title: Measuring the Optical Absorption Cross-sections of Au-Ag Nanocages and Au Nanorods by Photoacoustic Imaging.
abstract: 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 firstly obtained μ(a) 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. Additonally, 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.
authors.affiliation: Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63130.
authors.forename: Eun Chul
authors.initials: EC
authors.lastname: Cho
authors.forename: Chulhong
authors.initials: C
authors.lastname: Kim
authors.forename: Fei
authors.initials: F
authors.lastname: Zhou
authors.forename: Claire M
authors.initials: CM
authors.lastname: Cobley
authors.forename: Kwang Hyun
authors.initials: KH
authors.lastname: Song
authors.forename: Jingyi
authors.initials: J
authors.lastname: Chen
authors.forename: Zhi-Yuhan
authors.initials: ZY
authors.lastname: Li
authors.forename: Lihong V
authors.initials: LV
authors.lastname: Wang
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia
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