Studies on poly(ethylenimine)/purple membrane multilayer films fabricated by layer-by-layer self-assembly

In the present work, we have obtained organized PEI/PM (poly(ethylenimine)/purple membrane) multilayer films by layer-by-layer alternate adsorptions with positively charged polycation PEI and negatively charged purple membrane fragments. The results observed by UV–vis spectroscopy show that each transfer amount of PM fragments onto the substrate is equal and the characteristic absorption bands of bacteriorhodopsin (bR) are still preserved. AFM and SEM analysis investigated the morphology and cross-section of PM films, respectively. The photocurrent peaks of (PEI/PM)6 multilayer films corresponding to light-on and light-off are ca. 440 and 250 nA/cm2.