Photoluminescence of Gold Nanoparticles and Their Applications to Sensing and Cell Imaging - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 185

Figure 9.1 (A) Excitation (dashed) and emission (solid) spectra of various
Au NCs. Emission from the longest wavelength-emitting
sample was limited by the detector response. (B) Emissions
from the three shortest wavelength-emitting Au NC solutions
(from left to right) under long-wavelength UV lamp irradiation
(366 nm). (C) Correlation of the number of atoms, N , per NC
with emission energy. Reprinted with permission from Ref. 6.
See also Color Insert.
emission signals that can range from the ultraviolet to the NIR
region. 21 The discrete absorptions and emissions scale with the
number of atoms, N , as N 1/3 , precisely predicted by the spherical
jellium model, but different from the N 2/3 scaling for semiconductor
quantum dots (QDs), which do not exhibit the free-electron shell-
illing degeneracies that are characteristic of metals. 38-40 The jellium
approximation is the simplest model for describing the behavior
of delocalized, free conduction electrons relative to the atomic NC
core; it is also a basic model for explaining plasmon absorption in
large NPs. Figure 9.1 presents a luorescence image and discrete
excitation and emission spectra of various dendrimer-encapsulated
Au NCs in aqueous solutions. Varying the molar ratio of Au ions to