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1. Predicting kinetics of water-rich permeate flux through photocatalytic mesh under visible light illumination

   https://doi.org/10.1038/s41598-021-00607-w  

   Shrestha, Bishwash ; Ezazi, Mohammadamin ; Rad, Seyed Vahid ; Kwon, Gibum ( October 2021 , Scientific Reports)

   Membrane-based separation technologies are attractive to remediating unconventional water sources, including brackish, industrial, and municipal wastewater, due to their versatility and relatively high energy efficiency. However, membrane fouling by dissolved or suspended organic substances remains a primary challenge which can result in an irreversible decline of the permeate flux. To overcome this, membranes have been incorporated with photocatalytic materials that can degrade these organic substances deposited on the surface upon light illumination. While such photocatalytic membranes have demonstrated that they can recover their inherent permeability, less information is known about the effect of photocatalysis on the kinetics of the permeate flux. In this work, a photocatalytic mesh that can selectively permeate water while repelling oil was fabricated by coating a mixture of nitrogen-doped TiO₂(N-TiO₂) and perfluorosilane-grafted SiO₂(F-SiO₂) nanoparticles on a stainless steel mesh. Utilizing the photocatalytic mesh, the time-dependent evolution of the water-rich permeate flux as a result of photocatalytic degradation of the oil was studied under the visible light illumination. A mathematical model was developed that can relate the photocatalytic degradation of the organic substances deposited on a mesh surface to the evolution of the permeate flux. This model was established by integrating the Langmuir–Hinshelwood kinetics for photocatalysismore »and the Cassie–Baxter wettability analysis on a chemically heterogeneous mesh surface into a permeate flux relation. Consequently, the time-dependent water-rich permeate flux values are compared with those predicted by using the model. It is found that the model can predict the evolution of the water-rich permeate flux with a goodness of fit of 0.92.

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2. Experimental–theoretical study of laccase as a detoxifier of aflatoxins

   https://doi.org/10.1038/s41598-023-27519-1  

   Zaccaria, Marco ; Dawson, William ; Russel Kish, Darius ; Reverberi, Massimo ; Bonaccorsi di Patti, Maria Carmela ; Domin, Marek ; Cristiglio, Viviana ; Chan, Bun ; Dellafiora, Luca ; Gabel, Frank ; et al ( January 2023 , Scientific Reports)

   We investigate laccase-mediated detoxification of aflatoxins, fungal carcinogenic food contaminants. Our experimental comparison between two aflatoxins with similar structures (AFB₁and AFG₂) shows significant differences in laccase-mediated detoxification. A multi-scale modeling approach (Docking, Molecular Dynamics, and Density Functional Theory) identifies the highly substrate-specific changes required to improve laccase detoxifying performance. We employ a large-scale density functional theory-based approach, involving more than 7000 atoms, to identify the amino acid residues that determine the affinity of laccase for aflatoxins. From this study we conclude: (1) AFB₁is more challenging to degrade, to the point of complete degradation stalling; (2) AFG₂is easier to degrade by laccase due to its lack of side products and favorable binding dynamics; and (3) ample opportunities to optimize laccase for aflatoxin degradation exist, especially via mutations leading to π–π stacking. This study identifies a way to optimize laccase for aflatoxin bioremediation and, more generally, contributes to the research efforts aimed at rational enzyme optimization.
3. Iodine binding with thiophene and furan based dyes for DSCs

   https://doi.org/10.1039/c8cp03065k  

   Baumann, Alexandra ; Cheema, Hammad ; Sabuj, Md Abdus ; McNamara, Louis E. ; Zhang, Yanbing ; Peddapuram, Adithya ; Nguyen, Suong T. ; Watkins, Davita L. ; Hammer, Nathan I. ; Rai, Neeraj ; et al ( January 2018 , Physical Chemistry Chemical Physics)

   Iodine binding to thiophene rings in dyes for dye-sensitized solar cells (DSCs) has been hypothesized to be performance degrading in a number of literature cases. Binding of iodine to dyes near the semiconductor surface can promote undesirable electron transfers and lower the overall efficiency of devices. Six thiophene or furan containing dye analogs were synthesized to analyze iodine binding to the dyes via Raman spectroscopy, UV-Vis studies, device performance metrics and density functional theory (DFT) based computations. Evidence suggests I 2 binds thiophene-based dyes stronger than furan-based dyes. This leads to higher DSC device currents and voltages from furan analogues, and longer electron lifetimes in DSC devices using furan based dyes. Raman spectrum of the TiO 2 surface-bound dyes reveals additional and more instense peaks for thiophene dyes in the presence of I 2 relative to no I 2 . Additionally, broader and shifted UV-Vis peaks are observed for thiophene dyes in the presence of I 2 on TiO 2 films suggesting significant interaction between the dye molecules and I 2 . These observations are also supported by DFT and TD-DFT calculations which indicate the absence of a key geometric energy minimum in the dye–I 2 ground state for furanmore »dyes which are readily observed for the thiophene based analogues.« less
4. Guanine–adenine interactions in DNA tetranucleotide cation radicals revealed by UV/vis photodissociation action spectroscopy and theory

   https://doi.org/10.1039/d0cp02362k  

   Liu, Yue ; Huang, Shu R. ; Tureček, František ( July 2020 , Physical Chemistry Chemical Physics)

   Hydrogen-rich cation radicals (GATT + 2H) + ˙ and (AGTT + 2H) + ˙ represent oligonucleotide models of charged hydrogen atom adducts to DNA. These tetranucleotide cation radicals were generated in the gas phase by one-electron reduction of the respective (GATT + 2H) 2+ and (AGTT + 2H) 2+ dications in which the charging protons were placed on the guanine and adenine nucleobases. We used wavelength-dependent UV/Vis photodissociation in the valence-electron excitation region of 210–700 nm to produce action spectra of (GATT + 2H) + ˙ and (AGTT + 2H) + ˙ that showed radical-associated absorption bands in the near-UV (330 nm) and visible (400–440 nm) regions. Born–Oppenheimer molecular dynamics and density-functional theory calculations were used to obtain and rank by energy multiple (GATT + 2H) dication and cation-radical structures. Time-dependent density functional theory (TD-DFT) calculations of excited-state energies and electronic transitions in (GATT + 2H) + ˙ were augmented by vibronic spectra calculations at 310 K for selected low-energy cation radicals to provide a match with the action spectrum. The stable product of one-electron reduction was identified as having a 7,8-dihydroguanine cation radical moiety, formed by intramolecular hydrogen atom migration from adenine N-1–H. The hydrogen migration was calculated tomore »have a transition state with a low activation energy, E a = 96.5 kJ mol −1 , and positive activation entropy, Δ S ‡ = 75 J mol −1 K −1 . This allowed for a fast isomerization of the primary reduction products on the ion-trap time scale of 150 ms that was substantially accelerated by highly exothermic electron transfer.« less
5. In search of tris(trimethylsilylcyclopentadienyl) thorium

   https://doi.org/10.1039/C9DT03674A  

   Wedal, Justin C. ; Bekoe, Samuel ; Ziller, Joseph W. ; Furche, Filipp ; Evans, William J. ( November 2019 , Dalton Transactions)

   Reduction of Cp′ 3 ThCl, Cp′ 3 ThBr, and Cp′ 3 ThI (Cp′ = C 5 H 4 SiMe 3 ) with potassium graphite generates dark blue solutions with reactivity and spectroscopic properties consistent with the formation of Cp′ 3 Th. The EPR and UV-visible spectra of the solutions are similar to those of crystallographically-characterized tris(cyclopentadienyl) Th( iii ) complexes: [C 5 H 3 (SiMe 3 ) 2 ] 3 Th, (C 5 Me 4 H) 3 Th, (C 5 t Bu 2 H 3 ) 3 Th, and (C 5 Me 5 ) 3 Th. Density functional theory (DFT) analysis indicates that the UV-visible spectrum is consistent with Cp′ 3 Th and not [Cp′ 3 ThBr] 1− . Although single crystals of Cp′ 3 Th have not been isolated, the blue solution reacts with Me 3 SiCl, I 2 , and HCCPh to afford products expected from Cp′ 3 Th, namely, Cp′ 3 ThCl, Cp′ 3 ThI, and Cp′ 3 Th(CCPh), respectively. Reactions with MeI give mixtures of Cp′ 3 ThI and Cp′ 3 ThMe. Evidence for further reduction of the blue solutions to a Cp′-ligated Th( ii ) complex has not been observed. The crystal structures of Cp′more »3 ThMe and (Cp′ 3 Th) 2 (μ-O) were also determined as part of these studies.« less