Ultra-sharp and surfactant-free silver nanowire for scanning tunneling microscopy and tip-enhanced Raman spectroscopy
Ultra-sharp and surfactant-free silver nanowire for scanning tunneling microscopy and tip-enhanced Raman spectroscopy
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DOI：
10.1039/c8nr08983c
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发表时间：
2019-04-28
期刊：
影响因子：
6.7
通讯作者：
Liu, Ming
中科院分区：
文献类型：
--
作者：
Liu, Qiushi;Kim, Sanggon;Liu, Ming
化学合成的单晶银纳米线 (AgNW) 探针可以将扫描隧道显微镜 (STM) 技术与尖端增强拉曼散射光谱 (TERS) 相结合，以纳米级空间分辨率提供互补的形态和化学信息。然而，其性能受到钝纳米线尖端几何形状、AgNW 表面涂覆的绝缘表面活性剂层以及热引起的机械振动的限制。在这里，我们报告了一种可重复的制造方法，用于制备基于 AgNW 的尖头 TERS 探针。通过从 AgNW 表面去除聚乙烯吡咯烷酮 (PVP) 表面活性剂分子以获得稳定的电导率，并以 m 级精度控制突出长度以提高机械稳定性，我们展示了使用尖头 AgNW 探针的原子分辨率 STM 成像。此外，尖头AgNW具有出色的TER增强效果（约1.1 x 10(6)），约为常规AgNW的66倍。我们的实验表明，具有干净界面和适当尖端几何形状的 AgNW 可以提供可靠且可重复的 STM 和 TER 表征，从而消除了在基于 STM 的近场光学应用中为广大社区实施 AgNW 的障碍。
Chemically-synthesized single-crystalline silver nanowire (AgNW) probes can combine the scanning tunneling microscopy (STM) technique with tip-enhanced Raman scattering spectroscopy (TERS) for complementary morphological and chemical information with nanoscale spatial resolution. However, its performance has been limited by the blunt nanowire tip geometry, the insulating surfactant layer coating AgNW surfaces, and the thermal-induced mechanical vibrations. Here, we report a reproducible fabrication method for the preparation of sharp-tip AgNW-based TERS probes. By removing the polyvinylpyrrolidone (PVP) surfactant molecules from the AgNW surfaces for stable electrical conductivity and controlling the protruding length with m-level accuracy for improved mechanical stability, we demonstrate atomic-resolution STM imaging with the sharp-tip AgNW probe. Furthermore, the sharp-tip AgNW has an excellent TER enhancement (approximate to 1.1 x 10(6)), which is about 66 folds of that achieved by regular AgNWs. Our experiments demonstrate that AgNWs with clean interfaces and the proper tip geometry can provide reliable and reproducible STM and TER characterizations, which remove the hurdles preventing the implementation of AgNW in STM-based near-field optical applications for a broad community.