Department of Chemistry, Beijing Normal University, Beijing 100875, People's Republic of China.
J Phys Chem B. 2010 Mar 18;114(10):3648-54. doi: 10.1021/jp910048e.
Weak polybase branched poly(ethyleneimine) (BPEI) and strong polyacid poly(styrenesulfonate) (PSS) were assembled into BPEI/{PSS/BPEI}(n) layer-by-layer (LBL) films on electrodes by electrostatic interaction between them with spin-coating approach. The cyclic voltammetric (CV) response of ferrocenedicarboxylic acid (Fc(COOH)(2)) at BPEI/{PSS/BPEI}(n) film electrodes was very sensitive to the pH of the testing solutions. At pH 4.0, the probe showed a well-defined CV peak pair with relatively large peak currents for the films, while, at pH 7.0, the CV response was significantly depressed. By switching the film electrodes in buffers between pH 4.0 and 7.0, the CV peak currents changed periodically between a relatively high value at the "on" state and a very low value at the "off" state, indicating that the pH-sensitive "on-off" switching function of the films toward the probe is reversible. A series of comparative experiments indicates that the electrostatic interaction between the films and the probe plays a predominant role in deciding the pH-sensitive behavior of the films. This pH-dependent property of the films could be used to control or modulate the bioelectrocatalysis of glucose by glucose oxidase (GOD) with Fc(COOH)(2) as the mediator by changing the surrounding pH. This "smart" bioelectrocatalytic film system may establish a foundation for fabricating novel pH-controllable electrochemical biosensors.
弱聚电解质支化聚（亚乙基亚胺）（BPEI）和强聚电解质聚（苯乙烯磺酸盐）（PSS）通过它们之间的静电相互作用被组装到电极上的 BPEI/{PSS/BPEI}(n)层层（LBL）薄膜中，采用旋涂方法。二茂铁二羧酸（Fc（COOH）（2））在 BPEI/{PSS/BPEI}(n)薄膜电极上的循环伏安（CV）响应对测试溶液的 pH 值非常敏感。在 pH 4.0 时，探针显示出具有相对较大峰电流的定义良好的 CV 峰对，而在 pH 7.0 时，CV 响应明显受到抑制。通过在 pH 4.0 和 7.0 之间在缓冲液中切换薄膜电极，CV 峰电流在“开”状态下的相对高值和“关”状态下的非常低值之间周期性变化，表明薄膜对探针的 pH 敏感“开-关”切换功能是可逆的。一系列对比实验表明，薄膜与探针之间的静电相互作用在决定薄膜的 pH 敏感行为方面起着主导作用。该薄膜的这种 pH 依赖性可以通过改变周围 pH 值来控制或调节葡萄糖氧化酶（GOD）与 Fc（COOH）（2）作为介体的葡萄糖的生物电催化作用。这种“智能”生物电催化膜系统可能为制造新型 pH 可控电化学生物传感器奠定基础。
