2013 New's Items

We have investigated the effect of cobalt nanoparticle size in Fischer–Tropsch synthesis (CO/H2) and have compared it to data obtained for carbon dioxide hydrogenation (CO2/H2) using model catalysts produced by colloidal methods. Both reactions demonstrated size dependence, in which we observed an increase of the turnover frequency with increasing average particle size. In both case, a maximum activity was found for cobalt particles around 10–11 nm in size. Regarding the selectivity, no size-dependent...

We investigate the two-color three-pulse photon echo peak shift in a (left–right) binary system, where each component consists of a heterodimer. On the basis of the model, we find that the effect of the excitonic asymmetry between two components leads to an additional factor in the peak shift. A pseudo-rephasing and pseudo-free-induction-decay mechanism is proposed to explain the resultant negative peak shift, when the differences between the two left/right components have the opposite sign. In such a case, estimates of the electronic coupling strength via two- and one-color peak...

A cobalt-sulfide (Co–S) film prepared via electrochemical deposition on conductive substrates is shown to behave as an efficient and robust catalyst for electrochemical and photoelectrochemical hydrogen generation from neutral pH water. Electrochemical experiments demonstrate that the film exhibits a low catalytic onset overpotential (η) of 43 mV, a Tafel slope of 93 mV/dec, and near 100% Faradaic efficiency in pH 7 phosphate buffer. Catalytic current densities can approach 50 mA/cm2 and activity is maintained for at least 40 h. The catalyst can also be...

The ultrafast spectroscopy of single domains of polycrystalline films of TIPS-pentacene, a small-molecule organic semiconductor of interest in electronic and photovoltaic applications, is investigated using transient absorption microscopy. Individual domains are distinguished by their different polarization-dependent linear and nonlinear optical responses. As compared to bulk measurements, we show that the nonlinear response within a given domain can be tied more concretely to specific physical processes that transfer exciton populations between specified electronic states. By use of...