Optical and electrochemical properties of tunable host-guest complexes linked to plasmonic interfaces

This article describes the use of localized surface plasmon resonance (LSPR) interface to detect complexation/decomplexation steps of a controllable host-guest system at the solid-liquid interface. The LSPR interfaces consist of a sandwiched structure comprising a tin-doped indium oxide (ITO) substrate, gold nanostructures (Au NSs) and a thin ITO film overcoating. Click chemistry was used to covalently link an alkyne-functionalized pi-electron deficient tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT(4+)) unit to an azide-terminated LSPR interface. The modified interfaces were characterized using X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and UV-vis transmission spectroscopy. Tetrathiafulvalene (TTF) was used as a model guest molecule to demonstrate the possibility to follow the complexation/decomplexation events by monitoring the change in the LSPR signal. The results demonstrate that redox controlled host-guest complexation at the surface can be monitored effectively using LSPR.