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.

Semiconductor Gel Networks In article number 2101628, Nadja C. Bigall and co‐workers demonstrate that a single gold nanoparticle is able to quench the fluorescence of up to 9 semiconductor nanorods in mixed, co‐gelated gel networks. Upon varying the particle number ratio of CdSe/CdS and Au nanocrystals, the spatial extent of quenching, thus, the travel distance of photoexcited electrons is changed within the interconnected semiconductor backbone.

Due to their unique optical properties, nanoparticles are well suited for heating by laser irradiation. In this context, colloidally dispersed particles are of particular interest because in conventional ways of heating, the maximum attainable temperature is limited by the boiling point of the solvent. With the right choice of the used laser wavelength, it is possible to selectively heat these particles above the melting point of the material whereas the surrounding and laser-transparent medium remains comparatively cold. This type of laser process is called laser melting in liquids (LML). To further investigate the possibilities of laser-induced heating processes, colloidally dispersed copper(II) oxide (CuO) nanoparticles were synthesized, dispersed in ethanol, and irradiated with a nanosecond-pulsed Nd:YAG laser. In this way, a laser-induced phase transition into the copper richer copper(I) oxide (Cu 2 O) phase and into elemental copper can be observed. The conversion process is followed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED), and UV−vis spectroscopy. It is shown that in the initial LML process a minimum particle size of 23−29 nm is required for a successful phase transition likely due to the size dependent heating efficiency, cooling effects, and the formation of nanobubbles.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202206379.

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.