Browsing by Author "Olson, Jana"

Now showing 1 - 5 of 5
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    Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions
    (American Chemical Society, 2013) Dominguez-Medina, Sergio; Blankenburg, Jan; Olson, Jana; Landes, Christy F.; Link, Stephan; Laboratory for Nanophotonics
    We find that citrate-stabilized gold nanoparticles aggregate and precipitate in saline solutions below the NaCl concentration of many bodily fluids and blood plasma. Our experiments indicate that this is due to complexation of the citrate anions with Na+ cations in solution. A dramatically enhanced colloidal stability is achieved when bovine serum albumin is adsorbed to the gold nanoparticle surface, completely preventing nanoparticle aggregation under harsh environmental conditions where the NaCl concentration is well beyond the isotonic point. Furthermore, we explore the mechanism of the formation of this albumin "corona" and find that monolayer protein adsorption is most likely ruled by hydrophobic interactions. As for many nanotechnology-based biomedical and environmental applications, particle aggregation and sedimentation are undesirable and could substantially increase the risk of toxicological side-effects, the formation of the BSA corona presented here provides a low-cost bio-compatible strategy for nanoparticle stabilization and transport in highly ionic environments.
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    Development of an Active Display Using Plasmonic Nanorods and Liquid Crystals
    (2015-08-26) Olson, Jana; Link, Stephan; Halas, Naomi; Nordlander, Peter
    The current generation of display technology has already provided the public with displays that exhibit high color fidelity, faster than the eye can see frame rates, and screens spanning an order of magnitude in size, from hand-held to wall-sized. What has yet to be achieved is for display technology to become versatile, fitting into the human environment in a way that is unobtrusive, ergonomic, and promotes an improved quality of life. This thesis points to nanotechnology, particularly plasmonic nanomaterials, as a way to bring display technologies to that next level. The work presented in this thesis is the development of a nanomaterial that is vividly colored, electronically controllable, and highly versatile in its possible applications. First, an understanding of the electronic switching of nematic liquid crystals is gained via combination of randomly oriented gold nanorods with homogeneously aligned nematic liquid crystal. The nanorods are used to probe the birefringence of the liquid crystal as an in-plane bias is used to switch the alignment of the liquid crystal from a uniform parallel alignment to a 90 degree twisted alignment. This mechanism is confirmed with theoretical modeling using Jones Calculus. Second, the polarization sensitivity of the nanorods is exploited by creating a hexagonal array of co-oriented nanorods to form a plasmonic pixel using electron beam lithography. Aluminum was chosen as the plasmonic material because its plasmon resonance can span the whole visible region, and because of its compatibility with the semiconductor manufacturing industry. The outstanding vivid color of these pixels is dependent on the physical characteristics of the individual nanorods, and also on the inter-rod spacing. Dipole coupling within the array of ~300 nm separated nanorods is used to restrict plasmon scattering at both long- and short-wavelengths. A simple 3-step color control mechanism was developed that others can use to produce aluminum plasmonic pixels with colors on-par with standard red, green, and blue displays. Finally, mm-scale colored pixels are demonstrated to be switchable with a liquid crystal display, and therefore immediately compatible with current liquid crystal display technology.
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    High Chromaticity Aluminum Plasmonic Pixels for Active Liquid Crystal Displays
    (American Chemical Society, 2016) Olson, Jana; Manjavacas, Alejandro; Basu, Tiyash; Huang, Da; Schlather, Andrea E.; Zheng, Bob; Halas, Naomi; Nordlander, Peter; Link, Stephan; Laboratory for Nanophotonics
    Chromatic devices such as flat panel displays could, in principle, be substantially improved by incorporating aluminum plasmonic nanostructures instead of conventional chromophores that are susceptible to photobleaching. In nanostructure form, aluminum is capable of producing colors that span the visible region of the spectrum while contributing exceptional robustness, low cost, and streamlined manufacturability compatible with semiconductor manufacturing technology. However, individual aluminum nanostructures alone lack the vivid chromaticity of currently available chromophores because of the strong damping of the aluminum plasmon resonance in the visible region of the spectrum. In recent work, we showed that pixels formed by periodic arrays of Al nanostructures yield far more vivid coloration than the individual nanostructures. This progress was achieved by exploiting far-field diffractive coupling, which significantly suppresses the scattering response on the long-wavelength side of plasmonic pixel resonances. In the present work, we show that by utilizing another collective coupling effect, Fano interference, it is possible to substantially narrow theﾠshort-wavelengthﾠside of the pixel spectral response. Together, these two complementary effects provide unprecedented control of plasmonic pixel spectral line shape, resulting in aluminum pixels with far more vivid, monochromatic coloration across the entire RGB color gamut than previously attainable. We further demonstrate that pixels designed in this manner can be used directly as switchable elements in liquid crystal displays and determine the minimum and optimal numbers of nanorods required in an array to achieve good color quality and intensity.
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    Optical characterization of single plasmonic nanoparticles
    (Royal Society of Chemistry, 2014) Olson, Jana; Dominguez-Medina, Sergio; Hoggard, Anneli; Wang, Lin-Yung; Chang, Wei-Shun; Link, Stephan; Laboratory for Nanophotonics
    This tutorial review surveys the optical properties of plasmonic nanoparticles studied by various single particle spectroscopy techniques. The surface plasmon resonance of metallic nanoparticles depends sensitively on the nanoparticle geometry and its environment, with even relatively minor deviations causing significant changes in the optical spectrum. Because for chemically prepared nanoparticles a distribution of their size and shape is inherent, ensemble spectra of such samples are inhomogeneously broadened, hiding the properties of the individual nanoparticles. The ability to measure one nanoparticle at a time using single particle spectroscopy can overcome this limitation. This review provides an overview of different steady-state single particle spectroscopy techniques that provide detailed insight into the spectral characteristics of plasmonic nanoparticles.
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    Using the Plasmon Linewidth To Calculate the Time and Efficiency of Electron Transfer between Gold Nanorods and Graphene
    (American Chemical Society, 2013) Hoggard, Anneli; Wang, Lin-Yung; Ma, Lulu; Fang, Ying; You, Ge; Olson, Jana; Liu, Zheng; Chang, Wei-Shun; Ajayan, Pulickel M.; Link, Stephan; Laboratory for Nanophotonics
    We present a quantitative analysis of the electron transfer between single gold nanorods and monolayer graphene under no electrical bias. Using single-particle dark-field scattering and photoluminescence spectroscopy to access the homogeneous linewidth, we observe broadening of the surface plasmon resonance for gold nanorods on graphene compared to nanorods on a quartz substrate. Because of the absence of spectral plasmon shifts, dielectric interactions between the gold nanorods and graphene are not important and we instead assign the plasmon damping to charge transfer between plasmon-generated hot electrons and the graphene that acts as an efficient acceptor. Analysis of the plasmon linewidth yields an average electron transfer time of 160 ± 30 fs, which is otherwise difficult to measure directly in the time domain with single-particle sensitivity. In comparison to intrinsic hot electron decay and radiative relaxation, we furthermore calculate from the plasmon linewidth that charge transfer between the gold nanorods and the graphene support occurs with an efficiency of ∼10%. Our results are important for future applications of light harvesting with metal nanoparticle plasmons and efficient hot electron acceptors as well as for understanding hot electron transfer in plasmon-assisted chemical reactions.