Preparation of Dendritic Pt Thin Films and Their Anomalous Infrared Effects

Dendritic Pt thin films are electrodeposited on bulk Pt electrodes in 10x10(-3) mol . L-1 K2PtCl6+3x 10(-4) mol . L-1 PbAc2 + 0.5 mol . L-1 HClO4 using square-wave potential pulses. As the deposition time increases, the length of the Pt dendrites increases from 400 to 900 nm, and the distribution density of Pt nanoparticles (similar to 10 nm), which consist of coiled Pt dendrites, increases greatly. From hydrogen adsorption/desorption obtained from cyclic voltammograms (CV), the surface of the dendritic Pt thin film electrodes has a relative roughness (C-r), which increases from 9 to 36 as the deposition time increases. Maximum enhanced IR absorption of adsorbed CO (COad) is observed at the deposition time of 6 min. Anomalous infrared effects for COad are also seen on the dendritic Pt thin film electrodes. The line shapes of COad change with increasing deposition time, in order: bipolar -> downward -> bipolar -> upward -> bipolar -> downward bands. Fano-like infrared effects (bipolar), surface enhanced IR absorption (enhanced downward band), and abnormal IR effects (enhanced upward band) are highly dependent on the surface architecture of the nanostructures. The as-prepared dendritic Pt thin films provide model substrates for in-depth studies of the anomalous infrared effects of COad in metal nanostructures.National Natural Science Foundation of China [21073152, 20933004, 20833005, 21021002]; Outstanding Young Scientific Talents Cultivation Plan of Colleges in Fujian Province, China [JA10003