Proton magnetic relaxation rates of the three ethanols CD3CD2OH, CD3CH2OD, and CH3CD2OD at 30 MHz as a function of the temperature have been measured. The temperature range was 298 > T> 120K, thus the experimental results are also referring to the dispersion range where cot a; 1. By measuring suitable isotopic mixtures the intramolecular and intermolecular relaxation rates have been determined. The attempt was made to interpret the intramolecular relaxation rates in terms of the Woessner theory which involves internal group rotation of the CH3 or CH2 group. The corresponding analysis was not successful, the observed relaxation rates are lower than predicted by the theory. The interpretation of the intermolecular relaxation rates was satisfactory.Protonen-magnetische Relaxationsraten der drei Athanole CD3CD2OH, CD3CH2OD und CH3CD2OD wurden bei 30 MHz als Funktion der Temperatur gemessen. Der Temperaturbereich war 298 > T> 120 K, so daB sich die experimentellen Ergebnisse auch auf den Dispersionsbereich beziehen, wo gilt cot a; 1. Durch Messung geeigneter isotopischer Gemische konnten auch die intraund intermolekularen Relaxationsraten bestimmt werden. Es wurde der Versuch unternommen, die intramolekularen Relaxationsraten im Rahmen der Woessner-Theorie zu interpretieren, welche die innere Rotation von Gruppen, hier der CH3und CH2-Gruppe, einbezieht. Die diesbezugliche Analyse war nicht erfolgreich, die beobachteten Relaxationsraten waren niedriger als die von der Theorie vorhergesagten. Die Interpretation der intermolekularen Relaxation fiihrte zu befriedigenden Ergebnissen. 189 orientations relative to the external coordinate system which are interrelated by time independent coefficients. Then also one rotational propagator can be transformed to another one. But if the molecule has only partial rigidity the rotational motion relative to the laboratory system of the intramolecular coordinate systems placed in the various parts of the molecule will be different. One could consider to formulate a set of rotational diffusion

In direct methanol fuel cell technology, highly stable electrochemical catalysts are critically important for their practical utilization at the commercial scale. In this study, sub ~10 nm hollow Pt-Ni (1:1 at. ratio) nanoboxes supported on functionalized Vulcan carbon (Pt-Ni/C-R2) were synthesized through a facile method for the efficient electrooxidation of methanol. Two reaction procedures, namely, a simultaneous reduction and a modified sequential reduction method using a reverse microemulsion (RME) method, were adopted to synthesize solid Pt-Ni NPs and hollow nanoboxes, respectively. To correlate the alloy composition and surface structure with the enhanced catalytic activity, the results were compared with the nanocatalyst synthesized using a conventional NaBH4 reduction method. The calculated electroactive surface area for the Pt-Ni/C-R2 nanoboxes was 190.8 m2.g−1, which is significantly higher compared to that of the Pt-Ni nanocatalyst (96.4 m2.g−1) synthesized by a conventional reduction method. Hollow nanoboxes showed 34% and 44% increases in mass activity and rate of methanol oxidation reaction, respectively, compared to solid NPs. These results support the nanoreactor confinement effect of the hollow nanoboxes. The experimental results were supported by Density Functional Theory (DFT) studies, which revealed that the lowest CO poisoning of the Pt1Ni1 catalyst among all Ptm-Nin mixing ratios may account for the enhanced methanol oxidation. The synthesized hollow Pt-Ni/C (R2) nanoboxes may prove to be a valuable and highly efficient catalysts for the electrochemical oxidation of methanol due to their low cost, numerous catalytically active sites, low carbon monoxide poisoning, large electroactive surface area and long-term stability.

ABSTRACT:The sorption of lead(II) ions onto Haro river sand has been studied using voltammetric methods as well as the effect of different acid concentrations on the sorption process. The maximum sorption of Pb(II) ions onto the adsorbent surface was achieved from de-ionized water. It was found that the sorption data could be fitted by the

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The synthesis of Au x Cu (1Àx) nanoalloys (NAs) by a two-phase method employing amines acting simultaneously as coordinating ligands, phase transfer agents as well as nanoparticle (NP) stabilisers, is presented. The value of x was varied between 0 and 1 and dodecylamine (DDA) and hexadecylamine (HDA) were used as ligands. The nanoparticles were characterised by elemental analysis, UV-vis and IR spectroscopies, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning TEM (STEM) and X-ray photoelectron spectroscopy (XPS). Alloying with Au imparts significant stability to Cu nanoparticles. Interestingly, some degree of surface segregation for Cu in the synthesised Au x Cu (1Àx) NAs is revealed from the TEM analysis, contrary to expectations based on previously calculated segregation energies. XRD analysis demonstrates a high degree of crystallinity of the cores although the crystallite sizes obtained from the Scherrer equation are smaller than TEM measurements. A mild heat treatment is sufficient to enhance the overall particle crystallinity resulting in crystallite size estimates from XRD comparable to those obtained from TEM.