Surface-Enhanced Infrared Absorption on Arranged Pt Nanoantennas.

Surface plasmon-driven chemical reactions have attracted considerable attention as a means of developing specific chemical processes. To integrate plasmonic effects with heterogeneous catalytic reactions, it is desirable to use chemically active metals such as Pt, rather than inert materials like Au. In this study, we fabricated Pt nanoantennas and investigated surface plasmon responses with infrared transmission absorption measurements. Observed transmission absorption bands are attributed to surface plasmon excitations in the Pt nanoantennas. As the longitudinal length of the Pt nanoantennas increased, the resonance energy decreased and the linewidth narrowed, exhibiting similar behavior to that observed in Au nanoantennas. The present observations suggest that the Pt nanoantennas exhibited electric field enhancement due to infrared surface plasmon excitations. Furthermore, by adsorbing benzene molecules on the Si substrate with Pt nanoantennas at 100 K, surface-enhanced infrared absorption spectra were obtained. The enhancement factor for the C-C stretching vibrational mode was evaluated to be ∼900. The present work is an important step toward catalytic technologies that employ infrared surface plasmons to selectively and strongly excite specific vibrational modes.