Nanoparticles singularized

I. Romero, J. Aizpurua, G.W. Bryant, EJ. Garcia de Abajo, Plasmons in nearly touching metallic nanoparticles singular response in the limit of touching dimers. Opt. Exp. 14, 9988-... 

Indeed, in many cases the creation of soluble nanoparhcles has provided singular catalyhc activities/selectivities that differ from those expected for both molecular (single-site) and heterogeneous (mulh-site) catalysts [40, 41]. As a result, iridium nanoparticles have attracted much interest in terms of their catalyhc performance in the hydrogenation of olefins, ketones and aromahc compounds. 

DeVries et al.224 demonstrated experimentally that polar singularities form when a curved surface is coated with ordered monolayers (hairy-ball-theorem). The thiolates bound at the polar positions exchange faster than those in the bulk monolayer, thus allowing introduction of two—and only two—functional groups at the poles of a nanoparticle.224 This was the first example of divalent metal nanoparticles. This discovery opens up the path to new applications in the field of materials chemistry, and supramolecular chemistry, as stressed by Perepichka and Rosei.225 Undoubtedly, the regiochemical stability of these disubstituted nanoparticles and the chemical yield of their functionalization should be the subject of future studies. 

Theoretical and experimental studies demonstrated that the electromagnetic field enhancement is substantially increased at surface sites having local geometric singularities. In particular, enormous field enhancement occurs at the junction between two or more almost touching nanoparticles [5-7] due to plasmon coupling. For spacings of 1-2 nm, maximum enhancement factors of about lO -lO were calculated [6, 8]. 

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