Preparation of novel silver-gold bimetallic nanostructures by seeding with silver nanoplates and application in surface-enhanced Raman scattering

Novel silver-gold bimetallic nanostructures were prepared by seeding with silver nanoplates in the absence of any surfactants. During the synthesis process, it was found that the frameworks of silver nanoplates were normally kept though the basal plane of silver nanoplates became rugged. The real morphology of these nanostructures depended on the molar ratio of gold ions to the seed particles. When the molar ratio of gold ions to silver atoms increased from 0.5 to 4, porous or branched silver-gold bimetallic nanostructures could be made. The growth mechanism was qualitatively discussed based on template-engaged replacement reactions and seed-mediated deposition reactions. Due to the unusual structures, they exhibited interesting optical properties. Moreover, they were shown to be an active substrate for surface-enhanced Raman scattering measurements.

EDTA-controlled one-pot preparation of novel shaped gold microcrystals and their application in surface-enhanced Raman scattering

We report a one-pot preparation method for a series of novel shaped gold microcrystals by simply mixing HAuCl4 with disodium salt of ethylenediaminetetraacetic acid (Na(2)EDTA). Under the different reaction temperatures, spinous structures, multipod microspheres, and rough surfaced microspheres were obtained. These microcrystals exhibit high surface-enhanced Raman scattering (SERS) activity.

Self-assembled gold nanoparticle chains in presence of silver ions

A simple method has been developed to assemble gold nanoparticles to generate 1D assemblies by the assistance of silver ions. The lengths of nanoparticle chains can be controlled by adjusting the content of silver ions in the system. The assembly procedure of gold nanoparticles chains requires no template. The gold nanoparticle chains were characterized using TEM and XPS techniques.

Preparation of highly conductive, self-assembled gold/polyaniline nanocables and polyaniline nanotubes

One-dimensional gold/polyaniline (Au/PANI-CSA) coaxial nanocables with an average diameter of 5060 nm and lengths of more than 1 mu m were successfully synthesized by reacting aniline monomer with chlorauric acid (HAuCl4) through a self-assembly process in the presence Of D-camphor-10-sulfonic acid (CSA), which acts as both a dopant and surfactant. It was found that the formation probability and the size of the Au/PANI-CSA nanocables depends on the molar ratio of aniline to HAuCl4 and the concentration of CSA, respectively. A synergistic growth mechanism was proposed to interpret the formation of the Au/PANI-CSA nanocables. The directly measured conductivity of a single gold/polyaniline nanocable was found to be high (approximate to 77.2S cm(-1)). Hollow PANI-CSA nanotubes, with an average diameter of 50-60 nm, were also obtained successfully by dissolving the Au nanowire core of the Au/PANI-CSA nanocables.

Room-temperature strategy for networked nonspherical gold nanostructures from Au(III)-[G-2]-CO2H dendrimer complex

The present work describes a convenient approach to fabricate networked nonspherical gold nanostructures by using [G-2]-CO2H dendrimer and toluene as capping and bridging agents in a CH2Cl2 and H2O biphasic system. A controlled linear assembly is achieved without the use of any catalyst at room temperature. UV-vis spectrum, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD) analysis show that the product is well networked nanostructures with diameter of 4-10 nm and consists of coalesced face-centered cubic gold nanocrystals. Extended experiments reveal that both benzene and dimethylbenzene can also inhabit the gold ions to make them crosslinked, prolong the nucleation points and eventually facilitate the formation of the networks.

Wavelength Dependence of Raman Enhancement from Gold Nanorod Arrays: Quantitative Experiment and Modeling of a Hot Spot Dominated System

Surface-enhanced Raman scattering (SERS) spectra from molecules adsorbed on the surface of vertically aligned gold nanorod arrays exhibit a variation in enhancement factor (EF) as a function of excitation wavelength that displays little correlation with the elastic optical properties of the surface. The key to understanding this lack of correlation and to obtaining agreement between experimental and calculated EF spectra lies with consideration of randomly distributed, sub-10 nm gaps between nanorods forming the substrate. Intense fields in these enhancement “hot spots” make a dominant contribution to the Raman scattering and have a very different spectral profile to that of the elastic optical response. Detailed modeling of the electric field enhancement at both excitation and scattering wavelengths was used to quantitatively predict both the spectral profile and the magnitude of the observed EF.

Biological Routes to Gold Nanoplates

Much effort has been devoted to the synthesis of gold nanoparticles with different shapes, including the zero-dimensional nanospheres, one dimensional nanorods, and two-dimensional nanoplates. Compared to zero or one dimensional nanostructures, the synthesis of two-dimensional nanostructures in high yield has always been more involved, often requiring complex and time-consuming steps such as morphology transformation from the nanospheres, or the seeded growth process. Herein we report a high yield method for gold nanoplate synthesis using the extract of unicellular green alga Chlorella vulgaris, which can be carried out under ambient conditions. More than 90% of the total nanoparticle population is of the platelet morphology, surpassing the previously reported value of 45%. The control of the anisotropic growth of different planes; as well as the lateral size, has also been partially optimized.

Goethite (alpha-FeOOH) Nanorods as Suitable Antiferromagnetic Substrates

We propose goethite nanorods as suitable anti-ferromagnetic substrates. The great advantage of using these inorganic nanostructures as building blocks comes from the fact that it permits the design and fabrication of colloidal and supracolloidal assemblies knowing first their magnetic characteristics. As a proof of concept, we have developed mix multifunctional systems, driving on the surface of these AFM substrates, cobalt ferrite nanoparticles (the study of bimagnetic systems opens new degrees of freedom to tailor the overall properties and offers the Meiklejohn-Bean paradigm, but inverted), a silica shell (protection purposes, but also as a tailored spacer that permits controlling magnetic interactions), and metallic gold clusters (seeds that can favor the acquisition of optical or catalytic properties).

An indexing model for stormwater quality in the Gold Coast

In the era of climate change sustainable urban development and in particular provision of sustainable urban infrastructure has become a key concept in dealing with environmental challenges. This paper discusses issues affecting stormwater quality and introduces a new indexing model that is to be used in evaluation of the stormwater quality in urban areas. The model has recently been developed and will be tested in a number of pilot projects in the Gold Coast, one of the fastest growing and environmentally challenged cities of Australia.

Members abroad - Australia - Brisbane and the Gold Coast

Brisbane's sub-tropical climate, vegetation and urban history as a British settlement, endow the region with many characteristics that are familiar in KwaZulu-Natal. Brisbane settlement, firstly as a penal conlony to accommodate the hardiest criminals dispatched from Sydney, was established in 1825 on a wide river, several kilometers upstream from Moreton Bay with the Pacific Ocean beyond. The penal colony was short lived and was soon opened up to free settlement in 1842. The growth of the fledgling town was characterized by brick warehouse and service buildings to the port that was established on its riverbanks, resembling those of the old Point Road area in Durban. Government and administration buildings heralded Brisbane as the captial city of the State of Queensland, annexed from New South Wales in 1859. Morphological studies reveal that Brisbane had reached its first zenith around 1930 as a commerical city of four and five storey buildings. The urban form remained stagnant until the post-1960's building boom and the developments from this period on, consolidated land amalgamations largely ignoring the urban characteristics of the established city. Public space was poorly observed, resulting in a city that had turned its back on the river. It is only in recent times that the currency of good urban design, under the custodial direction of the City Council, has fostered a re-engagemed urban realm that, enabled by the recent building boom, has delivered high quality urban environments

An indexing model for sustainable urban environmental management : the case of Gold Coast, Australia

Improving urban ecosystems and the quality of life of citizens have become a central issue in the global effort of creating sustainable built environments. As human beings our lives completely depend on the sustainability of the nature and we need to protect and manage natural resources in a more sustainable way in order to sustain our existence. As a result of population growth and rapid urbanisation, increasing demand of productivity depletes and degrades natural resources. However, the increasing activities and rapid development require more resources, and therefore, ecological planning becomes an essential vehicle in preserving scarce natural resources. This paper aims to indentify the interation between urban ecosystems and human activities in the context of urban sustainability and explores the degrading environmental impacts of this interaction and the necessity and benefits of using sustainability indicators as a tool in sustainable urban evnironmental management. Additionally, the paper also introduces an environmental sustainability indexing model (ASSURE) as an innovative approach to evaluate the environmental conditions of built environment.

An indexing model for stormwater quality assessment : stormwater management in the Gold Coast

In the age of climate change and rapid urbanisation, stormwater management and water sensitive urban design have become important issues for urban policy makers. This paper reports the initial findings of a research study that develops an indexing model for assessing stormwater quality in the Gold Coast.

Interactions of phenyldithioesters with gold nanoparticles (AuNPs): Implications for AuNP functionalization and molecular barcoding of AuNP assemblies

The interactions of phenyldithioesters with gold nanoparticles (AuNPs) have been studied by monitoring changes in the surface plasmon resonance (SPR), depolarised light scattering, and surface enhanced Raman spectroscopy (SERS). Changes in the SPR indicated that an AuNP-phenyldithioester charge transfer complex forms in equilibrium with free AuNPs and phenyldithioester. Analysis of the Langmuir binding isotherms indicated that the equilibrium adsorption constant, Kads, was 2.3 ± 0.1 × 106 M−1, which corresponded to a free energy of adsorption of 36 ± 1 kJ mol−1. These values are comparable to those reported for interactions of aryl thiols with gold and are of a similar order of magnitude to moderate hydrogen bonding interactions. This has significant implications in the application of phenyldithioesters for the functionalization of AuNPs. The SERS results indicated that the phenyldithioesters interact with AuNPs through the C═S bond, and the molecules do not disassociate upon adsorption to the AuNPs. The SERS spectra are dominated by the portions of the molecule that dominate the charge transfer complex with the AuNPs. The significance of this in relation to the use of phenyldithioesters for molecular barcoding of nanoparticle assemblies is discussed.