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Published May 28, 2009 | Supplemental Material + Accepted Version
Journal Article Open

Measuring the Optical Absorption Cross Sections of Au−Ag Nanocages and Au Nanorods by Photoacoustic Imaging


This paper presents a method for measuring the optical absorption cross sections (σ_a) of Au−Ag nanocages and Au nanorods. The method is based on photoacoustic (PA) imaging, where the detected signal is directly proportional to the absorption coefficient (μ_a) of the nanostructure. For each type of nanostructure, we first obtained μ_a from the PA signal by benchmarking against a linear calibration curve (PA signal versus μ_a) derived from a set of methylene blue solutions with different concentrations. We then calculated σ_a by dividing the μ_a by the corresponding concentration of the Au nanostructure. Additionally, we obtained the extinction cross section (σ_e, sum of absorption and scattering) from the extinction spectrum recorded using a conventional UV−vis−NIR spectrometer. From the measurements of σ_a and σ_e, we were able to easily derive both the absorption and scattering cross sections for each type of gold nanostructure. The ratios of absorption to extinction obtained from experimental and theoretical approaches agreed well, demonstrating the potential use of this method in determining the optical absorption and scattering properties of gold nanostructures and other types of nanomaterials.

Additional Information

© 2009 American Chemical Society. Received: April 10, 2009; Revised Manuscript Received: April 23, 2009; Publication Date (Web): May 4, 2009. This work was supported, in part, by grants from National Institutes of Health (R01 EB000712, R01 EB008085, R01 NS46214, and U54 CA136398—the Network for Translational Research—to L.V.W.). L.V.W. has a financial interest in Endra, Inc., which, however, did not support this work. Y.X. thanks the National Institutes of Health for a 2006 Director's Pioneer Award (DP1 OD000798-04). Z.Y.L. was supported by the National Natural Science Foundation of China (60736041 and 10874238). E.C.C. was also partially supported by a fellowship from the Korea Research Foundation (KRF-2007-357-D00070) funded by the Korean Government.

Attached Files

Accepted Version - nihms115450.pdf

Supplemental Material - jp903343p_si_001.pdf


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