General Areas of Research:
- Nonlinear optical sum frequency, second harmonic generation
- Linear vibrational spectroscopies – Raman, IR reflection
- Surface Potential measurement and methodology
- Liquid surface imaging
- Interfacial structure, dynamics, and chemistry
- Water Surfaces
- Ion pairing and hydration at surfaces
- Surfactant science
- Lipid – binding mechanisms and ion recognition
- 2D molecular organization
- Electric fields at liquid surfaces
- Physical chemistry of liquid interfaces
- Atmospheric aerosol and ocean surface proxy systems
- Biomembranes, hydration, and organization
Patents:
- U.S Patent WO EP US
AUCA ES US10919979B2 Magliery, Sullivan, Allen, Martin, Hitchcock, Alten, Long. 2021 - U.S. Patent WO EP US US11678802B2 Coe, Allen, Hitchcock, Martin. 2023
- U.S. Patent WO US US12025561B2 Allen and Velez. 2024
- International Patent, pub. nu. WO 2020/214661 A1, PCT/US2020/028254 Image Capture / Raman Allen and Velez.
Current Research:
1. Rare Earth Extraction Mechanisms in Confined Interfacial Environments: Separation Science
Rare earth elements (REEs) are critical components for many technologies, yet limited supplies impact technological advancements in myriad areas: electronics, clean energy, space and weapons systems, medicine, and medical technologies. Supply limitations threaten U.S. industries and national security. U.S. mining sites are being considered a possible sources of REEs. The solvent, water or organic/low dielectric phase, and solvation environment in addition to extractant molecular class play key roles in facilitating REE extraction and extraction capacity, and equally important is that the interface is unique in that interfacial transfer can be tuned selectively. We investigate 3 interfacial environments to understand separation mechanisms and thus interfacial binding mechanism(s) and thermodynamic properties of the interfacial extractant-ion-solvent complexes with effects from the solvent(s) and selected co-ions.
2. Controlling Aqueous Interfacial Phenomena of Redox Active Ions (DOE-BES)
The organization of, and induced by, salt environments including redox ions Fe(II) and Fe(III) and at the hydrophobic air /water interface is being explored in our laboratory. Surface acidity, co-anion perturbation, ionic strength, electric fields (inherent and externally applied) and electrode effects, as well as the associated perturbations to hydration and organization to these ion interfacial systems are investigated. For these studies, we employ vibrational sum frequency generation spectroscopy, phase-sensitive second harmonic generation, surface tension and surface potential instrumentation. Expected outcomes of this project also include instrumentation development and advances in surface-sensitive spectroscopy.
3. Nanoplastic-induced molecular-level structural changes at lung alveolar surfaces (Herbert Hoover Foundation)
4. Molecular Recognition in Aqueous Environments
We now have advanced to molecular and, in general, ion recognition with collaborations with Amar Flood at Indiana University and more recently, collaboration with Jovica Badjic at Ohio State. Proteins for example exploit microenvironments of low dielectric constant and partial dehydration. Yet, such biologically inspired environments have rarely been examined in artificial receptors. There is a critical need to understand and discover new recognition modes at bioinspired receptor-water interfaces.