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In alloyed nanoparticles, synergistic electronic and/or geometric effects may enhance the catalytic properties compared to their monometallic counterparts. Herein, we address the synthesis of bimetallic Au/Cu nanoparticles with different compositions by wet chemical reduction in ionic liquids. The nanoparticles were successively supported on carbon. The ionic liquid could be recycled after synthesis. Annealing of the carbon‐supported NPs at 400 °C led to NPs of the ordered intermetallic L10 AuCu phase. The nanoparticle‐derived catalysts were characterized by X‐ray diffraction analysis, transmission electron microscopy, X‐ray photoelectron spectroscopy and optical emission spectroscopy with inductively coupled plasma. Oxidation of biomass‐derived furans is a prominent process for biomass transformation into value‐added chemicals. Herein, the oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) was chosen as a model reaction to evaluate the effect of Cu addition and intermetallic structure on the catalytic performance. Particularly Au/Cu nanoparticles with an Au/Cu ratio of 3 : 1 showed very high conversion to FDCA. [ABSTRACT FROM AUTHOR]

This article reports results from two distinct, originally unrelated studies that show unexpected behavior with respect to sodium sulfate solutions in contact with flat surfaces. On the one hand, we investigated immersion freezing of sulfate containing solutions (target salt was CaSO4 and Na2SO4 was used as one control) in the presence of flat sapphire‐0001 crystals using second‐harmonic generation (SHG) spectroscopy. Further control experiments were carried out with neat water and CaCl2. The SHG signals from CaSO4 and Na2SO4 solutions behave somewhat differently from those recorded for the two other cases, the neat water and CaCl2. The common pattern shows a decrease of the SHG signal with decreasing temperature down to about −15°C, whereupon the signal sharply drops, indicating freezing. With the Na2SO4 solution, although the signal initially follows closely the neat water curve, the trend increases sharply at about −10°C followed by a gradual decrease with further cooling. There is no plausible explanation for the distinct behavior of the Na2SO4 solution, and thermodynamic calculations do not suggest any precipitation of a sodium sulfate solid phase. At the end of the freeze–thaw cycle, the initial SHG for each system is retrieved, suggesting reversibility. On the other hand, in a separate investigation unrelated to the freezing study, it was repeatedly observed that sodium sulfate precipitates from solution on flat steel surfaces at room temperature. As in the freezing experiments, thermodynamic calculations for the bulk solution solubility of sodium sulfate indicate that precipitates should not be forming under the conditions of the studies. The crystals observed on the steel samples have snowflake shapes similar to one literature report. We conclude that Na2SO4 in the presence of flat surfaces shows unexpected behavior that should incite further detailed studies in the future to elucidate the phenomenon. [ABSTRACT FROM AUTHOR]

The exceptional physico-chemical properties of ionic liquids are exploited for the synthesis and catalytic application of heterometallic nanoparticles. Pt/Sn-based nanoparticles with 2-3 nm diameter are synthesized by chemical reduction of the metal salt precursors in the ionic liquid (i.e., methyltrioctylammonium bis(trifluoromethylsulfonyl)imide) using triethylborohydride as reducing agent. Investigations by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy suggest the formation of randomly alloyed Pt/Sn-based nanoparticles. The tin precursor and the platinum to tin ratio of the precursors are shown to influence the nature of the nanoparticles. The selective hydrogenation of cinnamaldehyde is used to probe the catalytic performance of the Pt/Sn nanoparticles, demonstrating the effect of tin alloying on the catalytic activity and selectivity to the α,β-unsaturated cinnamic alcohol. [ABSTRACT FROM AUTHOR]

Pentavalent uranium compounds are key components of uranium‘s redox chemistry and play important roles in environmental transport. Despite this, well‐characterized U(V) compounds are scarce primarily because of their instability with respect to disproportionation to U(IV) and U(VI). In this work, we provide an alternate route to incorporation of U(V) into a crystalline lattice where different oxidation states of uranium can be stabilized through the incorporation of secondary cations with different sizes and charges. We show that iriginite‐based crystalline layers allow for systematically replacing U(VI) with U(V) through aliovalent substitution of 2+ alkaline‐earth or 3+ rare‐earth cations as dopant ions under high‐temperature conditions, specifically Ca(UVIO2)W4O14 and Ln(UVO2)W4O14 (Ln=Nd, Sm, Eu, Gd, Yb). Evidence for the existence of U(V) and U(VI) is supported by single‐crystal X‐ray diffraction, high energy resolution X‐ray absorption near edge structure, X‐ray photoelectron spectroscopy, and optical absorption spectroscopy. In contrast with other reported U(V) materials, the U(V) single crystals obtained using this route are relatively large (several centimeters) and easily reproducible, and thus provide a substantial improvement in the facile synthesis and stabilization of U(V). [ABSTRACT FROM AUTHOR]