Localized and Propagating Surface Plasmons in Gold Particles of Near-Micron Size

Abstract

In this letter, we demonstrate that Au triangles between approximately 200 nm and 1.5 μm are transitioning from a predominantly localized surface plasmon resonance (LSPR) character to a regime where both LSPR and a short-range SPR mode are concomitantly present. The Au triangles are active in LSPR between approximately λ = 700 nm for the smaller triangles and λ = 2.5 μm for the largest Au triangles. Triangles with a base length of 200 and 300 nm do not exhibit an active short-range SPR mode, while triangles with 500 and 700 nm and 1.5 μm base lengths show a strong absorption peak in SPR at approximately λ = 800 nm, attributed to the short-range SPR mode. A low sensitivity of <50 nm/RIU is observed with this short-range SPR mode in triangles of near-micron size. Also, Au nanohole arrays exhibit features in both the submicron size, with gold “island” between neighboring nanoholes, and on the order of tens of microns, with gold “strips” along rows of nanoholes. The excitation of nanohole arrays in total internal reflection (TIR) results in the presence of both a short-range SPR mode similar to that of gold triangles and a propagating SPR mode similar to that of a thin Au film of macroscopic surface. For Au nanohole arrays of 820 nm periodicity, TIR experiments result in two overlapping absorption peaks at λ = 650 and 800 nm, corresponding respectively to propagating SPR in thin films (typically around λ = 615 nm) and the short-range SPR mode in Au triangles.

Nanoparticle Polydispersity Can Strongly Affect In Vitro Dose

“…The selection of particle sizes took into account the availability and ease of published synthesis methods, and the synthesis of large (i.e., near‐micron sized) AuNPs is rather challenging and relies on advanced non‐standard synthetic procedures, and therefore, AuNPs up to 100 nm were considered. For small AuNPs, i.e., 10 nm, where the average size promotes diffusion over settling, increasing results in slightly higher delivery rates, though the increase is not significant below (Figure A).…”

Surface plasmon resonance properties of silver nanoparticle 2D sheets on metal gratings

“…In particular, multilayered two-dimensional metal nanoparticles deposited on a metal surface showed extraordinary resonance changes. Furthermore, simultaneous propagating and localized SPR excitations have recently been reported (Yu et al 2006 ; Live et al 2009 ; Ding et al 2011 ). Smith et al showed that localized plasmon resonance could be observed when the density of gold nanoparticles increased on a flat gold surface, while propagating surface plasmons could also be observed in different visible wavelength regions by irradiating white light through a prism (Mock et al 2012 ).…”

Effect of Cavity Architecture on the Surface-Enhanced Emission from Site-Selective Nanostructured Cavity Arrays

“…Line 1 shows the path taken by a localised SP; it is confined to the distance between the cavities. Live et al reported that PSPP may be confined in space by the boundaries in nanocavity arrays [22]. Alternatively localized surface plasmon modes may arise from hybrid rim-surface plasmon mode [23].…”

“…Line 2 shows a possible path taken by a PSPP. This line traverses flat gold and avoids the edges of the nanocavities, thereby avoiding confinement [22]. These delocalised SPs are expected to contribute little to SERRS as they cannot be excited at an air metal interface by incident light [16].…”

“…Comparing SEL intensity from [Ru(bpy) 2 (Qbpy)] 2+ prepared in the voids of the 430 nm nanocavity array only to those prepared on the surface of the substrate shows a very similar changes in intensity as a function of angle. Studies of periodic cavity arrays proposed that there are different possible directions of PSPPs, whereby the propagation can be in one case confined between two neighbouring nanocavities, while in another case the surface plasmon is free to propagate in one direction for lengths potential larger than tens of microns, similar to propagating surface plasmon resonance on a continuous metallic film [22]. The presence of surface plasmons occurring in the short distance between adjacent nanocavities (annulus to localized surface plasmons) and a long axis between rows of nanocavities (comparable to propagating surface plasmons) was investigated using total internal reflection (TIF) measurements [22].…”