Chemical Sensors Based on Electrodeposited Metal Nanowires

分析和表面化学项目支持加州大学欧文分校Reginald Penner教授的项目，研究各种金属纳米线的合成及其作为化学传感器的用途的评估。纳米线是通过电化学步骤修饰的过程来制造的，已经证明钼可以制造出长度达150微米，横截面为半圆柱形，并且可以从所制备的表面上移除的纳米线。这种高纵横比的纳米线直径从10纳米到500纳米不等，可以在阶梯状石墨表面制备，转移到聚苯乙烯薄膜上，然后连接电极。电导率与大块金属相似。作为传感器，纳米线的功能是将金属表面暴露在分析物中，同时测量纳米线的导电性。例如，钼线与氧发生反应，当金属氧化物涂层形成时，电导率会大幅下降，但会稳定下降。未来的研究方向包括贵金属纳米线的制备。要测试的一种合成方案是通过汞合金制备金属丝。然后，传感器将用纳米线制造，要么是裸金属，要么是金属氧化物覆盖层。有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。目前迫切需要可靠、高效的纳米线合成技术。电化学台阶装饰是电化学基础知识的应用，已知的台阶特征自然发生在清洁的石墨表面上。石墨为电化学生长金属线的受控生长提供了模板。纳米线的表面积相对于金属原子的数量来说是非常高的。由于这个原因，电导率取决于附着在表面的分子的数量和种类，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.