Thermal Diffusivity of Film/Substrate Structures Characterized by Transient Thermal Grating Method

Transient thermal grating method is used to measure the thermal diffusivity of absorbing films deposited on transparent substrates. According to periodically modulated dielectric constant variations and thermoelastic deformations of the thin films caused by the transient thermal gratings, an improved optical diffraction theory is presented. In the experiment, the probing laser beam reflectively diffracted by the thermal grating is measured by a photomultiplier at different grating fringe spaces. The thermal diffusivity of the film can be evaluated by fitting the theoretical calculations of diffraction signals to the experimental measured data. The validity of the method is tested by measuring the thermal diffusivities of absorbing ZnO films deposited on glass substrates.     

不同亲水性探针分子在金电极上硫醇自组装跨膜动力学研究

采用扫描电化学显微镜测定了不同亲水性氧化还原电对在硫醇修饰的金电极表面上的异相电子转移速率常数. 分别选择铁氰化钾[K3Fe(CN)6]和N,N,N',N'-四甲基-1,4苯二胺(TMPD)作为氧化还原探针,根据得到的反馈曲线拟合出异相电子转移速率常数. 比较这些速率常数可以看出, 修饰层对疏水性的TMPD分子显示出更好的穿透性. 通过一个简单的模型可以解释TMPD的穿透过程, 在TMPD电子隧穿的前后存在着单层膜和水溶液间的快速平衡, 而隧穿作为决速步骤, 其表观速率常数也比K3Fe(CN)6的大. 通过计算得到TMPD的隧穿因子β为1.2/CH2.