Numerous preparation techniques for perovskite-based MIEC materials have been developed over the last years. Apart from the conventional methods of cathode preparation, including high temperature calcination, mechanical grinding of powders, screen printing and sintering of thick fi lm layers, alternative synthesis and deposition routes are available. Nanocrystalline LSC or La 1−x Sr x Co 1−y Fe y O 3− δ thin fi lms on electrolyte substrates were already fabricated by pulsed laser deposition, [6][7][8][9] DC, and RF sputtering, [ 10,11 ] spray pyrolysis, [ 12 ] and sol-gel deposition. [13][14][15][16][17] In this work the chemical and structural properties and the stability of nanoscaled La 0.6 Sr 0.4 CoO 3− δ LSC thin fi lm cathodes on polycrystalline Gd 0.1 Ce 0.9 O 1.95 (CGO) substrates were investigated thoroughly. The fabrication by a low-temperature sol-gel technique is favorable for tailoring the grain size, porosity and cathode-fi lm thickness. [ 18 ] The electrochemical properties of the nanoscaled LSC thin fi lm cathodes were already reported by Hayd et al. who presented an outstanding electrochemical performance and extraordinary low area specifi c resistances as low as ASR chem = 0.023 Ω cm 2 at an operating temperature of 600 ° C. [ 19,20 ] Interestingly enough, theoretical models predicted ASR chem values up to one order of magnitude larger than the experimental data. For obvious reasons, the excellent performance of our nanoscaled cathodes does not solely depend on microstructure (porosity, increased inner surface area) as reported in previous work, [ 21 ] but presumably on the enhanced catalytic properties of the La 0.6 Sr 0.4 CoO 3− δ . However, the outstanding electrochemical performance motivates the analysis of the microstructure and phase composition of the LSC cathodes presented in this work.The nanoscaled LSC thin-fi lm cathodes were studied by transmission and scanning transmission electron microscopy (TEM/STEM) combined with energy-dispersive X-ray spectroscopy (EDXS). Moreover, high-angle annular dark-fi eld (HAADF) STEM tomography was used to study the distribution of the pores and quantify the porosity, which was not reported for nanoscaled (La,Sr)CoO 3 -based materials in literature before. Although several techniques like μ -tomography, [ 22 ] FIB-tomography, [ 23,24 ] transmission X-ray microscope based X-ray tomography, [ 12 , 25 ] mercury intrusion, [ 22 , 26 ] nitrogen adsorption, [ 27 ] or the Archimedes method [ 22 , 28 ]

Mo(0), W(0), Fe(0), Ru(0), Re(0), and Zn(0) nanoparticles—essentially base metals—are prepared as a general strategy by a sodium naphthalenide ([NaNaph])-driven reduction of simple metal chlorides in ethers (1,2-dimethoxyethane (DME), tetrahydrofuran (THF)). All the nanoparticles have diameters ≤10 nm, and they can be obtained either as powder samples or long-term stable suspensions. Direct follow-up reactions (e.g., Mo(0)+S8, FeCl3+AsCl3, ReCl5+MoCl5), moreover, allow the preparation of MoS2, FeAs2, or Re4Mo nanoparticles of similar size as the pristine metals (≤10 nm).

Liquid ammonia on the nanoscale: Ammonia-in-oil microemulsions are used to synthesize Bi, Re, CoN, and GaN nanoparticles, which can be obtained without further thermal treatment. These microemulsions are as reproducible and simple as their water-in-oil conterparts, with the exception of the required low temperature of -40 °C.

Tungsten nanoparticles were obtained from liquid-ammonia-based synthesis via reduction of WCl6 with dissolved sodium. The W(0) nanoparticles exhibit a diameter of 1-2 nm and can be dispersed in alkanes, showing a grayish-orange color due to red-shifted plasmon resonance absorption.

Using a simple bifunctional bridging linker, nanosized gold and titanium dioxide composites are prepared containing different Au loadings. Linker is synthesized to contain both catechol and thiol moieties to enable binding to the TiO2 and Au surface respectively. Au/TiO2 nanocomposites are prepared using simple synthetic route that allows the control over the amount of Au nanoparticles, a property which plays a significant role in the catalytic activity of hybrid materials. Photocatalytic activity of materials prepared using different TiO2 precursors is investigated using reactive oxygen species sensitive assay based on activation of horseradish peroxidase (HRP) enzyme. Significant increase in catalytic activity is observed for all Au/TiO2 nanocomposites with Au/TiO2 prepared by use of the bridging linker being up to 5.5 times more active than bare commercial TiO2 nanoparticles. In addition to 365 nm light excitation, less energetic 470 nm light, which is more suitable for the use with biological systems, is used to induce photocatalytic activity. Finally, prepared photocatalytic materials are successfully used to exert temporal control over enzymatic activity, a feature which is important for the study of both enzymatic activity and design of novel bio‐sensing platforms.

GaN nanoparticles, 3-4 nm in size, are synthesized in a microemulsion using liquid ammonia as the polar droplet phase. Surprisingly, GaN is readily crystalline although prepared at -40 °C. The nanoparticles show a band gap of 4.4 eV as well as light emission with its maximum at 336 nm. Both confirm the expected quantum-confinement effect.

Pd@SnO2 and SnO2@Pd core@shell nanocomposites are prepared via a microemulsion approach. Both nanocomposites exhibit high‐surface, porous matrices of SnO2 shells (>150 m2 g−1) with very small SnO2 crystallites (<10 nm) and palladium (Pd) nanoparticles (<10 nm) that are uniformly distributed in the porous SnO2 matrix. Although similar by first sight, Pd@SnO2 and SnO2@Pd are significantly different in view of their structure with Pd inside or outside the SnO2 shell and in view of their sensor performance. As SMOX‐based sensors (SMOX: semiconducting metal oxide), both nanocomposites show a very good sensor performance for the detection of CO and H2. Especially, the Pd@SnO2 core@shell nanocomposite is unique and shows a fast response time (τ90 < 30 s) and a very good response at low temperature (<250 °C), especially under humid‐air conditions. Extraordinarily high sensor signals are observed when exposing the Pd@SnO2 nanocomposite to CO in humid air. Under these conditions, even commercial sensors (Figaro TGS 2442, Applied Sensor MLC, E2V MICS 5521) are outperformed.

The catalytic activity of Pd‐SnO2 core@shell nanocomposites in the oxidation of CO and their CO‐sensing behavior were compared. For this purpose, Pd particles were placed on the inside and the outside of SnO2 hollow spheres, as demonstrated by electron tomography, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy. Both the sensing and catalytic effect were studied in a systematic manner on such nanocomposites, and striking differences in the catalytic performance of the nanocomposites in CO oxidation and CO and H2 sensing were found. At low temperatures, SnO2@Pd was found to be a good sensor, and the light‐off temperature was significantly lower than that of Pd@SnO2. Above the ignition temperature, CO was probably rapidly removed from the gas so that the sensing effect disappeared. This demonstrated that understanding of the sensing and catalytic behavior can help in unraveling the functional properties of core@shell and Pd‐SnO2 nanocomposites in more detail.