In-situ Kontrolle der Synthese und Behandlung verschiedener Nanopartikel in einem Plasmasystem

Nanoparticles offer a range of desirable properties compared to their bulk material counterparts. Their nanoscale dimensions result in extreme surface-to-volume ratios as well as quantum confinement effects, which make them prime targets for applications in various fields such as catalysis, biomedicine, opto-electronics, or neuromorphic computing. This work is concerned with the synthesis and treatment of carbon and silicon nanoparticles, as well as silver-silicon core-shell nanoparticles using plasma discharges with a special focus on their in situ diagnostics. Continuous in situ monitoring via Fourier-transform infrared spectroscopy (FTIR) and localised surface plasmon resonance during the plasma treatment allows for fine-grained control of the nanoparticle properties such as size, chemical composition, or surface functionalisation, which are key for various applications. The results are confirmed by extracting particle samples for ex situ transmission electron microscopy.Der Übergang von Bulkmaterialien zu Nanopartikeln eröffnet eine Vielzahl an neuen Eigenschaften. Durch ihre Größe im Nanometerbereich besitzen diese ein extremes Verhältnis von Oberfläche zu Volumen und zeigen Quanteneinschlusseffekte, die in vielerlei Anwendungen zum Einsatz kommen, wie zum Beispiel der Katalyse, Biomedizin, Optoelektronik oder bei neuromorphen Systemen. Diese Arbeit beschäftigt sich mit der Erzeugung und Behandlung von Kohlenstoff-, Silizium- und Silber-Silika-Kern-Schalen-Nanopartikeln in einer Plasmaentladung mit besonderem Fokus auf die in-situ Diagnostik. Durchgehende in-situ Kontrolle durch Fourier-transformierte Infrarotspektroskopie (FTIR) und Oberflächenplasmonenresonanz (LSPR) während der Plasmabehandlung erlaubt eine exzellente Kontrolle der Partikelparameter wie ihrer Größe, ihrer chemischen Zusammensetzung oder ihrer Oberflächenfunktionalisierung, die von zentraler Bedeutung für die verschiedenen Anwendungen sind. Die Ergebnisse aus diesen Untersuchungen werden durch Extraktion von Proben und ex-situ Transmissionselektronenmikroskopie fundiert.Les nanoparticules se distinguent des matériaux bulk par une série de nouvelles propriétés. Leurs dimensions nanométriques sont la source de rapports surface-volume extrêmes et d'effets de confinement quantique. Ils ont donc des nombreuses applications dans divers domaines tels que la catalyse, la biomédecine, l'optoélectronique et les systèmes neuromorphiques. Cette thèse concerne la synthèse et le traitement de nanoparticules de carbone, de silicium et de type cœur-coquille d'argent-silice à l'aide de décharges de plasma, avec un accent particulier sur leur diagnostic in situ. Le monitorage continu in situ via la spectroscopie infrarouge à transformée de Fourier (FTIR) et la résonance plasmonique localisée de surface (LSPR) pendant le traitement au plasma permet un contrôle précis des propriétés des nanoparticules telles que leur taille, leur composition chimique ou leur fonctionnalisation de surface, qui sont essentielles pour leurs diverses applications. Les résultats sont confirmés par l'extraction d'échantillons pour la microscopie électronique en transmission ex situ

Decoupling of dust cloud and embedding plasma for high electron depletion in nanodusty plasmas

In recent years nanoparticles have become key technological products, e.g., as coatings with tunable optical gap in third generation solar cells, as nanocrystals for photonic applications, and as pharmaceutical nanocarriers. In particle sources, that use reactive, nanodusty plasmas, a high dust density changes the properties of the dusty plasma compared to a dust free plasma considerably, as electron depletion leads to a reduced number of free electrons. This is called the Havnes effect and was central for the understanding of the famous spokes in Saturns rings. We see here, that it is also important for technological applications. Using self excited dust density waves (DDW) as a diagnostic tool, we completely characterize an argon discharge with embedded amorphous hydrocarbon nanoparticles of different size and density. The results show, that electron depletion governs the charge of dust grains, while the size of the particles has only a weak influence. The ion density and electric potential profile are almost independent of both, dust size as well as dust density. This suggests, that the rf generated plasma and the dust cloud seem to coexist and coupling of both is weak

Growth and treatment of hydrogenated amorphous carbon nanoparticles in a low‐pressure plasma

A parallel ‐ plate, low ‐ pressure plasma for fundamental nanodusty plasma re- search is used to grow hydrogenated amorphous carbon nanoparticles using an argon ‐ acetylene gas mixture. The particles stay confined in the volume of the argon plasma after turning off the C H 2 2 gas flow and the effects of pro- longed treatment with noble gas (Ar) and reactive gas mixtures (Ar/ H 2, Ar/ D 2, or Ar/ O 2) are investigated using in situ infrared absorption spectroscopy. Additionally, ex situ scanning electron microscopy imaging of extracted na- noparticles is used to analyze their size and surface morphology. In 45 min of argon treatment, a size increase of about 50% is seen together with a decrease in sp CH x 2 bonds and an increase in C ═ O bonds, indicating incorporation of oxygen from gas impurities into the particle material. All reactive gas mixtures lead to the expected etching of the nanoparticle material without any ex- change reactions between gas ‐ phase deuterium and surface ‐ bonded hydrogen atoms. These results are important for in situ studies of nanoparticle clouds such as dust density wave diagnostics, but they also provide fundamental informa- tion about plasma interaction with a ‐ C:H material