Towards the design of effective multipodal contacts for use in the construction of Langmuir-Blodgett films and molecular junctions
Towards the design of effective multipodal contacts for use in the construction of Langmuir-Blodgett films and molecular junctions
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DOI：
10.1039/c9tc04710g
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发表时间：
2020-01-14
影响因子：
6.4
通讯作者：
Martin, Santiago
中科院分区：
文献类型：
--
作者：
Escorihuela, Enrique;Cea, Pilar;Martin, Santiago
作为优化分子电子元件电性能和稳定性的持续努力的一部分，通过多点连接（多极接触）将分子结合到电极表面的锚基团已经开始引起人们的注意。本文制备了一种低聚（芳烯）乙炔（OAE）衍生物，其在分子两端均具有“三脚”2,6-双（（甲基硫）甲基）吡啶锚定基团，并用于在空气-水界面形成有序的单层朗缪尔膜。这些薄膜被转移到固体载体上（表面转移压力为8 mN m(-1)），得到均匀、密集的单层Langmuir-Blodgett （LB）薄膜，有效地阻挡了金电极表面。通过x射线光电子能谱（XPS）和壳隔离纳米粒子增强拉曼光谱（SHINERS）测定，在表面支撑的LB膜内，分子取向与表面法线倾斜约30度，并通过“支撑”甲基硫醚基团和吡啶氮原子接触。通过“STM接触-接触”方法，由膜内单个分子接触形成的分子结，最可能的分子电导为4.4 x 10(-5)G(0)。该值与通过各种方法测定的1,4-双（吡啶-4-乙基）苯的单分子电导值(3.2-5.4 x 10（-5)G(0)）相当，表明支撑基团的加入不会干扰吡啶基接触基团的有利电特性。与这些电导数据一致的是，这种“支撑”的、与吡啶接触的OAE衍生物观察到一个过渡电压（V-trans = 0.48 V），表明金属电极费米能级和前沿分子轨道相对较好地对齐。
As part of on-going efforts to optimize the electrical performance and stability of molecular electronic components, anchor groups that bind molecules to electrode surfaces via multiple points of connection (multipodal contacts) have begun to attract attention. Here an oligo(arylene)ethynylene (OAE) derivative with 'tripodal' 2,6-bis((methylthio)methyl)pyridine anchoring groups at both molecular termini has been prepared and used to form well-ordered monolayer Langmuir films at the air-water interface. These films were transferred onto solid supports (surface pressure of transference 8 mN m(-1)) to give homogeneous, densely packed, monolayer Langmuir-Blodgett (LB) films, which efficiently block a gold electrode surface. Within the surface-supported LB film, the molecules are oriented with a tilt angle of approximately 30 degrees to the surface normal and contacted through both the 'buttressed' methylthioether groups and the pyridine nitrogen atom, as determined by X-ray photoelectron spectroscopy (XPS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Molecular junctions formed by contact of a single molecule within the film by the "STM touch-to-contact" method give a most probable molecular conductance of 4.4 x 10(-5)G(0). This value compares well with the single molecule conductance of 1,4-bis(pyridin-4-ylethynyl)benzene determined by a variety of methods (3.2-5.4 x 10(-5)G(0)), indicating that the addition of the buttressing groups does not perturb the favourable electrical characteristics of the pyridyl contacting group. Consistent with these conductance data, a transition voltage (V-trans = 0.48 V) was observed for this 'buttressed', pyridine-contacted OAE derivative, indicating relatively good alignment of the metal electrode Fermi level and the frontier molecular orbitals.