Physical Properties of Different Gold Nanoparticles: Ultraviolet-Visible an Fluorescence Measurements

Journal Article

Ghannam, Mohamed Anwar K Abdelhalim, Mohsen M. Mady and Magdy M. . 2012

• Publication Work Type: Research Work
• Magazine \ Newspaper: J Nanomed Nanotechol
• Issue Number: 3
• Volume Number: 3(3)
• Pages: 133-137.

Publication Abstract

Background: The light absorption and emission characteristics of Gold Nanoparticles (GNPs) are exploited in
detection and treatment of cancer. The properties of Nanoparticles (NPs) give them high potential for use in various
medical applications, particularly in diagnostics and therapy where they promise increased sensitivity, speed, and costeffectiveness.
The Ultraviolet-Visible and fluorescence properties of non-functionalized GNPs have not thus far been
comprehensively documented. This study evaluated the absorption and fluorescence spectra for solutions of GNPs at
different concentrations.
Methods: The mean sizes of these GNPs were calculated from Transmission Electron Microscope (TEM) images,
which were also used to study the morphology of the GNPs. UV–Visible and fluorescence measurements, were made
from 250-700 nm using 1 cm quartz cuvettes.
Results: When the GNP size changed from 10 nm to 50 nm, the maximum extinction of the Surface Plasmon Band
(SPB) shifted from 517 nm to 532 nm in the visible region which may be attributed to the surface plasmon oscillation
of free electrons. At constant GNP size, the absorbance was found to be proportional to the concentration of gold.
This is because an increased number of GNPs also increases the total surface for surface plasmon resonance. The
Photoluminescence (PL) band centre appears at 423 nm. An increase in fluorescence intensity with increase in GNP
size was observed. At a fixed GNP size of 10 nm, and with increasing GNP concentration, the intensity of the emission
band increased, which was consistent with the changes observed for the surface plasmon band of GNPs.
Conclusions: The absorption intensity and maxima are particle size dependent. The surface plasmon resonance
of the gold particles is red shifted (from 517 to 532 nm) with increasing particle size. These results indicate that the
fluorescence intensity and the absorption band of GNPs were concentration and particle size dependent.