A5062079922- Geochemistry and Elemental Analysis
- Clay minerals and soil interactions
- Iron oxide chemistry and applications
- Radioactive element chemistry and processing
- Geological and Geochemical Analysis
- Groundwater and Isotope Geochemistry
- Paleontology and Stratigraphy of Fossils
- Enzyme Structure and Function
- Enzyme Production and Characterization
- Chemical Synthesis and Characterization
- Minerals Flotation and Separation Techniques
- Soil and Unsaturated Flow
- Glass properties and applications
- Crystal Structures and Properties
- Metal Extraction and Bioleaching
- Extraction and Separation Processes
- Methane Hydrates and Related Phenomena
- X-ray Diffraction in Crystallography
- Nuclear materials and radiation effects
- Geochemistry and Geologic Mapping
- Electrochemical Analysis and Applications
- Calcium Carbonate Crystallization and Inhibition
- Recycling and Waste Management Techniques
- Zeolite Catalysis and Synthesis
- Supercapacitor Materials and Fabrication
Kangwon National University
2016-2025
Lawrence Berkeley National Laboratory
2008-2015
Sandia National Laboratories
2013-2014
Pennsylvania State University
2004-2013
University of Arizona
2004
Seoul National University
2004
2D nanomaterials have been found to show surface‐dominant phenomena and understanding this behavior is crucial for establishing a relationship between material's structure its properties. Here, the transition of molybdenum disulfide (MoS 2 ) from diffusion‐controlled intercalation an emergent surface redox capacitive demonstrated. The ultrafast pseudocapacitive MoS becomes more prominent when layered downscaled into nanometric sheets hybridized with reduced graphene oxide (RGO). This...
Quantum mechanical calculations were applied to resolve controversies about phosphate surface complexes on iron hydroxides. Six possible modeled: deprotonated, monoprotonated, and diprotonated versions of bridging bidentate monodentate complexes. The calculated frequencies compared experimental IR frequency data (Persson et al. J. Colloid Interface Sci. 1996, 177, 263−275; Arai Sparks 2001, 241, 317−326.). This study suggests that the change depending pH. Four species are a complex at pH...
Extracellular polymeric substances (EPS) constitute a heterogeneous mixture of polyelectrolytes that mediate biomineralization and bacterial adhesion stabilize biofilm matrixes in natural artificial environments. Although nucleic acids are exuded extracellularly purported to be required for formation, direct evidence the active mechanism is lacking. EPS were extracted from both Bacillus subtilis (a gram-positive bacterium) Pseudomonas aeruginosa gram-negative their interaction with goethite...
Summary Hybrid molecular orbital/density functional theory (MO/DFT) calculations on clusters were used to model infrared (IR) vibrational frequencies and interatomic distances obtained via extended X‐ray absorption fine structure (EXAFS) spectroscopy. Molecular found provide good agreement with experimental observations for the oxyanions carbonate, phosphate, sulphate, arsenate arsenite. The results show a consistent tendency form bidentate bridging surface complexes at low pH, but...
Enhanced photoconductivity of layered Mn(IV)O2 containing protonated Mn(IV) vacancy defects has been recently demonstrated, suggesting new technological possibilities for photoelectric conversion based on visible light harvesting. Using spin-polarized density functional theory, we provide the first direct evidence that such can indeed facilitate by (i) reducing band-gap energy and (ii) separating electron hole states. Our results thus support proposition nanosheet MnO2 offers an attractive...
Understanding of dissolution processes borosilicate glasses can shed light on mechanisms degradation nuclear waste forms. We have simulated structure sodium glass using classical molecular dynamics and calculated reaction barriers for hydrolysis reactions the surface density functional theory. The results indicate that in acidic conditions B ‐ O S i bridges are greatly reduced compared with neutral basic conditions. suggest considerably lower than i‐ conditions, but less so Our at initial...
Interaction of phosphate with the surfaces clays and metal oxyhydroxides is important for nutrient cycling in natural agricultural systems. We examined specific adsorption to boehmite (γ-AlOOH) by solid-state 31P NMR spectroscopy, which yields evidence presence two bridging bidentate surface complexes differing protonation. For samples prepared along sorption isotherm at pH 5, distinct environments are observed as major peaks spectra (chemical shifts 0 −6 ppm) that show little change...
Mackinawite is a naturally-occurring layer type FeS mineral well-known to be important in biogeochemical cycles and, more recently, the development of microbial fuel cells. Conflicting results have been published as magnetic properties this mineral, with M\"ossbauer spectroscopy indicating no ordering and density functional theory predicting an antiferromagnetic ground state, similar Fe-based high-temperature superconductors which it isostructural for known that magnetism suppressed by...
Korea has been operating groundwater monitoring systems since 1996 as the Groundwater Act enacted in 1994 enforces nationwide monitoring. Currently, there are six main networks operated by different government ministries with purposes: National Monitoring Network (NGMN), Quality (GQMN), Seawater Intrusion (SIMN), Rural (RGMN), Subsidiary (SGMN), and Drinking Water (DWMN). The Networks have a total of over 3500 wells majority them now equipped automatic data loggers remote terminal units....
The ability to predict coupled kinetic reactions of arsenic (As) that occur at the manganese oxide–aqueous solution interface is crucial for management and remediation As-contaminated sites worldwide. A quantitative understanding coupling between As oxidation adsorption/desorption kinetics will enable us more accurately behavior As. In this study, we developed a novel model adsorption/desorption/oxidation on δ-MnO2. As(III) adsorption δ-MnO2 was studied using stirred-flow method under...
Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to investigate dextran adsorption alumina and silica. Sensitive measurements combined determination of nanometer-scale polymer conformations demonstrate the utility this technique for studying biopolymer adsorption. The adsorbed amounts polymeric structures were determined on Al2O3 SiO2 by real-time resonance frequency energy changes (Δf ΔD). After sample rinsed, apparent mass retained 83 ng/cm2 surface 9 silica based...
Six possible complexes of glyphosate (O-PO(OH)-CH2NH2+CH2CO2H) with an Fe-hydroxide dimer were modeled hybrid molecular orbital/density functional theory calculations to establish the nature bonds on goethite (alpha-FeOOH). Monodentate and bidentate coordination phosphonate moiety considered, using three forms molecule appropriate for different pH ranges: both amino moieties protonated, unprotonated phosphonates, phosphonates no hydrogen ion group. The calculated infrared vibrational modes...
Describing the reactions that occur at glass–water interface and control development of altered layer constitutes one main scientific challenges impeding existing models from providing accurate radionuclide release estimates. Radionuclide estimates are a critical component safety basis for geologic repositories. The (i.e., amorphous hydrated surface crystalline reaction products) represents complex region, both physically chemically, sandwiched between two distinct boundaries—pristine glass...