Indium tin oxide modified with dendrimer-encapsulated Pt nanoparticles as efficient p-aminophenol redox cycling platforms

Abstract

In this work, we studied indium tin oxides (ITOs) modified with dendrimer-encapsulated Pt nanoparticles (Pt DENs) to develop efficient p-aminophenol (p-AP) redox cycling platforms. The ITO surfaces were modified via electro-oxidative grafting of the terminal amine groups of the dendrimers encapsulating catalytic Pt nanoparticles (i.e., Pt DENs). Compared to conventional ITO surfaces, the Pt DEN-modified ITOs showed highly enhanced electrochemical oxidation current of p-AP even at low potentials with no significant background oxidation current due to the catalytic activity of Pt nanoparticles, leading to high signal-to-background ratio for sensitive p-AP redox cycling. The enhanced p-AP redox cycling on the Pt DEN-modified ITOs led to ∼17.8 times higher sensitivity of the p-AP redox cycling than that obtained with conventional ITOs. In addition, the Pt DEN-modified ITOs were found to be suitable as platforms for the immobilization of oligonucleotides due to the globular structure of dendrimers, which have a high surface-to-volume ratio and multiple terminal functional groups, grafted on ITO surfaces. The DEN-modified ITOs could be further functionalized by the immobilization of single-strand DNA oligonucleotides with high surface density (i.e., (2.2 ± 0.4) × 1012 molecules/cm2), which is ∼4.4-fold higher than that on the surface of conventional ITOs.