BioCircuits Institute, University of California San Diego, La Jolla, California 92093-0402, United States.
Anal Chem. 2012 Sep 4;84(17):7502-10. doi: 10.1021/ac301506t. Epub 2012 Aug 21.
This paper presents a unique perspective on enhancing the physicochemical mechanisms of two distinct highly sensitive nanostructured metal oxide micro hot plate gas sensors by utilizing an innovative multifrequency interrogation method. The two types of sensors evaluated here employ an identical silicon transducer geometry but with a different morphological structure of the sensitive film. While the first sensing film consists of self-ordered tungsten oxide nanodots, limiting the response kinetics of the sensor-chemical species pair only to the reaction phenomena occurring at the sensitive film surface, the second modality is a three-dimensional array of tungsten oxide nanotubes, which in turn involves both the diffusion and adsorption of the gas during its reaction kinetics with the sensitive film itself. By utilizing the proposed multifrequency interrogation methodology, we demonstrate that the optimal temperature modulation frequencies employed for the nanotubes-based sensors to selectively detect hydrogen, carbon monoxide, ethanol, and dimethyl methyl phosphonate (DMMP) are significantly higher than those utilized for the nanodot-based sensors. This finding helps understand better the amelioration in selectivity that temperature modulation of metal oxides brings about, and, most importantly, it sets the grounds for the nanoengineering of gas-sensitive films to better exploit their practical usage.
本文提出了一种独特的观点，即通过利用创新的多频询问方法，增强两种截然不同的高灵敏度纳米结构金属氧化物微热板气体传感器的物理化学机制。这里评估的两种传感器采用相同的硅换能器几何形状，但敏感膜的形态结构不同。第一个传感膜由自组装的氧化钨纳米点组成，将传感器-化学物质对的响应动力学限制在仅发生在敏感膜表面的反应现象上，而第二种模态是氧化钨纳米管的三维阵列，这反过来又涉及到气体在与敏感膜本身反应动力学期间的扩散和吸附。通过利用所提出的多频询问方法，我们证明了用于基于纳米管的传感器选择性检测氢气、一氧化碳、乙醇和二甲基甲基膦酸酯（DMMP）的最佳温度调制频率明显高于基于纳米点的传感器所用的频率。这一发现有助于更好地理解金属氧化物温度调制带来的选择性改善，最重要的是，它为气体敏感膜的纳米工程奠定了基础，以更好地利用它们的实际用途。
