Browsing by Author "Johnson, Bruce R."

Now showing 1 - 6 of 6
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    All optical nanoscale sensor
    (2011-10-25) Halas, Nancy J.; Johnson, Don H.; Bishnoi, Sandra Whaley; Levin, Carly S.; Rozell, Christopher John; Johnson, Bruce R.; Rice University; United States Patent and Trademark Office
    A composition comprising a nanoparticle and at least one adsorbate associated with the nanoparticle, wherein the adsorbate displays at least one chemically responsive optical property. A method comprising associating an adsorbate with a nanoparticle, wherein the nanoparticle comprises a shell surrounding a core material with a lower conductivity than the shell material and the adsorbate displays at least one chemically responsive optical property, and engineering the nanoparticle to enhance the optical property of the adsorbate. A method comprising determining an optical response of an adsorbate associated with a nanoparticle as a function of a chemical parameter, and parameterizing the optical response to produce a one-dimensional representation of at least a portion of a spectral window of the optical response in a high dimensional vector space.
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    Bleach Imaged Plasmon Propagation (BlIPP) of Metallic Nanoparticle Waveguides
    (2013-09-16) Solis, David; Link, Stephan; Landes, Christy F.; Johnson, Bruce R.
    The high speed transfer of information in materials with dimensions below the sub-diffraction limit is essential for future technological developments. Metallic nanoparticle (NP) waveguides serve a unique role in efficient energy transfer in this size regime. Light may be confined to metallic structures and propagate along the surface of the waveguide via propagating plasmon waves known as surface plasmon polaritons (SPPs). Plasmon propagation of energy in metallic structures is not perfect however and damping losses from the waveguide material lead to a characteristic exponential decay in the plasmon near field intensity. This decay length is known as the propagation length and serves as an excellent metric to compare various waveguide materials and structures to one another at particular excitation wavelengths. This thesis presents recent work in the development of a novel measurement technique termed bleach imaged plasmon propagation (BlIPP). BlIPP uses the photobleaching property of fluorophores and far field fluorescence microscopy to probe the near-field intensity of propagating plasmons and determine the propagation length. The experimental setup, image analysis, conditions, and application of BlIPP are developed within this thesis and an in depth review of the 1-photon photobleaching mechanism is also investigated. The BlIPP method is used to investigate long plasmon propagation lengths along straight chains of tightly packed Au NPs through the coupling of light to sub-radiant propagating modes, where radiative energy losses are suppressed. The findings of this work reveal, experimentally, the importance of small gap distances for the propagation of energy. Complex chain architectures are then explored using BlIPP measurements of tightly packed straight and bent chains of spherical silver NPs. We observe the highly efficient propagation of energy around sharp corners with no additional bending losses. The findings of this thesis demonstrate the advantages and capabilities of using BlIPP propagation length measurement. Further, BlIPP is used to reveal the advantage of coupling light to sub-radiant modes of NP chains, which demonstrate the ability to guide light efficiently across long distances and around complex structures, bringing us a step closer to the goal of applying plasmonic devices and circuitry in ultra compact opto-electronic devices.
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    Compact support wavelet representations for solution of quantum and electromagnetic equations: Eigenvalues and dynamics
    (2010) Acevedo, Ramiro, Jr; Johnson, Bruce R.
    Wavelet-based algorithms are developed for solution of quantum and electromagnetic differential equations. Wavelets offer orthonormal localized bases with built-in multiscale properties for the representation of functions, differential operators, and multiplicative operators. The work described here is part of a series of tools for use in the ultimate goal of general, efficient, accurate and automated wavelet-based algorithms for solution of differential equations. The most recent work, and the focus here, is the elimination of operator matrices in wavelet bases. For molecular quantum eigenvalue and dynamics calculations in multiple dimensions, it is the coupled potential energy matrices that generally dominate storage requirements. A Coefficient Product Approximation (CPA) for the potential operator and wave function wavelet expansions dispenses with the matrix, reducing storage and coding complexity. New developments are required, however. It is determined that the CPA is most accurate for specific choices of wavelet families, and these are given here. They have relatively low approximation order (number of vanishing wavelet function moments), which would ordinarily be thought to compromise both wavelet reconstruction and differentiation accuracy. Higher-order convolutional coefficient filters are determined that overcome both apparent problems. The result is a practical wavelet method where the effect of applying the Hamiltonian matrix to a coefficient vector can be calculated accurately without constructing the matrix. The long-familiar Lanczos propagation algorithm, wherein one constructs and diagonalizes a symmetric tridiagonal matrix, uses both eigenvalues and eigenvectors. We show here that time-reversal-invariance for Hermitian Hamiltonians allows a new algorithm that avoids the usual need to keep a number Lanczos vectors around. The resulting Conjugate Symmetric Lanczos (CSL) method, which will apply for wavelets or other choices of basis or grid discretization, is simultaneously low-operation-count and low-storage. A modified CSL algorithm is used for solution of Maxwell's time-domain equations in Hamiltonian form for non-lossy media. The matrix-free algorithm is expected to complement previous work and to decrease both storage and computational overhead. It is expected- that near-field electromagnetic solutions around nanoparticles will benefit from these wavelet-based tools. Such systems are of importance in plasmon-enhanced spectroscopies.
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    Density matrix calculation of surface enhanced Raman scattering for silver nanoshells coated with p-mercaptoaniline
    (2005) Gibson, Joshua Wayne; Johnson, Bruce R.
    The tremendous increase in Raman-scattered photons seen in Surface-Enhanced Raman Scattering (SERS) has led to its adoption as a common analytical laboratory tool in spite of lingering questions about the phenomenon. One recent example is the demonstration by Jackson, et al., of SERS for silver nanoshells each consisting of an inner silica sphere encased in a silver shell. In concert with these experiments, the current investigation is directed at quantum mechanical calculation and modeling of the SERS signals to be expected for silver nanoshells coated by molecules based on ab initio calculations on an AgPMA salt model with the thiol bonding to silver rather than an H atom as in the free PMA molecule. We take the information from these calculations and consider a density matrix formalism including the effects of the strong electromagnetic near fields around the metal surface, the molecules' orientation and energy, and the associated Raman spectra.
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    Robert F. Curl, Jr.: Physical Chemist and Codiscoverer of Fullerenes
    (PNAS, 2022) Brooks, Philip R.; Weisman, R. Bruce; Johnson, Bruce R.
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    Teslaphoresis of Carbon Nanotubes
    (American Chemical Society, 2016) Bornhoeft, Lindsey R.; Castillo, Aida C.; Smalley, Preston R.; Kittrell, Carter; James, Dustin K.; Brinson, Bruce E.; Rybolt, Thomas R.; Johnson, Bruce R.; Cherukuri, Tonya K.; Cherukuri, Paul
    This paper introduces Teslaphoresis, the directed motion and self-assembly of matter by a Tesla coil, and studies this electrokinetic phenomenon using single-walled carbon nanotubes (CNTs). Conventional directed self-assembly of matter using electric fields has been restricted to small scale structures, but with Teslaphoresis, we exceed this limitation by using the Tesla coil’s antenna to create a gradient high-voltage force field that projects into free space. CNTs placed within the Teslaphoretic (TEP) field polarize and self-assemble into wires that span from the nanoscale to the macroscale, the longest thus far being 15 cm. We show that the TEP field not only directs the self-assembly of long nanotube wires at remote distances (>30 cm) but can also wirelessly power nanotube-based LED circuits. Furthermore, individualized CNTs self-organize to form long parallel arrays with high fidelity alignment to the TEP field. Thus, Teslaphoresis is effective for directed self-assembly from the bottom-up to the macroscale.