Division of Molecular Physics, Department of Physics, Chemistry, and Biology, Linkoping University, SE-581 83 Linkoping, Sweden.
Biointerphases. 2006 Mar;1(1):22. doi: 10.1116/1.2188521.
The formation of highly ordered self-assembled monolayers (SAMs) on gold from an unusually long and linear compound HS(CH(2))(15)CONH(CH(2)CH(2)O)(6)CH(2)CONH(CH(2))(15)CH(3) is investigated by contact angle goniometry, ex situ null ellipsometry, cyclic voltammetry and infrared reflection-absorption spectroscopy. The molecules are found to assemble in an upright position as a complete monolayer within 60 min. The overall structure of the SAM reaches equilibrium within 24 h as evidenced by infrared spectroscopy, although a slight improvement in water contact angles is observed over a period of a few weeks. The resulting SAM is 60 A thick and it displays an advancing water contact angle of 112 degrees and excellent electrochemical blocking characteristics with typical current densities about 20 times lower as compared to those observed for HS(CH(2))(15)CH(3) SAMs. The dominating crystalline phases of the supporting HS(CH(2))(15) and terminal (CH(2))(15)CH(3) alkyl portions, as well as the sealed oligo(ethylene glycol) (OEG) "core," appear as unusually sharp features in the infrared spectra at room temperature. For example, the splitting seen for the CH(3) stretching and CH(2) scissoring peaks is normally only observed for conformationally trapped alkylthiolate SAMs at low temperatures and for highly crystalline polymethylenes. Temperature-programmed infrared spectroscopy in ultrahigh vacuum reveals a significantly improved thermal stability of the SAM under investigation, as compared to two analogous OEG derivatives without the extended alkyl chain. Our study points out the advantages of adopting a "modular approach" in designing novel SAM-forming compounds with precisely positioned in plane stabilizing groups. We demonstrate also the potential of using the above set of compounds in the fabrication of "hydrogel-like" arrays with controlled wetting properties for application in the ever-growing fields of protein and cell analysis, as well as for bioanalytical applications.
从一个非常长且线性的化合物 HS(CH(2))(15)CONH(CH(2)CH(2)O)(6)CH(2)CONH(CH(2))(15)CH(3) 在金上形成高度有序的自组装单层 (SAM) 通过接触角测量法、外差椭圆测量法、循环伏安法和红外反射吸收光谱法进行研究。研究发现，这些分子在 60 分钟内以直立的方式组装成完整的单层。红外光谱表明，SAM 的整体结构在 24 小时内达到平衡，尽管在几周的时间内水接触角略有提高。得到的 SAM 厚 60Å，其前进水接触角为 112 度，并且具有出色的电化学阻断特性，与 HS(CH(2))(15)CH(3)SAMs 相比，典型电流密度低约 20 倍。支撑 HS(CH(2))(15)和末端 (CH(2))(15)CH(3)烷基部分以及封闭的低聚(乙二醇) (OEG)“核心”的主要结晶相在室温下的红外光谱中呈现出异常尖锐的特征。例如，CH(3)伸缩和 CH(2)剪断峰的分裂通常仅在低温下观察到构象捕获的烷基硫醇 SAMs 中以及高度结晶的聚甲基中观察到。在超高真空中的程序升温红外光谱表明，与没有扩展烷基链的两个类似的 OEG 衍生物相比，所研究的 SAM 具有显著提高的热稳定性。我们的研究表明，在设计具有精确平面稳定基团的新型 SAM 形成化合物时，采用“模块化方法”的优势。我们还展示了使用上述化合物在制造具有受控润湿性的“水凝胶样”阵列中的潜力，该阵列可应用于蛋白质和细胞分析以及生物分析应用等领域的不断发展。
