Herein we present some initial results demonstrating the room temperature oxidation of secondary alcohols catalyzed by the reduced salt-inclusion polyoxometalate, Cs5(V14As8O42Cl).
Due to a high surface
area to volume ratio, two-dimensional nanosheets
have gained interest for photo and/or electro-catalytic water splitting.
In particular, experimental Rh doping of lepidocrocite TiO2 nanosheets has significantly increased catalytic activity. We use
first-principles density functional theory to consider the oxygen
evolution reaction (OER) on both pristine and transition metal doped
systems. While the undoped TiO2 nanosheets exhibit several
limitations and require high overpotentials during the water splitting
reaction, selected dopants modify the binding strength of reaction
intermediates and can reduce rate limiting thermodynamic barriers
and theoretical required overpotentials. We present an activity volcano
for these nanosheets, with the full spectrum of 3d, 4d, and 5d transition
metals as candidate dopants. Subsequent photocatalytic measurements
of OER activity with selected dopants are carried out to validate
the predictions, and the trends are found to be consistent. These
results help describe how surface dopants affect reaction mechanisms
and provide general design principles for high performance catalysts
during the water splitting reaction.
We demonstrate the ability to fabricate vertically stacked Si quantum dots (QDs) within SiGe nanowires with QD diameters down to 2 nm. These QDs are formed during hightemperature dry oxidation of Si/SiGe heterostructure pillars, during which Ge diffuses along the pillars' sidewalls and encapsulates the Si layers. Continued oxidation results in QDs with sizes dependent on oxidation time. The formation of a Gerich shell that encapsulates the Si QDs is observed, a configuration which is confirmed to be thermodynamically favorable with molecular dynamics and density functional theory. The type-II band alignment of the Si dot/SiGe pillar suggests that charge trapping on the Si QDs is possible, and electron energy loss spectra show that a conduction band offset of at least 200 meV is maintained for even the smallest Si QDs. Our approach is compatible with current Si-based manufacturing processes, offering a new avenue for realizing Si QD devices.
Sixty-five strains of Neisseria were tested. They included 12 species and several serogroups of N. meningitidis. A variety of acids, including keto acids, were detected by gas chromatography. Many of the acids detected have not been previously reported. Strains of N. meningitidis and N. catarrhalis were found to comprise a heterogeneous group. Cultures of N. flavescens, N. sicca, N. subflava, N. perflava, and N. cinerea produced acid patterns like N. meningitidis serogroup B. N. flava and N. mucosa were also like this group except that phenylpyruvic acid was detected in cultures of the former organisms. Strains of N. gonorrhoeae differed from strains of N. meningitidis in that acetic acid was produced, propionic acid was not used, and only a moderate amount of α-ketoisocaproic acid was detected. Strains of N. lactamicus, N. haemolysans, N. ovis, and N. catarrhalis also produced characteristic patterns that distinguished them from other species tested. The data indicate that criteria in addition to those now routinely used should be established to identify some members of the genus properly.
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