Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Lab Chip. 2017 Dec 19;18(1):139-152. doi: 10.1039/c7lc01047h.
The vertical dimensions of complex nanostructures determine the functions of diverse nanotechnologies. In this paper, we investigate the unknown limits of such structure-function relationships at subnanometer scales. We begin with a quantitative evaluation of measurement uncertainty from atomic force microscopy, which propagates through our investigation from ion beam fabrication to fluorescent particle characterization. We use a focused beam of gallium ions to subtractively pattern silicon surfaces, and silicon nitride and silicon dioxide films. Our study of material responses quantifies the atomic limits of forming complex topographies with subnanometer resolution of vertical features over a wide range of vertical and lateral dimensions. Our results demonstrate the underutilized capability of this standard system for rapid prototyping of subnanometer structures in hard materials. We directly apply this unprecedented dimensional control to fabricate nanofluidic devices for the analytical separation of colloidal nanoparticles by size exclusion. Optical microscopy of single nanoparticles within such reference materials establishes a subnanometer limit of the fluidic manipulation of particulate matter and enables critical-dimension particle tracking with subnanometer accuracy. After calibrating for optical interference within our multifunctional devices, which also enables device metrology and integrated spectroscopy, we reveal an unexpected relationship between nanoparticle size and emission intensity for common fluorescent probes. Emission intensity increases supervolumetrically with nanoparticle diameter and then decreases as nanoparticles with different diameters photobleach to similar values of terminal intensity. We propose a simple model to empirically interpret these surprising results. Our investigation enables new control and study of structure-function relationships at subnanometer scales.
复杂纳米结构的垂直尺寸决定了各种纳米技术的功能。在本文中，我们研究了亚纳米尺度下这种结构-功能关系的未知极限。我们从原子力显微镜的测量不确定度定量评估开始，该评估贯穿于我们从离子束制造到荧光粒子特性的研究。我们使用聚焦的镓离子束对硅表面、氮化硅和二氧化硅薄膜进行选择性图案化。我们对材料响应的研究量化了以亚纳米分辨率垂直特征在广泛的垂直和横向尺寸范围内形成复杂形貌的原子极限。我们的结果表明，这种标准系统在硬材料中亚纳米结构的快速原型制作方面的能力未得到充分利用。我们直接将这种前所未有的尺寸控制应用于制造用于通过尺寸排阻分析分离胶体纳米粒子的纳米流控装置。在这些参考材料中，单个纳米粒子的光学显微镜为颗粒物质的亚纳米级流体操纵建立了一个极限，并能够以亚纳米级的精度进行关键尺寸的颗粒跟踪。在对我们多功能设备中的光学干扰进行校准后，该设备还能够进行设备计量学和集成光谱学，我们揭示了常见荧光探针的纳米粒子尺寸和发射强度之间的意外关系。发射强度随纳米粒子直径超体积增加，然后当不同直径的纳米粒子光漂白到相似的终强度值时，发射强度减小。我们提出了一个简单的模型来经验性地解释这些令人惊讶的结果。我们的研究使我们能够在亚纳米尺度上对结构-功能关系进行新的控制和研究。
