Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, United States.
ACS Nano. 2010 Nov 23;4(11):6914-22. doi: 10.1021/nn101198u. Epub 2010 Oct 28.
Biosensors utilizing carbon nanotube field-effect transistors have a tremendous potential to serve as the basis for the next generation of diagnostic systems. While nanotubes have been employed in the fabrication of multiple sensors, little attention has previously been paid to how the nanotube density affects the biosensor performance. We conducted a systematic study of the effect of density on the performance of nanotube biosensors and discovered that this parameter is crucial to achieving consistently high performance. We found that devices with lower density offer higher sensitivity in terms of both detection limit and magnitude of response. The low density nanotube devices resulted in a detection limit of 1 pM in an electrolyte buffer containing high levels of electrolytes (ionic concentration ∼140 mM, matching the ionic strength of serum and plasma). Further investigation suggested that the enhanced sensitivity arises from the semiconductor-like behavior-strong gate dependence and lower capacitance-of the nanotube network at low density. Finally, we used the density-optimized nanotube biosensors to detect the nucleocapsid (N) protein of the SARS virus and demonstrated improved detection limits under physiological conditions. Our results show that it is critical to carefully tune the nanotube density in order to fabricate sensitive and reliable devices.
基于碳纳米管场效应晶体管的生物传感器具有成为下一代诊断系统基础的巨大潜力。虽然已经有多种传感器采用了纳米管，但之前很少关注纳米管密度如何影响生物传感器的性能。我们系统地研究了密度对纳米管生物传感器性能的影响，发现这个参数对于实现始终如一的高性能至关重要。我们发现，在含有高浓度电解质的电解质缓冲液中（离子浓度约为 140mM，与血清和血浆的离子强度相匹配），密度较低的器件在检测限和响应幅度方面提供了更高的灵敏度。低密度纳米管器件在含有高浓度电解质的电解质缓冲液中的检测限达到 1pM。进一步的研究表明，灵敏度的增强源于低密度下纳米管网络的半导体行为——强栅极依赖性和较低的电容。最后，我们使用密度优化的纳米管生物传感器来检测 SARS 病毒的核衣壳（N）蛋白，并在生理条件下证明了检测限的提高。我们的结果表明，为了制造灵敏可靠的器件，仔细调整纳米管密度是至关重要的。
