Matrix effects on the surface plasmon resonance of dry supported gold nanocrystals

Abstract

We present a method to characterize surface-chemical properties of gold nanocrystals. Spherical, 60 nm gold nanocrystals were immobilized on quartz substrates by a coupling agent and cleaned in a hydrogen plasma. The nanocrystals were then functionalized with alkanethiol self-assembled monolayers (SAM) of varying chain lengths by adsorption from the gas phase, and localized surface plasmon resonance (LSPR) spectroscopy was performed on the samples. Depending on the alkanethiol chain length, the adsorption of the SAM redshifted the LSPR to different extents, in accordance with Mie theory. SAM thickness differences below 1 nm could be easily resolved. Our results demonstrate that LSPR spectroscopy can be applied to characterize thin organic layers on dry supported gold particles with high sensitivity.

Near-field Coupling Effect between Individual Au Nanospheres and their Supporting SiO2/Si Substrate

“…An often-used experimental configuration of the aforementioned applications is to place the NPs on or close to a substrate. This proximity can shift the wavelength of the LSP owing to the NP interaction with the substrate [8][9][10][11][12]. A better knowledge of the shift tendency versus the distance between the NP and the substrate is interesting and important for understanding their intrinsic properties and it can also provide guidelines for their applications in nano-photonics, sensing, SERS/TERS, etc.…”

“…By comparison, far-field techniques are free of tip effect and provide a spatial resolution high enough for our analysis [16]. The far-field experiments about the substrate effect previously concentrated on the discussion of ensemble NPs [8][9][10][11]. To correlate the optical properties with the corresponding specific NPs' structure, one has to overcome the size distribution of the particle collection and the nanostructures' effect may even be smeared out.…”

“…To correlate the optical properties with the corresponding specific NPs' structure, one has to overcome the size distribution of the particle collection and the nanostructures' effect may even be smeared out. Furthermore, previous experiments [8][9][10][11] mainly deal with metal substrates while reports about dielectric substrates are still limited. Only recently, far-field experiments on different dielectric substrates' effect on the LSP properties down to individual NPs were reported [16,17].…”

Multiple-scattering model for the coherent reflection and transmission of light from a disordered monolayer of particles

“…where α 2πρ s ∕k m k i z , k r k i yây − k i zâz is the wave vector of a specularly reflected wave from the plane of the monolayer, and the fields ρ s η C 3 B r and ρ s η −C 3 B r involve the integral of only evanescent fields. The superscripts C 3 and −C 3 denote integration contours in the complex plane.…”

“…The optical properties of monolayers of small particles are of interest, for instance, in the design of diverse physical and chemical sensors consisting of a monolayer of metallic particles interacting with their environment, and where changes of their physical or chemical state are detected through changes of their optical reflectivity (e.g., see [1][2][3][4]).…”