Laser Raman Spectroscopy has been used very effectively for some time to probe heterogeneous catalytic reactions in situ (e.g. Wachs & Roberts Chem. Soc. Rev., 39, 5002), in particular the surface structures of oxide catalysts, but also precious metal catalyzed oxidation of alcohols. It offers obvious advantages of compatibility with many reaction conditions (in particular pressure not accessible with electron or soft X-ray spectroscopies). For Raman, unlike IR, this even includes reaction conditions with high concentrations of water. However, it has shortcomings of possible low cross section, low surface sensitivity and possible sample damage from the heat dissipated on absorbing the incident laser light � all undesirable in an in situ technique. For studying self assembled monolayers of delicate molecules, the Raman analogue of attenuated total reflection (ATR) IR spectroscopy has been employed to great effect to study low coverages (1% of a monolayer) of delicate organic molecules on Silica (Tyrode et al., J. Am. Chem. Soc., 130, 17434). Using evanescent wave Raman spectroscopy has several key advantages � primarily that the reaction and spectroscopy can be split into two and the laser power is not depleted in the sample but largely reflected, dramatically reducing sample damage. Here we report the recent observation of species absorbed during a prototypical metal nanoparticle catalyzed reaction, demonstrating the utility of this novel approach for studying heterogeneous catalytic processes on nanoparticles in situ.

Total internal Raman: A new approach to in situ and operando Raman studies of nanoparticle catalysts

248th National Meeting (2014)

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