In Situ, Nonlinear Optical Probe of Surfactant Adsorption on the Surface of Microparticles in Colloids

Abstract

The demonstration of a nonlinear optical technique for directly monitoring adsorption of surfactants on the surface of microparticles in colloids is reported. In this approach, dye molecules with strong hyperpolarizability are first adsorbed on the particle surface to give detectable second-harmonic generation. The surfactant is then added to the colloidal solution in competition with dye for adsorption on the surface. The displacement of the dye molecules on the surface results in a decrease of the second-harmonic signal, indicating the adsorption of the surfactant molecules. A continuous flow/titration system in combination with a high-repetition-rate femtosecond laser allows the adsorption to be monitored in real time. This approach was first demonstrated on a methacrylate polymeric surfactant on latex and talc particles in an aqueous solution. The adsorption free energy and surface density of this surfactant on these particles have been determined.

Adsorption and transport of charged vs. neutral hydrophobic molecules at the membrane of murine erythroleukemia (MEL) cells

“…It is noted that the SH response of BCP adsorbing onto a colloidal suspension of talc particles has previously been demonstrated [43]. In the current study, in an attempt to measure the adsorption isotherm, the titration experiment (Fig.…”

“…The experimental setup for measuring the SH signal is similar to that for studying SH light scattering from other colloidal systems; the details of which have been reported previously [17,18,43]. In general, a fast pulsed laser source with a high peak power is necessary for inducing SHG, in which the low pulse energy ensures that laser-induced heating of the sample is kept to a minimum.…”

Генерация Суммарной Частоты От Тонкого Цилиндрического Слоя

“…На практике генерация суммарной частоты (и ее частный случай генерация второй гармоники) применяется для исследо-вания капель воды [1,2], адсорбированных поверхностно активных веществ [3], биополимеров [4], коллоидных объектов [5], мембран биологических клеток [6], моле-кул ДНК [7].…”

Plasmonic enhancement of second harmonic generation on metal coated nanoparticles

“…For centrosymmetric materials SH is generated at the surface of nano-particles, because symmetry is broken at that interface as Wang has demonstrated experimentally for the first time [2]. SHG has been applied to study the surface and buried micro-structure of colloidal nano-particles [3][4][5][6][7][8][9][10][11][12][13] or as probing technique in bio-physical experiments [14][15][16][17][18]. We have used SHG to determine the nonlinear susceptibility ( ) 2 χ of a thin layer of Malachite Green [19], to study the layer of oriented water near polystyrene particles [20] and the organization of polyelectrolyte chains, depending on the salt concentration of the solvent [21].…”