We show that thermophoresis (particle drift driven by thermal gradients) in aqueous solutions can be measured by using an all-optical thermal-lensing setup, where a temperature gradient is set by a near-infrared laser beam with no need of light-absorbing dyes. After discussing the principles of the method, we study by numerical simulation the nature and extent of parasitic thermal-convection effects, and we describe an optical setup designed to limit them. We finally present preliminary results on thermophoresis in micellar solutions and colloidal dispersions.
© 2004 Optical Society of America
(000.6850) General : Thermodynamics
(160.6060) Materials : Solgel
(190.4870) Nonlinear optics : Photothermal effects
(220.4830) Optical design and fabrication : Systems design
(350.6830) Other areas of optics : Thermal lensing
Roberto Rusconi, Lucio Isa, and Roberto Piazza, "Thermal-lensing measurement of particle thermophoresis in aqueous dispersions," J. Opt. Soc. Am. B 21, 605-616 (2004)