Li Xiaoling, Xu Weiqing, Jia Huiying, Wang Xu, Zhao Bing, Li Bofu, Ozaki Yukihiro
Key Laboratory for Supermolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023, P. R. China.
Appl Spectrosc. 2004 Mar;58(3):287-91. doi: 10.1366/000370204322886627.
A self-assembled monolayer (SAM) film of 5,10,15,20-tetra-(para-chlorophenyl)-porphyrin terbium (or lutetium) hydroxy compound (TbOH/LuOH) fabricated on a silver substrate premodified with a SAM of 4-mercaptopyridine (PySH) was studied by ultraviolet-visible (UV-Vis) spectroscopy and surface-enhanced Raman scattering (SERS) spectroscopy. PySH can modify the substrate and deliver its pyridyl group pointing out from the silver surface. Thus, we can investigate the effects of the central metals of the metalloporphyrins in the formation of the composite films. For the TbOH-PySH composite film, a new absorption band arising from TbOH appears at 425 nm, and a band at 512 nm due to the PySH-modified silver substrate shifts to a longer wavelength (538 nm). The results suggest that TbOH is successfully assembled on the top of PySH-modified silver film and that there is an interaction between TbOH and PySH in the film. The frequency shifts and relative intensity changes of bands due to PySH in the SERS spectra imply the coordination of the pyridyl group on Tb in the SAM. As for the LuOH-PySH composite film, its SERS spectrum shows bands arising from both the LuOH and PySH moieties, indicating that LuOH is assembled on the PySH-modified silver film. Furthermore, a band at 1221 cm(-1) due to the in-plane C-H bending mode of PySH disappears, implying that the pyridyl moiety of PySH becomes more parallel to the silver surface upon the formation of the LuOH-PySH composite film. Additionally, an absorption band at 515 nm shifts to a longer wavelength (541 nm) and becomes broad upon the formation of the composite film, suggesting an interaction between LuOH and PySH in the film. By comparing the spectral changes between the two self-assembled composite films, we find that the central metal is crucial in the formation of the composite films. The structure and orientation of the composite films depend on the central metal of the metalloporphyrin compounds.
通过紫外可见（UV-Vis）光谱和表面增强拉曼散射（SERS）光谱，研究了在预先用4-巯基吡啶（PySH）自组装单层修饰的银基底上制备的5,10,15,20-四（对氯苯基）卟啉铽（或镥）羟基化合物（TbOH/LuOH）的自组装单层（SAM）膜。PySH可以修饰基底，并使其吡啶基团从银表面伸出。因此，我们可以研究金属卟啉的中心金属在复合膜形成过程中的作用。对于TbOH-PySH复合膜，TbOH产生的一个新吸收带出现在425nm处，由于PySH修饰的银基底产生的位于512nm处的吸收带移至更长波长（538nm）。结果表明，TbOH成功组装在PySH修饰的银膜顶部，且膜中TbOH与PySH之间存在相互作用。SERS光谱中由于PySH产生的谱带的频率位移和相对强度变化意味着SAM中吡啶基团与Tb之间的配位。对于LuOH-PySH复合膜，其SERS光谱显示出源于LuOH和PySH部分的谱带，表明LuOH组装在PySH修饰的银膜上。此外，由于PySH的面内C-H弯曲模式产生的位于1221cm(-1)处的谱带消失，这意味着在形成LuOH-PySH复合膜时，PySH的吡啶部分变得更平行于银表面。另外，在形成复合膜时，位于515nm处的吸收带移至更长波长（541nm）并变宽，表明膜中LuOH与PySH之间存在相互作用。通过比较两种自组装复合膜之间的光谱变化，我们发现中心金属在复合膜的形成中至关重要。复合膜的结构和取向取决于金属卟啉化合物的中心金属。
