Quasi-fractal Gold Nanoparticles for Sers: Effect of Nanoparticle Morphology and Concentration

Abstract

<p>Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles leads to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle interactions, as these affect the oscillation modes of electrons on the nanoparticle surfaces. The effect of the particle morphologies on the LSPR and further on the surface-enhancing capabilities of these nanoparticles is explored by comparing different nanoparticle morphologies and concentrations. We show that in a fixed nanoparticle concentration regime, Quasi-fractal gold nanoparticles provide the highest level of surface enhancement, whereas spherical nanoparticles provide the largest enhancement in a fixed gold concentration regime. The presence of highly branched features enables these nanoparticles to couple with a laser wavelength despite having no strong absorption band and hence no single surface plasmon resonance. This cumulative LSPR may allow these nanoparticle to be used in a variety of applications where laser wavelength flexibility is beneficial, such as in medical imaging applications where fluorescence at short laser wavelengths may be coupled with non-fluorescing long laser wavelengths for molecular sensing. </p>

Functionalized Gold Nanoparticles: Synthesis, Properties and Biomedical Applications

“…(b) UV/Visible spectra for gold nanocaltrop samples before and after a ten‐fold suspension concentrating. Concentrated samples show no change in absorption profile other than in increase in absorbance [56] . Reprinted with permission from [56].…”

“…The hot spot is also related to the curvature and surface characteristics of the location. When the surface of nanoparticles has the characteristics of dense interaction sites between incident photons and plasmon, the enhancement of Raman spectra is very significant [56] …”

“…(a) A‐set nanoparticle substrates from suspensions with a constant Au atom concentration, (b) B‐set nanoparticle substrates from suspensions with constant nanoparticle concentration. Spectra have been shifted by 400 counts/sec each for clarity [56] . Reprinted with permission from [56].…”