The extraordinary infrared transmission of metal microarrays for enhanced absorption spectroscopy of monolayers, nanocoatings, and catalytic surface reactions

by Rodriguez, Kenneth Ralph

Sampling materials on the nano-scale (with the least amount of material, good signal-tonoise in order to obtain important structural information) is a continuous venture that has lead to novel devices. A research program has been developed that uses the unique optical transmission properties of metallic microarray meshes with subwavelength holes to study and understand several interesting chemical problems. This phenomenon, involves transmitting more light than that incident on the holes. This work primarily involves working in the mid-infrared region of the electro-magnetic spectrum which leads to vibrational and orientation information. Light incident upon the metal excites the conducting electrons at the metal surface as surface plasmon (SP) polaritons. They can: propagate along the metal until a hole is reached, tunnel through the hole, and reemerge as light again. Three types of enhancements have been attributed to enhanced IR absorption. The use of this special form of light has allowed us to study: (1) self assembled monolayers (SAMs) of alkanethiol chains in an all-trans configuration supported on copper and nickel mesh, (2) catalytic conversion of benzyl alcohol on Ni/NiO to benzyl benzoate, (3) the interaction of a surface plasmon resonance with a molecular vibration, (4) the effect of TiO2 nano-coatings on surface plasmon transmission ii resonances, and (5) carbon thin films on nickel mesh which are attenuated in the visible, act like windows in the infrared. iii