Instituto de Física, Universidade de São Paulo, P.O. Box 66318, São Paulo, 05314-970, SP, Brazil.
J Phys Chem B. 2010 Mar 18;114(10):3467-71. doi: 10.1021/jp910114y.
We investigate the dielectric dispersion of water, specially in the low-frequency range, by using the impedance spectroscopy technique. The frequency dependencies of the real R and imaginary chi parts of the impedance could not be explained by means of the usual description of the dielectric properties of the water as an insulating liquid containing ions. This is due to the incomplete knowledge of the parameters entering in the fundamental equations describing the evolution of the system, and on the mechanisms regulating the exchange of charge of the cell with the external circuit. We propose a simple description of our experimental data based on the model of Debye, by invoking a dc conductivity of the cell, related to the nonblocking character of the electrodes. A discussion on the electric circuits able to simulate the cell under investigation, based on bulk and surface elements, is also reported. We find that the simple circuit formed by a series of two parallels of resistance and capacitance is able to reproduce the experimental data concerning the real and imaginary part of the electrical impedance of the cell for frequency larger than 1 Hz. According to this description, one of the parallels takes into account the electrical properties of interface between the electrode and water, and the other of the bulk. For frequency lower than 1 Hz, a good agreement with the experimental data is obtained by simulating the electrical properties of the interface by means of the constant phase element.
我们通过阻抗谱技术研究了水的介电色散，特别是在低频范围内。阻抗的实部 R 和虚部 χ 的频率依赖性不能用通常描述水的介电特性的方法来解释，因为这是一种含有离子的绝缘液体。这是由于描述系统演化的基本方程中参数的不完全了解，以及调节细胞与外部电路电荷交换的机制。我们提出了一种基于德拜模型的简单描述，通过引入与电极非阻塞特性相关的细胞直流电导率。还报告了基于体相和表面元素的能够模拟研究中细胞的电路的讨论。我们发现，由两个电阻和电容并联组成的简单电路能够重现大于 1 Hz 时细胞的电阻抗实部和虚部的实验数据。根据这种描述，其中一个并联考虑了电极和水之间界面的电特性，另一个则考虑了体相的电特性。对于低于 1 Hz 的频率，通过使用恒相位元件模拟界面的电特性，可以很好地与实验数据相吻合。
