Chemical Sensors Based on Electrodeposited Metal Nanowires

分析和表面化学计划支持加州大学欧文分校的Reginald Penner教授关于各种金属纳米线的合成和对其用作化学传感器的评估的项目。纳米线是通过电化学阶梯装饰的过程来制造的，钼已经被证明可以制造出长度可达150微米、横截面为半圆柱的、可从制备表面上移除的纳米线。这种直径在10到500纳米之间的高深宽比纳米线可以在阶梯状石墨表面制备尺寸选择性的纳米线，转移到聚苯乙烯薄膜上，然后连接电极。这种导电性与块状金属的导电性相似。作为传感器，纳米线的功能是将金属表面暴露在分析物中，同时测量纳米线的电导率。例如，随着金属氧化物涂层的形成，钼丝与氧气发生反应，产生大量但稳定的电导率下降。未来的研究方向包括贵金属纳米线的制备。一种待测试的合成方案是通过汞齐制备金属线。然后，传感器将用纳米线制造，要么是裸露的金属，要么是金属氧化物的覆盖层。尚待确定的是将分析物浓度与金属纳米线电导率变化联系起来的物理模型。新一代化学传感器将有广泛的应用，从生物医学到污染控制。随着纳米技术从实验室走向实际应用，设备的合成必须得到改进；更快、更便宜、更好。人们迫切需要可靠、高效地合成纳米线。电化学阶梯装饰是电化学基础知识的应用，已知的阶梯特征自然出现在清洁的石墨表面上。该石墨为电化学生长的金属线的受控生长提供了模板。与纳米线中金属原子的数量相比，纳米线具有极高的表面积。因此，导电性取决于附着在表面的分子的数量和种类，这使得纳米线成为新一代传感器的合理组成部分。

The Analytical and Surface Chemistry Program supports this project by Prof. Reginald Penner at the University of California at Irvine on the synthesis of nanowires of various metals and an evaluation of their use as chemical sensors. Nanowires are to be fabricated by the procedure of electrochemical step decoration, which has been demonstrated for molybdenum to make wires that are up to 150 micrometers in length, hemicylindrical in cross-section, and removable from the surfaces on which prepared. The high-aspect ratio nanowires, with diameters ranging from 10 to 500 nanometers, can be prepared size-selective on stepped graphite surfaces, transferred to a polystyrene film, and then electrodes attached. The conductivity is similar to that of bulk metal. As a sensor, the nanowires function by exposure of the metal surface to an analyte while measuring the electrical conductivity of the nanowires. For example, molybdenum wires are reactive with oxygen yielding a substantial, but stable drop in conductivity as a metal oxide coating is made. The future research directions include preparation of noble metal nanowires. One synthetic scheme to be tested is metal wire preparation via a mercury amalgam. Then, sensors are to be fabricated with nanowires, either bare metal or with a metal oxide overlayer. Yet to be determined is the physical model to connect analyte concentration with the change in metal nanowire conductivity. New generation chemical sensors will have a wide range of applications, from biomedical to pollution control. As nanotechnology moves from the laboratory to practical applications, the synthesis of devices must be improved; faster, cheaper, better. There is a great need for reliable and efficient synthesis of nanowires. Electrochemical step decoration is an application of fundamental knowledge of electrochemistry with the known step features naturally occurring on a clean graphite surface. The graphite provides a template for the controlled growth of an electrochemically grown metal wire. The nanowires have an extremely high surface area in relation to the number of metal atoms in the wire. For this reason, electrical conductivity depends upon the number and kind of molecules attached to the surface, making nanowires a logical component of new generation sensors.