Kinetics and Thermodynamics of Au Colloid Monolayer Self-Assembly: Undergraduate Experiments in Surface and Nanomaterials Chemistry

Christine D. Keating , Michael D. Musick , Melinda H. Keefe and Michael J. Natan
The Pennsylvania State University, Department of Chemistry, University Park, PA 16802
J. Chem. Educ., 1999, 76 (7), p 949
DOI: 10.1021/ed076p949
Publication Date (Web): July 1, 1999

Abstract

This paper describes three closely related experiments utilizing colloidal Au nanoparticles to teach basic concepts in physical chemistry. This is done in the context of surface chemistry and nanomaterials synthesis, areas of intense current research interest in both academics and industry. First, students investigate the optical properties and stability of aqueous Au colloidal suspensions, determining the amount of a protein (protein A) necessary to prevent salt-induced flocculation of colloidal Au. Then, the kinetics of Au nanoparticle surface immobilization on silanized glass slides is followed by visible spectrophotometry. Data are fit to a (time)1/2 curve that describes particle diffusion and adsorption from an unstirred solution onto a planar substrate. Finally, the adsorption isotherm data are fit to a Frumkin isotherm, demonstrating the effects of interparticle repulsions upon the thermodynamics of Au particle monolayer formation. Each experiment benefits from the intense visible absorption of colloidal Au particles, allowing all aspects of surface assembly to be monitored using only a spectrophotometer.

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  • Received: August 03, 2009

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