The development of surface-active materials to improve the performance of electrochemical processes is becoming increasingly important in response to the growing challenges of sustainability. Due to their high active surface area, arrangements of nanoparticles are strong candidates for electrode materials. However, the surface activity of nanoparticles is often affected by the presence of stabilization agents such as organic ligand layers on the particle surface. This work investigates the postsynthetic aerobic and anaerobic pyrolysis of iron oxide mesocrystals to transform the organic ligand shell into an electrochemically active surface. This process introduces fissures into the nanoparticle assemblies while concomitantly reducing the particle separation distances, thereby enhancing both capacitance and magnetic coupling. Our findings demonstrate that anaerobic pyrolysis preserves mesocrystalline order, whereas aerobic pyrolysis disrupts order but significantly improves electrochemical activity by enhancing the active surface area.

The synthesis of alkali metal selenides often requires harsh reaction conditions and the use of solvents. In this article, we report the synthesis of alkali metal selenides through reactive ball milling under an argon atmosphere. This mechanochemical pathway is solvent‐free and can be performed at room temperature within minutes to hours. The synthesis of several sodium polyselenides (Na 2 Se n , n = 1–6) and alkali metal selenides ( A 2 Se, A = K, Rb, Cs) is investigated and the received products are characterised by powder X‐ray diffraction. We successfully synthesise the sodium selenides Na 2 Se n ( n = 1–4), K 2 Se, Cs 2 Se and a so far unreported polymorph of Rb 2 Se. Additionally, we observe a fierce acceleration of the reaction by PTFE, reducing the reaction time to a few minutes.

Proton-coupled electron transfers (PCETs) to metal oxides are key reactions for sustainable catalytic and energy storage processes. The factors that control PCET reactions on metal oxides are, however, not well understood, with the effect of particle morphology/surface faceting on the thermodynamics and kinetics of PCET being essentially untested. We measured the thermodynamics and kinetics of PCET from CpCr(CO)3H to five V2O5 samples of varying morphologies/surface faceting. Their nanostructures were assessed by Rietveld refinement accounting for preferred crystallite orientation, giving a semiquantitative measurement of surface faceting. PCET to V2O5 occurs via proton insertion-coupled electron transfer (PICET), where H· diffuses into the bulk of the particle. The thermodynamics of PICET are controlled by particle structure, with nonequilibrium morphologies requiring structural rearrangement during PICET. The kinetics of PICET are controlled by the rate of H· diffusion into the bulk, with diffusion along the interconnected V2O5 layers being 10x faster than between the layers. Samples with hindered H· diffusion also show low activity in the oxidation of methanol, demonstrating that diffusion of H· into the bulk occurs during catalysis. This work demonstrates that particle morphology is critical for PCET reactions to anisotropic metal oxides and must be considered when examining their reactivity.

Boron-doped diamond, an outstanding electrode material, is commonly synthesised via chemical vapour deposition (CVD) using expensive and toxic boron-containing gases. Alternative boron sources are therefore attractive; however, their use in the growth of phase-pure diamond films is so far limited. This study presents how trimethyl borate (TMBT; B(OCH 3) 3) can be used as a liquid precursor of boron for the growth of high-quality, heavily boron-doped diamond films in a custom-made, microwave plasmaassisted CVD system. These polycrystalline films were deposited on Si plates at a very high boron-tocarbon molar ratio (105,000 ppm) with homogeneous distribution throughout the film. The films exhibit an atypical surface morphology, composed of {110} and {100} crystallographic facets. Typical growth rates of about 1.5 μm/h were achieved for the process carried out without enhancements. The average concentration of boron in the films was determined to be 6.48×10 21 cm-3. Moreover, the films are characterised by negative electron affinity. The availability of these diamond films from a highly reproducible and very accessible procedure is opening new possibilities for electrochemistry, sensing and photo-electrocatalytic applications.

Levitated optomechanics is an emerging field in quantum science that explores the quantum motion of mesoscopic particles levitated in a vacuum. Expanding this approach to particles with intrinsic quantum defects opens new opportunities for quantum sensing and nontrivial quantum state generation. Here, we explore silicon carbide (SiC) nanoparticles as a promising platform that offers a range of controllable quantum defects and material tunability. We demonstrate stable optical levitation of 3C-polytype SiC nanoparticles containing single photon emitters in a vacuum. We observe stable fluorescence from the levitated particle, confirming the preservation of the emitters in the levitated state. We also investigate particle loss at low pressure and explore thermal annealing as a potential method to improve trapping stability. Our results establish SiC as a viable platform for levitated optomechanics, providing additional quantum degrees of freedom and material engineering capabilities.

We report on the series of the alkali metal intercalates of VSe2 synthesised by electrochemical means in an aqueous environment. For all alkali metals we find water-conintercalated structures (stage I and stage II), of which only the sodium structure had been reported so far. The new structures are analyzed by powder X-ray diffraction and Rietveld refinement. Their (meta-)stability is investigated in terms of the open circuit potential, revealing the sensitivity towards oxygen. Except for the lithium intercalate these structures transform into water-free alkali metal intercalates under vacuum. In addition, scanning electron microscopy reveals the impact of different electrochemical intercalation techniques yielding different intercalation rates. This paves the way for future single crystal investigations.

The reaction between PrO2 and SiO2 was investigated at various pressure points up to 29 GPa in a diamond anvil cell using laser heating and in situ single-crystal structure analysis. The pressure points at 5 and 10 GPa produced Pr2III(Si2O7), whereas Pr4IIISi3O12 and Pr2IV(O2)O3 were obtained at 15 GPa. Pr4IIISi3O12 can be interpreted as a high-pressure modification of the still unknown orthosilicate Pr4III(SiO4)3. PrIVSi3O8 and Pr2IVSi7O18 that contain praseodymium in its rare + IV oxidation state were identified at 29 GPa. After the pressure was released from the reaction chamber, the Pr(IV) silicates could be recovered, indicating that they are metastable at ambient pressure. Density functional theory calculations of the electronic structure corroborate the oxidation state of praseodymium in both PrIVSi3O8 and Pr2IVSi7O18. Both silicates are the first structurally characterized representatives of Pr4+-containing salts with oxoanions. All three silicates contain condensed networks of [SiO6] octahedra which is unprecedented in the rich chemistry of lanthanoid silicates.

Perovskite-derived tungsten bronzes are formed from tungsten oxide by electrochemical intercalation of all alkali metals from aqueous solutions. In two steps, we yield two different polymorphs, where the first step is reversible and the second step is irreversible. The electrochemical approach affords precise control of the composition, while ex situ X-ray diffraction and particularly in situ X-ray diffraction allow the analysis of the atomic structure. For the heavy alkali metals, rubidium and cesium, the in situ synchrotron X-ray diffraction experiments reveal in sum four new structures and their formation process. The irreversible deintercalation step yields at room temperature, the alpha-WO3 phase, a tungsten oxide polymorph which is thermodynamically only stable above 1073 K. Finally, analyzing the full alkali metal series allows us to conclude that the symmetry and structure of the formed bronzes are dictated by the electron count on the tungsten oxide network and the size of the ions plays a negligible role.

The reaction of the trivalent lanthanoide triflates Ln(OTf)(3) (Ln=Sm, Eu; OTf=CF3SO3-) with the respective metals in acetonitrile leads to the Ln(II)-triflates Eu(OTf)(2)(CH3CN) (monoclinic, P2(1)/n, Z=4, a=1053.54(1), b=610.28(5), c=1946.92(2) pm, beta =98.611(4)) and Sm(OTf)(2)(CH3CN) (monoclinic, P2(1)/n, Z=4, a=1054.41(4), b=612.16(2), c=1952.65(7) pm, beta =98.524(2)). The isotypic strontium compound Sr(OTf)(2)(CH3CN) (monoclinic, P2(1)/n, Z=4, a=1056.39(5), b=610.05(3), c=1950.1(1) pm, beta =98.900(2)degrees) has been obtained from SrCO3 and triflic acid. The compounds have been investigated by X-ray diffraction, vibrational spectroscopy, luminescence spectroscopy, cyclic voltammetry, thermal analysis, and magnetic measurements.

Electrochemistry and diffraction complement each other particularly well when it comes to the investigation of solids and their surfaces. The electrochemical experiment provides access to thermodynamic and kinetic information, while diffraction provides insights into the atomic structure of crystalline but also amorphous compounds. Gaining these in-formation in one experiment in situ means to trigger phase transitions at ambient temperatures, track rapid changes, and avoid environmental instabilities. Consequently, otherwise non-accessible metastable and transitional phases and structures can be discovered. However, this method is not only limited to bulk phases but also provides information on electrode sur-faces. Understanding and building batteries have been one of the main driving forces to establish this technique; neverthe-less, this short review intends to provide a "survival guide" how to apply the powerful in situ diffraction of electrochemical ex-periments beyond battery materials. Therefore, we briefly discuss the method together with the available setups and present selected recent examples.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

(SO4)-rich silicate analogue borosulfates are able to stabilise cationic cluster-like and chain-like aggregates. Single crystals of [Au3Cl4][B(S2O7)(2)] and [Au2Cl4][B(S2O7)(2)](SO3) were obtained by solvothermal reaction with SO3, and the electronic properties were investigated by means of density functional theory-based calculations. [Au3Cl4][B(S2O7)(2)] exhibits a cluster-like cation, and the cationic gold-chloride strands in [Au2Cl4][B(S2O7)(2)](SO3) are found to resemble one-dimensional metallic wires. This is confirmed by polarisation microscopy.

AbstractZum 9. Mal fand in diesem Jahr am Department Chemie der Universität Köln die „Carnival Conference Session“ (CCS‐2022) mit etwa 50 Teilnehmer:innen statt. Corona hatte den ursprünglich karnevalistischen Termin dieses Jahr in den Sommer verschoben. Zur CCS werden aufstrebende Forscher:innen aus allen Bereichen der Chemie nach Köln eingeladen. Die Vorträge adressieren Forschende aus den Arbeitsgruppen und Studierende. Das interdisziplinäre Programm bestand in diesem Jahr aus vier Vorträgen und bot Einblicke in die Spektroskopie, die Batterieforschung, das Züchten von Volumenkristallen und die Hochdruckchemie von Uran.

Starting from EuX2 (X = Cl, Br, I), we systematically investigated a variety of divalent europium complexes containing bidentate 1,10-phenanthroline (Phen) ligands. Depending on the Eu/Phen ratio, mono-, di-, and polynuclear complexes are formed, with the latter yielding one-dimensional ∞1[EuBr2(phen)] chains. Seven new divalent europium complexes, [Eu(phen)4(H2O)]Br2·2MeCN, [Eu(phen)4]I2·1.7Tol, [EuBr(phen)3]2Br2·4MeCN, [EuCl2(phen)2]2·2MeCN, [EuBr2(phen)2]2, [EuI2(phen)2]2, and [EuBr2(phen)]x, are presented in this work. All species show remarkable optical properties based on a partial electron transfer from the EuII center to the Phen ligand. The photophysical characterization is further supported by electrochemistry studies in order to describe the intermediate valence of the Eu center.

We report on a new compound composed of a phenanthroline network in which emerging channels are alternately occupied by selenous acid (H2SeO3) and dioxane molecules. The material undergoes a variety of structural changes due to both its redox activity as well as its thermal decomposition. We investigate an internal redox system of the incorporated selenous acid and the aldehyde groups of the phenanthroline framework. The reduction process of the selenium species was further elucidated by cyclic voltammetry, while the oxidation process was also monitored by 1H NMR spectra. The thermal behavior reveals that the material can undergo a reversible, topotactic transition due to dioxane and water (de)intercalation.

A method is presented to use atomic force microscopy to measure the cleavage energy of van der Waals materials and similar quasi-two-dimensional materials. The cleavage energy of graphite is measured to be 0.36 J/m2, in good agreement with literature data. The same method yields a cleavage energy of 0.6 J/m2 for MoS2 as a representative of the dichalcogenides. In the case of the weak topological insulator Bi14Rh3I9 no cleavage energy is obtained, although cleavage is successful with an adapted approach. The cleavage energies of these materials are evaluated by means of density-functional calculations and literature data. This further validates the presented method and sets an upper limit of about 0.7 J/m2 to the cleavage energy that can be measured by the present setup. In addition, this method can be used as a tool for manipulating exfoliated flakes, prior to or after contacting, which may open a new route for the fabrication of nanostructures.

Single crystals of [Au3Cl4][B(S2O7)2] and [Au2Cl4][B(S2O7)2](SO3) were obtained from a solvothermal reaction with SO3, and their electronic properties were investigated by means of density functional theory–based calculations. [Au3Cl4][B(S2O7)2] exhibits a cluster-like cation, and the cationic gold–chloride strands in [Au2Cl4][B(S2O7)2](SO3) are found to resemble one-dimensional metallic wires; this was further confirmed by polarization microscopy. More information can be found in the Research Article by B. Rasche, J. Bruns et al. (DOI: 10.1002/chem.202200004).