Selective Reduction of CO₂ on Ti₂C(OH)₂ MXene through Spontaneous Crossing of Transition States

Direct reduction of gas-phase CO2 to renewable fuels and chemical feedstock without any external energy source or rare-metal catalyst is one of the foremost challenges. Here, using density functional theory and ab initio molecular dynamics (AIMD) simulations, we predict Ti2C(OH)2 MXene as an efficient electron-coupled proton donor exhibiting simultaneously high reactivity and selectivity for CO2 reduction reaction (CRR) by yielding valuable chemicals, formate, and formic acid. This is caused by CO2 spontaneously crossing the activation barrier involved in the formation of multiple intermediates. Metallic Ti2C(OH)2 contains easily donatable protons on the surface and high-energy electrons near the Fermi level that leads to its high reactivity. High selectivity arises from low activation barrier for CRR as predicted by proposed mechanistic interpretations. Furthermore, H vacancies generated during the product formation can be replenished by exposure to moisture, ensuring the uninterrupted formation of the products. Our study provides a single-step solution for CRR to valuable chemicals without necessitating the expensive electrochemical or low-efficiency photochemical cells and hence is of immense interest for recycling the carbon

New anti-inflammatory triterpene from the root of <i>Ricinus communis</i>

<div><p>Liquid–liquid partitioning of <i>Ricinus communis</i> root methanol extract resulted in enrichment of compounds. Purification of the <i>n</i>-hexane fraction led to the isolation and characterisation of two triterpenes: one known compound lupeol (<b>1</b>) and a new diketone pentacyclic triterpene named as erandone (urs-6-ene-3,16-dione) (<b>2</b>), from the plant. Their structures were determined by various spectroscopic techniques. Crude methanolic, enriched <i>n</i>-hexane fraction and isolates at doses 100 mg/kg p.o. exhibited significant (<i>P</i> < 0.001) anti-inflammatory activity in carrageenan-induced hind paw oedema model.</p></div

Mechanistic Insight into the Chemical Exfoliation and Functionalization of Ti₃C₂ MXene

MXene, a two-dimensional layer of transition metal carbides/nitrides, showed great promise for energy storage, sensing, and electronic applications. MXene are chemically exfoliated from the bulk MAX phase; however, mechanistic understanding of exfoliation and subsequent functionalization of these technologically important materials is still lacking. Here, using density-functional theory we show that exfoliation of Ti₃C₂ MXene proceeds via HF insertion through edges of Ti₃AlC₂ MAX phase. Spontaneous dissociation of HF and subsequent termination of edge Ti atoms by H/F weakens Al–MXene bonds. Consequent opening of the interlayer gap allows further insertion of HF that leads to the formation of AlF₃ and H₂, which eventually come out of the MAX, leaving fluorinated MXene behind. Density of state and electron localization function shows robust binding between F/OH and Ti, which makes it very difficult to obtain controlled functionalized or pristine MXene. Analysis of the calculated Gibbs free energy (Δ<i>G</i>) shows fully fluorinated MXene to be lowest in energy, whereas the formation of pristine MXene is thermodynamically least favorable. In the presence of water, mixed functionalized Ti₃C₂F_<i>x</i>(OH)_1–<i>x</i> (<i>x</i> ranges from 0 to 1) MXene can be obtained. The Δ<i>G</i> values for the mixed functionalized MXenes are very close in energy, indicating the random and nonuniform functionalization of MXene. The microscopic understanding gained here unveils the challenges in exfoliation and controlling the functionalization of MXene, which is essential for its practical application

sj-pdf-2-cms-10.1177_12034754241232689 – Supplemental material for Hidradenitis Suppurativa-Associated Cutaneous Squamous Cell Carcinoma in a Diverse Population

Supplemental material, sj-pdf-2-cms-10.1177_12034754241232689 for Hidradenitis Suppurativa-Associated Cutaneous Squamous Cell Carcinoma in a Diverse Population by Michelle Toker, Lindsay Pattison, Pooja Srivastava, Bijal Amin, Beth N. McLellan and Steven R. Cohen in Journal of Cutaneous Medicine and Surgery</p

sj-docx-1-cms-10.1177_12034754241232689 – Supplemental material for Hidradenitis Suppurativa-Associated Cutaneous Squamous Cell Carcinoma in a Diverse Population

Supplemental material, sj-docx-1-cms-10.1177_12034754241232689 for Hidradenitis Suppurativa-Associated Cutaneous Squamous Cell Carcinoma in a Diverse Population by Michelle Toker, Lindsay Pattison, Pooja Srivastava, Bijal Amin, Beth N. McLellan and Steven R. Cohen in Journal of Cutaneous Medicine and Surgery</p

Tuning the Electronic and Magnetic Properties of Phosphorene by Vacancies and Adatoms

We report a density functional theory (DFT) study regarding the effects of atomic defects, such as vacancies and adatom adsorption, on the electronic and magnetic properties of phosphorene (a two-dimensional monolayer of black phosphorus). A monovacancy in the phosphorene creates an in-gap state in the band gap of pristine phosphorene and induces a magnetic moment, even though pristine phosphorene is nonmagnetic. In contrast, both planar and staggered divacancies do not change the magnetic properties of phosphorene, although a staggered divacancy creates states in the gap. Our DFT calculations also show that adsorption of nonmetallic elements (C, N, and O) and transition metal elements (Fe, Co, and Ni) can change the magnetic properties of phosphorene with or without vacancies. For example, the nonmagnetic pristine phosphorene becomes magnetic after the adsorption of N, Fe, or Co adatoms, and the magnetic phosphorene with a monovacancy becomes nonmagnetic after the adsorption of C, N, or Co atoms. We also demonstrate that for O- or Fe-adsorbed monovacancy structure the electronic and magnetic properties are tunable via the control of charge on the phosphorene system. These results provide insight for achieving metal-free magnetism and a tunable band gap for various electronic and spintronic devices based on phosphorene

Atomistic Origin of Phase Stability in Oxygen-Functionalized MXene: A Comparative Study

Oxygen-functionalized MXene, M₂CO₂ (M = group III–V metals), are emergent formidable two-dimensional (2D) materials with a tantalizing possibility for device applications. Using first-principles calculations, we perform an intensive study on the stability of fully O-functionalized (M₂CO₂) MXenes. Depending on the position of O atoms, the M₂CO₂ can exist in two different structural phases. On one side of MXene, the O atom occupies a site which is exactly on the top of the metal atom from the opposite side. On the other side, the O atom can occupy either the site on the top of the metal atom of the opposite side (BB′ phase) or on the top of the C atom (CB phase). We find that for M = Sc and Y the CB phase is stable, whereas for M = Ti, Zr, Hf, V, Nb, and Ta the stable phase is BB′. The electron localization function, the atom-projected density of states, the charge transfer, and the Bader charge analyses provide a rational explanation for the relative stability of these two phases and justify the ground state structure by giving information about the preferential site of adsorption for the O atoms. We also calculate the phonon dispersion relations for both phases of M₂CO₂. The BB′-Sc₂CO₂ and the CB-Ti₂CO₂ are found to be dynamically unstable. Finally, we find that the instability of BB′-M₂CO₂ (M = Sc and Y) originates from the weakening of M–C interactions, which manifest as a phonon mode with imaginary frequency corresponding to the motion of C atom in the <i>a</i>–<i>b</i> plane. The insight into the stability of these competing structural phases of M₂CO₂ presented in this study is an important step in the direction of identifying the stable phases of these 2D materials