Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Nanotechnology. 2012 May 4;23(17):175501. doi: 10.1088/0957-4484/23/17/175501. Epub 2012 Apr 5.
We demonstrate a new method for tailoring the selectivity of chemical sensors using semiconductor nanowires (NWs) decorated with metal and metal oxide multicomponent nanoclusters (NCs). Here we present the change of selectivity of titanium dioxide (TiO(2)) nanocluster-coated gallium nitride (GaN) nanowire sensor devices on the addition of platinum (Pt) nanoclusters. The hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO(2) and/or Pt nanoclusters (NCs) using the sputtering technique. This paper present the sensing characteristics of GaN/(TiO(2)-Pt) nanowire-nanocluster (NWNC) hybrids and GaN/(Pt) NWNC hybrids, and compare their selectivity with that of the previously reported GaN/TiO(2) sensors. The GaN/TiO(2) NWNC hybrids showed remarkable selectivity to benzene and related aromatic compounds, with no measurable response for other analytes. Addition of Pt NCs to GaN/TiO(2) sensors dramatically altered their sensing behavior, making them sensitive only to methanol, ethanol and hydrogen, but not to any other chemicals we tested. The GaN/(TiO(2)-Pt) hybrids were able to detect ethanol and methanol concentrations as low as 100 nmol mol(-1) (ppb) in air in approximately 100 s, and hydrogen concentrations from 1 µmol mol(-1) (ppm) to 1% in nitrogen in less than 60 s. However, GaN/Pt NWNC hybrids showed limited sensitivity only towards hydrogen and not towards any alcohols. All these hybrid sensors worked at room temperature and are photomodulated, i.e. they responded to analytes only in the presence of ultraviolet (UV) light. We propose a qualitative explanation based on the heat of adsorption, ionization energy and solvent polarity to explain the observed selectivity of the different hybrids. These results are significant from the standpoint of applications requiring room-temperature hydrogen sensing and sensitive alcohol monitoring. These results demonstrate the tremendous potential for tailoring the selectivity of the hybrid nanosensors for a multitude of environmental and industrial sensing applications.
我们展示了一种使用半导体纳米线（NWs）修饰的金属和金属氧化物多组分纳米簇（NCs）来定制化学传感器选择性的新方法。在这里，我们介绍了在添加铂（Pt）纳米簇的情况下，二氧化钛（TiO2）纳米簇涂覆的氮化镓（GaN）纳米线传感器器件选择性的变化。通过使用溅射技术在单个 GaN NW 上沉积 TiO2 和/或 Pt 纳米簇（NCs）来制造两端器件，开发了混合传感器器件。本文介绍了 GaN/（TiO2-Pt）纳米线-纳米簇（NWNC）杂化和 GaN/（Pt）NWNC 杂化的传感特性，并将其与先前报道的 GaN/TiO2 传感器的选择性进行了比较。GaN/TiO2 NWNC 杂化物对苯和相关芳香族化合物表现出显著的选择性，对其他分析物没有可测量的响应。将 Pt NC 添加到 GaN/TiO2 传感器中，大大改变了它们的传感行为，使它们仅对甲醇、乙醇和氢气敏感，而对我们测试的其他任何化学物质都不敏感。GaN/（TiO2-Pt）杂化物能够以低至空气中 100 nmol mol-1（ppb）的浓度检测乙醇和甲醇，在不到 60 秒的时间内检测氮气中 1 μmol mol-1（ppm）至 1%的氢气浓度。然而，GaN/Pt NWNC 杂化物仅对氢气表现出有限的敏感性，而对任何醇都不敏感。所有这些混合传感器都在室温下工作并且是光调制的，即它们仅在存在紫外线（UV）光的情况下才对分析物作出响应。我们基于吸附热、电离能和溶剂极性提出了一个定性解释，以解释不同杂化物的观察到的选择性。从需要室温氢气传感和灵敏酒精监测的应用的角度来看，这些结果具有重要意义。这些结果表明，对于多种环境和工业传感应用，定制混合纳米传感器选择性的潜力巨大。
