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Journal of Spectroscopy
Volume 2015, Article ID 762352, 7 pages
http://dx.doi.org/10.1155/2015/762352
Research Article

Broadband Spectroscopic Thermoacoustic Characterization of Single-Walled Carbon Nanotubes

1Department of Medical Imaging, University of Arizona, Tucson, AZ 85724, USA
2College of Optical Sciences, University of Arizona, Tucson, AZ 85724, USA
3Raytheon Missile Systems, Raytheon Corporation, Tucson, AZ 85736, USA
4Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85724, USA

Received 6 February 2015; Accepted 27 April 2015

Academic Editor: Nanda Gopal Sahoo

Copyright © 2015 Daniel R. Bauer et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Carbon nanotubes have attracted interest as contrast agents for biomedical imaging because they strongly absorb electromagnetic radiation in the optical and microwave regions. This study applies thermoacoustic (TA) imaging and spectroscopy to measure the frequency-dependent absorption profile of single-walled carbon nanotubes (SWNT) in the ranges of 2.7–3.1 GHz and 7–9 GHz using two tunable microwave sources. Between 7 and 9 GHz, the peak TA signal for solutions containing semiconducting and metallic SWNTs increased monotonically with a slope of 1.75 AU/GHz () and 2.8 AU/GHz (), respectively, relative to a water baseline. However, after compensating for the background signal from water, it was revealed that the TA signal from metallic SWNTs increased exponentially within this frequency band. Results suggest that TA imaging and spectroscopy could be a powerful tool for quantifying the absorption properties of SWNTs and optimizing their performance as contrast agents for imaging or heat sources for thermal therapy.