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1. Radwan, Radwan Mohamed Sarhan. Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy.

Degree: PhD, 2019, Universität Potsdam

Plasmonic metal nanostructures can be tuned to efficiently interact with light, converting the photons into energetic charge carriers and heat. Therefore, the plasmonic nanoparticles such as gold and silver nanoparticles act as nano-reactors, where the molecules attached to their surfaces benefit from the enhanced electromagnetic field along with the generated energetic charge carriers and heat for possible chemical transformations. Hence, plasmonic chemistry presents metal nanoparticles as a unique playground for chemical reactions on the nanoscale remotely controlled by light. However, defining the elementary concepts behind these reactions represents the main challenge for understanding their mechanism in the context of the plasmonically assisted chemistry. Surface-enhanced Raman scattering (SERS) is a powerful technique employing the plasmon-enhanced electromagnetic field, which can be used for probing the vibrational modes of molecules adsorbed on plasmonic nanoparticles. In this cumulative dissertation, I use SERS to probe the dimerization reaction of 4-nitrothiophenol (4-NTP) as a model example of plasmonic chemistry. I first demonstrate that plasmonic nanostructures such as gold nanotriangles and nanoflowers have a high SERS efficiency, as evidenced by probing the vibrations of the rhodamine dye R6G and the 4-nitrothiophenol 4-NTP. The high signal enhancement enabled the measurements of SERS spectra with a short acquisition time, which allows monitoring the kinetics of chemical reactions in real time. To get insight into the reaction mechanism, several time-dependent SERS measurements of the 4-NTP have been performed under different laser and temperature conditions. Analysis of the results within a mechanistic framework has shown that the plasmonic heating significantly enhances the reaction rate, while the reaction is probably initiated by the energetic electrons. The reaction was shown to be intensity-dependent, where a certain light intensity is required to drive the reaction. Finally, first attempts to scale up the plasmonic catalysis have been performed showing the necessity to achieve the reaction threshold intensity. Meanwhile, the induced heat needs to quickly dissipate from the reaction substrate, since otherwise the reactants and the reaction platform melt. This study might open the way for further work seeking the possibilities to quickly dissipate the plasmonic heat generated during the reaction and therefore, scaling up the plasmonic catalysis.

Plasmonische Metallnanostrukturen können so eingestellt werden, dass sie effizient mit Licht interagieren, Photonen in energetische Ladungsträger und wärmeenergie umwandeln. Aus diesem Grund wirken plasmonische Nanopartikel wie Gold und Silbernanopartikel als Nanoreaktoren, wenn Moleküle mit deren Oberfläche verbunden sind. Durch das verstärkte elektromagnetische Feld und den somit erzeugten energetischen Ladungsträgern und der wärmeenergie können chemische Umwandlungen entstehen. Das bedeutet, in der plasmonischen Chemie sind Metallnanopartikel ein…

Advisors/Committee Members: Bargheer, Matias (advisor), Schlücker, Sebastian (advisor), Bald, Ilko (advisor).

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APA (6th Edition):

Radwan, R. M. S. (2019). Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy. (Doctoral Dissertation). Universität Potsdam. Retrieved from https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/43330

Chicago Manual of Style (16th Edition):

Radwan, Radwan Mohamed Sarhan. “Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy.” 2019. Doctoral Dissertation, Universität Potsdam. Accessed September 19, 2019. https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/43330.

MLA Handbook (7th Edition):

Radwan, Radwan Mohamed Sarhan. “Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy.” 2019. Web. 19 Sep 2019.

Vancouver:

Radwan RMS. Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy. [Internet] [Doctoral dissertation]. Universität Potsdam; 2019. [cited 2019 Sep 19]. Available from: https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/43330.

Council of Science Editors:

Radwan RMS. Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy. [Doctoral Dissertation]. Universität Potsdam; 2019. Available from: https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/43330

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