Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, PA 19122 (USA).
Angew Chem Int Ed Engl. 2014 Jan 20;53(4):1098-102. doi: 10.1002/anie.201308398. Epub 2013 Dec 11.
Sensors play a significant role in the detection of toxic species and explosives, and in the remote control of chemical processes. In this work, we report a single-molecule-based pH switch/sensor that exploits the sensitivity of dye molecules to environmental pH to build metal-molecule-metal (m-M-m) devices using the scanning tunneling microscopy (STM) break junction technique. Dyes undergo pH-induced electronic modulation due to reversible structural transformation between a conjugated and a nonconjugated form, resulting in a change in the HOMO-LUMO gap. The dye-mediated m-M-m devices react to environmental pH with a high on/off ratio (≈100:1) of device conductivity. Density functional theory (DFT) calculations, carried out under the non-equilibrium Green's function (NEGF) framework, model charge transport through these molecules in the two possible forms and confirm that the HOMO-LUMO gap of dyes is nearly twice as large in the nonconjugated form as in the conjugated form.
传感器在检测有毒物种和爆炸物以及远程控制化学过程方面发挥着重要作用。在这项工作中，我们报告了一种基于单分子的 pH 开关/传感器，该传感器利用染料分子对环境 pH 的敏感性，使用扫描隧道显微镜 (STM) 断键技术构建金属-分子-金属 (m-M-m) 器件。由于在共轭和非共轭形式之间发生可逆的结构转变，染料经历 pH 诱导的电子调制，导致 HOMO-LUMO 能隙发生变化。受染料介导的 m-M-m 器件对环境 pH 的反应具有高开关比（≈100:1）的器件电导率。在非平衡格林函数 (NEGF) 框架下进行的密度泛函理论 (DFT) 计算模拟了这两种可能形式下通过这些分子的电荷输运，并证实染料的 HOMO-LUMO 能隙在非共轭形式下几乎是共轭形式下的两倍。
