Authors:	Klünker, Martin
Title:	Chemical Design and Application of Organized Multicomponent Hybrid Nanostructures
Online publication date:	6-Jul-2022
Year of first publication:	2022
Language:	english
Abstract:	Multicomponent inorganic nanostructures containing metal/metal oxide components connected through a solid interface are, unlike conventional single material nanoparticles, able to combine different or even incompatible properties within a single entity. They are multifunctional and resemble molecular amphiphiles, which makes them especially attractive for self-assembling complex structures, drug delivery, bioimaging or catalysis. The range of capabilities can be even advanced by selective surface functionalization. Three forms of heterodimeric nanoparticles are most intriguing: (i) two-domain systems with solid state interface, often also with different surface functionalization of the metal and the metal oxide domain, known as eponym Janus particles, (ii) colloidal superparticles, i.e. mesoscale particles defined as size- and shape-controlled assemblies from nanoscale building blocks, and (iii) core-shell nanoparticles, where a core material is covered by a shell of another material, often with variable shell thickness. The present thesis focusses on these three types of multicomponent inorganic nanostructures and presents their enhanced performance in various applications. It combines the synthesis of complex nanoparticles, using the noble metals Pd and Au as well as the metal oxides from Fe and Zn, with their thorough characterization and selected applications ranging from catalysis and enzyme mimetic to imaging and biomedical application. The different nanoparticle types are analyzed by means of i.a. (aberration corrected) high resolution transmission electron microscopy (HR-TEM), powder X-Ray diffraction (XRD), UV-vis spectroscopy, Mössbauer spectroscopy, electron diffraction (ED), energy dispersive X-ray spectroscopy (EDX), nuclear magnetic resonance spectroscopy (NMR) and magnetic measurements (SQUID) to evaluate their chemical composition and physical properties. Pd@-Fe2O3 superparticles and FexO@FexO superparticles of various morphologies are presented, where Pd or FexO template nanoparticles are overgrown with iron oxide nanorods or nanodomains to yield highly organized nanostructures. This approach demonstrates the ability to obtain tailor-made nanostructures with well-definedsize, morphology and chemical composition by systematic adjustment of reaction parameters and educt composition. Moreover, the synthesized superparticles display enhanced application properties compared to the respective seed particles. The Pd@-Fe2O3 superparticles exhibit superior peroxidase-like activity as enzyme mimetics compared to isolated iron oxide nanorods, whereas the FexO@FexO superparticles lead to a shortening of the longitudinal and transversal relaxation times in magnetic resonance imaging (MRI). This is attributed to a synergistic effect through the interface of the different materials based on the unique structure of the superparticles, whose components are interfaced via shared crystals faces compared to superstructures from self-assembled small nanoparticles stabilized by van der Waals interactions. Advantages such as electronic communication, due to the absence of separating organic surface layers, and increased physical stability make the superparticles promising candidates for catalytic, biomedical, or nanodevice applications. Pd@FexO heterodimer nanoparticles are presented as hybrid nanostructures with separated metal and metal oxide domains in order to use the surface availability of both components as well as their distinct properties to establish a novel template-free synthesis of a nanocomposite material. The Pd@FexO heterodimer nanoparticles are adopted to fabricate a macroporous, hydrophobic, magnetically active and three-dimensional(3D) hybrid foam, capable of repeatedly separating oil contaminants from water. The Pd domains in the Pd@FexO heterodimers act as nanocatalyst for a hydrosilylation reaction, while the FexO component confers magnetic properties to the final functional material. The nanocomposite material finally consists of a polysiloxane foam with embedded Pd@FexO heterodimer nanoparticles. Additionally, the Pd@FexO heterodimer nanoparticles also display advanced peroxidase-like activity as enzyme mimetics, which is compared to the Pd@-Fe2O3 superparticles. ZnO nanoparticles of different morphologies are presented for the evaluation of their cell uptake and toxicity mechanisms. ZnO, especially in nano-dimensions, is subject to increased environmental release due to its use in sunscreens, paints and pharmaceutical products, while toxic effects to human health have been reported, but are poorly understood so far. ZnO nanoparticles functionalized with a silica shell and fluorescein dye are taken up into various cancer cell types and demonstrate gradual dissolution and successive increase in cytotoxicity. ZnO nanoparticles without silica coating are used to explore the mechanisms of ZnO mediated toxicity, unveiling that nanoparticle cell adhesion and uptake are crucial for the toxicity after the first hours of application, while the amount, biochemical character and properties of the released Zn2+ ions determine the toxicity in the following hours. Finally, Au@Pd and Pd@Au heterodimer nanostructures, designed for a catalytic application and synthesized by a seed mediated growth in organic media, are shown. Ex situ surface modification of the Au and Pd seed nanoparticles with the long chain organic thiol 1-octadecanethiol allow to control and tune the morphology and catalytic activity of the heterodimers. For unraveling the influence of the thiol coating on the surface dynamics and reaction process detailed 1H- and 19F-NMR studies on 1-octadecanethiol functionalized Au nanoparticles are used, unveiling that ligand exchange is an equilibrium reaction associated with a Nernst distribution. Efficient surface coverage is found to depend on repeated exchange reactions with large ligand excess. In addition, the size of the nanoparticles, i.e. the surface curvature, surface defects and reactivity has a contribution as well as the size of the ligand.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-7071
URN:	urn:nbn:de:hebis:77-openscience-56733ca1-a422-4435-8044-6ee9ae29d6fe4
Version:	Original work
Publication type:	Dissertation
License:	CC BY-ND
Information on rights of use:	https://creativecommons.org/licenses/by-nd/4.0/
Extent:	iv, 261 Seiten (Illustrationen. Diagramme)
Appears in collections:	JGU-Publikationen