4 research outputs found
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<sup>–1</sup>. 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><sub>NDM</sub>-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