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Miniaturized gas ionization sensors using carbon nanotubes

Abstract

Gas sensors operate by a variety of fundamentally different mechanisms1,2,3,4,5,6,7,8,9,10,11,12,13,14. Ionization sensors13,14 work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems15,16,17. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

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Figure 1: The nanotube sensor device.
Figure 2: Current–voltage (IV) curves for electrical breakdown.
Figure 3: Effect of gas concentration on electrical breakdown.
Figure 4: Effect of electrode separation, and detection of gases in mixtures.

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Acknowledgements

This work was supported by NSF (NSEC, NER awards), US Army Research Office, Philip Morris USA, and RPI.

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Correspondence to Nikhil Koratkar or Pulickel M. Ajayan.

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The authors declare that they have no competing financial interests.

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Modi, A., Koratkar, N., Lass, E. et al. Miniaturized gas ionization sensors using carbon nanotubes. Nature 424, 171–174 (2003). https://doi.org/10.1038/nature01777

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