Metal vibrational signature

The results of this DFT study confirm that aluminium and PT oligomers interact preferentially through the formation of covalent bonds between Al-atoms and the a-carbons of thiophene rings. This type of reaction is expected to take place when A1 is deposited on the polymer layer as well as when PT is adsorbed on the metal surface. In all cases, the formation of the Al-C bonds and the geometric modifications induced in the organic molecules lead to important changes in the vibrational spectra which should allow the experimental detection of the vibrational signatures of the species formed at the Al-PT interface. 

Cagmat EB, Szczepanski J, Pearson WL, Powell DH, Eyler JR, Polfer NC (2010) Vibrational signatures of metal-chelated monosaccharide epimers gas-phase infrared spectroscopy of Rb -tagged glucuronic and iduronic acid. Phys Chem Chem Phys 12 3474-3479... 

SERS (Surface Enhanced Raman Scattering) and, more recently, SEIRA (Surface Enhanced Infrared Absorption) spectroscopies have rapidly expanded their field of applications. These techniques are based on the use of noble metal nanoparticles (NPs) supporting Localized Surface Plasmons (LSP). They are extremely attractive due to unique high sensitivity and their potential for molecule-specific sensing technologies utilizing vibrational signatures 1,2). 

For ferromagnetic cobalt particles in zeolite X, spin-echo ferromagnetic resonance has been used to obtain unique structural information (S6). In addition, study of the catalytic signature of metal/zeolite catalysts has been used by the groups of Jacobs (87), Lunsford (88), and Sachtler (47,73,89). Brpnsted acid protons are identified by their O—H vibration (90,91) in FTIR or indirectly, by using guest molecules such as pyridine or trimethylphosphine (92,93). An ingenious method to characterize acid sites in zeolites was introduced by Kazansky et al., who showed by diffuse reflection IR spectroscopy that physisorbed H2 clearly discerns different types of acid sites (94). Also, the weak adsorption of CO on Brpnsted and Lewis acid sites has been used for their identification by FTIR (95). The characterization of the acid sites was achieved also by proton NMR (96). 

As already mentioned for other surface systems, an indirect but efficient way to monitor changes in the electronic structure of a supported metal particle with respect to the free species is to analyze variations of properties of an adsorbed probe molecule. This is similar to the experimental approach to examine the acidity or basicity of a given adsorption site by measuring indirectly the flow of charge between the adsorbate and the substrate [201] (see Section 4). Comparison of spectral signatures of adsorbed CO molecules (e.g., the frequency of the C-0 vibration) offers valuable information on the electronic state of the substrate. We analyzed computationally the properties of CO molecules adsorbed on free and supported model Pd4 and Pds clusters [176]. 

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