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Plasmonische Nanopartikel faszinieren seit Jahrhunderten durch ihre intensive Farbe. In dieser Arbeit liegt der Fokus auf der Reaktion plasmonischer Nanopartikel auf externe Stimuli, mit dem Ziel die optischen Eigenschaften reversibel zu verändern. Zunächst wurde hierfür die Synthese von Nanopartikeln aus Materialien mit Metall-Isolator-Übergang verfolgt. Ein solcher Übergang geht mit einer Änderung der Ladungsträgerdichte einher, sodass die Präsenz der lokalisierten Oberflächenplasmonenresonanz (LSPR) mittels Temperaturänderung geschaltet werden kann. Hierfür sollten Synthesen für Nanopartikel aus Vanadium(IV)dioxid und Nickel(II)sulfidselenid entwickelt werden. Trotz Variationen von Präkursoren und Reaktionsbedingungen konnten keine Nanopartikel aus diesen Materialien synthetisiert werden. Weiterhin ist die spektrale Position einer LSPR abhängig von der Permittivität des umgebenden Mediums. Diese Abhängigkeit kann genutzt werden, um die LSPR durch Änderung der Umgebung der Nanopartikel zu schalten. Hierfür wurden erfolgreich konkave Nanopartikel aus dem plasmonischen Material Kupfer(I)sulfid über zwei verschiedene Routen synthetisiert. Durch Einlagerung von Nanopartikeln in die Kavitäten der konkaven Nanopartikeln ergibt sich eine Änderung der dielektrischen Umgebung der Nanopartikel, sodass eine Verschiebung der LSPR zu erwarten ist. Dies konnte experimentell jedoch nicht untersucht werden. Ebenso wurden zwei Arten dualplasmonischer Nanopartikel (Gold/Indium(III)zinn(IV)oxid und Gold/Kupfer(I,II)sulfid) synthetisiert. Durch die spektral getrennten LSPR war es mittels transienter Absorptionsspektroskopie möglich die Reaktion des Systems auf die resonante Anregung jeweils einer der beiden LSPR zu beobachten. Es zeigte sich eine transiente Antwort beider Materialien, unabhängig davon welche LSPR resonant angeregt wurde. Es konnte erstmals die Interaktion zweier LSPR in heterostrukturierten Nanopartikeln miteinander gezeigt werden. Die erhaltenen Daten legen nahe, da, Plasmonic nanoparticles fascinate since hundreds of years because of their intense colours. This work focuses on the response of plasmonic nanoparticles to external stimuli, with the purpose of reversibly changing the optical properties. First, the synthesis of nanoparticles from materials with a metal-insulator-transition was pursued. This transition is accompanied by a change of the free charge carrier density, so that the presence of the localised surface plasmon resonance (LSPR) can be switched with a change in temperature. For this purpose synthesis of nanoparticles from vanadium(IV)dioxide and nickel(II)sulfideselenide should be developed. Despite variations in precursors and reaction conditions, no nanoparticles from these materials could be synthesised. Furthermore, the spectral position is depending on the permittivity of the surrounding media. This dependency can be used to switch the LSPR by changes in the surrounding of the nanoparticles. For this reason concave nanoparticles from the plasmonic material copper(I)sulfide were successfully synthesised via two different routes. The embedding of nanoparticles into cavities of concave nanoparticles results in a change of the dielectric surrounding of the nanoparticles, therefore a shift of the LSPR is expected. This could not be investigated experimentally. Moreover, two kinds of dualplasmonic nanoparticles (gold/indium(III)tin(IV)oxide and gold/copper(I,II)sulfide) were synthesised. The spectral separated LSPRs made it possible to observe the response of the system to the resonant excitation with transient absorption spectroscopy to excitation of one of the two LSPRs. Both materials showed a transient response regardless of which LSPR was resonantly excited. For the first time, the interaction of two LSPR with each other in heterostructured nanoparticles could be shown. The obtained data suggest, that this interaction is based on Landau-damping.

Due to their optical properties (localized surface plasmon resonance, LSPR), colloidally dispersed metal nanoparticles are well suited for selective heating by high-energy laser radiation above their melting point without being limited by the boiling point of the solvent, which represents an excellent complement to wet-chemical nanoparticle synthesis. By combining wet-chemical synthesis and postsynthesis laser treatment, the advantages of both methods can be used to specifically control the properties of nanoparticles. Especially in the colloidal synthesis of nanoalloys consisting of two or more metals with different redox potentials, wet-chemical synthesis quickly reaches its limits in terms of composition control and homogeneity. For this reason, the direct synthesis path is divided into two parts to take the strengths of both methods. After preparing Au–Cu hetero nanoparticles by wet-chemical synthesis, nanoalloys with previous adjusted composition can be formed by postsynthesis laser treatment. The formation of these nanoalloys can be followed by different characterization methods, such as transmission electron microscopy (TEM), where the fusion of both metal domains and the formation of spherical and homogeneous Au–Cu nanoparticles can be observed. Moreover, the alloy formation can be followed by different shifts of X-ray diffraction (XRD) reflections and LSPR maxima depending on the composition.

In this work, a new type of multicomponent nanostructures is introduced by forming interpenetrating networks of two different nanomaterials. In detail, gel networks from semiconductor nanorods are interpenetrated by Au nanowires. Two different types of gelling agents, namely S2− and Yb3+, are employed to trigger the network formation. The structural and electrochemical properties of the resulting materials are discussed. (Photo)electrochemical measurements are performed on the structures to compare the materials in terms of their conductivity as well as their efficiency in converting photonic energy to electrical energy. The new type of CdSe/CdS:Au nanostructure gelled with S2− shows one order of magnitude higher photocurrent than the system gelled with Yb3+. Moreover, the introduction of Au nanowires exhibit a photocurrent which is two orders of magnitudes higher than in samples without Au nanowires.

Heterostructured Au/CuS nanocrystals (NCs) exhibit localized surface plasmon resonance (LSPR) centered at two different wavelengths (551 and 1051 nm) with a slight broadening compared to respective homostructured Au and CuS NC spectra. By applying ultrafast transient absorption spectroscopy we show that a resonant excitation at the respective LSPR maxima of the heterostructured Au/CuS NCs leads to the characteristic hot charge carrier relaxation associated with both LSPRs in both cases. A comparison of the dual plasmonic heterostructure with a colloidal mixture of homostructured Au and CuS NCs shows that the coupled dual plasmonic interaction is only active in the heterostructured Au/CuS NCs. By investigating the charge carrier dynamics of the process, we find that the observed interaction is faster than phononic or thermal processes (< 100 fs). The relaxation of the generated hot charge carriers is faster for heterostructured nanocrystals and indicates that the interaction occurs as an energy transfer (we propose Landau damping or interaction via LSPR beat oscillations as possible mechanisms) or charge carrier transfer between both materials. Our results strengthen the understanding of multiplasmonic interactions in heterostructured Au/CuS NCs and will significantly advance applications where these interactions are essential, such as catalytic reactions.

Investigations on gold and gold-zinc oxide nanocrystals encapsulated in a matrix of a metal-organic framework (ZIF-8) upon plasmonic heating with nanosecond laser pulses are presented. Irradiation of Au@ZIF-8 composite particles leads to heating of the gold core and decomposition of surrounding matrix acting as temperature probe. Cavities inside the ZIF-8 matrix are found on TEM images after irradiation. Their size is determined dependent on laser energy density and the generated heat at the gold core after absorption of a laser pulse approximated. The surrounding of the gold cores can be heated up to ZIF-8 decomposition over a distance up to 60 nm. This represents a method to visualize heat transfer from the gold cores to the ZIF-8 matrix in three dimensions. Studies on ZIF-8 encapsulated Au@ZnO dot-rod particles give insight in heat transfer between the particle components and show the applicability of the method to different, more complex systems. © 2022 The Authors. ChemNanoMat published by Wiley-VCH GmbH.

In this work, mixing and co-gelation of Au nanoparticles (NPs) and highly luminescent CdSe/CdS core/shell nanorods (NRs) are used as tools to obtain noble metal particle-decorated macroscopic semiconductor gel networks. The hybrid nature of the macrostructures facilitates the control over the optical properties: while the holes are trapped in the CdSe cores, the connected CdSe/CdS NRs support the mobility of excited electrons throughout the porous, hyperbranched gel networks. Due to the presence of Au NPs in the mixed gels, electron trapping in the gold NPs leads to a suppressed radiative recombination, namely, quenches the fluorescence in certain fragments of the multicomponent gel. The extent of fluorescence quenching can be influenced by the quantity of the noble metal domains. The optical properties are monitored as a function of the NR:NP ratio of a model system CdSe/CdS:Au. By this correlation, it demonstrates that the spatial extent of quenching initiated by a single Au NP exceeds the dimensions of one NR, which the Au is connected to (with a length of 45.8 nm ± 4.1 nm) and can reach the number of nine NRs per Au NP, which roughly corresponds to 400 nm of total electron travel distance within the network structure.