Adopting low-index single-crystal surfaces as models for metal nanoparticle catalysts has been questioned by the experimental findings of adsorbate-induced formation of subnanometer clusters on several single-crystal surfaces. We used density functional theory calculations to elucidate the conditions that lead to cluster formation and show how adatom formation energies enable efficient screening of the conditions required for adsorbate-induced cluster formation. We studied a combination of eight face-centered cubic transition metals and 18 common surface intermediates and identified systems relevant to catalytic reactions, such as carbon monoxide (CO) oxidation and ammonia (NH 3 ) oxidation. We used kinetic Monte Carlo simulations to elucidate the CO-induced cluster formation process on a copper surface. Scanning tunneling microscopy of CO on a nickel (111) surface that contains steps and dislocations points to the structure sensitivity of this phenomenon. Metal-metal bond breaking that leads to the evolution of catalyst structures under realistic reaction conditions occurs much more broadly than previously thought.

In recent years, Ge and Ge 1−x Sn x materials and devices have achieved rapid progress in integrated photonics. However, conventional heteroepitaxy of active photonic devices compromises the area on Si for CMOS electronics, limiting the scale of integration. Furthermore, it is not possible to grow GeSn epitaxially on amorphous and/or flexible substrates toward 3D photonic integration in mid-infrared (MIR) regime. Here, we present low-temperature crystallization of direct bandgap, high crystallinity Ge 1−x Sn x (0.08 < x < 0.26) on amorphous dielectrics insulators (GeSnOI) toward 3D and flexible MIR integrated photonics. Utilizing eutectically-enhanced crystallization (EEC), an extraordinarily large average grain size of ∼100 µm has been achieved in blanket GeSn films crystallized on SiO 2 layers, flexible glass, and polyimide substrates alike. Furthermore, using Sn nanodot enhanced composition enhancement (NICE), we have achieved an average Sn composition as high as 26 at.% to further extend the optical response of GeSn toward λ = 3-5 µm. The achieved Sn composition of 8-26 at.% far exceeds that of the equilibrium solubility limit of <1 at.%, even though the crystallization temperature of 350-450 • C far exceeds the typical epitaxial growth temperature of GeSn. This result indicates that crystallization from amorphous GeSn (a-GeSn) may offer better metastability compared to direct epitaxial growth of GeSn. Attesting to the high crystallinity, a peak optical gain of 2,900 cm −1 with a lifetime approaching 0.1 ns is achieved at λ = 2,200-2,350 nm at 300 K. The gain lifetime is on the same order as epitaxial GeSn, and it is >100x longer than the direct gap transition in Ge, confirming the indirect-to-direct band gap transition in GeSn at ∼9 at. Sn composition. Moreover, a prototype p-GeSn/n-Si photodiode from a-GeSn crystallization achieves 100 mA/W responsivity at λ = 2,050 nm and T = 300 K, approaching the level of some commercial PbS detectors. The device also demonstrates photovoltaic behavior and a low dark current density of 1 mA/cm 2 at −1 V reverse bias, comparable to epitaxial Ge/Si photodiodes. These results indicate that crystallization of GeSnOI offers a promising solution for active devices toward 3D MIR photonic integration and/or MIR photonics on flexible substrates.

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The title compounds, both C8H4F3NO4, represent two isomers of nitro trifluoromethyl benzoic acid. The compounds each contain a nitro functionality para to the carboxylic acid group, with the trifluoromethyl substituent ortho to the acid group in the 2-isomer and ortho to the nitro group in the 3-isomer. The regiochemistry with respect to the trifluoromethyl group results in steric interactions that rotate the carboxylic acid group or the nitro group out of the aromatic plane in the 2- and 3-isomer, respectively. Each molecule engages in intermolecular hydrogen bonding, forming head-to-tail dimers with graph-set notation R 2 2(8) and donor–acceptor hydrogen-bonding distances of 2.7042 (14) Å in the 2-isomer and 2.6337 (16) in the 3-isomer. Recrystallization attempts did not yield untwinned crystals.

Carbon nanotubes (CNTs) have been deposited by chemical vapor deposition (CVD) onto a nickel catalyst that had been electroplated onto a metal base electrode. The CNTs were characterized by Cyclic Voltammetry (CV) and Scanning Electron Microscopy (SEM). Prussian Blue (PB) was electrochemically deposited onto the CNT electrode from a solution of K3Fe(CN)6 by repeated cycling between -0.1 V and 0.8 V verses an Ag/AgCl reference. The ferricyanide redox couple occurs approximately at 0.25V-0.5 V while the deposition of PB was seen as a growing redox couple approximately at 0.65V-1.0 V. This suggests that utilizing CV is a viable method to functionalize CNT electrodes with PB. However, the exact structure and location of the PB bonding is unknown and was the focus of this study. SEM was utilized to image the electrode surface after each step of the functionalization process in order to study PB bonding onto the CNT electrode.