Solution-Phase, Triangular Ag Nanotriangles Fabricated by Nanosphere Lithography

Haes, Amanda J.; Zhao, Jing; Zou, Shengli; Own, Christopher S.; Marks, Laurence D.; Schatz, George C.; Duyne, Richard P. Van

doi:10.1021/jp051178g

Cited by 112 publications

(85 citation statements)

References 61 publications

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“…Especially in buffer solutions, commonly used in bio-assays, metal nanoparticles tend to easily get washed off the surface. [277][278] Only recently, this problem has started to attract attention and first solutions have been proposed. [45,279] Nanoparticles have been anchored to small holes in the substrates and the decrease in signal intensity over one hour improved from 50% loss in untreated samples to 13% loss for surface anchored particles.…”

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confidence: 99%

Surface Patterning with Colloidal Monolayers

Vogel

2012

Springer Theses

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This thesis focuses on the controlled assembly of monodisperse polymer colloids into ordered two-dimensional arrangements. These assemblies, commonly referred to as colloidal monolayers, are subsequently used as masks for the generation of arrays of complex metal nanostructures on solid substrates.The motivation of the research presented here is twofold. First, monolayer crystallization methods were developed to simplify the assembly of colloids and to produce more complex arrangements of colloids in a precise way. Second, various approaches to colloidal lithography are designed with the aim to include novel features or functions to arrays of metal nanostructures.The air/water interface was exploited for the crystallization of colloidal monolayer architectures as it combines a two-dimensional confinement with a high lateral mobility of the colloids that is beneficial for the creation of high long range order. A direct assembly of colloids is presented that provides a cheap, fast and conceptually simple methodology for the preparation of ordered colloidal monolayers. The produced two-dimensional crystals can be transformed into nonclose-packed architectures by a plasma-induced size reduction step, thus providing valuable masks for more sophisticated lithographic processes. Finally, the controlled co-assembly of binary colloidal crystals with defined stoichiometries on a Langmuir trough is introduced and characterized with respect to accessible configurations and size ratios.Several approaches to lithography are presented that aim at introducing different features to colloidal lithography. First, using metal-complex containing latex particles, the synthesis of which is described as well, symmetric arrays of metal nanoparticles can be created by controlled combustion of the organic material of the colloids. The process does not feature an inherent limit in nanoparticle size and is able to produce complex materials as will be demonstrated for FePt alloy particles. Precise control over both size and spacing of the particle array is presented.Second, two lithographic processes are introduced to create sophisticated nanoparticle dimer units consisting of two crescent shaped nanostructures in close proximity; essentially by using a single colloid as mask to generate two structures simultaneously. Strong coupling processes of the parental plasmon resonances of the two objects are observed that are accompanied by high near-field enhancements. A plasmon hybridization model is elaborated to explain all polarization dependent shifts of the resonance positions. Last, a technique to produce laterally patterned, ultra-flat substrates without surface topographies by embedding gold nanoparticles in a silicon dioxide matrix is applied to construct robust and re-usable sensing architectures and to introduce an approach for the nanoscale patterning of solid supported lipid bilayer membranes.

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confidence: 99%

Surface Patterning with Colloidal Monolayers

Vogel

2012

Springer Theses

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“…In contrast, the LSPR sensing region in Ag nanoparticles is confined to a thin (25 -30 nm) shell around the nanoparticle. 12 As a result, LSPR sensors possess 40-fold greater spatial resolution normal to the sensor surface, allowing improved detection of low molecular weight binding events. Monitoring LSPR changes in real-time provides information about the dynamics of binding events and protein folding, with much less interference from bulk refractive index changes.…”

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confidence: 99%

A Calcium-Modulated Plasmonic Switch

et al. 2008

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Cellular activities are mediated by proteins, which often undergo conformational changes to regulate binding and enzymatic activities that direct signaling pathways. Hence, it is important to develop and apply tools to characterize dynamic changes in protein conformation. A variety of approaches are available, including those based on NMR, 1 FRET, 2 and plasmonics. 3,4 Plasmonic approaches are particularly useful because they provide an intense signal that does not bleach and allow non-destructive measurement over long periods of time. In addition to acting as probes of molecular interactions, plasmonic devices have significant potential as nanoscale optical switches, waveguides, light sources, microscopes and lithographic tools. 3,4 Herein, we demonstrate a plasmonic switching device based on the calcium-induced conformational changes of calmodulin. The extinction maximum (λ max ) of a Localized Surface Plasmon Resonance (LSPR) sensor functionalized with calmodulin reversibly shifts by 2-3 nm in response to changes in Ca 2+ concentration, creating a unique on/off switch and providing information about the dynamics and structure of the protein. A high resolution (HR)-LSPR spectrometer with a wavelength resolution (3σ) of 1.5×10 -2 nm was used to detect the calciummodulated wavelength shifts (supporting information).The LSPR is a unique nanoscale phenomenon that gives rise to an intense extinction and scattering spectrum in noble metal nanoparticles that is highly dependent on the local refractive index at the nanoparticle surface. Biomolecule adsorption to a nanoparticle alters the local refractive index, causing shifts in the extinction maximum (λ max ). The magnitude and direction of these shifts provide detailed information about the packing density of the adsorbed species. 5 LSPR sensors can be used to characterize and detect a wide variety of biological events, including DNA hybridization, 6 carbohydrate-protein binding, 7 and antigen-antibody interactions. 8,9 A commercially established technology based on propagating SPR in thin Au films can sense changes in refractive index up to 1 μm away from the sensor surface. Such SPR sensors have been used to detect protein conformational changes due to denaturation. 10 11, However, the relatively large sensing region of propagating SPR sensors gives rise to interference from bulk refractive index changes. In contrast, the LSPR sensing region in Ag nanoparticles is confined to a thin (25 -30 nm) shell around the nanoparticle. 12 As a result, LSPR sensors possess 40-fold greater spatial resolution normal to the sensor surface, allowing improved detection of low molecular weight binding events. Monitoring LSPR changes in real-time provides information about the dynamics of binding events and protein folding, with much less interference from bulk refractive index changes.vanduyne@northwestern.edu Supporting Information Available: Experimental details and data not shown in the manuscript are available free of charge via the internet at http://pubs.acs.org. To immobiliz...

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“…These approaches can be summarized into two categories, topdown and bottom-up (Stewart et al 2008 ). Top-down techniques involve using various forms of conventional lithographic techniques to pattern nanostructures (e.g., on to planar substrate), whereas in bottom-up methods, nanostructures are " built " or " assembled " from atoms, molecules, and/or more complex mesoscale objects (Prikulis et al 2004, Haes et al 2005, Hicks et al 2007, Stewart et al 2008. Freely-floating AuNP colloids are usually made through the bottom-up approach.…”

Section: Synthesis/fabrication and Functionalization Of Aunp Probesmentioning

confidence: 99%

Detection of chemical pollutants in water using gold nanoparticles as sensors: a review

Wang

2012

Reviews in Analytical Chemistry

147

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Rapid and accurate evaluation of pollutant contamination in water is one of the key tasks of environmental monitoring. To make onsite assessment feasible, the analytical tools should be easy to operate, with minimal sample preparation needs. Gold nanoparticle (AuNP)-based sensors have the potential to detect toxins, heavy metals, and inorganic and organic pollutants in water rapidly with high sensitivity, and they are expected to play an increasingly important role in environmental monitoring. In this article, the synthesis, fabrication and functionalization of AuNPs are discussed, and the recent advances in the development and application of AuNP-based sensors for the determination of various pollutants contamination in water are reviewed.

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Solution-Phase, Triangular Ag Nanotriangles Fabricated by Nanosphere Lithography

Cited by 112 publications

References 61 publications

Surface Patterning with Colloidal Monolayers

Surface Patterning with Colloidal Monolayers

A Calcium-Modulated Plasmonic Switch

Detection of chemical pollutants in water using gold nanoparticles as sensors: a review

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