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Author: Deckert, Volker × End date: 2015 × Start date: 2014 × Type: Text × WGL Institute: IPHT ×

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Now showing 1 - 5 of 5
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    Single molecule level plasmonic catalysis – a dilution study of p-nitrothiophenol on gold dimers
    (Cambridge : Soc., 2015) Zhang, Zhenglong; Deckert-Gaudig, Tanja; Singh, Pushkar; Deckert, Volker
    Surface plasmons on isolated gold dimers can initiate intermolecular reactions of adsorbed p-nitrothiophenol. At the single molecule level when dimerization is not possible an intramolecular reaction can be observed. Experimental evidence indicates that plasmon-induced hot electrons provide the required activation energy.
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    Differences in single and aggregated nanoparticle plasmon spectroscopy
    (Cambridge : RSC Publ., 2014) Singh, Pushkar; Deckert-Gaudig, Tanja; Schneidewind, Henrik; Kirsch, Konstantin; van Schrojenstein Lantman, Evelien M.; Weckhuysen, Bert M.; Deckert, Volker
    Vibrational spectroscopy usually provides structural information averaged over many molecules. We report a larger peak position variation and reproducibly smaller FWHM of TERS spectra compared to SERS spectra indicating that the number of molecules excited in a TERS experiment is extremely low. Thus, orientational averaging effects are suppressed and micro ensembles are investigated. This is shown for a thiophenol molecule adsorbed on Au nanoplates and nanoparticles.
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    Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles
    (Cambridge : RSC Publ., 2015) Rodriguez, Raul D.; Sheremet, Evgeniya; Deckert-Gaudig, Tanja; Chaneac, Corinne; Hietschold, Michael; Deckert, Volker; Zahn, Dietrich R. T.
    Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm−1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal–nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.
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    A manual and an automatic TERS based virus discrimination
    (Cambridge : RSC Publ., 2015) Olschewski, Konstanze; Kämmer, Evelyn; Stöckel, Stephan; Bocklitz, Thomas; Deckert-Gaudig, Tanja; Zell, Roland; Cialla-May, Dana; Weber, Karina; Deckert, Volker; Popp, Jürgen
    Rapid techniques for virus identification are more relevant today than ever. Conventional virus detection and identification strategies generally rest upon various microbiological methods and genomic approaches, which are not suited for the analysis of single virus particles. In contrast, the highly sensitive spectroscopic technique tip-enhanced Raman spectroscopy (TERS) allows the characterisation of biological nano-structures like virions on a single-particle level. In this study, the feasibility of TERS in combination with chemometrics to discriminate two pathogenic viruses, Varicella-zoster virus (VZV) and Porcine teschovirus (PTV), was investigated. In a first step, chemometric methods transformed the spectral data in such a way that a rapid visual discrimination of the two examined viruses was enabled. In a further step, these methods were utilised to perform an automatic quality rating of the measured spectra. Spectra that passed this test were eventually used to calculate a classification model, through which a successful discrimination of the two viral species based on TERS spectra of single virus particles was also realised with a classification accuracy of 91%.
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    Label-free monitoring of plasmonic catalysis on the nanoscale
    (Cambridge : Soc., 2015) Zhang, Zhenglong; Deckert-Gaudig, Tanja; Deckert, Volker
    Plasmonics is the description of specific light matter interactions of metallic structures. In general the size of such structures is well in the nanometer regime and also determines such specific characteristics as color, field confinement etc. Plasmon-induced hot electrons play a vital role in so-called plasmonic catalysis, a field that has recently attracted attention as a new reaction platform. Current reports introduce such nanoscale catalysis as an effective approach to concentrate the energy of visible light and direct it to adsorbed molecules, thereby increasing the chemical reaction rate, and controlling the reaction selectivity. In this review, we present various plasmon-catalyzed reactions specifically monitored with Raman spectroscopy, namely surface-enhanced Raman scattering (SERS), remote SERS (Re-SERS) and tip-enhanced Raman scattering (TERS). These techniques utilize the signal enhancing effect of the metal nanoparticles. However, at the same time they can be used to control the actual reactivity. In the first part, the mechanism of plasmonic catalysis is introduced. Then it is shown how catalytic reactions can be spectroscopically investigated far beyond the diffraction limit using TERS. Finally, the sensitivity of the methods is discussed.