Visible absorption properties of retinoic acid controlled on hydrogenated amorphous silicon thin film

Langmuir-Blodgett (LB) films of retinoic acid and LB films of retinoic acid mixed with a peptide that contains an alaninelysine-valine (AKV) amino acid sequence deposited on a hydrogenated amorphous silicon (a-Si:H) film prepared by electron cyclotron resonance (ECR) plasma sputtering were fabricated, and their light absorption spectrums were compared. A specific visible light absorption at approximately 500nm occurred in a film that had a film thickness of more than 80nm and a hydrogen concentration of more than 20% in the sputtering process gas. Mixing the AKV sequence peptide with retinoic acid caused a 6 nm blueshift, from 363 to 357 nm, of the absorption maximum of the composite LB film on a SiO₂ substrate. Using the same peptide, a large 30 nm blueshift, from 500 to 470 nm, was induced in the composite LB film on the a-Si:H film.