Correlated Structure and Optical Property Studies of Plasmonic Nanoparticles

Abstract

This article provides a review of our recent studies of single metal nanoparticles and single nanoparticle clusters aimed at correlating the structural and plasmonic properties of the same entity. The correlation between the structure and the optical properties arising from the localized surface plasmon resonance (LSPR) on single nanoparticles from various samples is described. Nanoparticles of different materials (Ag and Au) and shapes (spheres, cubes, triangles) are considered. Experiments were carried out using transmission electron microscopy (TEM), dark-field spectroscopy, and surface-enhanced Raman spectroscopy (SERS). Results of those measurements were compared with electrodynamics calculations to provide insight into the interpretation and physical meaning of the experimental results. We examine correlated studies of triangular nanoparticle arrays to highlight the significance of single entity measurements over ensemble-averaged measurements. Furthermore, we show how an examination of statistics on large data sets helps draw quantitative structureÀLSPR relationships. We also show that implementing SERS in correlated measurements improves the understanding of factors important in determining SERS enhancements. Finally, we extend the scope of correlated measurements to the tracking and controlled manipulation of single nanoparticles, thus paving the way for in vivo diagnostics using nanomaterials.

Photon-induced near-field electron microscopy: Mathematical formulation of the relation between the experimental observables and the optically driven charge density of nanoparticles

“…The near-field integral then is obtained from the projected induced charge density convoluted with the K 0 radial profile using Eq. (17). The field integralF 0 by a numerical integration and the near-field integralF c show excellent agreement, confirming that the electron-photon interaction is dominated by the near-field component and the retardation effect is negligible.…”

“…Equation (17) shows that the near-field integral is a convolution of the projected charge density and a 2D radial response function which monotonically decreases as a function of the impact parameter b. Note that the modified Bessel function can be approximated asK 0 (z) ≈ − ln z 2 − γ for z 1, where γ is the Euler-Mascheroni constant.…”

“…It was also demonstrated that energy-filtered transmission electron microscopy (EFTEM) can be equivalently employed to obtain the same information [8]. Plasmons in nanoparticles of other geometries were also visualized with SI methods [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In particular, to investigate SERS activity, Guiton et al employed STEM-EELS to probe the fields of plasmons in silver nanorods and correlated this with far-field scattering spectroscopy [15].…”

Defect tolerance and the effect of structural inhomogeneity in plasmonic DNA-nanoparticle superlattices

“…In addition, the nanoparticles used in these systems are inherently inhomogeneous: varying in size, shape, and radius of curvature. Although the effects of inhomogeneity have been investigated at the individual nanoparticle level (15,16), the effects of inhomogeneity on plasmonic assemblies are not as well understood. Determining the defect resilience of emergent properties is crucial for the continued development of scalable nanomaterial devices with reproducible properties.…”

Photon-induced near field electron microscopy

“…6 Plasmons in nanoparticles of other geometries were also visualized by SI methods. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Consequently, simulations of EELS of nanoparticles have been studied extensively to reveal their relation to plasmon fields. 2,[22][23][24] In particular, to investigatte SERS activity, Guiton et.…”