Effects of Electrolyte and pH on the Behavior of Cross-Linked Films of Ferrocene-Modified Poly(ethylenimine)

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• 作者：Stephen A. Merchant ; Daniel T. Glatzhofer ; David W. Schmidtke
• 刊名：Langmuir
• 出版年：2007
• 出版时间：October 23, 2007
• 年：2007
• 卷：23
• 期：22
• 页码：11295 - 11302
• 全文大小：178K
• 年卷期：v.23,no.22(October 23, 2007)
• ISSN：1520-5827

文摘

Ferrocene redox polymers based on the coupling of ferrocenecarboxaldehyde to both linear and branched poly(ethylenimine) (PEI) have been prepared to investigate the effects of pH, electrolyte, and cross-linking on electroncharge transport and film swelling. The redox behavior of both ferrocene-modified linear PEI and ferrocene-modifiedbranched PEI was investigated by cyclic voltammetry, while electron diffusion coefficients reported for PEI-basedredox polymers were determined by electrochemical impedance spectroscopy. In phosphate solutions at pH > 7,cross-linked films of both redox polymers exhibited multiple redox wave behavior and were unstable. In contrast,in non-phosphate solutions, cross-linked films exhibited stable electrochemical behavior and fast electron transfer insolutions with pH < 11. Gel swelling experiments suggested that the multiple wave behavior and instability exhibitedin either phosphate solutions or at high pH in non-phosphate solutions were related to a combination of film collapseand electrolyte binding within the hydrogel. The electron diffusion coefficients for these polymers are on the orderof 10^-8 (mol cm^-2 s^-1/2), which are approximately 40 times greater than other ferrocene-modified polymers. Incorporationof the enzyme, glucose oxidase, into these films demonstrated that these redox polymers were able to electricallycommunicate with the enzyme's flavin adenine dinucleotide (FAD) redox centers. Glucose sensors based on thesefilms exhibited enzyme saturation current densities that ranged from 240 to 480 A/cm² in response to glucose, whichwere dependent upon the supporting electrolyte and pH. The sensitivity of these sensors at 5 mM glucose ranged from10 to 48 A·cm^-2·mM^-1.