School of Engineering, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA.
ACS Nano. 2013 Jun 25;7(6):5621-7. doi: 10.1021/nn4020642. Epub 2013 May 28.
Solid-state nanopores can be fabricated in a variety of ways and form the basis for label-free sensing of single nanoparticles: as individual nanoparticles traverse the nanopore, they alter the ionic current across it in a characteristic way. Typically, nanopores are described by the diameter of their limiting aperture, and less attention has been paid to other, fabrication-dependent parameters. Here, we report a comprehensive analysis of the properties and sensing performance of three types of nanopore with identical 50 nm aperture, but fabricated using three different techniques: direct ion beam milling, ion beam sculpting, and electron beam sculpting. The nanopores differ substantially in physical shape and chemical composition as identified by ion-beam assisted cross-sectioning and energy dispersive X-ray spectroscopy. Concomitant differences in electrical sensing of single 30 nm beads, such as variations in blockade depth, duration, and electric field dependence, are observed and modeled using hydrodynamic simulations. The excellent agreement between experiment and physical modeling shows that the physical properties (shape) and not the chemical surface composition determine the sensing performance of a solid-state nanopore in the absence of deliberate surface modification. Consequently, nanoparticle sensing performance can be accurately predicted once the full three-dimensional structure of the nanopore is known.
固态纳米孔可以通过多种方式制造，并且是用于单颗粒无标记传感的基础：当单个纳米颗粒穿过纳米孔时，它们会以特征方式改变穿过纳米孔的离子电流。通常，纳米孔由其极限孔径的直径来描述，而对其他依赖于制造的参数关注较少。在这里，我们报告了三种具有相同 50nm 孔径的纳米孔的特性和传感性能的全面分析，但它们是使用三种不同的技术制造的：直接离子束铣削、离子束雕刻和电子束雕刻。通过离子束辅助截面分析和能量色散 X 射线光谱，可以确定纳米孔在物理形状和化学成分上有很大的差异。同时，对单个 30nm 珠粒的电传感也存在差异，例如阻断深度、持续时间和电场依赖性的变化，并用流体动力学模拟进行了观察和建模。实验和物理建模之间的极好一致性表明，在没有故意表面修饰的情况下，决定固态纳米孔传感性能的是物理特性（形状）而不是化学表面组成。因此，一旦知道纳米孔的完整三维结构，就可以准确地预测纳米颗粒的传感性能。
