Visualizing the Size, Shape, Morphology, and Localized Surface Plasmon Resonance of Individual Gold Nanoshells by Near-Infrared Multispectral Imaging Microscopy

Abstract

We have successfully utilized the newly developed near-infrared multispectral imaging (NIR-MSI) microscope to observe and measure directly the localized surface plasmon absorption (LSPR) of individual gold nanoshells. The NIR-MSI is suited for this task because it can simultaneously record spectral and spatial information of a sample with high sensitivity (single pixel resolution) and high spatial resolution (approximately 0.9 microm/pixel). Importantly, the LSPR of individual nanoshells measured by the NIR-MSI microscope agrees well with the spectra calculated theoretically using Mie scattering for the nanoshells (i.e., nanoshells with silica cores approximately 800 nm in diameter and gold shell thicknesses of approximately 35 nm). Additionally, the NIR-MSI microscope enables measurement of LSPR at different positions within a single nanoshell. LSPR spectra were found to be distinct at various positions within a single nanoshell. Since LSPR spectra are known to depend on the shape and morphology of the nanoshells, these results seem to suggest that the individual nanoshells are not smooth and well-defined, but are rather rough and inhomogeneous. The LSPR spectra of single nanoshells in several different solvents were also examined using NIR-MSI and were found to depend on the dielectric constant of the medium. However, the relationship was discovered to be more complex than simply following the Drude equation. Specifically, when (lambda(max)/fwhm)(2) values of LSPR for single gold nanoshells were plotted as a function of 2n(2) (or 2epsilon) for nanoshells in six different solvents, a linear relationship was found for only three solvents: D(2)O, acetonitrile-d(3), and ethyl acetate. Acetone-d(6) showed a slight deviation, whereas formamide and pyridine-d(5) exhibited distinctly different correlations.

Structural and functional photoacoustic molecular tomography aided by emerging contrast agents

“…The LSPR effect arises from the collective oscillation of conduction electrons in the shell structure where the electrons oscillate with all the ions and efficiently couple the light into heat. 125,126 The absorption peak of the nanoshell in the NIR region is tunable by varying the silica core size relative to the thickness of the gold shell. Poly(ethylene glycol)-coated nanoshells circulating in rat brain vessels were continuously mapped in vivo .…”

Synthesis and Deposition of Ag Nanoparticles by Combining Laser Ablation and Electrophoretic Deposition Techniques

“…The peak around 400 nm corresponds to dipolar mode excitation of spherical silver nanoparticles, but there is no significant position shifting of LSPR due to their size increasing from a few nanometers to tens of nanometers [34]. The large full Together with the important specific area of the nanoparticles, their LSPR show dependence on their size and shape as well as the dielectric properties of the surrounding media [30,31]. The nanoparticles exhibit irregular shape rather than spherical morphology, which can favor the excitation of higher-order plasmon modes over small nanospheres.…”

“…Together with the important specific area of the nanoparticles, their LSPR show dependence on their size and shape as well as the dielectric properties of the surrounding media [30,31]. The nanoparticles exhibit irregular shape rather than spherical morphology, which can favor the excitation of higher-order plasmon modes over small nanospheres.…”

Determination of Chemical Homogeneity of Fire Retardant Polymeric Nanocomposite Materials by Near-Infrared Multispectral Imaging Microscopy

“…The acousto-optic tunable filter (AOTF) based NIR multispectral imaging microscope used in this work is similar to those used in previous studies (Khait, Smirnov, andTran 2001, Tran 2003;2005;Tran, Grishko, and Challa 2008;Mejac et al 2009) except for the replacement of the focusing microscopic lenses in the microscope with a pair of 0.58 N.A. A 15X reflecting Cassegrains to avoid possible aberrations in the NIR region.…”