Enhanced Electrochemiluminescence on Indium Tin Oxide Modified with Dendrimer-Encapsulated Nanoparticles

Abstract

Here, we report enhanced electrochemiluminescence (ECL) on indium tin oxide (ITO) electrodes modified with amine-terminated dendrimers encapsulating catalytic nanoparticles, which can be applied for sensitive electrochemiluminescence(ECL)-based assay. Specifically, we prepared Pt and Au dendrimer-encapsulated nanoparticles (DENs) using amine-terminated polyamidoamine (PAMAM) dendrimers, and subsequently immobilized the DENs onto ITO surfaces via electrooxidative grafting of the terminal amines of dendrimers to the surfaces.[1] The resulting DEN-modified ITOs preserved good optical transparency of ITO and exhibited highly catalyzed electrochemical oxidation of Ru(bpy)3 2+ (bpy, 2,2’-bipyridine)/ tri-n-propylamine (TPrA), leading to significantly increased ECL emission.[2] Especially, the Pt DEN-modified ITO electrode provides negligible transmittance drop, i.e. only ~1.99% over the entire visible region, and exhibited not only much enhanced (i.e., ~213-fold increase compared to ECL obtained from bare ITO), but also stable ECL emission under consecutive potential scans from 0.00 to 1.10 V for 10 cycles, which allowed ~329 times more sensitive ECL-based analysis of nicotine using the Pt DEN-modified ITO compared with the use of bare ITO. However, we observed relatively poor stability of Au DENs on the ITO surfaces.[2] We found that the poor stability of Au DENs is closely related with the presence of chloride ions in electrolyte solutions.[3] In the absence of chloride ions, we demonstrated that the Au DEN-modified ITOs could be used as a versatile ECL based platform for sensitive electroanalysis of reactive oxygen species (ROS), such as hydrogen peroxide. [1] S. B. Lee, Y. Ju, Y. Kim, C. M. Koo, and J. Kim, Chem . Com un . 2013, 49, 8913. [2] Y. Kim and J. Kim, Anal . C hem . 2014, 86, 1654. [3] Lee, S. B.; Kwon, J.; Kim, J. Electroanalysis 2015 , 27, 2180-2186.