The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
ACS Appl Mater Interfaces. 2013 Mar;5(6):2289-99. doi: 10.1021/am4004649. Epub 2013 Mar 15.
Molecular layers attached to a silicon nanowire field effect transistor (SiNW FET) can serve as antennas for signal transduction of volatile organic compounds (VOCs). Nevertheless, the mutual relationship between the molecular layers and VOCs is still a puzzle. In the present paper, we explore the effect of the molecular layer's end (functional) groups on the sensing properties of VOCs. Toward this end, SiNW FETs were modified with tailor-made molecular layers that have the same backbone but differ in their end groups. Changes in the threshold voltage (ΔVth) and changes in the mobility (Δμh) were then recorded upon exposure to various VOCs. Model-based analysis indicates that the interaction between molecular layers and VOCs can be classified to three main scenarios: (a) dipole-dipole interaction between the molecular layer and the polar VOCs; (b) induced dipole-dipole interaction between the molecular layers and the nonpolar VOCs; and (c) molecular layer tilt as a result of VOCs diffusion. Based on these scenarios, it is likely that the electron-donating/withdrawing properties of the functional groups control the dipole moment orientation of the adsorbed VOCs and, as a result, determine the direction (or sign) of the ΔVth. Additionally, it is likely the diffusion of VOCs into the molecular layer, determined by the type of functional groups, is the main reason for the Δμh responses. The reported findings are expected to provide an efficient way to design chemical sensors that are based on SiNW FETs to nonpolar VOCs, which do not exchange carriers with the molecular layers.
附着在硅纳米线场效应晶体管（SiNW FET）上的分子层可以作为挥发性有机化合物（VOCs）信号转导的天线。然而，分子层与 VOCs 之间的相互关系仍然是一个谜。在本文中，我们探讨了分子层末端（功能）基团对 VOCs 传感性能的影响。为此，我们使用具有相同骨架但末端基团不同的定制分子层对 SiNW FET 进行了修饰。然后记录暴露于各种 VOCs 时阈值电压（ΔVth）的变化和迁移率（Δμh）的变化。基于模型的分析表明，分子层与 VOCs 之间的相互作用可以分为三种主要情况：（a）分子层与极性 VOCs 之间的偶极-偶极相互作用；（b）分子层与非极性 VOCs 之间的诱导偶极-偶极相互作用；（c）VOCs 扩散导致分子层倾斜。基于这些情况，很可能是功能基团的供电子/吸电子性质控制了吸附 VOCs 的偶极矩方向，从而决定了 ΔVth 的方向（或符号）。此外，很可能是 VOCs 扩散到分子层中，由功能基团的类型决定，是 Δμh 响应的主要原因。预计这些发现将为设计基于 SiNW FET 的化学传感器提供一种有效方法，以检测不与分子层交换载流子的非极性 VOCs。
