Chemical Sensors Based Upon Metal Nanowires and Nanogaps in Metal Nanowires Transduced Using Impedance

在化学系化学测量与成像（CMI）项目的支持下，加州大学欧文分校的Reginald Penner教授正在开发将金纳米线配置为化学传感器的新概念。在过去的25年里，纳米科学为构建小型和高灵敏度的化学传感器和生物传感器提供了新的构建模块——纳米材料。这种“纳米传感器”已被用于测量水溶液中的重金属，以及血液和尿液等体液中的代谢物。最重要的纳米材料是碳纳米管、半导体（如硅）纳米线和聚合物（如聚苯胺）纳米纤维。相比之下，金属纳米线在化学传感中的作用几乎没有被证明。唯一的例外是氢气传感，钯纳米线已经成功应用。金属纳米线作为传感器的适用性受到限制，因为这些结构的显著导电性几乎不受金属表面成分的影响。彭纳研究小组描述了将金纳米线配置为化学传感器的两个新概念。这两个概念的关键是应用交流电测量纳米线电阻，用于探测纳米线表面附近溶液的组成。该项目旨在重新定义金属纳米线作为金属离子（Fe3+）、蛋白质（如凝血酶结合蛋白）和ph等分析物传感器的功能。基于碳纳米管、半导体纳米线和金属氧化物纳米线的化学和生物传感器在数千种出版物中都有描述，但实际上没有类似的基于金属纳米线的传感器的应用报道。本项目将开发两种基于单金属纳米线的新型化学传感器。这两种类型是固体金属纳米线(1)和包含单个纳米间隙的金属纳米线(2)。金属纳米线中的纳米间隙，宽度为5 - 40纳米，将采用自动反馈控制的电迁移技术生产。基于金属纳米线的传感概念是通过一种新的模式来实现的，这种模式可以对在这些金属纳米线表面捕获的分析物产生的信号进行转导，涉及使用导线电阻抗谱（EIS）。当分析物存在于金属纳米线表面时，EIS测量这些金属纳米线结构的电容扰动。一个单一的“通用”等效电路描述了所研究的两种纳米线传感器的EIS响应。该项目旨在阐明这两种金属纳米线结构的基本能力，同时也为金属离子（Fe3+）、蛋白质（如凝血酶结合蛋白）和ph等分析物开发实用的基于纳米线的传感器。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) program in the Division of Chemistry, Professor Reginald Penner at the University of California, Irvine is developing new concepts for configuring gold nanowires as chemical sensors. Over the last twenty five years, nanoscience has provided new building blocks - nanomaterials - for constructing small and highly sensitive chemical sensors and biosensors. Such “nano-enabled” sensors have been used for the measurement of heavy metals in aqueous solutions, and metabolites in bodily fluids like blood and urine. The most important nanomaterials have been carbon nanotubes, semiconductor (e.g., silicon) nanowires, and polymer (e.g., polyaniline) nanofibers. In contrast, almost no role for metal nanowires in chemical sensing has been demonstrated. The only exception is for hydrogen gas sensing, where palladium nanowires have been successfully applied. The applicability of metal nanowires as sensors is limited because the significant electrical conductivity of these structures is hardly affected by the composition of the metal surface. The Penner research group has described two new concepts for configuring gold nanowires as chemical sensors. The key for both concepts is the application of an alternating current measurement of the nanowire resistance that is designed to probe the composition of a solution in close proximity to the nanowire surface. This project seeks to redefine the capabilities of metal nanowires for functioning as sensors for analytes such as metal ions (Fe3+), proteins (e.g., thrombin binding protein), and pH.Chemical and bio-sensors based upon carbon nanotubes, semiconductor nanowires, and metal oxide nanowires have each been described in thousands of publications, but virtually no applications of analogous metal nanowire-based sensors have been reported. In this project, two new types of chemical sensors based upon single metal nanowires will be developed. The two types are solid metal nanowires (1), and metal nanowires containing a single nanogap (2). Nanogaps in metal nanowire, with widths of 5 – 40 nm, will be produced using automated, feedback-controlled, electromigration. The concept of metal nanowire-based sensing is made possible by a new modality for transducing the signal produced by analyte species captured at the surfaces of these metal nanowires, involving the use of through-wire electrical impedance spectroscopy (EIS). EIS measures the perturbation of the capacitance of these metal nanowire structures when analyte species are present at wire surfaces. A single “universal” equivalent circuit describes the EIS response of both types of nanowire sensors under investigation. This project is designed to elucidate the fundamental capabilities of these two metal nanowire architectures, but also to develop practical nanowire-based sensors for analytes such as metal ions (Fe3+), proteins (e.g., thrombin binding protein), and pH.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.