Solid-phase synthesis and photochromic switching of a polymeric photochromic layer on a gold surface

The preparation of a novel carboxymethylated dextran photochromic polymer on a gold surface is presented here. Ethylester-dihydroindolizine is attached by amine coupling to a carboxymethylated dextran polymer on the gold surface of a Surface Plasmon Resonance (SPR) sensor. The photoinduced switch between the two isomers of the ethylester-dihydroindolizine photochromic polymer was investigated by fiber optics based surface plasmon resonance. The different solvent effect on the SPR shift is also reported. A larger absolute shift was obtained in solvents with low relative dielectric constants, than in solvents with a larger relative dielectric constant. A blue shift was observed with organic solvents and a red shift for the aqueous solvent. Moreover, by changing the solvent, the refractive index of the surrounding media in contact with the gold surface also changes and the wavelength used to excite the surface plasmon can be shifted outside the excitation/relaxation range of the photochromic system.