Thermo-optical properties of gold nanoparticles in colloidal systems

Abstract

In this work, we report the thermo-optical properties of nanoparticles in colloidal suspensions. Spherical gold nanoparticles obtained by laser ablation in condensed media were characterized using thermal lens spectroscopy pumping at 532 nm with a 10 ns pulse laser-Nd-YAG system. The obtained nanoparticles were stabilized in the time by surfactants (sodium dodecyl sulfate or SDS) in water with different molar concentrations. The morphology and size of the gold nanoparticles were determined by transmission electron microscopy (TEM) and UV-visible techniques. The plasmonic resonance bands in gold nanoparticles are responsible for the light optical absorption, and the positions of the absorption maximum and bandwidth in the UV-visible spectra are given by the morphological characteristics of these systems. The thermo-optical constants such as thermal diffusion, thermal diffusivity, and (dn/dT) are functions of the nanoparticle sizes and the dielectric function of the media. For these reasons, the thermal lens (TL) signal is also dependent on nanoparticle sizes. An analysis of the TL signal of the nanoparticles reveals the existence of an inverse dependence between the thermo-optical functions and the size. This methodology can be used in order to evaluate these systems and characterize nanoparticles in different media. These results are expected to have an impact in bioimaging, biosensors, and other technological applications such as cooling systems.

The extended time evolution size decrease of gold nanoparticles formed by the Turkevich method

“…1 Current research has employed Au NPs for the enhancement of optical properties in semiconductor thin films via composite formation, [2][3][4][5][6][7] the destruction of bacteria, [8][9][10] improvements in detection of cancer 11 and DNA 12 and even single molecule detection via surface enhanced Raman spectroscopy (SERS). 13,14 Several methods have been used to produce Au NPs for example sonolysis, 15 laser ablation, 16,17 protein reduction, 18 CVD 19 and more commonly the Brust-Schiffrin reduction, 20 each with associated implications on the size and shape distribution. The method used in this paper was devised by Turkevich et al, 21 which involves the reduction of an auric acid solution by sodium citrate forming predominantly spherical Au NPs.…”

The effect of initiation method on the size, monodispersity and shape of gold nanoparticles formed by the Turkevich method

“…1 There is an abundance of literature that demonstrate the diversity of Au NPs applications; from the optical property enhancement of composite semiconductor thin-films, [2][3][4][5][6][7] bactericides, [8][9][10] improvements in cancer care through to DNA and single molecule detection. [11][12][13][14] Several methods have been used to initiate colloidal gold formation, such as sonolysis, [15][16][17][18] laser ablation, 19,20 ultra-violet irradiation, [21][22][23][24][25][26][27] microwave assisted heating, [28][29][30][31] thermal heating [32][33][34][35][36][37] and pH mediated synthesis; 38 each with associated implications on particle size and shape. Furthermore, the variety of reductants, surfactants and growth directing media in addition to the diversity of solutions (aqueous, organic and inorganic) in which the colloids are grown is extensive.…”

Therapy with Gold Nanoparticles and Lasers: What Really Kills The Cells?

“…However, this does not happen (Figure 5 The experience obtained by us and other researchers is that low-power 633 -nm laser radiation does not influence cell viability in the presence of spherical GNPs [9-11, [16][17][18]. In addition, several other groups have shown that 633-nm laser radiation does not heat GNPs significantly [19][20][21];…”