Spori Doris M, Venkataraman Nagaiyanallur V, Tosatti Samuele G P, Durmaz Firat, Spencer Nicholas D, Zürcher Stefan
Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
Langmuir. 2007 Jul 17;23(15):8053-60. doi: 10.1021/la700474v. Epub 2007 Jun 15.
A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length.
已经合成了一系列烷基链长度从C10到C18的烷基磷酸酯。通过将基底浸入正庚烷/异丙醇中浓度为0.5 mM的烷基磷酸酯溶液中，在氧化钛表面制备了这些分子的自组装单分子层（SAMs）。通过动态水接触角（dCA）测量、可变角度光谱椭偏仪（VASE）、X射线光电子能谱（XPS）和偏振调制红外反射吸收光谱（PM-IRRAS）对SAMs进行了表征。发现烷基链长度超过15个碳原子的烷基磷酸酯在单分子层内具有更高的有序度和堆积密度。这反映在较低的dCA滞后现象以及VASE和XPS测量的膜厚度接近平均烷基链相对于表面法线倾斜角度为30度的SAMs的预期值。此外，在PM-IRRAS光谱中观察到对称和反对称C-H伸缩模式向更低波数的移动。这些发现意味着由具有更长烷基链长度的烷基磷酸酯衍生的薄膜具有更高的二维结晶度。
