Glenn became interested in mineral structure and crystal chemistry while in graduate school at UCLA where he did Mössbauer, optical spectroscopy and x-ray diffraction on the detailed structure of oxide solid solutions for his thesis (Advisor Wayne Dollase). Arriving at Stanford’s Center for Materials Research in 1978 as staff scientist, he soon started doing some of the first mineralogical synchrotron X-ray absorption spectroscopy at SSRL in collaboration with Gordon Brown. Early studies broke ground in terms of soft-x-ray spectroscopy on the Al, Mg and Na K-edges in glasses and silicate minerals, and the structure of network-modifying ions in silicate melts. Later this work involved arsenate uptake on ferrihydrite and other oxides, for which he is well known, in collaboration with Jim Davis and colleagues at the USGS. These early sorption studies helped to inspire the development of mineral-water interface investigations at the (then new) APS synchrotron, notably at the GSECARS beamlines where Glenn was on the development team, including some of the first surface x-ray scattering measurements of oxide interfaces with water present. Glenn came to LBNL/ESD in 1997, and extended these studies with UHV characterization of solid interfaces, and structure refinements of the wet hematite, corundum and goethite surfaces. More recently, in cooperation with Ron Shen in the physics department at UC Berkeley, Glenn has been using non-linear optical measurements to help describe the hydroxyl and water part of the mineral-water interface. The goal is to create a complete picture of the interface region, including the water structure, as a function of pH and solution chemistry.
The interface work coincides with an interest in natural nanoparticles, the structure of which is often affected by interfacial interactions, and poorly crystalline solids. Together with Jill Banfield, Glenn helped form the Berkeley Nanogeoscience Center in 2005 to study nanoparticle structure, formation, aggregation and transformations. With colleagues Ben Gilbert, Heng Zhang and numerous postdocs and visitors, the center has produced important studies on ZnS, Fe oxide, TiO2, UO2 and several other types of nanoparticles. Work on the structural nature of amorphous carbonate phases and their “solid solutions”, and carbonate nucleation processes, is currently ongoing as part of the ESD EFRC dedicated to carbon sequestration processes.
Glenn has authored or coauthored over 160 publications and his work has been cited more than 5000 times. He is a fellow of the Mineralogical Society of America, is currently chair of the SSRL Scientific Advisory Committee, and sits on several other national and international scientific advisory committees.