A strong linear correlation between the surface charge density on Ag nanoparticles and the amount of propylene adsorbed

Abstract

The partial positive charge density of the surface of Ag nanoparticles was modulated by an electron acceptor, 7,7,8,8-tetracyanoquinodimethane (TCNQ), to improve their reversible interactions with olefins such as propylene, but not with paraffin. The silver binding energy in Ag NPs, representing the surface charge density, exhibited a maximum at a TCNQ concentration of 0.05 mol% (0.26 molecules per nm(2)). The amount of propylene adsorbed on the surface of the Ag NPs was strongly correlated with the silver binding energy with a high correlation factor of 0.97. In addition propylenes were found to be adsorbed on the TCNQ-uncovered, vacant sites of Ag NPs according to quantum mechanical calculation. It was therefore concluded that the enhanced interaction between the surface-modulated Ag NPs and propylene is attributable to the high separation performance for olefin-paraffin mixtures based on selective facilitated olefin transport.