Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060-0212, United States.
J Colloid Interface Sci. 2010 Feb 15;342(2):499-504. doi: 10.1016/j.jcis.2009.10.033. Epub 2009 Oct 21.
Electrochemical impedance spectroscopy and the quartz crystal microbalance measurements are used to examine the ability of potential applied to a substrate to create, in situ, conditions favorable for the electrostatic deposition of polyelectrolytes onto a gold substrate modified by the self-assembly of cysteine. Cysteine is a zwitterionic compound that, when confined to a substrate, has the ability to establish either a net positive or a net negative interfacial charge, depending on the conditions. As such, cysteine modified interfaces could possibly be used as a versatile substrate for deposition of either cationic or anionic polyelectrolytes. The potential of zero charge of a gold electrode modified by self-assembly with cysteine in the presence of 0.10molL(-1) KCl and buffered at pH 5 is found by differential capacitance measurement to be -0.12(+/-0.02)V vs. Ag/AgCl. When -0.05V vs. Ag/AgCl is applied to the substrate (a potential positive of the PZC) in the presence of different polyelectrolytes, both impedance spectroscopy and quartz crystal microbalance data suggest the accumulation of anionic poly(sodium styrenesulfonate) along the cysteine modified interface. Conversely, when -0.40V vs. Ag/AgCl is applied to the substrate (a potential negative of the PZC), experimental results suggest the accumulation of cationic poly(diallydimethylammonium chloride).
电化学阻抗谱和石英晶体微天平测量用于研究施加于基底的电势在金基底上原位创造有利于聚电解质静电沉积的条件的能力，该金基底由半胱氨酸的自组装修饰。半胱氨酸是一种两性离子化合物，当局限于基底时，根据条件可以建立净正或净负界面电荷。因此，半胱氨酸修饰的界面可能可用作沉积阳离子或阴离子聚电解质的通用基底。在存在 0.10mol/L KCl 和 pH5 缓冲液的情况下，通过差分电容测量发现金电极经半胱氨酸自组装修饰后的零电荷电位为-0.12(+/-0.02)V vs. Ag/AgCl。当在存在不同聚电解质的情况下将-0.05V vs. Ag/AgCl 施加于基底（相对于 PZC 为正电势）时，阻抗谱和石英晶体微天平数据均表明阴离子聚（苯乙烯磺酸钠）沿半胱氨酸修饰界面积累。相反，当将-0.40V vs. Ag/AgCl 施加于基底（相对于 PZC 为负电势）时，实验结果表明阳离子聚（二烯丙基二甲基氯化铵）的积累。
