Wang Xintai, Alajmi Asma, Wei Zhangchenyu, Alzanbaqi Mohammed, Wei Naixu, Lambert Colin, Ismael Ali
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 China.
Physics Department, Lancaster University, Lancaster LA1 4YB, U.K.
ACS Appl Mater Interfaces. 2024 Dec 4;16(48):66290-66300. doi: 10.1021/acsami.4c15796. Epub 2024 Nov 19.
The inherent large HOMO-LUMO gap of alkyl thiol (CnS) self-assembled monolayers (SAMs) has limited their application in molecular electronics. This work demonstrates significant enhancement of mechano-electrical sensitivity in CnS SAMs by external compression, achieving a gauge factor (GF) of approximately 10 for C10S SAMs. This GF surpasses values reported for conjugated wires and DNA strands, highlighting the potential of CnS SAMs in mechanosensitive devices. Conductive atomic force microscopy (cAFM) investigations reveal a strong dependence of GF on the alkyl chain length in probe/CnS/Au junctions. This dependence arises from the combined influence of molecular tilting and probe penetration, facilitated by the low Young's modulus of alkyl chains. Theoretical simulations corroborate these findings, demonstrating a shift in the electrode Fermi level toward the molecular resonance region with increasing chain length and compression. Introducing a rigid graphene interlayer prevents probe penetration, resulting in a GF that is largely independent of the alkyl chain length. This highlights the critical role of probe penetration in maximizing mechano-electrical sensitivity. These findings pave the way for incorporating CnS SAMs into mechanosensitive and mechanocontrollable molecular electronic devices, including touch-sensitive electronic skin and advanced sensor technologies. This work demonstrates the potential of tailoring mechanical and electrical properties of SAMs through molecular engineering and interface modifications for optimized performance in specific applications.
烷基硫醇（CnS）自组装单分子层（SAMs）固有的较大的最高占据分子轨道（HOMO）-最低未占分子轨道（LUMO）能隙限制了它们在分子电子学中的应用。这项工作表明，通过外部压缩可显著提高CnS SAMs的机电灵敏度，对于C10S SAMs实现了约10的应变灵敏度因子（GF）。该GF超过了共轭线和DNA链报道的值，突出了CnS SAMs在机械敏感器件中的潜力。导电原子力显微镜（cAFM）研究揭示了GF对探针/CnS/金结中烷基链长度的强烈依赖性。这种依赖性源于分子倾斜和探针穿透的综合影响，烷基链的低杨氏模量促进了这种影响。理论模拟证实了这些发现，表明随着链长增加和压缩，电极费米能级向分子共振区域移动。引入刚性石墨烯中间层可防止探针穿透，导致GF在很大程度上与烷基链长度无关。这突出了探针穿透在最大化机电灵敏度方面的关键作用。这些发现为将CnS SAMs纳入机械敏感和机械可控分子电子器件铺平了道路，包括触敏电子皮肤和先进传感器技术。这项工作展示了通过分子工程和界面修饰来调整SAMs的机械和电学性质以在特定应用中实现优化性能的潜力。
