Photoinduced refractive index change of self-assembled spiroxazaine monolayer based on surface plasmon resonance

The self-assembly of a photochromic, spiroxazine-containing alkanethiol monolayer on a gold surface is described. Contact angle measurements confirm the presence of a hydrophilic surface in the self-assembled monolayer. Atomic force microscopy (AFM) images and measurements confirm that this monolayer was formed by stepwise chemical assembly. Evidence for self-assembled monolayer-photochromism was gathered from UV¯visible spectral evaluation before and after irradiation at 366 nm. Surface plasmon resonance (SPR) revealed that a resonance angle change of 0.13° which corresponded to a refractive index change, deltan, of 0.0034.