Research areas include the development and application of electron magnetic resonance methods including electron spin echo spectrometry and electron nuclear double resonance to disordered media. Specific projects include paramagnetic probes of microporous and mesoporous oxide surfaces, synthesis and characterization of microporous materials containing transition metal ions in framework and nonframework sites, paramagnetic transition metal species and adsorbate interactions in microporous and mesoporous oxides and their relation to catalytic activity and photoionization processes in oxide materials with built-in electron acceptors as related to light energy storage.
Current research efforts are focused on the following areas:
(1) Electron magnetic resonance methods to measure weak electron-nuclear hyperfine interactions as a geometrical probe in disordered media are being developed. Attention is particularly focused on pulsed, time domain methods involving electron spin echo modulation spectrometry.
(2) Catalytically important paramagnetic transition metal species are being incorporated into microporous molecular materials like aluminosilicates (zeolites) and silicoaluminophosphates (SAPO) and mesoporous MCM-41 and SBA-15 silica tube materials both in ion-exchanged sites and in framework sites to understand the geometrical constraints that control catalytic activity. Adsorbate geometries for the transition metal ion within the molecular sieve interacting with an adsorbate to be catalyzed can be uniquely determined by electron spin echo modulation methods developed in our laboratory.
(3) Electron magnetic resonance and optical studies of the photoionization of solute molecules constrained in microporous and mesoporous oxide materials are being applied to delineate the structural requirements for optimization of charge separation for light energy storage.