Self-organization Of Gold Nanoparticles Research Articles

Spontaneous Formation of Cold-Welded Plasmonic Nanoassemblies with Refracted Shapes for Intense Raman Scattering.

Nanostructures with concave shapes made from continuous segments of plasmonic metals are known to dramatically enhance Raman scattering. Their synthesis in solutions is hindered, however, by their thermodynamic instability due to large surface area and high curvature of refracted geometries with nanoscale dimensions. Herein, we show that nanostructures with concave geometries can spontaneously form via self-organization of gold nanoparticles (NPs) at the air-water interface. The weakly bound surface ligands on the particle surface make possible their spontaneous accumulation and self-assembly at the air-water interface, forming monoparticulate films. Upon heating to 80 °C, the NPs further assemble into concave nanostructures where NPs are cold-welded to each other. Furthermore, the nanoassemblies effectively adsorb molecular analytes during their migration from the bulk solution to the surface where they can be probed by laser spectroscopies. We demonstrate that these films with local concentration of analytes increased by orders of magnitude and favorable plasmonic shapes can be exploited for surface-enhanced Raman scattering for high-sensitivity analysis of aliphatic molecules.

Self-organization of gold nanoparticles on silanated surfaces.

The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications.

Self-Organization of Gold Nanoparticles Coated with a Monolayer of Azobenzene Liquid Crystals

A gold nanoparticle having a monolayer of azobenzene liquid crystal (LC) was synthesized. The size of the gold nanoparticle obtained was 4.7 nm in average diameter, and it was soluble in common non-polar organic solvents such as toluene and dichloromethane. We confirmed that the reversible photochemical and thermal isomerization of the azobenzene could take place on the surface of the gold nanoparticles in analogy with free azobenzenes in solutions. Furthermore, a 1-dimensional self-organization of the nanoparticle was observed by transmission electron microscopy. However, a gold nanoparticle without LC molecules never showed such self-organization. Therefore, we conclude that the self-organization of the gold nanoparticle is based on the liquid crystallinity of the organic ligands attached on their surface.

ChemInform Abstract: Carbon Nanocage Structures Formed by One-Dimensional Self-Organization of Gold Nanoparticles.

Carbon nanocapsules and nanotubes have been formed by one-dimensional self-organization of gold nanoparticles, caused by the adhesive force at the step edge of amorphous carbon thin films; the present result is expected to be a promising fabrication technique for self-assembling nanowires and cluster-protected quantum dots at scales beyond the limits of current photolithography.

Three-dimensional self-organization of crystalline gold nanoparticles in amorphous alumina

Multilayered heterostructures containing gold nanoparticles embedded in amorphous alumina matrices were deposited on silicon (001) substrates using pulsed laser deposition. The three-dimensional ordering of gold nanoparticles within these multilayered heterostructures was investigated using cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in films grown at 20 and at 320°C. Self-organization occurred by means of two different growth modes; both vertically correlated growth (top-on-top) and anticorrelated growth (top-on-middle) mechanisms were observed. The results of these studies suggest that the driving force for vertical ordering in this material is related to the long-range elastic interactions among the nanoparticles within the growing films.

Two-Dimensional Self-Organization of Gold Nanoparticles on Supramolecular Aggregates

Alkanethiol-capped gold (Au) nanoparticles, dispersed in toluene and spin-coated on atactic polystyrene films that are themselves spin-coated on fused quartz plates, self-assemble into a characteristic two-dimensional pattern-a network of the Au-thiol nano-composite separating polystyrene 'islands' of dimensions around 200 nm. This pattern changes on varying the concentration of the nanoparticles in the coating solution, evolving into the network from isolated nanoparticle clusters, and then going over to a distribution of 'pinholes' on a surface covered by the nano-composite, resembling a partially wetted surface with near-full coverage. Study of the pristine polystyrene surface reveals a pattern of low-cohesion regions separating 'islands' of polystyrene, where the latter are known to be supramolecular aggregates. It is suggested that these regions play the role of low-resistance channels to the flow of the nano-composite during spin coating.

Vertically self-organized gold nanoparticles in amorphous alumina matrices

ABSTRACTIn this study, self-organized growth of gold nanoparticles dispersed in amorphous alumina matrices was investigated. Au/Al2O3 multilayered structures were grown on silicon (001) substrates using pulsed laser deposition. Vertical ordering of particles was examined with cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in the samples grown at room temperature and 320 °C. This process occurred through two-different growth modes, known as top-on-top growth and top-on-middle growth. The driving force for the vertical ordering was attributed to long-range elastic interactions among nanoparticles during the film deposition process.

Self-organization of Gold Nanoparticles into 2D Superlattice through π-π Interacton

Gold nanoparticle protected by alkylthiols with pyrene moieties was prepared and characterized by 1 H NMR, UV-vis, and elemental analysis. TEM image shows that these nanoparticles possess a narrow size distribution and 2D superlattice structures. In comparison with those nanoparticles protected by alkylthiols prepared under the same experimental condition, these superlattice structures may be attributed to the π-π interaction of the terminal pyrene moieties adsorbed onto the surface of gold nanoparticle. This may provide a convenient method to obtain 2D superlattice other than tedious size-selective precipitation.

Self-Organization of Gold Nanoparticles on Surface-Modified Conducting Polymer Films

AbstractThiol-coated gold nanoparticles with a diameter of approximately 7.5 nanometers and a narrow particle distribution were prepared from sodium tetrachloroaurate under phase transfer conditions. The thiols used were 1-mercaptododecane (1) and 1-mercapto-9,11-heptadecadiyne (4). The particles were cast onto thin films of polyaniline and poly (3,4-ethylenedioxythiophene), as well as onto thiol-coated versions of the same polymer. Surface modification of the polymers with long chain thiols encourages the spontaneous self-assembly of the particles into twodimensional arrays and may offer a unique method for stabilization of nanoparticle assemblies on polymer substrates.

One-dimensional positioning of carbon nanocapsules and spontaneous formation of carbon nanotubes by self-organization of gold nanoparticles

Gold nanoparticles and nanowires encapsulated in carbon nanocapsules and nanotubes were spontaneously formed from one-dimensional self-organized gold nanoparticles on carbon thin films by annealing at low temperatures of 200–400°C. The one-dimensional arrangement of gold nanoparticles was found to be strongly dependent on the adhesive force at the atomic step edges of amorphous carbon thin films. The gold crystals inside the nanotubes are distorted by the crystal growth of the nanowires. The present result is expected as a future fabrication technique for self-assembled ultra-large-scale-integration nanowires and cluster-protected quantum dots protected by nanocapsules and nanotubes at scales beyond the limits of current photolithography.

Carbon nanocage structures formed by one-dimensional self-organization of gold nanoparticles

Carbon nanocapsules and nanotubes have been formed by one-dimensional self-organization of gold nanoparticles, caused by the adhesive force at the step edge of amorphous carbon thin films; the present result is expected to be a promising fabrication technique for self-assembling nanowires and cluster-protected quantum dots at scales beyond the limits of current photolithography.