Our Research

Our top publications based on synchrotron research demonstrate disciplinary breadth and worldwide impact.

 

“Electrochemical Reduction of CO₂ to CH₃OH at Copper Oxide Surfaces” Flake et al., Journal of the Electrochemical Society (2011) 158, 5, E45-E49

The direct electrochemical conversion of CO₂ to methanol offers a promising pathway for producing liquid fuels such as dimethyl ether and synthetic gasoline, as well as valuable feedstocks for organic synthesis. In this work, Cu L-edge XANES spectra were used to evaluate the performance of cuprous oxide thin films in comparison with air-oxidized and anodized copper electrodes. The results indicate that the cuprous oxide electrodes generate substantially higher methanol yields and efficiencies, suggesting that Cu(I) species play a critical role in enhancing selectivity toward methanol.

“A General Synthesis of Supported Bimetallic Nanoparticles via Surface Inorganometallic Chemistry” Ding, Roy et al., Science (2018) 362, 6414, 560–564

This paper, co-authored by Louisiana Light Source researcher Amitava Roy, appeared in Science and reported a broadly applicable synthesis strategy for bimetallic nanoparticles. Highly impactful for catalysis and materials science communities.

“Selective Electrocatalytic Reduction of CO₂ into CO at Small, Thiol-Capped Au/Cu Nanoparticles” Kauffman et al., The Journal of Physical Chemistry C (2018) 122, 49, 27991-28000

Kauffman’s paper studied the electronic structure and local atomic environment of the Au/Cu nanoparticles with XAS under reaction-relevant conditions, confirming alloy formation and surface bonding characteristics influenced by thiol ligands. The results indicated the Au/Cu nanoparticles enhanced catalytic selectivity, leading to highly efficient conversion of CO₂ to CO with improved activity compared to monometallic counterparts.

“Characterization of Ashes from Waste Biomass Power Plants and Phosphorus Recovery” Stegemann et al., Science of the Total Environment (2019) 690, November 10, 573-583

The collaborative work determined the speciation and local chemical environment of phosphorus and associated metals in meat and bone meal and poultry litter ashes. XRD and XAS analyses revealed that phosphorus is primarily bound within stable mineral phases (e.g., with Ca, Fe, or Al), which affects its recoverability and highlights the conditions necessary for efficient phosphorus extraction and bioavailability.

“CoCrFeNi High-Entropy Alloy as an Enhanced Hydrogen Evolution Catalyst in an Acidic Solution” Xu et al., The Journal of Physical Chemistry C (2021) 125, 31, 17008−17018

XAS and XPS techniques were performed to analyze the oxidation states and local chemical environment of elements in the CoCrFeNi high-entropy alloy, revealing how the surface oxidation changes under reaction conditions. The results showed that Ni sites remain least oxidized and a partially oxidized HEA surface is formed under acidic hydrogen evolution reaction conditions, leading to enhanced catalytic activity with low overpotential compared to Pt metal.

“Formation of Environmentally Persistent Free Radical (EPFR) in Iron(III) Cation-Exchanged Smectite Clay” Cook et al., Environmental Science: Processes & Impacts (2016) 18 (1), 42–50

The adsorption mechanism of phenol by iron(III)-exchanged calcium montmorillonite clay was investigated to elucidate the processes responsible for the formation of environmentally persistent free radicals on the clay surface. XAS results revealed that the reduction of Fe(III) to Fe(II) and the presence of iron sites facilitate electron transfer with phenol, leading to the generation and stabilization of these radicals.

“Solvent-Free Depolymerization of Plastic Waste Enabled by Plastic-Catalyst Interfacial Engineering” Ding et al., Angewandte Chemie International Edition (2023) 62, 46, e202309949

Ding’s group discovered that constructing plastic–catalyst solid–solid interfaces enables solvent-free depolymerization of polyethylene terephthalate via vapor-phase methanolysis at relatively low temperatures. A zinc catalyst introduced through electrostatic adsorption effectively catalyzes the process, and CAMD’s XAS beamline was used to probe the catalyst’s surface structure and interfacial interactions.

“Adsorption and Catalytic Activity of Gold Nanoparticles in Mesoporous Silica: Effect of Pore Size and Dispersion Salinity” Ma et al., The Journal of Physical Chemistry B (2022) 126, 5, 2531–2541

SAXS results showed charged gold nanoparticles are absorbed inside porous surface-modified silica particles. Depending on the pore size and salinity, different arrangements of the NP are found. The filling of the pores affects the catalytic rate of a model reaction with the largest pores as most active.

“Lead Uptake in Diverse Plant Families: A Study Applying X‑ray Absorption Near Edge Spectroscopy” Hormes et al., Environmental Science & Technology (2013) 47, 9, 4375-4382

The study used synchrotron-based Pb L₃-edge X-ray Absorption Near Edge Spectroscopy (XANES) to examine how lead is taken up and chemically speciated in different plant families and a lichen. The group observed that lead enters plant roots through the outer apoplast as either Pb²⁺(aq) or Pb₄(OH)₄⁴⁺(aq), depending on soil pH and lead concentration. The Pb L₃-edge XANES spectra of dried and fresh plant samples were nearly identical, indicating that sorption remained unaffected by water removal and was influenced primarily by the initial ionic strength. No evidence of bonding to biologically important groups (–S, –N) or precipitation as phosphate (–PO₄) was observed.

“Electronic Signatures of a Model Pollutant–Particle System: Chemisorbed Phenol on TiO₂(110)” Sprunger et al., Langmuir (2015) 31, 13, 3869-3875

Environmentally persistent free radicals (EPFRs) produce reactive oxygen species in aqueous environments, and their introduction into living tissues can induce oxidative stress, cell death, and heightened vulnerability to viral infections. Understanding the fundamental mechanisms governing EPFR formation is therefore crucial for elucidating their environmental toxicity and developing effective remediation strategies. Sprunger’s group utilized photoelectron spectroscopy and electron energy loss spectroscopy on a well-defined model system—phenol chemisorbed on TiO₂(110)—to directly monitor changes in the electronic structure of both the oxide and the adsorbed phenol as a function of adsorption temperature. The results provide strong evidence that high-temperature exposure leads to filling of empty states in TiO₂ and depopulation of the phenol HOMO, consistent with the conceptual model proposed for EPFR formation.

“A Noble-Transition Alloy Excels at Hot-Carrier Generation in the Near Infrared” McPeak et al., Advanced Materials (2020) 32, 23, 1906478, 1-8

Materials capable of efficient hot-carrier generation and transport in the near-infrared (NIR) can revolutionize semiconductor technologies and advance NIR optoelectronic devices. Alloys, unlike pure metals, exhibit emergent properties that enable new design strategies. LSU’s Chemical Engineering Professor McPeak and his collaborators demonstrate that a noble-transition alloy, AuₓPd₁₋ₓ, outperforms its constituent metals in both hot-carrier generation and lifetime under NIR excitation, owing to hybridized Au–Pd d-bands near the Fermi level. Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements at Louisiana Light Source revealed the nature of these hybridized states. These results highlight noble-transition alloys as promising materials for efficient, long-lived NIR hot-carrier applications.

“Acetaminophen Interactions with Phospholipid Vesicles Induced Changes in Morphology and Lipid Dynamics” De Mel et al., Langmuir (2021) 37, 31, 9560–9570

In this work, SAXS measurements found the medically relevant acetaminophen assembles inside the hydrophobic part of the bilayer of phospholipid vesicles, which act as a cell membrane model system. This results in reduced membrane rigidity as proven by NSE and a deformed shape, as observed by cryo-TEM.

“Three-Dimensional Chemical Analysis with Synchrotron Tomography at Multiple X-ray Energies: Brominated Aromatic Flame Retardant and Antimony Oxide in Polystyrene” Ham, Butler et al., Chemistry of Materials (2004) 16, 21, 4032–4042

This paper demonstrated synchrotron X-ray tomography at multiple energies to determine 3D chemical distributions of brominated flame retardants and antimony oxide in polystyrene, establishing Louisiana Light Source’s multi-energy CT methodology that has been applied across materials science and environmental chemistry.

“Non-destructive Evaluation of Additively Manufactured Polymer Objects Using X-ray Interferometry” Kio, et al., Additive Manufacturing (2018) 24, 364-372

This paper, co-authored by Louisiana Light Source’s Kyungmin Ham, demonstrated X-ray interferometry to examine 3D printed objects’ defects. X-ray interferometry provides a dark-field image, essentially a small-angle X-ray scattering image, of the voids and print defects in an additively manufactured polymer object. The interferometers used were tuned to scattering length 2-5 μm and configured to measure scattering along both vertical and horizontal directions. The dark-field projection images show orientation-dependent X-ray scattering due to anisotropic voids and gaps at the filament-to-filament interface in fused-deposition-modeling additive manufacturing objects. The absorption and dark-field volumes are used to correlate printhead trajectory with print defect density.

“Synchrotron X-ray Tomography for 3D Chemical Distribution Measurement of a Flame Retardant and Synergist in a Fiberglass-Reinforced Polymer Blend” Butler et al., The Journal of Physical Chemistry B (2010) 114, 1, 2–9

This work extended synchrotron X-ray tomography to measure 3D chemical distributions of flame retardants and synergists in fiberglass-reinforced polymer blends, demonstrating industrial materials characterization with direct relevance to fire-safety engineering.

“Calcium X-ray Absorption Near Edge Structure (XANES) Spectra: A Thermometer for the Firing Temperature of Ceramics?” Hormes et al., Microchemical Journal (2020) Volume 154, May, 104571

This paper investigated whether calcium X-ray Absorption Near Edge Structure (XANES) spectra can serve as a “thermometer” to estimate the firing temperature of clays from the UNESCO World Heritage Site of Poverty Point by analyzing how calcium’s local coordination environment changes upon heating. Synchrotron-based XANES measurements revealed clear, systematic variations in pre-edge and white-line features with increasing firing temperature, providing the first direct evidence supporting the hypothesis that at least some of the Poverty Point objects were used as cooking stones.

“A Process Inspired by Fractals for Embedding Digital Codes into Additively Manufactured Components for Supply Chain Security” Nemati et al., Scientific Reports (2025) 15, 3167

This study, co-authored by Louisiana Light Source’s Kyungmin Ham, describes procedures for embedding digital information into additively manufactured components as well as procedures for readout and tensile testing. X-ray imaging, both conventional and interferometry, was explored to detect the digital information. X-ray interferometry showed increased void detectability, one advantage of loose powder. These results suggest a standard selective laser sintering printer with typical metal powders could reasonably expect to print 100 bits of embedded digital information in a gauge volume 6 mm in diameter as 300 μm voids while still maintaining tensile specifications.