Chemical Sensors Based on Electrodeposited Metal Nanowires: Three New Mechanisms for Sensing

大分子、超分子和纳米化学以及化学测量和成像计划共同支持加州大学欧文分校化学系的Reginald M.Penner教授研究基于金属纳米线的化学传感器。本项目开发了三种利用金属纳米线检测分子的新模式，这三种模式符合三个目标：1)利用贵金属纳米线的表面电子散射来检测气相分子。一个具体的例子是一根金纳米线，它能够在高温下快速检测空气中1ppm的NO2和NO。2)利用分子化学吸附的热作为利用悬浮金属纳米线阵列检测气相中的吸附物的手段。这些研究主要集中在铂上的乙烯和钯上的乙醇。3)创建基于金属纳米线中的纳米盖子的纳米化学传感器家族，所述金属纳米线通过插入亲和介质进行修饰，所述亲和介质例如为目标分析物分子印迹的导电有机聚合物，以及在从溶液聚合期间掺入抗体的导电聚合物。这项研究活动的一个更广泛的影响是一个涉及加州圣安娜学区经济困难高中生的外展项目。每年，圣安娜高中的一名学生都会在彭纳教授的实验室里进行为期十周的全日制有偿暑期研究。随着化学传感器变得越来越小，它对被测分子浓度变化的反应也更快。在这个项目中，使用金属纳米线制造了一系列高度小型化的化学传感器。这些纳米线是使用与半导体工业中用于制备集成电路的工艺密切相关的工艺制备的。由此产生的纳米线由金、钯或铂组成，直径约为人类头发的1/100，但长度相似，约为毫米或厘米。当分子附着在导线表面时，这些微小导线的电阻会增加，这个过程提供了一种在几秒钟内非常快速地检测这些分子的方法。在这些研究中检测到的分子是二氧化氮、二氧化硫、一氧化碳，以及甲烷和乙烷等碳氢化合物。除了快速响应外，这些基于纳米线的化学传感器的第二个优势是它们的简单性：化学传感器由一根金属纳米线、与该纳米线的两个电接触以及用于测量其电阻的仪器组成。因此，这些传感器可能非常便宜。

The Macromolecular, Supramolecular, and Nanochemistry and Chemical Measurement and Imaging Programs jointly support Professor Reginald M. Penner of the Department of Chemistry at the University of California at Irvine to investigate chemical sensors based upon metal nanowires. Three new modes for detecting molecules using metal nanowires are being developed in this project, which coincide with three objectives: 1) the use of surface electron scattering to detect gas phase molecules using noble metal nanowires. A specific example is a single gold nanowire that is capable of rapidly detecting 1 ppm NO2 and NO in air at elevated temperatures. 2) To exploit the heat of molecular chemisorption as means for detecting adsorbates in the gas phase using arrays of suspended metal nanowires. These investigations focus on ethylene on platinum and ethanol on palladium. 3) To create a family of nanoscopic chemical sensors based upon nanogaps in metal nanowires that are modified by the insertion of an affinity medium, such as a conductive organic polymer imprinted for the analyte molecule of interest, as well as a conductive polymer with incorporated antibodies during polymerization from solution. A broader impact of this research activity is a project involving outreach to economically disadvantaged high school students in the Santa Ana, California school district. Each year this provides a student from Santa Ana High School ten weeks of full-time paid summer research in Professor Penner's laboratory.As a chemical sensor is made progressively smaller, it responds more rapidly to changing concentrations of the molecule that is being measured. In this project, a family of highly miniaturized chemical sensors are created using metal nanowires. These nanowires are prepared using a process that is closely related to those used in the semiconductor industry to prepare integrated circuits. The resulting nanowires, composed of gold, palladium, or platinum, are approximately 1/100th the diameter of a human hair, but of similar lengths on the order of millimeters or centimeters. The electrical resistance of these diminutive wires increases when molecules attach to the surfaces of the wire, and this process provides a means for detecting these molecules very rapidly, within a few seconds. The molecules that are being detected in these studies are nitrogen dioxide, sulfur dioxide, carbon monoxide, and hydrocarbons like methane and ethane. In addition to a rapid response, a second advantage of these nanowire-based chemical sensors is their simplicity: A chemical sensor consists of a single metal nanowire, two electrical contacts to this nanowire, and an instrument for measuring its electrical resistance. Consequently, these sensors can be very inexpensive.