Polypeptide multilayer films on colloidal particles: An in situ electro-optical study

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• 作者：Tsetska Radeva ; Kamelia Kamburova
• 关键词：Polypeptide multilayers ; Electro-optics of multilayers ; Multilayers on colloidal particles ; Mechanism of multilayer growth ; Electrical polarizability of multilayers
• 刊名：Journal of Colloid and Interface Science
• 出版年：2007
• 出版时间：15 April 2007
• 年：2007
• 卷：308
• 期：2
• 页码：309-317
• 全文大小：296 K

文摘

The buildup of poly(l-glutamic acid) (PGA) and poly(l-lysine) (PLL) multilayers on ;2;-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse “in” and “out” of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.