The importance of particle-support interaction on particle size determination by gas chemisorption

The discovery, characterisation and understanding of the unique properties of materials with dimensions between 10 −9 and 10 −10 m (nano- and sub-nano scale) is currently one of the most active research areas due to their potential application in a wide range of fields from catalysis, sensors, biological labelling, photonics, plasmonics, data storage (Pankhurst et al. 2003 ; Panyam and Labhasetwar 2003 ), etc. Specifically, metal clusters and particles present unique chemical and physical properties which are strongly dependent on their size (Kelly et al. 2003 ; Daniel and Astruc 2004 ). Focusing on catalysis, the strong relationship between the size of the metal particle and its activity and selectivity has been demonstrated for multiple systems (Panigrahi et al. 2007 ; Wang et al. 2008 ). Furthermore, for a given reaction and metal, an optimum particle size range exists outside which its reactivity is considerably lower or even negligible (Schmid 2008 ). In addition to this, computational chemists, aided by advanced characterisation techniques, have also revealed the key relationship between catalytic activity and shape of the metal nanoparticles due to the selective exposure of different cluster facets and their effect on the adsorption strength of reactants. Indeed, several authors support the fact that the high activity of the metal nanoparticles is directly related to the high concentration of uncoordinated atoms in nano-sized particles (Lemire et al. 2004 ), further promoted by specific 3D shapes (Molina et al. 2011 ; Yasumatsu and Fukui 2015 ). For example, it is known that the optical response from metal nanoparticles and nanostructures is dominated by surface plasmon generation and is critically dependent on the local structure and geometry such as a range of polyicosahedral shapes or ellipsoids (Rossi et al. 2004 ; Bosman et al. 2007 ). As a consequence, control of the metal particle size and shape in addition to accurate characterisation are crucial for further development in the field.