Acquisition of Optical Second Harmonic Generation Instrumentation for the Study of Molecular Adsorption at the Mineral/Water Interface

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9725993 Eggleston This grant provides partial support of the costs of acquiring components to develop optical second harmonic generation (SHG) instrumentation to study molecular structure of adsorbed organic molecules on mineral surfaces. Coupled with the existing scanning probe microscope (EAR-9634143) at the University of Wyoming, this technique could yield unprecedented information on the orientation of adsorbed organics on mineral surfaces with single-crystal face specificity. SHG promises significant advantages over other analytical techniques for the analysis of molecular structure at mineral-fluid interfaces (i.e. X-ray absorption spectroscopy and Fourier transform infrared spectroscopy), the most important being that is useable in situ, at atmospheric pressure, and on non-powdered samples. Knowledge of the atomic-scale structure of fluid-rock geochemical interactions is fundamental to studies of mineral dissolution/growth and the fate of environmental pollutants. Therefore, analytical advances in mineral surface chemistry are at the frontier of our understanding of problems of pressing environmental significance. To that end, development of SHG should advance our knowledge of the pH dependency of surface electric fields, molecular adsorption and orientation, and fundamental electron transfer properties of redox centers at mineral surfaces. ***