Thermal diffusivity measurement of spherical gold nanofluids of different sizes/concentrations (original) (raw)
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The European Physical Journal Special Topics, 2008
Dual beam thermal lens technique is used to determine the thermal diffusivity of different solvents in presence of gold nanoparticles. In this technique an Ar + laser (wavelength 514 nm, power 40 mW) and intensity stabilized He-Ne laser were used as the heating source and probe beam respectively. The experimental results showed that thermal diffusivity values of the studied solvents (water, ethanol and ethylene glycol (EG)) were enhanced by the presence of gold nanoparticles.
In this paper, the application of photoflash technique to measuring the thermal diffusivity of gold nanofluids of very low concentration at room temperature was presented. The nanofluid samples were prepared from the pulse laser ablation procedure. The thermal dif-fusivity was obtained by fitting the theoretical temperature signal to the experimental data, and it was found to increase linearly from 1.47 Â 10 À3 cm 2 s À1 to 1.68 Â 10 À3 cm 2 s À1 as the concentration increased from 1.11 mg/L to 3.18 mg/L. The increase in thermal diffu-sivity in these multidispersed nanofluids was attributed to the higher nanoparticle concentration as well as to the increasing presence of the smaller size nanoparticles.
Thermo-optical properties of silver and gold nanofluids
Journal of Thermal Analysis and Calorimetry, 2013
This work focuses on the study of thermal diffusivity and physical properties of nanofluids with very low concentrations of silver or gold nanoparticles. Thermal measurements were performed by means of thermal lens spectroscopy in the dual beam configuration. Improvements of 20 and 16 % in the thermal diffusivity were observed for silver and gold nanofluids, respectively, in comparison with pure water. The estimation of the size distribution of the metallic nanoparticles was obtained through the fitting of the extinction spectra via Mie theory and images of field emission gun scanning electron microscopy.
Measurement of the Optical Properties of Gold Colloids by Photoacoustic Spectroscopy
International Journal of Thermophysics, 2018
The particular features of gold have generated widespread interest for applications in different areas of science and technology. Notably, gold nanoparticles can be prepared with different sizes and forms and can be easily functionalized with a wide range of ligands. Developing effective experimental techniques to characterize such properties is thus important. In this work, photoacoustic spectroscopy was used to explore the relationship between the nanoparticle size and the optical absorption coefficient (at 405 nm and 532 nm) of gold colloid solutions, according to the Beer-Lambert's law. A correlation between this optical parameter and the nanoparticle size was found. In addition, for comparison purposes, conventional UV-visible spectroscopy was used for measuring the absorbance at these two wavelengths. Very good agreement was obtained between the optical properties measured by the two methodologies at 405 nm. However, large discrepancies were obtained when measurements were performed at 532 nm. At the latter wavelength, the extent of radiation dispersion is too large for the Beer-Lambert's law to be valid when the conventional spectroscopy technique is used. Unlike the UV-visible spectroscopy, the photoacoustic method is minimally affected by radiation dispersion effects. Thus, the photoacoustic method presents fewer limitations in that regard in characterizing the optical properties of metallic colloidal suspensions. Keywords Gold nanoparticles • Optical • Photoacoustic • Plasmon This article is part of the selected papers presented at the 19th International Conference on Photoacoustic and Photothermal Phenomena.
The Journal of Physical Chemistry C
Silica-coated gold nanoparticles are commonly employed in biomedical photoacoustic (PA) imaging applications. We investigate theoretically and experimentally the PA signal generation by silica-coated gold nanospheres in water. Our theoretical model considers thermoelastic expansion in the long-pulse illumination regime, and the PA signals are determined based on a semianalytical solution to the thermal diffusion equations and a finite-difference in time domain (FDTD) solution to the thermoelastic equations. Both the influence of interfacial thermal (Kapitza) resistance at the gold-water boundary and the influence of the silica coating on PA signal generation were investigated. Our results indicate that for the nanosecond pulses commonly employed in PA imaging, Kapitza resistance has a negligible effect on photoacoustic signal generation. Moreover, our model shows that the presence of a silica coating causes a reduction in the PA signal amplitude, with the level of signal reduction increasing with thicker silica coating. Our theoretical predictions are qualitatively consistent with our experimental results, where suspensions of in-house-synthesized and commercially available silica-coated gold nanosphere suspensions were excited with nanosecond-pulsed laser illumination at 532 nm. The PA signal amplitudes from silica-coated nanospheres were lower than the signal amplitudes for uncoated gold nanospheres of the same core gold diameter. The amount of reduction of the experimentally PA signal amplitude due to the silica coating was found to increase with thicker silica coating, in agreement with our theoretical predictions.
International Journal of Thermophysics, 2006
Thermal diffusivity measurements are carried out in nanofluids, solutions containing gold nanoparticles (∼ 10-40 nm size), using the mode-mismatched dual-beam thermal lens technique. An Ar+ laser is used as the heating source, and an intensity stabilized He-Ne laser serves as the probe beam. This technique provides a reliable photothermal alternative for measuring thermal diffusivities of nanofluids and semitransparent samples. The characteristic time constant of the transient thermal lens was obtained by fitting the experimental data to the theoretical expression for the transient thermal lens. From this characteristic time, the fluid thermal diffusivity, which increases when the particle sizes increase was obtained. The size of the nanoparticles was obtained from transmission electron microscopy (TEM) analysis.
Thermo-optical properties of gold nanoparticles in colloidal systems
Journal of Optics A: Pure and Applied Optics, 2008
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.
Effect of structural character of gold nanoparticles in nanofluid on heat pipe thermal performance
Materials Letters, 2004
Nanofluid is employed as working medium for conventional circular heat pipe. The nanofluid used in the present study is an aqueous solution of various-sized gold nanoparticles. The thermal resistance of heat pipe with nanofluid or with DI water was measured. The heat pipe was designed as a heat spreader for CPU in a notebook or a desktop PC. At a same charge volume, there is a significant reduction in thermal resistance of heat pipe with nanofluid as compared with DI water. The measured results also show that the thermal resistance of a vertical meshed heat pipe varies with the size of gold nanoparticles. D
Photoacoustic excitation profiles of gold nanoparticles
Photoacoustics, 2014
The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This ''photoacoustic excitation profile'' can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems.