Voltammetric peak broadening for cytochrome c/alkanethiolate monolayer structures: Dispersion of formal potentials
Voltammetric peak broadening for cytochrome c/alkanethiolate monolayer structures: Dispersion of formal potentials
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DOI：
10.1021/la960650
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发表时间：
1997-02-05
期刊：
影响因子：
3.9
通讯作者：
Bowden, EF
中科院分区：
文献类型：
--
作者：
Clark, RA;Bowden, EF
细胞色素c（cyt c）吸附在COOH-烷基硫醇盐/Au自组装单分子膜电极上的循环伏安曲线中，出现了异常峰展宽现象。这种加宽的起源已通过电活性细胞色素c表面浓度（伽马）的变化进行了探索。使用两种不同的方法制备细胞色素亚单层。在第一种方法中，通过暴露于更高离子强度的缓冲液，通过电活性细胞色素C单层的部分解吸来产生亚单层。这些亚单分子膜的表观伏安特性依赖于γ，表现出降低的形式电位，增加电子转移速率，并降低峰宽γ-> 0。另一方面，根据第二种方法制备的亚单层，其中电惰性卟啉cyt c的预吸附封闭单层的部分解吸之后是活性cyt c吸附到未封闭位点，表现出相反的趋势，即，增加正式的潜力和。随着γ-> 1，电子转移速率降低。这些结果表明，由于分布的界面环境和吸附能的SAM/Au表面上的细胞色素C吸附物的异质性人口。在可逆电化学条件下的峰加宽特别归因于CytC微分吸附能的热力学分布（即，铁-相对于铁-细胞C）。基于形式电位的高斯分布的拟合导致对于cyt c/HOOC（CH 2）（11）S/Au系统的40 mV的标准偏差sigma（E（ω））。物理模型的基础上固有的表面不均匀性和吸附引起的空间排斥所产生的不均匀性，提出了解释的形式电位的分散。
Anomalous peak broadening is a persistent feature observed in the cyclic voltammetry of cytochrome c (cyt c) adsorbed on COOH-alkylthiolate/Au self-assembled monolayer electrodes. The origins of this broadening have been explored through variation of the electroactive cytochrome c surface concentration (Gamma). Cytochrome submonolayers were prepared using two different methods. In the first method, submonolayers were created by partial desorption of an electroactive cyt c monolayer by exposure to higher ionic strength buffers. The apparent voltammetric properties of these submonolayers were dependent on Gamma, exhibiting decreasing formal potentials, increasing electron-transfer rates, and decreasing peak widths as Gamma --> 0. On the other hand, submonolayers prepared according to the second method, in which partial desorption of a preadsorbed blocking monolayer of electroinactive porphyrin cyt c was followed by adsorption of active cyt c to the unblocked sites, exhibited opposite trends, i.e., increasing formal potentials and. decreasing electron-transfer rate as Gamma --> 1. These results are indicative of a heterogeneous population of cyt c adsorbates on the SAM/Au surface due to a distribution of interfacial environments and adsorption energies. Peak broadening under reversible electrochemical conditions has been specifically attributed to a thermodynamic distribution of cyt c differential adsorption energies (i.e., ferri- vs ferro-cyt c). Fitting based on a Gaussian distribution of formal potentials resulted in a standard deviation, sigma(E(o)'), of 40 mV for the cyt c/HOOC(CH2)(11)S/Au system. Physical models based on intrinsic surface heterogeneity and adsorption-induced heterogeneity arising from steric exclusion are proposed to explain the dispersion of formal potentials.