Photoacoustic quantification of the optical absorption cross-sections of gold nanostructures
This study demonstrates a method for measuring the optical absorption cross-sections (σ_a) of Au-Ag nanocages and Au nanorods using photoacoustic (PA) sensing. PA signals are directly proportional to the absorption coefficient (μ_a) of the nanostructure. For each type of nanostructure, we first obtained μa from the PA signal by benchmarking against a linear calibration curve (PA signal vs. 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 cross-sections) 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. This method can potentially provide the optical absorption and scattering properties of gold nanostructures and other types of nanomaterials.
Additional Information© 2010 Society of Photo-Optical Instrumentation Engineers (SPIE). 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 award from the Korea Research Foundation (KRF-2007-357-D00070) funded by the Korean Government.
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