This study demonstrates the utility of the novel Field Sweep Fourier Transform (FSFT) method for acquiring wideline (195)Pt NMR data from various sized Pt nanoparticles, Pt-Sn intermetallics/bimetallics used to catalyse oxidative processes in fuel cell applications, and various other related Pt3X alloys (X = Al, Sc, Nb, Ti, Hf and Zr) which can facilitate oxygen reduction catalysis. The (195)Pt and (119)Sn NMR lineshapes measured from the PtSn intermetallic and Pt3Sn bimetallic systems suggest that these are more ordered than other closely related bimetallic alloys; this observation is supported by other characterisation techniques such as XRD. From these reconstructed spectra the mean number of atoms in a Pt nanoparticle can be accurately determined, along with detailed information regarding the number of atoms present effectively in each layer from the surface. This can be compared with theoretical predictions of the number of Pt atoms in these various layers for cubo-octahedral nanoparticles, thereby providing an estimate of the particle size. A comparison of the common NMR techniques used to acquire wideline data from the I = 1/2 (195)Pt nucleus illustrates the advantages of the automated FSFT technique over the Spin Echo Height Spectroscopy (SEHS) (or Spin Echo Integration Spectroscopy (SEIS)) approach that dominates the literature in this area of study. This work also presents the first (195)Pt NMR characterisation of novel small Pt13 nanoclusters which are diamagnetic and thus devoid of metallic character. This unique system provides a direct measure of an isotropic chemical shift for these Pt nanoparticles and affords a better basis for determining the actual Knight shift when compared to referencing against the primary IUPAC shift standard (1.2 M Na2PtCl6(aq)) which has a very different local chemical environment.
Polycrystalline bis(dialkyldithiophosphato)Pt(II) complexes of the form Pt{S 2 P(OR) 2 } 2 (R = ethyl, iso-propyl, iso-butyl, sec-butyl or cyclo-hexyl group) were studied using solid-state 31 P and 195 Pt NMR spectroscopy to determine the influence of the alkyl substituents to the structure of the central chromophore. The results for 195 Pt CS tensors demonstrated that differences in alkyl substitutes of dialkyldithiophosphate ligands in the complexes studied have an insignificant effect on the distorted-square form structure of the central PtS 4 core. However, the principal values of 31 P chemical shift tensors in dialkyldithiophosphate ligands do differ significantly, which may be used to distinguish between different complexes. Relativistic effects (both scalar and spin-orbit) were shown to be important for the NMR parameters of both 31 P and 195 Pt nuclei. The effects due to the periodic crystal lattice were found to be non-negligible, especially for the CS tensor of the heavy-metal 195 Pt isotope. A particular correction model for incorporating lattice effects was adopted to avoid a severe deterioration of the anisotropic parameters due to the high requirements posed on the pseudopotential quality in such calculations. It seems that the pseudopotentials available in standard software may be inadequate for periodic calculations of anisotropic NMR parameters.
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