Scattering and Absorption Cross-Section Spectral Measurements of Gold Nanorods in Water

Abstract

The usually measured attenuation (extinction) spectra of gold nanorods in water include two unresolving contributions: absorption and scattering. The present study is to separate these two contributions by measuring the total scattering losses as a function of wavelengths. Knowing the total-attenuation spectrum and the scattering-loss spectrum, the pure absorption spectrum can be finally determined for a given sample system. Two approaches are employed for experimentally estimating the pure scattering losses: one is direct measurement using a calibrated large-area photodetector to collect the scattered energy along a certain solid angle; the other is comparison measurement by using polystyrene microspheres in water as a standard sample whose scattering cross section is known well. These two methods have given nearly the same results and are finally compared with the theoretical calculations.

Optical properties of plasmon-resonant bare and silica-coated nanostars used for cell imaging

“…The absorption and scattering behaviors of PRNP suspensions define their applicability for biomedical optics; thus, both properties were measured for different types of particles with integrating spheres 49 and by OCT. 50 He et al 51 used a monochromatic laser beam passing through the sample medium and then measured the absolute scattered energy within a small solid angle, and the total absolute scattering losses were finally obtained by integration over a 4π solid angle. Bogatyrev et al 52 used a collimated light beam passing through the sample and measured the scattering spectrum along the 90 deg direction.…”

“…4,5 Branched and star-shaped gold NPs become perspective candidates for use as a plasmon-resonant core of nanocomposites (NCs) due to their strong absorption in the near-infrared (NIR) wavelength range, optimal for the "diagnostic/therapeutic window" with enhanced light penetration into biotissue. Although some experimental data on the relationship between the absorption and scattering properties of nanospheres and nanoshells, 13,14 nanorods, 15,16 and nanocages 17 are available, the majority of studies are devoted to the absorption properties of plasmonic NPs. 12 Integration of plasmon-resonant nanoparticles (PRNPs) into biomedical applications requires the ability to change their absorption and scattering properties and tune the position of the resonance peak and associated scattering and absorption for optimal use.…”

Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

“…First, a wider spectrum light source could be used to improve the spectral contrast between GNR and native tissue with a broad SLoW ratio distribution, like the RPE. To elaborate, the slope of the GNR extinction curve, which has the same shape as the reflectance/scattering curve [24,25], within the OCT spectral window is a key determining factor of spectral contrast. The theoretical model predicts that capturing more of the GNR SPR slope within a wider OCT spectral window would lead to increased contrast.…”

Observation of stimulated Mie-Bragg scattering from large-size-gold-nanorod suspension in water

“…As an example, Fig. 2(a) shows the measured overall extinction spectral curve and the scattering extinction curve of the Au nanorods (∼10.5 nm in diameter and ∼75 nm in length) in water [21]. The normalized peak value of the scattering extinction coefficient is about 1/30 of that of the overall extinction, while the scattering coefficient values in the gap range between those two extinction bands remain comparable to those in the band ranges.…”

“…Shown in Fig. 2(b) is the measured angular dependence of scattering intensity from an Au-nanorod-water sample (with a nanorod diameter of ∼16 nm and length of ∼65 nm), which was obtained by using an unfocused 778 nm pulsed laser as the incident light linearly polarized along a 45 • direction with the observation plane [21]. By contrast, Fig.…”