be induced, probably because of high-affinity interactions between the charged primary amine groups and the gold surface. These observations are intended to pave the way for future engineering of functional surfaces based on polypeptide scaffolds where folding is known to be crucial for function.     

Design and synthesis of the polyaniline interface for polyamide 66/multi-walled carbon nanotube electrically conductive composites

A polyaniline interface had been designed and built between multi-walled carbon nanotubes (MWCNTs) and polyamide 66 (PA66) in order to help in the dispersion of MWCNTs in PA66 and improve the interfacial combination between them. Transmission electron microscopy characterizations indicated that functionalized MWCNTs (f-MWCNTs) could be well-distributed in PA66 matrix and the interfacial boundary between them was indiscernible. The mixing conditions, such as f-MWCNT content, temperature, and mixing speed, played important roles in determining the formation of the conductive network and the electrical conductivities of PA66/f-MWCNT composites synthesized. A continuous conductive network was formed at 10 wt% f-MWCNT content, and the corresponding PA66/f-MWCNT composite exhibited an electrical conductivity of 8 orders of magnitude higher than pure PA66. The conducting mechanism agreed well with a thermal fluctuation-induced tunneling model.     

Zero-voltage conductance of short gold nanowires

Using the Landauer formula, the conductance of short gold wires is studied. The required electronic structure calculations are performed with a self-consistent tight-binding method. We consider gold wires of single-atom diameter with a variable number (N=1, em leader,5) of atoms. Depending on N, we find considerable conductance variations with one conductance quantum being the upper limit. The results are confirmed by means of Friedel's sum rule. Tip-shaped clusters are used to provide the contact-wire interfaces and the relation between various tip structures and the conductance is discussed. Our predictions about the conductance variations agree qualitatively with new experimental results.     

Crystalline phases of electrically conductive poly(p-phenylene vinylene)

Poly(p-phenylene vinylene) (PPV) undergoes a first-order crystal-crystal phase transition when chemically doped with AsF₅, SbF₅, or H₂SO₄ or electrochemically oxidized with ClO^-₄ as the counterion. These structures have been observed using wide-angle x-ray diffraction. Doping with these agents does not disrupt the original orientation of the PPV crystallites. The crystalline phases obtained with all dopants employed here are similar in character, indicating a closely related family of electrically conductive structures having orthorhombic symmetry. An electrically conductive phase consisting of layers of polymer chains separated by a layer of the chemical dopant is proposed.     

Facile synthesis of noble metal nanotubes by using ZnO nanowires as sacrificial scaffolds and their electrocatalytic properties

Pt and Pd nanotubes could be prepared rapidly with high yields and good uniformity through the reduction of metal precursors in the presence of ZnO nanowires as inexpensive sacrificial templates. The prepared nanotubes showed efficient electrocatalytic properties toward alcohol oxidation.     

DNA as a template for synthesis of fluorescent gold nanoclusters

Water-soluble blue-emitting gold nanoclusters have been synthesized using dsDNA as a template without any additional reducing agent. The features of the formed nanoclusters have been revealed by fluorescence and electronic absorption spectroscopy as well as transmission electron microscopy. The prepared gold nanoclusters have been highly stable at physiological pH without any further modification.     

Solution-based assembly of conductive gold film on flexible polymer substrates

Conductive films of gold were assembled on flexible polymer substrates such as Kapton and polyethylene using a solution-based process. The polymer substrates were modified by using argon plasma and subsequent coupling of silanes with amino- or mercapto- terminal groups. These modified surfaces were examined by X-ray photoelectron spectroscopy and contact angle measurements. Colloidal gold was assembled onto the silane-modified surface from solution. The gold particles are attached to the surface by covalent interactions with the thiol or amine group. Formation of a conductive film is achieved by increasing the coverage of gold by using a "seeding" method to increase the size of the attached gold particles. Field emission scanning electron microscopy was used to follow the growth of the film. The surface resistance of the films, measured using a four-point probe, was about 1 Omega/sq.     

One-step synthesis of silver nanoparticles, nanorods, and nanowires on the surface of DNA network

Here, we describe a one-step synthesis of silver nanoparticles, nanorods, and nanowires on DNA network surface in the absence of surfactant. Silver ions were first adsorbed onto the DNA network and then reduced in sodium borohydride solution. Silver nanoparticles, nanorods, and nanowires were formed by controlling the size of pores of the DNA network. The diameter of the silver nanoparticles and the aspect ratio of the silver nanorods and nanowires can be controlled by adjusting the DNA concentration and reduction time.     

Ellipsometric examination of electrically conductive films of poly(2,5-thiophenediyl)

A polymer film formed by anodic oxidation of thiophene in acetonitrile on platinum at 2.08 V was examined by ellipsometry. The refraction index and absorption index were determined as a function of the wavelengths. The optical thickness was determined and compared with the electrical charge. Stoichiometric film growth by a two-electron reaction followed this comparison. The film properties studied were almost independent of the potential between −0.1 and +2.08 V. The time dependence of the ellipsometric parameter showed the film growth to be approximately linear with square root of time, typical for a diffusion controlled reaction.