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Disordered nanohole arrays were formed in silver films by colloidal lithography techniques and characterized for their surface-plasmon activity. Careful control of the reagent concentration, deposition solution ionic strength, and assembly time allowed generation of a wide variety of nanohole densities. The fractional coverage of the nanospheres across the surface was varied from 0.05-0.36. Electrical sheet resistance measurements as a function of nanohole coverage fit well to percolation theory indicating that the electrical behavior of the films is determined by bulk silver characteristics. The transmission and reflection spectra were measured as a function of coverage and the results indicate that the optical behavior of the films is dominated by surface plasmon phenomena. Angle-resolved transmission and reflection spectra were measured, yielding insight into the nature of the excitations taking place on the metal films. The tunability of the colloidal lithography assembly method holds much promise as a means to generate customized transparent electrodes with high surface plasmon activity throughout the visible and NIR spectrum over large surface areas.
ACS Nano 2010 Feb 23
PMID:Controlling the optical properties of plasmonic disordered nanohole silver films. 2011 34

The symmetry-broken geometry and variation of metal composition of semishells induce new plasmonic properties. A system of separated metallic semishells embedded in a poly(dimethylsiloxane) polymer film provides an ideal platform to investigate the localized surface plasmon resonance modes of semishells. We demonstrate experimentally that silver, gold, copper, and aluminum semishells can offer distinct plasmonic responses due to the wide range of their material parameters. Numerical calculations combined with the plasmon hybridization theory render us a clear understanding and assignment of the plasmonic modes of the semishells.
ACS Nano 2010 Mar 23
PMID:Plasmonic modes of metallic semishells in a polymer film. 2013 53

Fabricating plasmonic nanostructures with robust optical and chemical properties remains a challenging task, especially with silver, which has superior optical properties but poor environmental stability. In this work, conformal atomic layer deposition (ALD) of thin alumina overlayers is used to precisely tune the optical transmission properties of periodic nanohole arrays made in gold and silver films. Experiments and computer simulations confirm that ALD overlayers with optimized thicknesses tune and enhance the transmitted intensity due to refractive index matching effects and by modifying the dielectric properties of each nanohole. Furthermore, encapsulating silver nanohole arrays with thin alumina overlayers protects the patterned surfaces against unwanted oxidation and contamination. The ability to precisely tune the optical properties while simultaneously providing robust chemical stability can benefit a broad range of applications, including biosensing and fluorescence imaging.
ACS Nano 2010 Feb 23
PMID:Atomic layer deposition of dielectric overlayers for enhancing the optical properties and chemical stability of plasmonic nanoholes. 2013 70

Here we describe a simple yet efficient gel-matrix-assisted preparation method that improves synthetic control over the interface between inorganic nanomaterials and biopolymers and yields stable biofunctionalized silver nanoparticles. Covalent functionalization of the noble metal surface is aided by the confinement of polyethylene glycol acetic acid functionalized silver nanoparticles in thin slabs of a 1% agarose gel. The gel-confined nanoparticles can be transferred between reaction and washing media simply by immersing the gel slab in the solution of interest. The agarose matrix retains nanoparticles but is swiftly penetrated by the antibodies of interest. The antibodies are covalently anchored to the nanoparticles using conventional cross-linking strategies, and the resulting antibody functionalized nanoparticles are recovered from the gel through electroelution. We demonstrate the efficacy of this nanoparticle functionalization approach by labeling specific receptors on cellular surfaces with functionalized silver nanoparticles that are stable under physiological conditions.
ACS Appl Mater Interfaces 2010 Jan
PMID:Control of colloid surface chemistry through matrix confinement: facile preparation of stable antibody functionalized silver nanoparticles. 2016 60

In this work we demonstrate two building blocks of a scalable manufacturing technology for nanoscale electronic devices based on direct-write printing: an architecture for high-yield printing of electrode gaps with 100 nm dimension and a low-temperature silver complex ink for integration of organic materials with high conductivity metal interconnects. We use single printed droplets that are made to dewet slowly from each other to allow reliable, high yield patterning even in the presence of certain surface defects.
ACS Nano 2010 Mar 23
PMID:High yield, single droplet electrode arrays for nanoscale printed electronics. 2016 29

A simplified template-assisted layering approach for preparing catalytic conical tube microjet engines based on sequential deposition of platinum and gold on an etched silver wire template followed by dicing and dissolution of the template is described. The method allows detailed control over the tube parameters and hence upon the performance of the microengine. The recoiling bubble propulsion mechanism of the tubular microengine, associated with the ejection of internally generated oxygen microbubbles, addresses the ionic-strength limitation of catalytic nanowire motors and leads to a salt-independent movement. Similar rates of bubble generation and motor speeds are observed in salt-free and salt-rich media (at elevated ionic-strength environments as high as 1 M NaCl). Plating of an intermediate nickel layer facilitates a magnetically guided motion as well as the pickup and transport of large (magnetic) "cargo". Surfactant addition is shown to decrease the surface tension and offer a more frequent formation of dense smaller bubbles. The new and improved motor capabilities along with the simple preparation route hold great promise for using catalytic micromotors in diverse and important applications.
ACS Nano 2010 Apr 27
PMID:Template-assisted fabrication of salt-independent catalytic tubular microengines. 2042 Apr 69

The novel application of gold and silver nanorods as irreversible thermochromic dyes in polymeric ionic liquid (PIL) nanocomposites is proposed here. These materials have been synthesized by anion exchange of an imidazolium-based PIL in a solution that also contained gold nanorods. This resulted in the entrapment of the nanoobjects within a solid polymer precipitate. In this article, the effect of the temperature was studied in relation to the change of shape and, consequently, color of the gold or silver nanorods within the films. For the nanocomposites studied here, a maximum of two visual thermochromic transitions was observed for gold nanorods and up to three transitions were observed for silver nanorods.
ACS Appl Mater Interfaces 2009 Feb
PMID:Irreversible thermochromic behavior in gold and silver nanorod/polymeric ionic liquid nanocomposite films. 2035 22

We present strong photoluminescence from single Ag nanowires (NWs), their disordered blinking behavior, and their dependence on substrate potential. The stochastic bursts (<10 ms) in the photoluminescence trajectories of single Ag NWs in air are observed and attributed to the photoactivated fluorescence silver clusters. The dynamic changes in the photoluminescence are analyzed using autocorrelation function, statistical analysis of the stochastic durations, and probability density function to reveal the disordered nature of the spontaneous photochemical reaction at each individual Ag NWs under laser irradiation. Stable PL is observed for single Ag NWs in alkaline electrolyte and is found to be highly dependent on the electrochemical potential. The PL from single Ag NWs is found to be weakly dependent on polarization direction of the incident light and strongly dependent on the interactions with adjacent NWs.
ACS Nano 2010 Apr 27
PMID:Photoluminescence and spectroelectrochemistry of single ag nanowires. 2035 37

Adding conductive fillers to nonconductive polymers is a common way to make soft conductive materials such as conductive adhesives. An important issue is how to achieve high volume conductivity with acceptable mechanical performance. Two questions pertaining to this issue were studied in this paper. One question was whether the maximum conductivity benefits from larger or smaller particle sizes. The second was what is the maximum achievable conductivity. One incentive for this work is the recent availability of nanomaterials that provide opportunities to make conductive composites using much smaller particles than in the past. We found that the conductivity of platinum, carbon black, and silver particles in their polyurethane composites did not vary greatly with particle size (from micrometer to nanometer range). What was unexpected was that in all the composite examples, the highest conductivity achieved was only on the order of 1% of that of the pure bulk conductive materials. Further experiments to emulate these conductive composites with platinum, carbon black, copper, and nickel particles without polymer matrix showed similar results, indicating the issue is not simply dispersion homogeneity, nano versus macro particles, particle connectivity/percolation, or the presence of the matrix materials. We interpret this to mean that the composite systems are intrinsically limited by the contact between filler particles.
ACS Appl Mater Interfaces 2009 Jan
PMID:Maximum conductivity of packed nanoparticles and their polymer composites. 2035 60

A facile ambient temperature route to the fabrication of surface silver-metallized polyimide films is described. Silver(I) trifluoromethanesulfonate or silver(I) nitrate and a polyimide, derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and an equimolar amount of 4,4'-oxydianiline and 3,5-diaminobenzoic acid, were dissolved together in dimethylacetamide. Silver(I)-doped films were prepared at thicknesses of 25-40 microm and depleted of solvent by evaporation at ambient temperature and low humidity. The silver(I)-ion-containing films were then treated with aqueous solutions of the reducing agents hydrazine hydrate and hydroxylamine, which brought forth surface-silvered films exhibiting conductivity on the order of bulk polycrystalline silver accompanied by modest-to-high specular reflectivity.
ACS Appl Mater Interfaces 2009 Jan
PMID:Latent synthesis of electrically conductive surface-silvered polyimide films. 2035 73


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