Jiao Jieying, Anariba Franklin, Tiznado Hugo, Schmidt Izabela, Lindsey Jonathan S, Zaera Francisco, Bocian David F
Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
J Am Chem Soc. 2006 May 31;128(21):6965-74. doi: 10.1021/ja060906q.
A major challenge in molecular electronics and related fields entails the fabrication of elaborate molecular architectures on electroactive surfaces to yield hybrid molecular/semiconductor systems. A method has been developed for the stepwise synthesis of oligomers of porphyrins linked covalently via imide units. A triallyl-porphyrin bearing an amino group serves as the base unit on Si(100), and the alternating use of a dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) and a porphyrin-diamine for reaction enables the rapid and simple buildup of oligomers composed of 2-5 porphyrins. The properties of these porphyrin "multad" films on Si(100) were interrogated using a variety of techniques. The charge densities of the redox-active porphyrin oligomers were determined via electrochemical methods. The stepwise growth was evaluated in detail via Fourier transform infrared (FTIR) spectroscopy and by selected X-ray photoelectron spectroscopic (XPS) studies. The morphology was probed via AFM methods. Finally, the thickness was evaluated by using a combination of ellipsometry and AFM height profiling, accompanied by selected XPS studies. Collectively, these studies demonstrate that high charge density, ultrathin, multiporphyrin films of relatively well-controlled thickness can be grown in a stepwise fashion using the imide-forming reaction. The increased charge densities afforded by the porphyrin multads may prove important for the fabrication of molecular-based information-storage devices. This bottom-up process for construction of surface-tethered molecular architectures complements the top-down lithographic approach for construction of functional devices with nanoscale dimensions.
分子电子学及相关领域的一个主要挑战是在电活性表面制备精细的分子结构，以产生分子/半导体混合体系。已开发出一种方法，用于逐步合成通过酰亚胺单元共价连接的卟啉低聚物。带有氨基的三烯丙基卟啉用作Si(100)上的基础单元，通过交替使用二酐（3,3',4,4'-联苯四羧酸二酐）和卟啉二胺进行反应，能够快速简便地构建由2至5个卟啉组成的低聚物。使用多种技术对这些Si(100)上的卟啉“多联体”薄膜的性质进行了研究。通过电化学方法测定了氧化还原活性卟啉低聚物的电荷密度。通过傅里叶变换红外（FTIR）光谱和选定的X射线光电子能谱（XPS）研究详细评估了逐步生长过程。通过原子力显微镜（AFM）方法探测了形态。最后，结合椭偏仪和AFM高度轮廓分析，并辅以选定的XPS研究，评估了薄膜厚度。总体而言这些研究表明，利用形成酰亚胺的反应，可以逐步生长出具有相对可控厚度的高电荷密度、超薄多卟啉薄膜。卟啉多联体提供的电荷密度增加可能对基于分子的信息存储器件的制造具有重要意义这种构建表面连接分子结构的自下而上的过程补充了构建纳米级功能器件的自上而下的光刻方法。
