A5047017018- Geological and Geochemical Analysis
- Clay minerals and soil interactions
- Geology and Paleoclimatology Research
- Geochemistry and Elemental Analysis
- Iron oxide chemistry and applications
- Geomagnetism and Paleomagnetism Studies
- Electrocatalysts for Energy Conversion
- Radioactive element chemistry and processing
- Crystal Structures and Properties
- Mine drainage and remediation techniques
- Paleontology and Stratigraphy of Fossils
- CO2 Reduction Techniques and Catalysts
- Geochemistry and Geologic Mapping
- Advanced Thermoelectric Materials and Devices
- Planetary Science and Exploration
- Mineralogy and Gemology Studies
- Nanoporous metals and alloys
- High-pressure geophysics and materials
- Intermetallics and Advanced Alloy Properties
- Calcium Carbonate Crystallization and Inhibition
- Advanced Cellulose Research Studies
- Heavy metals in environment
- Arsenic contamination and mitigation
- Hydrocarbon exploration and reservoir analysis
- Electron and X-Ray Spectroscopy Techniques
Johns Hopkins University
2016-2025
Materials Science & Engineering
2018
Imaging Center
2011-2015
University of Delaware
2009-2010
Institute of Inorganic Methodologies and Plasmas
2009
Planetary Science Institute
2005
Universidad de Granada
2001
Stony Brook University
1981-1987
State University of New York
1981-1987
Electrochemical reduction of CO2, an artificial way carbon recycling, represents one promising solution for energy and environmental sustainability. However, it is challenged by the lack active selective catalysts. Here, we report a two-step synthesis highly dense Cu nanowires as advanced electrocatalysts CO2 reduction. CuO were first grown oxidation mesh in air then reduced either annealing presence hydrogen or applying cathodic electrochemical potential to produce nanowires. The two...
Arsenite (AsIII) oxidation by manganese oxides (Mn-oxides) serves to detoxify and, under many conditions, immobilize arsenic (As) forming arsenate (AsV). AsIII MnIV-oxides can be quite complex, involving simultaneous forward reactions and subsequent back reactions. During Mn-oxides, a reduction in rate is often observed, which attributed Mn-oxide surface passivation. X-ray absorption spectroscopy (XAS) diffraction (XRD) data show that MnII sorption on poorly crystalline hexagonal birnessite...
• The nickel (Ni) hyperaccumulator Alyssum murale has been developed as a commercial crop for phytoremediation/phytomining Ni from metal-enriched soils. Here, metal co-tolerance, accumulation and localization were investigated A. exposed to co-contaminants. was irrigated with Ni-enriched nutrient solutions containing basal or elevated concentrations of cobalt (Co) zinc (Zn). Metal elemental associations in situ synchrotron X-ray microfluorescence (SXRF) computed-microtomography (CMT)....
Abstract Recent advances in oxygen reduction reaction catalysis for proton exchange membrane fuel cells (PEMFCs) include i) the use of electrochemical dealloying to produce high surface area and sometimes nanoporous catalysts with a Pt‐enriched outer surface, ii) observation that materials can be potentially enhanced by confinement effects, particularly if chemical environment within pores bias toward completion. Here, these are combined incorporating hydrophobic, protic ionic liquid,...
Bimetallic reductants are frequently more reactive toward organohalides than unamended iron and can also alter product distributions, yet a molecular-level explanation for these phenomena remains elusive. In this study, surface characterization of six iron-based bimetallic (Au/Fe, Co/Fe, Cu/Fe, Ni/Fe, Pd/Fe, Pt/Fe) revealed that displacement plating produced non-uniform overlayer metallic additive on iron. Batch studies demonstrated not all additives enhanced rates 1,1,1-trichloroethane...
We report on Cu nanowires as highly active and selective catalysts for electroreduction of CO at low overpotentials. The were synthesized by reducing pregrown CuO nanowires, with the surface structures tailored tuning reduction conditions improved catalytic performance. optimized achieved 65% faradaic efficiency (FE) 50% FE toward production ethanol potentials more positive than −0.5 V (versus reversible hydrogen electrode, RHE). Structural analyses computational simulations suggest that...
The surface of a polysulfone membrane was modified with bioinspired polydopamine (PDA) film followed by the in situ formation silver nanoparticles (AgNPs) to mitigate biofouling. PDA modification enhanced membrane's bacterial anti-adhesive properties increasing hydrophilicity, while AgNPs imparted strong antimicrobial membrane. could be generated on simply exposing AgNO3 solutions. Ag+ ions were reduced catechol groups PDA; AgNP mass loading increased exposure time, and firmly immobilized...
Recent developments of copper (Cu)-based nanomaterials have enabled the electroreduction CO2 at low overpotentials. The mechanism low-overpotential reduction on these nanocatalysts, however, largely remains elusive. We report here a systematic investigation highly dense Cu nanowires, with focus placed understanding surface structure effects formation *CO (* denotes an adsorption site catalyst surface) and evolution gas-phase CO product (CO(g)) overpotentials (more positive than −0.5 V)....
The synthesis of alloys with long-range atomic-scale ordering (ordered intermetallics) is an emerging field nanochemistry. Ordered intermetallic nanoparticles are useful for a wide variety applications such as catalysis, superconductors, and magnetic devices. However, the preparation nanostructured ordered intermetallics challenging in comparison to disordered alloys, hindering progress material development. Herein, we report process converting colloidally synthesized PdBi2 Pd3Bi under...
Argon ion milling is the conventional means by which mineral sections are thinned to electron transparency for transmission microscope (TEM) analysis, but this technique exhibits significant shortcomings. In particular, selective thinning and imaging of submicrometer inclusions during sample highly problematic. We have achieved successful results using focused beam (FIB) lift-out technique, utilizes a 30 kV Ga+ extract transparent specimens with nanometer scale precision. Using procedure, we...
Permeable reactive barriers employing iron as a surface have received extensive attention. A remaining issue, however, relates to their longevity. As an integral part of long-term column study conducted examine the influence inorganic cosolutes on reactivity toward chlorinated solvents and nitroaromatic compounds, Master Builder grains were characterized via scanning transmission electron microscopy, energy loss spectroscopy (EELS), micro-Raman spectroscopy, X-ray diffraction. Prior exposure...
The electrochemistry of dealloying silver/gold alloys in neutral pH silver nitrate solution to form nanoporous gold (NPG) is discussed. At 7, porosity evolution was observed occur at high potentials, above that required for oxygen evolution, and within the nominal domain Pourbaix diagram where would be expected a passivating oxide. Electron microscopy shows small pore NPG formed over potential regime vs normal hydrogen electrode, but electrochemical measurements show specific capacitance...
To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) layered double hydroxide (LDH) phases in soils, we systematically examined presence Al role mineral dissolution during Zn sorption/precipitation on γ-Al(2)O(3) (γ-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder diffraction (SR-XRD), (27)Al solid-state NMR. The...
The Cr(III)-oxidizing capacity of three layered poorly crystalline Mn(IV)O2 phases, i.e. δ-MnO2, Random Stacked Birnessite (RSB), and Acid (AB), was determined in real-time situ, using Quick X-ray Absorption Fine Structure Spectroscopy (Q-XAFS). results obtained with this technique, which allows the measurement total amount Cr(VI) produced system, indicated that Cr(III) oxidation reaction had ceased between 30 min 1 h under most experimental conditions. However, cessation not observed a...
High-temperature superconductivity has a range of applications from sensors to energy distribution. Recent reports this phenomenon in compounds containing electronically active BiS2 layers have the potential open new chapter field superconductivity. Here we report identification and basic properties two ternary Bi-O-S compounds, Bi2OS2 Bi3O2S3. The former is non-superconducting; latter likely explains at T(c) = 4.5 K previously reported "Bi4O4S3". Bi3O2S3 found be sensitive number...
The six week eruption of Eyjafjallajökull volcano in 2010 produced heavy ash fall a sparsely populated area southern and south eastern Iceland disrupted European commercial flights for at least 6 days. We adopted protocol the rapid analysis volcanic particles, purpose informing respiratory health risk assessments. Ash collected from deposits underwent multi-laboratory physicochemical toxicological investigation their mineralogical parameters associated with bio-reactivity, selected vitro...
Abstract Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report observation of structural instability present in pyrochlores A 2 Zr O 6 Oʹ ( = Pr, La) and Yb Ti Oʹ, that exists despite ideal stoichiometry, cation-ordering, absence lone pair effects, a lack magnetic order. Though these materials appear good long-range order, local probes find displacements, order 0.01 nm, within pyrochlore framework....
Dirac material LaCuSb 2 shows anisotropic superconducting response to applied magnetic fields.