Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 N Cramer Street, Milwaukee, WI 53211, USA.
Nanoscale. 2012 Sep 28;4(19):5887-94. doi: 10.1039/c2nr31556d. Epub 2012 Aug 17.
We have investigated the room-temperature sensing enhancement of Ag nanoparticles (NPs) for multiwalled carbon nanotube (MWCNT)-based gas sensors using electrical measurements, in situ infrared (IR) microspectroscopy, and density functional theory (DFT) calculations. Multiple hybrid nanosensors with structures of MWCNTs/SnO(2)/Ag and MWCNTs/Ag have been synthesized using a process that combines a simple mini-arc plasma with electrostatic force directed assembly, and characterized by electron microscopy techniques. Ag NPs were found to enhance the sensing behavior through the "electronic sensitization" mechanism. In contrast to sensors based on bare MWCNTs and MWCNTs/SnO(2), sensors with Ag NPs show not only higher sensitivity and faster response to NO(2) but also significantly enhanced sensitivity to NH(3). Our DFT calculations indicate that the increased sensitivity to NO(2) is attributed to the formation of a NO(3) complex with oxygen on the Ag surface accompanying a charge rearrangement and a net electron transfer from the hybrid to NO(2). The significant response to NH(3) is predicted to arise because NH(3) is attracted to hollow sites on the oxidized Ag surface with the H atoms pointing towards Ag atoms and electron donation from H to the hybrid sensor.
我们使用电学测量、原位红外（IR）微光谱和密度泛函理论（DFT）计算研究了 Ag 纳米颗粒（NPs）对基于多壁碳纳米管（MWCNT）的气体传感器在室温下的传感增强作用。通过将简单的微弧等离子体与静电定向组装相结合的过程，合成了具有 MWCNTs/SnO(2)/Ag 和 MWCNTs/Ag 结构的多种混合纳米传感器，并通过电子显微镜技术进行了表征。Ag NPs 通过“电子敏化”机制增强了传感行为。与基于裸 MWCNTs 和 MWCNTs/SnO(2)的传感器相比，具有 Ag NPs 的传感器不仅对 NO(2)表现出更高的灵敏度和更快的响应，而且对 NH(3)的灵敏度也显著增强。我们的 DFT 计算表明，对 NO(2)的灵敏度增加归因于 Ag 表面上与氧形成的 NO(3)配合物，伴随着电荷重排和从混合体到 NO(2)的净电子转移。对 NH(3)的显著响应预计是因为 NH(3)被氧化的 Ag 表面上的中空位吸引，H 原子指向 Ag 原子，并且 H 向混合传感器提供电子。
