ARC Centre of Excellence for Electromaterials Science and Intelligent Polymer Research Institute, University of Wollongong, Innovation Campus, Squires Way, North Wollongong, NSW 2500, Australia.
Langmuir. 2011 Nov 1;27(21):12944-50. doi: 10.1021/la202598c. Epub 2011 Sep 29.
The determination of the orientation and molecular density for several porphyrin dyes adsorbed on planar TiO(2) surfaces using X-ray reflectometry (XRR) is reported. Adsorption of nanoscale water layers occurred rapidly upon exposure of freshly prepared TiO(2) surfaces to ambient conditions; however, this was successfully eliminated, resulting in clearly discernible adsorbed dye layers for sensitized surfaces. Adsorbed dye orientations, determined from computations constrained by the measured dye layer thickness, were calculated to have a binding tilt angle of 35°-40°. Combining the XXR data with the orientation models indicates that the porphyrins form densely packed surfaces with an intermolecular spacing of 3-4 Å, consistent with π-π stacking interactions. Changes in the molecular size of probe dyes were reflected in corresponding changes in the measured dye layer thickness, confirming the ability of this technique to resolve small variations in dye layer thickness and consequently adsorption orientation. Application of these results to understanding the behavior of dye-sensitized devices is discussed.
本文报道了使用 X 射线反射法（XRR）测定吸附在平面 TiO(2)表面上的几种卟啉染料的取向和分子密度。新制备的 TiO(2)表面暴露于环境条件下时，纳米级水层会迅速吸附；然而，通过成功地消除了这一现象，使得敏化表面上的吸附染料层清晰可见。通过受测量的染料层厚度约束的计算，确定了吸附染料的取向，其结合倾斜角为 35°-40°。将 XRR 数据与取向模型相结合表明，卟啉形成了具有 3-4 Å 分子间间距的密集堆积表面，这与π-π堆积相互作用一致。探针染料分子尺寸的变化反映在测量的染料层厚度的相应变化中，证实了该技术能够分辨染料层厚度和吸附取向的微小变化。讨论了将这些结果应用于理解染料敏化器件行为的情况。
