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Author: Csáki, Andrea × End date: 2019 × Start date: 2010 × Type: Text × Publisher: Amsterdam [u.a.] : Elsevier × WGL Institute: IPHT ×

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    Wet-chemical Passivation of Anisotropic Plasmonic Nanoparticles for LSPR-sensing by a Silica Shell
    (Amsterdam [u.a.] : Elsevier, 2015) Thiele, Matthias; Götz, Isabell; Trautmann, Steffen; Müller, Robert; Csáki, Andrea; Henkel, Thomas; Fritzsche, Wolfgang
    Metal nanoparticles showing the effect of localized surface plasmon resonance (LSPR), a collective oscillation of the conduction electrons upon interaction with light, represent an interesting tool for bioanalytics. This resonance is influenced by changes in the environment, and can be therefore used for the detection of molecular layers. The sensitivity, this means the extent of wavelength resonance shift per change in refractive index in the environment, represents an important performance parameter. It is higher for silver compared to gold particles, and is also increased for anisotropic particles. So silver triangles show a high potential for highly sensitive plasmonic nanoparticles. However, the stability under ambient conditions is rather poor. The paper demonstrates the passivation of silver triangles by silica coating using a wet-chemical approach. It compares the sensitivity for particles with and without passivation, and visualizes the passivation effect in a high resolution, single particle TEM study.
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    Propagating and localized surface plasmon resonance sensing — A critical comparison based on measurements and theory
    (Amsterdam [u.a.] : Elsevier, 2016) Jatschka, Jacqueline; Dathe, André; Csáki, Andrea; Fritzsche, Wolfgang; Stranik, Ondrej
    With its potential for ultrasensitive, label-free detection of molecular interactions, sensing methods based on the surface plasmon resonance (SPR) effect fully meet the requirements for modern analytical techniques. Already established by using propagating SPR in thin gold layers, the last years witnessed the emergence of another related technique utilizing extremely miniaturized noble metal sensor structures, based on a localized SPR. This paper provides a critical comparison of these kinds of SPR sensing, reviews the foundation of both general approaches, presents experimental data on exactly the same molecular model system using both techniques, as well as theoretical considerations in order to allow reasonable comparison. It highlights the specific features and effects, in order to provide guidance in choosing the right technique for given bioanalytical tasks. The study demonstrated the capabilities of LSPR for sensing of molecular layers even in the lower nanometer dimension. For the detection of small (bio)molecules, smaller particle diameters are favored regarding highest sensitivity. It also presents an approach to obtain refractive index and the thickness of a molecular film by analyzing the signal response of plasmonic sensors with metal nanoparticles. Moreover, an additional method for the improvement of the parameters' determination is introduced.