Second Harmonic Generation as a Probe of Multisite Adsorption at Solid-Liquid Interfaces of Aqueous Colloid Suspensions

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• 作者：R. Kramer Campen ; De-sheng Zheng ; Hongfei Wang ; Eric Borguet
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：June 28, 2007
• 年：2007
• 卷：111
• 期：25
• 页码：8805 - 8813
• 全文大小：193K
• 年卷期：v.111,no.25(June 28, 2007)
• ISSN：1932-7455

文摘

Chemistry at the surface of solid particles in colloidal dispersions is important in the description of suchdiverse topics as nutrient and contaminant flow in the environment and the creation of better paints andcosmetics. Particles in these systems are often characterized by molecular-level, surface heterogeneity. Thismolecular heterogeneity influences many aspects of the chemical processes of interest, among the simplest ofwhich is physisorption. In this study we construct adsorption isotherms for the triphenylmethane dye MalachiteGreen on various latex particles using the flow through Second Harmonic Generation (ftSHG) technique.This technique makes it possible to construct significantly higher resolution isotherms than conventionalseparation methods. Here we chose both particles that we expect to be chemically homogeneous (plainpolystyrene) and particles whose surface we expect to have molecular level heterogeneity (carboxylated andhydroxylated polystyrene). We find that, using the ftSHG isotherms, we are able to quantify the adsorptionenergies and site densities of multiple adsorption sites on the carboxylated and hydroxylated polystyreneparticles but find only a single type of adsorption site on the plain polystyrene. We expect the ability tomeasure adsorption site energy and density on chemically heterogeneous latex colloids will be useful in thecreation of better biosensors and that the application of ftSHG to other chemically heterogeneous colloidsshould provide insight into a variety of natural and engineered processes.