Titanium dioxide (TiO2) is among the most studied model (photo)­catalyst materials. The influence of surface point defects, like oxygen vacancies and particularly bulk defects such as Ti3+ interstitials, is usually underestimated or even ignored. We present a systematic study under well-defined UHV conditions illustrating the importance of such defects for the thermal reaction of methanol at the rutile TiO2 (110) single crystal surface by using temperature-programmed reaction spectroscopy (TPRS) and Fourier-transform infrared reflection–absorption spectroscopy (FT-IRRAS). It will be shown that the population of different reaction pathways, namely, the partial oxidation of methanol to formaldehyde and the deoxygenation forming hydrocarbons, especially methane, depends on the bulk defect density and the presence or absence of oxygen adsorbates. While at elevated temperatures molecular desorption is pronounced for the less defective substrates, for higher reduction grades the high-temperature deoxygenation channel via methoxy intermediates is favored. In addition, preadsorption of oxygen enables low- and high-temperature partial oxidation forming formaldehyde, likely from a dioxomethylene-like adsorbate.

Electrostaticversussterical ligand stabilization: competitive stabilization mechanism play a key role in the control of nanomaterial properties.

Although nanomaterials are widely involved in technological applications, common synthetic recipes for such colloids are restricted to special, optimized conditions, particularly for anisotropic shapes. Ligand exchange is frequently necessary for further functionalization. While such protocols are well established for spherical particles, it is more demanding to keep the corpus for thermodynamically less stable shapes. We highlight the temperature as one key for the formation of anisotropic gold nanoparticles, but also for ligand exchange protocols under shape retention or deliberate reshaping at the example of gold nanocubes. In the first part, the synthesis of CTAB capped gold nanocubes in aqueous solution is examined highlighting the narrow temperature window in which selective adsorption site blocking by bromide ions leads to the formation of gold nanocubes. While too low temperatures yield multiple particle shapes due to a low surface mobility, temperatures above the appropriate window result in more thermodynamically favored shapes. Furthermore, two protocols are presented for the exchange of the ammonium ligand CTAB by oleylamine as an organic amine including water removal from a slurrish water‐amine paste through the gas phase. In turn, precise temperature control allows to either maintain the cubic shape or induce a reshaping process towards other, thermodynamically preferred shapes such as for example truncated octahedra.

Platinum nanocrystals in the size range of a few nanometers are especially interesting candidates for catalytic applications. We present an easy, low-temperature procedure, which allows for a precise size control of this material. Uniform platinum nanoparticles were obtained by reduction of platinumIJIV)chloride with tetrabutylammonium borohydride in toluene solution at room temperature. Dodecylamine served as a ligand. The size of the resulting particles could be controlled in the range between 2 and 5 nm by slow addition of platinum monomers and the reducing agent to preformed 2 nm seeds. Furthermore, particles with a tetrapod shape could be synthesized. In contrast to the usual kinetic control leading to the formation of elongated structures, the analysis of the growth process of the tetrapods suggests a reactioncontrolled growth process. Their structure was investigated by powder X-ray diffraction and highresolution electron microscopy, which revealed that two branches of the tetrapods grow along the 〈111〉 direction, while the other two show growth in the 〈220〉 direction. This uncommon shape of the tetrapods is attributable to the presence of a twin defect parallel to the 〈220〉 direction. Thus, the method presented in the article allows for the formation of platinum particles with a single twin defect with a high yield.

Quaternary ammonium halides are an important class of compounds because they are not only used as structural templates ororganic surface modifiers for inorganic minerals and other aluminosilicates such as zeolites, but are also well-known and widespread as phase-transfer catalysts and stabilizing agents for colloidal metal nanoparticle synthesis. Moreover, quaternary ammonium ions are frequently exploited as weakly coordinating cations in various ionic liquids. Thus, it is important to monitor, understand, and utilize thermal effects and limits of application. Herein, we report the thermal conversion of didodecyldimethylammonium bromide (DDAB) into organic amines on the surface of gold nanoparticles. In contrast to the pure compound, in which this decomposition appears as an endothermic process, the on-particle reaction is exothermic. This in situ modification of the ligand shell not only involves the essential step of halide removal through the gas phase but also turns out to be a valuable tool to produce uncovered metal sites and thus impacts the fabrication of nanostructured metal catalysts for ligand-directed chemistry.