Publications by authors named "David P Durkin"

Natural fiber-welded (NFW) biopolymer composites are rapidly garnering industrial and commercial attention in the textile sector, and a recent disclosure demonstrating the production of mesoporous NFW materials suggests a bright future as sorbents, filters, and nanoparticle scaffolds. A significant roadblock in the mass production of mesoporous NFW composites for research and development is their lengthy preparation time: 24 h of water rinses to remove the ionic liquid (IL) serving as a welding medium and then 72 h of solvent exchanges (polar to nonpolar), followed by oven drying to attain a mesoporous composite. In this work, the rinsing procedure is systematically truncated using the solution conductivity as a yardstick to monitor IL removal.

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Seemingly nonporous biopolymer composites prepared by natural fiber welding (NFW) possess latent pores that can be exfoliated by conscientious solvation. We present a seminal demonstration of this concept for cellulose and explore the impact of latent pores on the manufacture and commercialization of NFW products.

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In this work, a series of novel boronium-bis(trifluoromethylsulfonyl)imide [TFSI] ionic liquids (IL) are introduced and investigated. The boronium cations were designed with specific structural motifs that delivered improved electrochemical and physical properties, as evaluated through cyclic voltammetry, broadband dielectric spectroscopy, densitometry, thermogravimetric analysis, and differential scanning calorimetry. Boronium cations, which were appended with -alkylpyrrolidinium substituents, exhibited superior physicochemical properties, including high conductivity, low viscosity, and electrochemical windows surpassing 6 V.

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Peroxides find broad applications for disinfecting environmental pathogens particularly in the COVID-19 pandemic; however, the extensive use of chemical disinfectants can threaten human health and ecosystems. To achieve robust and sustainable disinfection with minimal adverse impacts, we developed Fe single-atom and Fe-Fe double-atom catalysts for activating peroxymonosulfate (PMS). The Fe-Fe double-atom catalyst supported on sulfur-doped graphitic carbon nitride outperformed other catalysts for oxidation, and it activated PMS likely through a nonradical route of catalyst-mediated electron transfer.

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Ion dynamics and charge transport in 1-methyl-3-octylimidazolium ionic liquids with chloride, bromide, tetrafluoroborate, tricyanomethanide, hexafluorophosphate, triflate, tetrachloroaluminate, bis(trifluoromethylsulfonyl)imide, and heptachlorodialuminate anions are investigated by broadband dielectric spectroscopy, rheology, viscometry, and differential scanning calorimetry. A detailed analysis reveals an anion and temperature-dependent separation of characteristic molecular relaxation rates extracted from various representations of the dielectric spectra. The separation in rates extracted from the electric modulus and conductivity formalisms is interpreted as an experimental signature of significant heterogeneity in the local ion dynamics associated with the structural glass transition, viscosity, and dc ion conductivity.

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Graphitic carbon nitride (g-CN) nanomaterials hold great promise in diverse applications; however, their stability in engineering systems and transformation in nature are largely underexplored. We evaluated the stability, aging, and environmental impact of g-CN nanosheets under the attack of free chlorine and reactive chlorine species (RCS), a widely used oxidant/disinfectant and a class of ubiquitous radical species, respectively. g-CN nanosheets were slowly oxidized by free chlorine even at a high concentration of 200-1200 mg L, but they decomposed rapidly when ClO· and/or Cl were the key oxidants.

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The innate immune protection provided by cationic antimicrobial peptides (CAMPs) has been shown to extend to antiviral activity, with putative mechanisms of action including direct interaction with host cells or pathogen membranes. The lack of therapeutics available for the treatment of viruses such as Venezuelan equine encephalitis virus (VEEV) underscores the urgency of novel strategies for antiviral discovery. American alligator plasma has been shown to exhibit strong in vitro antibacterial activity, and functionalized hydrogel particles have been successfully employed for the identification of specific CAMPs from alligator plasma.

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Solar-driven photocatalytic generation of HO over metal-free catalysts is a sustainable approach for value-added chemical production. Here, we synthesized chlorine-doped graphitic carbon nitride (Cl-doped g-CN) through a solvothermal method to effectively produce HO with a rate of 1.19 ± 0.

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All-cellulose xerogel composites were fabricated using a facile, scalable three-step process-(1) partial ionic liquid dissolution, (2) non-solvent rinsing, and (3) drying. The xerogel composites are composed of two phases where the yarn center is non-porous highly crystalline cellulose I surrounded by mesoporous amorphous regenerated cellulose. The composite had high 149 m g Brunauer-Emmett-Teller (BET) surface area with 11.

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Understanding the transformation of graphitic carbon nitride (g-CN) is essential to assess nanomaterial robustness and environmental risks. Using an integrated experimental and simulation approach, our work has demonstrated that the photoinduced hole (h) on g-CN nanosheets significantly enhances nanomaterial decomposition under OH attack. Two g-CN nanosheet samples D and M2 were synthesized, among which M2 had more pores, defects, and edges, and they were subjected to treatments with OH alone and both OH and h.

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We prepared a single-atom Fe catalyst supported on an oxygen-doped, nitrogen-rich carbon support (SAFe-OCN) for degrading a broad spectrum of contaminants of emerging concern (CECs) by activating peroxides such as peroxymonosulfate (PMS). In the SAFe-OCN/PMS system, most selected CECs were amenable to degradation and high-valent Fe species were present for oxidation. Moreover, SAFe-OCN showed excellent performance for contaminant degradation in complex water matrices and high stability in oxidation.

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Airborne transmission of SARS-CoV-2 plays a critical role in spreading COVID-19. To protect public health, we designed and fabricated electrospun nanofibrous air filters that hold promise for applications in personal protective equipment (PPE) and the indoor environment. Due to ultrafine nanofibers (∼300 nm), the electrospun air filters had a much smaller pore size in comparison to the surgical mask and cloth masks (a couple of micrometers versus tens to hundreds of micrometers).

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Photocatalysis holds promise for inactivating environmental pathogens. Visible-light-responsive composites of carbon-doped graphitic carbon nitride and chitosan with high reactivity and processability were fabricated, and they can control pathogenic biofilms for environmental, food, biomedical, and building applications. The broad-spectrum biofilm inhibition and eradication of the photocatalytic composites against Staphylococcus epidermidis, Pseudomonas aeruginosa PAO1, and Escherichia coli O157: H7 under visible light irradiation were demonstrated.

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Carbon nanotubes (CNTs) have unique physical and chemical properties that drive their use in a variety of commercial and industrial applications. CNTs are commonly oxidized prior to their use to enhance dispersion in polar solvents by deliberately grafting oxygen-containing functional groups onto CNT surfaces. In addition, CNT surface oxides can be unintentionally formed or modified after CNTs are released into the environment through exposure to reactive oxygen species and/or ultraviolet irradiation.

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Solar-energy-enabled photocatalysis is promising for sustainable water purification. However, photoreactor design, especially immobilizing nano-sized photocatalysts, remains a major barrier preventing industrial-scale application of photocatalysis. In this study, we immobilized photocatalytic graphitic carbon nitride on chitosan to produce g-CN/chitosan hydrogel beads (GCHBs), and evaluated GCHB photoreactivity for degrading phenol and emerging persistent micropollutants in a 3D printed compound parabolic collector (CPC) reactor.

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Commercially available lumber, pressure-treated with micronized copper azole (MCA), has largely replaced other inorganic biocides for residential wood treatment in the USA, yet little is known about how different outdoor environmental conditions impact the release of ionic, nano-scale, or larger (micron-scale) copper from this product. Therefore, we weathered pressure treated lumber for 18 months in five different climates across the continental United States. Copper release was quantified every month and local weather conditions were recorded continuously to determine the extent to which local climate regulated the release of copper from this nano-enabled product during its use phase.

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Novel Pd-based catalysts (i.e., Pd and Pd-Cu) supported on graphitic carbon nitride (g-CN) were prepared for nitrite and nitrate hydrogenation.

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Graphitic carbon nitride (g-CN) has recently emerged as a promising visible-light-responsive polymeric photocatalyst; however, a molecular-level understanding of material properties and its application for water purification were underexplored. In this study, we rationally designed nonmetal doped, supramolecule-based g-CN with improved surface area and charge separation. Density functional theory (DFT) simulations indicated that carbon-doped g-CN showed a thermodynamically stable structure, promoted charge separation, and had suitable energy levels of conduction and valence bands for photocatalytic oxidation compared to phosphorus-doped g-CN.

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We report a facile synthesis method for carbon nanofiber (CNF) supported Pd catalysts via one-pot electrospinning and their application for nitrite hydrogenation. A mixture of Pd acetylacetonate (Pd(acac)2), polyacrylonitrile (PAN), and nonfunctionalized multiwalled carbon nanotubes (MWCNTs) was electrospun and thermally treated to produce Pd/CNF-MWCNT catalysts. The addition of MWCNTs with a mass loading of 1.

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