Physical properties of metal cluster compounds III: NMR study of platinum carbonyl clusters

Pronk, B.J.; Brom, H.B.; Ceriotti, A.; Longoni, Giuliano

doi:10.1016/0038-1098(87)90508-4

Cited by 25 publications

(7 citation statements)

References 22 publications

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“…A suppression of the Korringa relation and a decrease in spin-lattice relaxation rates by four orders of magnitude at I K have been observed by Brom and coworkers [8] in platinum carbonyl cluster compounds of nuclearity 26 and 38 (Fig. 4).…”

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confidence: 58%

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Electronic properties of small platinum particles as seen by NMR

Klink

1989

Z Phys D - Atoms, Molecules and Clusters

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No doubt partially because of their catalytic activity, small platinum particles on mineral supports have been extensively studied by NMR during recent years. Here we will discuss these data in relation to the expected electronic properties of small metal particles. Experimentally, no quantum size effects are found, but the local densities of state at the Fermi energy show considerable site-dependence when going from the surface to the interior of the particle. Such effects have been theoretically predicted for an infinite film. PACS: 76.60.Cg; 36.40. + d This paper focuses on magnetism-related NMR effects that arise through the hyperfine coupling between the electronic and nuclear spins: in bulk metals, the static part of the hyperfine coupling results in the Knight shift K and the dynamic part in the Korringa relation T~-loeT (the spin-lattice relaxation rate is proportional to the temperature). We will restrict the discussion mainly to the case of 195pt NMR for which detailed data have become available since the first studies by C.P. Slichter's group, reported at the Lausanne edition of this conference [1].In theoretical descriptions of the magnetic quantum size effect (QSE) one imagines a collection of particles all containing the same number of atoms; the size-parameter is expressed as = 4 EF/3N

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confidence: 58%

“…The fraction of particles with any level in that interval is given by: Define (El -E_ t)j = 2Aj (8) where the index j refers to the j-th particle in our collection. Its susceptibility at these tow temperatures is:…”

mentioning

confidence: 99%

Electronic properties of small platinum particles as seen by NMR

Klink

1989

Z Phys D - Atoms, Molecules and Clusters

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“…As previously mentioned, the total shift is the result of the Knight shift and the chemical shift contributions. 39 However, Pt in the bulk metal is generally surrounded by 42 These presumptions can only be made for a perfectly cubo-octahedral stabilised Pt 13 cluster, whereas difficulties in this synthesis has led to a dispersion in the Pt cluster size.…”

Section: Nmr Of Clustersmentioning

confidence: 99%

“…It has been suggested that trialkyl aluminium weakly bonds to platinum with no band overlap. 42 If this assertion is correct then a 27 Al NMR investigation of the bound trialkyl aluminium should yield a single resonance.…”

Section: Platinum Clustersmentioning

confidence: 99%

Characterisation of platinum-based fuel cell catalyst materials using 195Pt wideline solid state NMR

Rees

Orr

Barrett

et al. 2013

Phys. Chem. Chem. Phys.

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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.

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“…The molecules of these compounds consist of a metal atom core surrounded by a shell of ligands [2]. As part of a general research program on polynuclear cluster compounds in our group [3,4,5] we have used NMR to study the microscopic properties of these compounds. In contrast to the particles produced by these techniques, however, the cores of the cluster molecules are strictly uniform throughout a sample.…”

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confidence: 99%