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Now showing items 1 - 16 of 4085

  • Multi-resonant plasmonic nanodome arrays for label-free biosensing applications

    Choi, Charles J.   Semancik, Steve  

    The characteristics and utility of plasmonic nanodome arrays capable of supporting multiple resonance modes are described. A low-cost, large-area replica molding process is used to produce, on flexible plastic substrates, two-dimensional periodic arrays of cylinders that are subsequently coated with SiO2 and Ag thin films to form dome-shaped structures, with 14 nm spacing between the features, in a precise and reproducible fashion. Three distinct optical resonance modes, a grating diffraction mode and two localized surface plasmon resonance (LSPR) modes, are observed experimentally and confirmed by finite-difference-time-domain (FDTD) modeling which is used to calculate the electromagnetic field distribution of each resonance around the nanodome array structure. Each optical mode is characterized by measuring sensitivity to bulk refractive index changes and to surface effects, which are examined using stacked polyelectrolyte layers. The utility of the plasmonic nanodome array as a functional interface for biosensing applications is demonstrated by performing a bioassay to measure the binding affinity constant between protein A and human immunoglobulin G (IgG) as a model system. The nanoreplica molding process presented in this work allows for simple, inexpensive, high-throughput fabrication of nanoscale plasmonic structures over a large surface area (120 x 120 mm(2)) without the requirement for high resolution lithography or additional processes such as etching or liftoff. The availability of multiple resonant modes, each with different optical properties, allows the nanodome array surface to address a wide range of biosensing problems with various target analytes of different sizes and configurations.
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  • Single-step fabrication and characterization of photonic crystal biosensors with polymer microfluidic channels

    Choi, Charles J.   Cunningham, Brian T.  

    A method for simultaneously integrating label-free photonic crystal biosensor technology into microfluidic channels by a single-step replica molding process is presented. By fabricating both the sub-micron features of the photonic crystal sensor structure and the > 10 mu m features of a flow channel network in one step at room temperature on a plastic substrate, the sensors are automatically self-aligned with the flow channels, and patterns of arbitrary shape may be produced. By measuring changes in the resonant peak reflected wavelength from the photonic crystal structure induced by changes in dielectric permittivity within an evanescent field region near its surface, detection of bulk refractive index changes in the fluid channel or adsorption of biological material to the sensor surface is demonstrated. An imaging detection instrument is used to characterize the spatial distribution of the photonic crystal resonant wavelength, gathering thousands of independent sensor readings within a single fluid channel.
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  • Effect of interdome spacing on the resonance properties of plasmonic nanodome arrays for label-free optical sensing

    Choi, Charles J.   Semancik, Steve  

    In this paper, we report on experimental and theoretical studies that investigate how the structural properties of plasmonic nanodome array devices determine their optical properties and sensing performance. We examined the effect of the interdome gap spacing within the plasmonic array structures on the performance for detection of change in local refractive index environment for label-free capture affinity biosensing applications. Optical sensing properties were characterized for nanodome array devices with interdome spacings of 14 nm, 40 nm, and 79 nm, as well as for a device where adjacent domes are in contact. For each interdome spacing, the extinction spectrum was measured using a broadband reflection instrumentation, and finite-difference-time-domain (FDTD) simulation was used to model the local electric field distribution associated with the resonances. Based on these studies, we predict that nanodome array devices with gap between 14 nm to 20 nm provide optimal label-free capture affinity biosensing performances, where the dipole resonance mode exhibits the highest overall surface sensitivity, as well as the lowest limit of detection. (C) 2013 Optical Society of America
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  • Label-Free Photonic Crystal Biosensor Integrated Microfluidic Chip for Determination of Kinetic Reaction Rate Constants

    Choi, Charles J.   Block, Ian D.   Bole, Brian   Dralle, David   Cunningham, Brian T.  

    We demonstrate a photonic crystal integrated microfluidic chip that is compatible with a 384-well microplate format for measuring kinetic reaction rate constants in high-throughput biomolecular interaction screening applications. The device enables low volume kinetic analysis of protein-protein interactions with low flow latency, and control of five analyte flow channels with a single control point. The structure is fabricated with a replica molding process that produces the submicron photonic crystal structure simultaneously with the micrometer-scale fluid channel structure. The device significantly reduces the kinetic assay time required compared with a conventional biosensor microplate in which reagents reach the active detection surface by diffusion. Using the photonic crystal sensor fluid network system, we demonstrate determination of the kinetic association/dissociation rate constants between immobilized ligands and analytes in the flow stream, using the heparin/lactoferrin system as an example.
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  • Charles J. Fillmore

    Ackerman, Farrell; Kay, Paul; O’Connor, Mary Catherine  

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  • Charles J. Fillmore

    Jurafsky   Dan  

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  • Charles J. Lightdale

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  • Charles J. Burstone, 1928-2015

    Nanda, Ravindra   Roberts, W. Eugene  

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  • Charles J. Erasmus (1921-2012)

    O\"Connor   Mary I.  

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  • Charles J. Limb: Inner Sparks

    Anstead   Alicia  

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  • In Memoriam Charles J. Burstone (1928-2015)

    Démogé Paul-Hugues  

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  • Charles J. Adams 1924-2011

    Issa J. Boullata  

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  • Charles J. Pedersen\"s legacy to chemistry

    Izatt   Reed M.  

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  • In memoriam: Charles J. Epstein

    John C. Carey   Mahin Golabi   Julie R. Korenberg  

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  • Population Fluctuations in Rodentsby Charles J. Krebs

    Review by: Kenneth B. Armitage  

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  • Professor ir. Charles J. Hoogendoorn (1930-2012)

    Chris Kleijn  

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