The Effect of Gold Nanorods Clustering on Near-Infrared Radiation Absorption

Abstract

In this paper, the plasmonic resonant absorption of gold nanorods (GNRs) and GNR solutions was studied both numerically and experimentally. The heat generation in clustered GNR solutions with various concentrations was measured by exposing them to Near Infrared (NIR) light in experiment. Correspondingly, calculations based on the discrete-dipole approximation (DDA) revealed the same relationship between the maximum absorption efficiency and the nanorod orientation for the incident radiation. Additionally, both the plasmonic wavelength and the maximum absorption efficiency of a single nanorod were found to increase linearly with increasing aspect ratio (for a fixed nanorod volume). The wavelength of the surface plasmonic resonance (SPR) was found to change when the gold nanorods were closely spaced. Specifically, both a shift and a broadening of the resonance peak were attained when the distance between the nanorods was set to about 50 nm or less. The absorbance spectra of suspended nanorods at various volume fractions also showed that the plasmonic wavelength of the nanorods solution was at 780 ± 10 nm, which was in good agreement with the computational predictions for coupled side-by-side nanorods. When heated by NIR light, the rate of increase for both the temperature of solution and the absorbed light diminished when the volume fraction of suspended nanorods reached a value of 1.24×10−6. This matches with expectations for a partially clustered suspension of nanorods in water. Overall, this study reveals that particle clustering should be considered to accurately gauge the heat generation of the GNR hyperthermia treatments.

Advances in Plasmonic Sensing at the NIR—A Review

“…A linear relationship can be found between aspect ratio and resonant wavelength. The proportional factor found is just a little lower than what is presented in other works, where this factor is estimated to be between 95 and 115 [ 60 , 61 , 62 , 159 , 160 ]. The mismatch can be understood by the surface chemicals present, as in some works, still present significant CTAB concentrations at their surface, or by aggregation factors, which can shift the band, although typically to higher wavelengths, it presents a poorly defined behavior.…”

Photothermal conversion of SiO2@Au nanoparticles mediated by surface morphology of gold cluster layer

“…13 The coupling and aggregation effects of the particles affect the distribution of the temperature eld and the photothermal property of the whole dispersion system. 27 From a practical point of view, designing and preparing nanoparticle arrays (clusters) with strong interaction are very important for studying plasmon congurations. There have been many studies on tunable LSPR by varying the gap and size of AuNPs.…”

Hydroxyethyl Starch-Based Functionalization of Gold Nanorods: A Possible Alternative to Polyethylene Glycol as a Surface Modifier

“…The "absorption maxima" in longitudinal plasmon resonance of AuNRs was measured 804 nm in UVvisible spectrophotometry, whereas 527 nm of maximum absorption was found in transverse plasmon resonance mode. The gold nanorods prepared at the NIR region have potential applications in photothermal ablation of cancer cells, where they strongly absorb NIR light and generate heat upon excitation thereby resulting in a selective heating of the tumor cells [40][41][42]. The optical image and UV spectra of synthesized AuNRs with 804 nm are shown in Figure S2 and Figure 3(c), respectively.…”