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Two-dimensional (2D) materials exhibit the potential to transform semiconductor technology. Their rich compositional and stacking varieties allow tailoring materials' properties toward device applications. Monolayer to multilayer gallium sulfide (GaS) with its ultraviolet band gap, which can be tuned by varying the layer number, holds promise for solar-blind photodiodes and light-emitting diodes as applications. However, achieving commercial viability requires wafer-scale integration, contrasting with established, limited methods such as mechanical exfoliation. Here the one-step synthesis of 2D GaS is introduced via metal-organic chemical vapor deposition on sapphire substrates. The pulsed-mode deposition of industry-standard precursors promotes 2D growth by inhibiting the vapor phase and on-surface pre-reactions. The interface chemistry with the growth of a Ga adlayer that results in an epitaxial relationship is revealed. Probing structure and composition validate thin-film quality and 2D nature with the possibility to control the thickness by the number of GaS pulses. The results highlight the adaptability of established growth facilities for producing atomically thin to multilayered 2D semiconductor materials, paving the way for practical applications., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Herein, we present the synthesis of two pyrene-functionalized clusters, [(R pyr Sn) 4 S 6 ]⋅2 CH 2 Cl 2 (4) and [(R pyr Sn) 4 Sn 2 S 10 ]⋅n CH 2 Cl 2 (n=4, 5 a; n=2, 5 b; R pyr =CMe 2 CH 2 C(Me)N-NC(H)C 16 H 9 ), both of which form in reactions of the organotin sulfide cluster [(R N Sn) 4 S 6 ] (C; R N =CMe 2 CH 2 C(Me)N-NH 2 ) with the well-known fluorescent dye 1-pyrenecarboxaldehyde (B). In contrast, reactions using an organotin sulfide cluster with another core structure, [(R N Sn) 3 S 4 Cl] (A), leads to formation of small molecular fragments, [(R pyr Cl 2 Sn) 2 S] (1), (pyren-1-ylmethylene)hydrazine (2), and 1,2-bis(pyren-1-ylmethylene)hydrazine (3). Besides synthesis and structures of the new compounds, we report the influence of the inorganic core on the optical properties of the dye, which was analyzed exemplarily for compound 5 a via absorption and fluorescence spectroscopy. This cluster was also used for exploring the potential of such non-volatile clusters for deposition on a metal surface under vacuum conditions., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Ring/chain competition in oligomerization reactions represents a long-standing topic of synthetic chemistry and was treated extensively for solution reactions but is not well-understood for the two-dimensional confinement of surface reactions. Here, the kinetic and thermodynamic principles of ring/chain competition in on-surface synthesis are addressed by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and Monte Carlo simulations applied to azulene-based organometallic oligomers on Cu(111). Analysis of experiments and simulations reveals how the ring/chain ratio can be controlled through variation of coverage and temperature. At room temperature, non-equilibrium conditions prevail and kinetic control leads to preferential formation of the entropically favored chains. In contrast, high-temperature equilibrium conditions are associated with thermodynamic control, resulting in increased yields of the energetically favored rings. The optimum conditions for ring formation include the lowest possible temperature within the regime of thermodynamic control and a low coverage. The general implications are discussed and compared to the solution case., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The binary lead fluoride Pb 3 F 8 was synthesized by the reaction of anhydrous HF with Pb 3 O 4 or by the reaction of BrF 3 with PbF 2 . The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS 19 F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Tip-enhanced Raman spectroscopy combines scanning probe techniques with Raman spectroscopy. Latest developments permit the chemical mapping of individual adsorbed molecules by monitoring molecular vibrations with sub-nanometer resolution. Increased efficiency and reduced photodegradation make this method suitable for studies of adsorbed organic and biomolecules in surface science, catalysis, biochemistry, and related fields., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A hexagonal macrocycle consisting of 18 phenylene units (hyperbenzene) was synthesized on a Cu(111) surface in ultrahigh vacuum by Ullmann coupling of six 4,4''-dibromo-m-terphenyl molecules. The large diameter of 21.3 Å and the ability to assemble in arrays makes hyperbenzene an interesting candidate for a nanotrough that could enclose metallic, semiconducting, or molecular quantum dots., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel class of heterogeneous gold catalysts supported on zeolite beta-NH4+ was prepared by the deposition-precipitation method. This new class of catalyst showed interesting catalytic activities for the intramolecular cycloisomerization of gamma-acetylenic carboxylic acids leading to functionalized gamma-alkylidene gamma-butyrolactones. Analysis of the supported gold species with in situ X-ray photoelectron spectroscopy (in situ XPS) suggests that cationic Au (possibly AuIII) can play an important role in such reactions. The high discrepancy in catalyst stability in favor of the Au supported on the zeolite system over bulk Au2O3 is explained by 1) the size of the particles and 2) the reversibility of the redox deactivating process (AuIII-->AuI) in the presence of oxygen for the supported system. The efficiency of this system allowed reaction under mild heterogeneous conditions. The potential for catalyst recycling was also highlighted.