03 Fakultät Chemie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4

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2014 - 201912020 - 20223

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Author: search.filters.author.Fischer, PeerSubject: search.filters.subject.540

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    Light- and magnetically actuated FePt microswimmers
    (2021) Kadiri, Vincent Mauricio; Günther, Jan-Philipp; Kottapalli, Sai Nikhilesh; Goyal, Rahul; Peter, Florian; Alarcón-Correa, Mariana; Son, Kwanghyo; Barad, Hannah-Noa; Börsch, Michael; Fischer, Peer
    Externally controlled microswimmers offer prospects for transport in biological research and medical applications. This requires biocompatibility of the swimmers and the possibility to tailor their propulsion mechanisms to the respective low Reynolds number environment. Here, we incorporate low amounts of the biocompatible alloy of iron and platinum (FePt) in its L10 phase in microstructures by a versatile one-step physical vapor deposition process. We show that the hard magnetic properties of L10 FePt are beneficial for the propulsion of helical micropropellers with rotating magnetic fields. Finally, we find that the FePt coatings are catalytically active and also make for Janus microswimmers that can be light-actuated and magnetically guided.
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    Chiroptical spectroscopy of a freely diffusing single nanoparticle
    (2020) Sachs, Johannes; Günther, Jan-Philipp; Mark, Andrew G.; Fischer, Peer
    Chiral plasmonic nanoparticles can exhibit strong chiroptical signals compared to the corresponding molecular response. Observations are, however, generally restricted to measurements on stationary single particles with a fixed orientation, which complicates the spectral analysis. Here, we report the spectroscopic observation of a freely diffusing single chiral nanoparticle in solution. By acquiring time-resolved circular differential scattering signals we show that the spectral interpretation is significantly simplified. We experimentally demonstrate the equivalence between time-averaged chiral spectra observed for an individual nanostructure and the corresponding ensemble spectra, and thereby demonstrate the ergodic principle for chiroptical spectroscopy. We also show how it is possible for an achiral particle to yield an instantaneous chiroptical response, whereas the time-averaged signals are an unequivocal measure of chirality. Time-resolved chiroptical spectroscopy on a freely moving chiral nanoparticle advances the field of single-particle spectroscopy, and is a means to obtain the true signature of the nanoparticle’s chirality.
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    Shape control in wafer-based aperiodic 3D nanostructures
    (2014) Jeong, Hyeon-Ho; Mark, Andrew G.; Gibbs, John G.; Reindl, Thomas; Waizmann, Ulrike; Weis, Jürgen; Fischer, Peer
    Controlled local fabrication of three-dimensional (3D) nanostructures is important to explore and enhance the function of single nanodevices, but is experimentally challenging. We present a scheme based on e-beam lithography (EBL) written seeds, and glancing angle deposition (GLAD) grown structures to create nanoscale objects with defined shapes but in aperiodic arrangements. By using a continuous sacrificial corral surrounding the features of interest we grow isolated 3D nanostructures that have complex cross-sections and sidewall morphology that are surrounded by zones of clean substrate.
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    Plasmonic nanostructure engineering with shadow growth
    (2022) Han, Jang‐Hwan; Kim, Doeun; Kim, Juhwan; Kim, Gyurin; Fischer, Peer; Jeong, Hyeon‐Ho
    Physical shadow growth is a vacuum deposition technique that permits a wide variety of 3D-shaped nanoparticles and structures to be fabricated from a large library of materials. Recent advances in the control of the shadow effect at the nanoscale expand the scope of nanomaterials from spherical nanoparticles to complex 3D shaped hybrid nanoparticles and structures. In particular, plasmonically active nanomaterials can be engineered in their shape and material composition so that they exhibit unique physical and chemical properties. Here, the recent progress in the development of shadow growth techniques to realize hybrid plasmonic nanomaterials is discussed. The review describes how fabrication permits the material response to be engineered and highlights novel functions. Potential fields of application with a focus on photonic devices, biomedical, and chiral spectroscopic applications are discussed.