Kinetics of HCN Decomposition on the Pt(111) Surface by Time-Dependent Infrared Spectroscopy

Time-dependent reflection absorption infrared spectroscopy has been used to investigate the kinetics of HCN decomposition on the Pt(111) surface over the temperature range of 120 to 135 K. At these low temperatures, HCN bonds at an atop site with the HCN axis perpendicular to the surface, which gives rise to an intense C–H stretch at ∼3300 cm^–1. Further support for this HCN adsorption geometry is obtained through HCN/CO coadsorption experiments in which both molecules are seen to compete for the atop sites. The disappearance of the C–H stretch peak of HCN at low temperatures is indicative of dissociation to produce adsorbed H and CN. When the decrease in HCN coverage is followed for a sufficiently long time, the data deviate from the expected first-order rate law, and the temperature dependence of the rate constant deviates from the Arrhenius form. Over a more restricted coverage range, simpler behavior is observed, and an activation energy for HCN dissociation of 0.33 eV is obtained

Formation of Benzonitrile from the Reaction of Styrene with Nitrogen on the Pt(111) Surface

Temperature-programmed reaction spectroscopy (TPRS) and reflection absorption infrared spectroscopy (RAIRS) were used to investigate the adsorption and reaction chemistry of styrene with clean and nitrogen covered Pt(111). The RAIR spectra indicate that the adsorption geometry of styrene is altered by both coverage effects and by the presence of nitrogen atoms on the surface. For an annealed monolayer of styrene on the clean Pt(111) surface, the most intense peaks correspond to out-of-plane bending vibrations indicating that the molecular plane is oriented parallel to the surface. For monolayer styrene on the nitrogen-precovered surface and for an unannealed monolayer of styrene, the in-plane and out-of-plane vibrations have comparable intensities indicating a more random orientation of the molecular plane. Upon heating, styrene reacts with the coadsorbed nitrogen atoms to form benzonitrile, which desorbs at 380 K. When benzonitrile is directly adsorbed on the Pt(111) surface, TPRS and RAIRS reveal that it desorbs at 350 K, indicating that its desorption at 380 K when formed from the reaction of styrene with nitrogen is reaction limited

Water-in-Oil Pickering Emulsions Stabilized by Hydrophobized Protein Microspheres

Water-in-oil (w/o) Pickering emulsions have gained considerable attention in colloid science and daily applications. However, for the formation of w/o emulsions, especially those with high internal water content, the particulate stabilizers are required to be sufficiently hydrophobic, and synthetic or chemically modified particles have been mostly reported until now, which are not biocompatible and sustainable. We present a zein protein-based microsphere derived from the Pickering emulsion template, in which protein microspheres are feasibly in situ hydrophobized by silica nanoparticles, enabling the stabilization of w/o Pickering emulsions. The effects of microsphere concentration, water/oil volume ratio, oil types, and pH on the stabilization of prepared w/o emulsions are systematically studied, revealing prominent characteristics of the controllable size, high water fraction, universal adaptation of oils, as well as broad pH stability. As a demonstration, the Pickering emulsion effectively encapsulates vitamin C and shows high stability for long storage duration against ultraviolet radiation/heat. Therefore, this novel proteinaceous particle-stabilized w/o Pickering emulsion has great potential in the delivery and protection of water-soluble bioactive substrates

Higher Isolation of NDM<i>-</i>1 Producing <i>Acinetobacter baumannii</i> from the Sewage of the Hospitals in Beijing

<div><p>Multidrug resistant microbes present in the environment are a potential public health risk. In this study, we investigate the presence of New Delhi metallo-β-lactamase 1 (NDM-1) producing bacteria in the 99 water samples in Beijing City, including river water, treated drinking water, raw water samples from the pools and sewage from 4 comprehensive hospitals. For the <i>bla</i>_NDM-1 positive isolate, antimicrobial susceptibility testing was further analyzed, and Pulsed Field Gel Electrophoresis (PFGE) was performed to determine the genetic relationship among the NDM-1 producing isolates from sewage and human, as well as the clinical strains without NDM-1. The results indicate that there was a higher isolation of NDM-1 producing <i>Acinetobacter baumannii</i> from the sewage of the hospitals, while no NDM-1 producing isolates were recovered from samples obtained from the river, drinking, or fishpond water. Surprisingly, these isolates were markedly different from the clinical isolates in drug resistance and pulsed field gel electrophoresis profiles, suggesting different evolutionary relationships. Our results showed that the hospital sewage may be one of the diffusion reservoirs of NDM-1 producing bacteria.</p></div