Thermal diffusion and Soret feedback of gold-doped polyorganosiloxane nanospheres in toluene

Abstract

We have investigated diffusion and thermal diffusion properties of light-absorbing colloidal polyorganosiloxane microgels containing tiny nanometer-sized gold clusters dispersed in toluene. Transient holographic gratings allow for very subtle perturbations in the linear regime where Soret feedback is negligible. Gold-doped colloids of different size and crosslink ratios show different Soret coefficients but identical thermal diffusion coefficients D(T). Undoped colloids tend to aggregate, but a consistent interpretation is obtained if an identical D(T) is assumed for the doped, the undoped, and the aggregated particles. Previously reported Soret feedback measurements on similar systems incidentally yielded comparable Soret coefficients. We show, however, that they suffer from strong convective perturbations.

Thermal nonlinear refraction properties of Ag2S semiconductor nanocrystals with its application as a low power optical limiter

“…It seems laser light scattering may also play major contributions in limiting response of nanoparticle colloidal systems. However, as side effects, light absorption by the nanoparticles may cause local heating, thermal diffusion and convection [51,52]. Our results show that the nonlinear self defocusing and the self phase modulation effects play important roles in strong optical limiting performance of the silver sulfide nanoparticles dispersed in the DMSO.…”

Thermomagnetic convection of magnetic fluids in a cylindrical geometry

“…Also different convection patterns can be expected with the presence of a vertical temperature gradient. In order to come to a correct statement about the contribution of mass and thermal diffusion to the diffraction patterns in magnetic fluids, spatial temperature measurements and independent measurements of all relevant material parameters as in [12,13] for an organic dispersion are highly desirable. …”

“…An analysis of the physical quantities reveals that both characteristic time scales are several orders of magnitude apart (below and [11]). Direct spatial temperature measurements [12] and independent measurements of all relevant material parameters for organic dispersions [13] showed that the ring pattern is essentially caused by the temperature contribution and not by the concentration contribution.…”

“…Presently there is no sound theoretical description for the dependence of the size of the outmost of the concentric rings on the laser power (see Fig. 2 in [13]). …”

Aging of the nonlinear optical susceptibility in doped colloidal suspensions

“…At the microscopic level, the observed data can be interpreted by taking into account the so-called Ludwig-Soret effect, [24][25][26] i. e., the Laponite platelet concentration ͑c͒ gradient induced by the presence of a temperature gradient. Specifically, as the value of ٌc depends, at fixed ٌT, 27 on mass self-diffusion coefficient, in turn, strongly related to the aging time, we expect a waiting time dependence of ٌc.…”