Synthesis and optical properties of hybrid and alloy plasmonic nanoparticles

Synthesis and optical properties of hybrid and alloy plasmonic nanoparticles hybrid systems that display a plasmon resonance in the visible or near-visible regions of the spectrum are studied. In the hybrid system, also called passive metallo-dielectric hybrids, the functionalities of the parts remain reasonably independent. The optical properties of these structures are explained by the properties of the individual parts, except for some bathochromic shifting of the plasmon resonance of the metallic component due to the increase in local dielectric constant due to the other component. Metal-metal hybrids and their closely related alloyed nanoparticles exhibit more complex behavior. The plasmon resonance or resonances of the parts can be enhanced, shifted, or suppressed. In the case of core-shell particles, the dielectric properties of the shell material will dominate above some modest thickness, and in the limit, the result is as if the hybrid was composed throughout of the shell material

Formation of gold nanorods by a stochastic "popcorn" mechanism

Gold nanorods have significant technological potential and are of broad interest to the nanotechnology community. The discovery of the seeded, wet-chemical synthetic process to produce them may be regarded as a landmark in the control of metal nanoparticle shape. However, the mechanism by which the initial spherical gold seeds acquire anisotropy is a critical, yet poorly understood, factor. Here we examine the very early stages of rod growth using a combination of techniques including cryogenic transmission electron microscopy, optical spectroscopy, and computational modeling. Reconciliation of the available experimental observations can only be achieved by invoking a stochastic, "popcorn"-like mechanism of growth, in which individual seeds lie quiescent for some time before suddenly and rapidly growing into rods. This is quite different from the steady, concurrent growth of nanorods that has been previously generally assumed. Furthermore we propose that the shape is controlled by the ratio of surface energy of rod sides to rod ends, with values of this quantity in the range of 0.3-0.8 indicated for typical growth solutions. © 2012 American Chemical Society

Convenient synthesis and purification of [Bu<inf>4</inf>N] <inf>2</inf>[Ru(4-carboxy-4-carboxylate-2,2′-bipyridine) <inf>2</inf>(NCS)<inf>2</inf>]: A landmark DSC Dye

We present here a convenient synthesis of the landmark dye-sensitized solar cell dye [Bu4N]2[Ru(4-carboxy-4-carboxylate-2,2?- bipyridine)2(NCS)2] (N719). Key to this synthetic procedure is the protection of the carboxyl functionalities with iso-butyl ester groups. This strategy allows the use of silica chromatography to remove the less efficient S-bound isomers and significantly reduces the time and difficulty of the synthesis. © CSIRO 2008

Synthesis and characterization of anthracene-2,6-dithioacetate: A rigid, conjugated molecule for the formation of monolayers on gold

The synthesis and characterization of a new photoswitchable anthracene compound, anthracene-2,6-dithioacetate, is presented. The compound dimerizes in solution on irradiation with UV light, and thin films can be formed on gold surfaces from both the monomer and photodimer. © CSIRO 2008

A straightforward route to tetrachloroauric acid from gold metal and molecular chlorine for nanoparticle synthesis

© 2015 by the authors; licensee MDPI, Basel, Switzerland. Aqueous solutions of tetrachloroauric acid of high purity and stability were synthesised using the known reaction of gold metal with chlorine gas. The straightforward procedure developed here allows the resulting solution to be used directly for gold nanoparticle synthesis. The procedure involves bubbling chlorine gas through pure water containing a pellet of gold. The reaction is quantitative and progressed at a satisfactory rate at 50 °C. The gold(III) chloride solutions produced by this method show no evidence of returning to metallic gold over at least twelve months. This procedure also provides a straightforward method to determine the concentration of the resulting solution using the initial mass of gold and volume of water

Thin films of a dimeric ruthenium phthalocyanine complex on gold

Thin films of a new dimeric ruthenium phthalocyanine complex bearing a thioester-functionalized axial ligand were formed on gold surfaces. Characterization of the thin films by laser ablation-inductively coupled-mass spectrometry and scanning tunneling microscopy revealed that the films do not have any long-range order. © 2009 Elsevier B.V. All rights reserved

Metal-containing nanoparticles and nano-structured particles in fingermark detection

This article reviews the application of metal-containing nanoparticles and nano-structured particles to fingermark detection. This area of research is attracting significant interest as advances in nanoscience are being incorporated into the field of forensic fingermark detection. Although more research is needed before some of the techniques presented can be implemented in routine casework, nanotechnology is likely to play a major role in the future to deliver more selective and more sensitive ways to detect and enhance fingermarks. © 2008 Elsevier Ireland Ltd. All rights reserved

Spectrally selective coatings of gold nanorods on architectural glass

Infrared-blocking coatings on window glass can be produced by dispersing gold nanorods into a polymer coating. The spectral selectivity of the coating is controlled by the shape and aspect ratio of the nanoparticles, which are in turn determined by the conditions applied during their synthesis. Coatings of nanorods in polyvinyl alcohol were deposited onto glass and characterized in both laboratory and sun-lit conditions. Selective attenuation of the near-infrared was demonstrated with the test panels transmitting approximately one-third of the incident solar radiation and absorbing nearly two-thirds. The high absorptive cross sections of the gold nanorods suggest that they can be applied in efficacious coatings at relatively low volume fractions. © 2010 Springer Science+Business Media B.V

On the reactivity of zinc hydroxide acetate dihydrate in ethanol

Zinc hydroxide acetate dihydrate, Zn5(OH)8(CH 3CO2)2·2H2O, reacts in ethanol at room temperature to yield a mixture of zinc oxide and anhydrous zinc acetate. The process is driven by dehydration of the starting salt. Dehydration of Zn5(OH)8(CH3CO2) 2·2H2O also occurs when it is heated in air, but the product obtained in that case depends on the heating rate, environment and temperature. For example, when it is kept in a sealed silica capillary at 100 °C, Zn5(OH)8(CH3CO2) 2·1.5H2O is formed after 15 min, whereas treatment in the range 90-100°C in an open environment results in the formation of anhydrous zinc hydroxide acetate. Heating of any of these products further causes their decomposition to Zn(CH3CO2)2 and ZnO. The coordination bonding mode of the acetate groups in the anhydrous layered zinc hydroxide acetate prepared by reaction with ethanol was studied by using solid-state NMR spectroscopy. The presence of chelating, unidentate and bidentate bridging modes for the carbonyl carbon atom was revealed, but there was no evidence for the inclusion of ethanol in the resultant structure. Therefore, the reaction in ethanol offers a convenient strategy to prepare anhydrous zinc hydroxide acetate and/or zinc oxide, because it avoids the sensitivity of the thermally induced dehydroxlation process to time, temperature and environment. Decomposition of zinc hydroxide acetate dihydrate in ethanol can be exploited to generate ZnO nanoparticles at room temperature. The mechanism involves the removal of waters of hydration and the formation of Zn5(OH)8(CH3CO2)2 followed by the generation of Zn(CH3CO)2 and ZnO. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A new class of self-assembled monolayers on gold using an alkynyl group as a linker

The geometry and energetics for adsorption of ethynylbenzene on Au(111) have been studied using Density Functional Theory. The alkynyl group, following removal of the terminal H atom, adsorbs covalently to the surface in the fcc hollow site with a bond energy of about 70 kcal.mol-1. Intermediate adsorption states are also possible via a hydrogen 1,2 shift to form a surface-bound vinylidene, or through the opening of the C-C triple bond without removing the hydrogen atom. © 2006 IEEE