Density Functional Studies on Layered Perovskite Oxyhalide Bi₄MO₈X Photocatalysts (M = Nb and Ta, X = Cl, Br, and I)

Layered perovskite oxyhalides Bi₄MO₈X (M = Nb and Ta, X = Cl, Br, and I) have recently emerged as suitable photocatalysts for the photocatalytic water splitting reaction and degradation of organics. Here, we present a comparative study on the crystal structure, electronic structure, water adsorption, and oxygen evolution reaction of these systems. The calculated band gaps using hybrid density functional method HSE06 are smaller than 2.75 eV and increase with the increase of X atomic number, which is in excellent agreement with experimental data. All Bi₄MO₈X systems possess indirect band gaps, which benefits the separation of photogenerated electron–hole pairs. The density of states reveals that, for all the Bi₄MO₈X cases, the valence band maximum is mostly composed of O 2p states rather than X np states, which can explain the observed stability of these materials against photocorrosion. It is found that the molecular adsorption of water is energetically favorable on Bi₄MO₈X­(001) surfaces. As a result, the computed free energy changes for every step in the oxygen evolution reaction show that the rate-determining step is the first step of generating OH* species for all the cases. The computed overpotentials (0.69–0.77 V) of Bi₄MO₈X for the oxygen evolution reaction are comparable to and even lower than those of widely used photocatalysts for water oxidation, such as TiO₂, WO₃, BiVO₄, and α-Fe₂O₃. The calculations suggest that Bi₄MO₈X (M = Ta and Nb, X = Cl, Br, and I) are potential photocatalysts for overall water splitting in the visible light region, and we hope that the results reported in this work will stimulate experimental tests of our predictions

Insights into solvent polarity associated geometries and ESIPT behaviours for Prz3HC: a theoretical study

Given the potential significance of 3-hydroxychromone derivatives, our focus in this study is to investigate the solvent-polarity-associated photo-induced behaviours for 3-hydroxy-2-(1-ethyl-1H-pyrazol-3-yl)-4H-chromen-4-one (Prz3HC). We firstly examine the coexistence of three conformations (i.e. Prz3HC-I, Prz3HC-II and Prz3HC-III) and present a mechanism for their coexistence between Prz3HC-I and Prz3HC-III. Notably, non-polar solvents contain mainly Prz3HC-I while polar solvents contain mainly Prz3HC-III. Analysing infrared vibrational spectra and geometrical variations between S0 and S1 states, we demonstrate a hydrogen bonding strengthening phenomenon that facilitates excited-state intramolecular proton transfer (ESIPT) behaviour for both Prz3HC-I and Prz3HC-III. To qualitatively investigate photo-induced behaviours, by frontier molecular orbitals (MOs), we have discovered that charge redistribution significantly enhances the propensity for ESIPT. By comparing the barriers of potential energy curves (PECs) for twisting dihedral angles and ESIPT paths, we have unequivocally ruled out any mutual transformations in the S1 state. We also propose a solvent-polarity-regulated ESIPT behaviour for Prz3HC-I and Prz3HC-III. Furthermore, through an exploration of transition states (TS), we have further scrutinised the intricate mechanism underlying ESIPT. We sincerely hope this study can elucidate the solvent-polarity-regulated excited-state behaviours of Prz3HC while simultaneously paving the way for future explorations and applications of other 3-hydroxychromone derivatives.</p

Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin

As the most important component of deep red pigments, alkannin is investigated theoretically in detail based on time-dependent density functional theory (TDDFT) method. Exploring the dual intramolecular hydrogen bonds (O1–H2···O3 and O4–H5···O6) of alkannin, we confirm the O1–H2···O3 may play a more important role in the first excited state than the O4–H5···O6 one. Infrared (IR) vibrational analyses and subsequent charge redistribution also support this viewpoint. Via constructing the S₁-state potential energy surface (PES) and searching transition state (TS) structures, we illuminate the excited state double proton transfer (ESDPT) mechanism of alkannin is the stepwise process that can be first launched by the O1–H2···O3 hydrogen bond wire in gas state, acetonitrile (CH₃CN) and cyclohexane (CYH) solvents. We present a novel mechanism that polar aprotic solvents can contribute to the first-step proton transfer (PT) process in the S₁ state, and nonpolar solvents play important roles in lowering the potential energy barrier of the second-step PT reaction

Experimental and Computational Evidence for the Reduction Mechanisms of Aromatic <i>N</i>‑oxides by Aqueous Fe^II–Tiron Complex

A combined experimental-theoretical approach was taken to elucidate the reduction mechanisms of five representative aromatic <i>N</i>-oxides (ANOs) by Fe^II–tiron complex and to identify the rate-limiting step. Based on the possible types of complexes formed with the reductant, three groups of ANOs were studied: type I refers to those forming 5-membered ring complexes through the N and O atoms on the side chain; type II refers to those forming 6-membered ring complexes through the <i>N</i>-oxide O atom and the O atom on the side chain; and type III refers to complexation through the <i>N</i>-oxide O atom only. Density functional theory calculations suggested that the elementary reactions, including protonation, N–O bond cleavage, and the second electron transfer processes, are barrierless, indicating that the first electron transfer is rate-limiting. Consistent with the theoretical results, the experimental solvent isotope effect, KIE_H, for the reduction of quinoline <i>N</i>-oxide (a type III ANO) was obtained to be 1.072 ± 0.025, suggesting protonation was not involved in the rate-limiting step. The measured nitrogen kinetic isotope effect, KIE_N, for the reduction of pyridine <i>N</i>-oxide (a type III ANO) (1.022 ± 0.006) is in good agreement with the calculated KIE_N for its first electron transfer (1.011–1.028), confirming that the first electron transfer is rate-limiting. Electrochemical cell experiments demonstrated that the electron transfer process can be facilitated significantly by type I complexation with FeL₂^6– (1:2 Fe^II–tiron complex), to some extent by type II complexation with free Fe^II, but not by weak type III complexation

Tailoring Structural, Electronic, Optical, and Photocatalytic Properties of Y₂Ti₂O₇ through a Passivated Codoping Approach

The large band gap of the Y2Ti2O7 photocatalyst has limited its application only in the ultraviolet region. To enhance its photocatalytic activity for overall water splitting in the visible-light region, we have utilized a passivated codoping approach to construct eleven (X + M)-doped Y2Ti2O7 systems (X = C, N, M = Ti, V, Zr, Nb, Mo, Hf, Ta, W), where a Ti/Y site is replaced with a metal dopant. The calculated negative formation energies indicate that all of the (X + M)-doped systems are easy to synthesize, especially under the O-rich condition. The implantation of dopants can change the crystal structure to different extents. The less the deformation of the crystal, the easier the formation of the (X + M)-doped Y2Ti2O7. The passivated codoping can effectively narrow the band gap without generating isolated defect states in the forbidden gap. (X + M)-doped Y2Ti2O7 retains the direct band gap characteristics and possesses the separation rate of photogenerated carriers similar to or even higher than that of the pure crystal. Compared to (N + M)-doped systems, (C + M)-doped systems exhibit more remarkable influence on narrowing the band gap and extending the absorption edge mainly because the C dopant has deeper acceptor energy levels and a stronger interaction with the metal dopant than the N dopant. The capabilities of photooxidation and photoreduction of water have been enhanced by adopting the codoping strategy. By considering the binding energy, band gap, optical absorption, and the relative position of band edges, we propose that (C + Mo)-, (C + W)-, (N + V)-, (C + V)-, (C + Nb)- and (C + Ta)-doped Y2Ti2O7 are potential visible-light-responsive photocatalysts for overall water splitting

Image2_Identification of cuproptosis related subtypes and construction of prognostic signature in gastric cancer.tif

Cuprotosis is a novel mechanism of cell death that differs from known mechanisms, which depends on mitochondrial respiration and is closely related to lipoylated components of the tricarboxylic acid (TCA) cycle. However, it is unclear whether cuprotosis-related genes (CRGs) affect the tumor microenvironment (TME) and prognosis of patients with gastric cancer. In this study, the genetic and transcriptional characteristics of CRGs in gastric cancer (GC) were analyzed, and five CRGs that were differentially expressed and correlated with the survival of patients were obtained. Two different molecular subtypes were identified according to the five CRGs. Then, we constructed a CRG_score applied to patients of any age, gender, and stage. Subsequently, we found that cluster B and a high CRG_score had a worse prognosis, fewer immune checkpoints, and higher tumor immune dysfunction and exclusion (TIDE) compared to cluster A and a low CRG_score. In addition, two subtypes and the CRG_score were closely associated with clinicopathological characteristics, human leukocyte antigens (HLAs) and TME cell infiltration. A high CRG_score was featured with decreased microsatellite instability-high (MSI-H) and mutational burden. Meanwhile, the CRG_score was significantly related to the cancer stem cell (CSC) index and chemotherapeutic response. Moreover, we developed a nomogram to predict the survival probability of patients. Our study explained the role of CRGs in GC, and the prognostic signature could potentially provide an approach for personalized tumor therapy.</p

Results of quality assessment by Cochrane risk of bias.

<p>a. each risk of bias item presented as percentages across all included studies. b. each risk of bias item for each included study.</p

Whole-Cell Biocatalytic Synthesis of Cinnamyl Acetate with a Novel Esterase from the DNA Library of Acinetobacter hemolyticus

Cinnamyl acetate has a wide application in the flavor and fragrance industry because of its sweet, balsamic, and floral odor. Up to now, lipases have been mainly used in enzyme-mediated synthesis of cinnamyl acetate, whereas esterases are used in only a few cases. Moreover, the use of purified enzymes is often a disadvantage, which leads to increases of the production costs. In this paper, a genomic DNA library of Acinetobacter hemolyticus was constructed, and a novel esterase (EstK1) was identified. After expression in Escherichia coli, the whole-cell catalyst of EstK1 displayed high transesterification activity to produce cinnamyl acetate in nonaqueous systems. Furthermore, under optimal conditions (vinyl acetate as acyl donor, isooctane as solvent, molar ratio 1:4, temperature 40 °C), the conversion ratio of cinnamyl alcohol could be up to 94.1% at 1 h, and it reached an even higher level (97.1%) at 2 h

Flow diagram of studies identified, included, and excluded.

<p>Flow diagram of studies identified, included, and excluded.</p

CO₂ insufflation versus air insufflation for endoscopic submucosal dissection: A meta-analysis of randomized controlled trials

<div><p>Background</p><p>Carbon dioxide (CO₂) insufflation is increasingly used for endoscopic submucosal dissection (ESD) owing to the faster absorption of CO₂ as compared to that of air. Studies comparing CO₂ insufflation and air insufflation have reported conflicting results.</p><p>Objectives</p><p>This meta-analysis is aimed to assess the efficacy and safety of use of CO₂ insufflation for ESD.</p><p>Methods</p><p>Clinical trials of CO₂ insufflation versus air insufflation for ESD were searched in PubMed, Embase, the Cochrane Library and Chinese Biomedical Literature Database. We performed a meta-analysis of all randomized controlled trials (RCTs).</p><p>Results</p><p>Eleven studies which compared the use of CO₂ insufflation and air insufflation, with a combined study population of 1026 patients, were included in the meta-analysis (n = 506 for CO₂ insufflation; n = 522 for air insufflation). Abdominal pain and VAS scores at 6h and 24h post-procedure in the CO₂ insufflation group were significantly lower than those in the air insufflation group, but not at 1h and 3h after ESD. The percentage of patients who experienced pain 1h and 24h post-procedure was obviously decreased. Use of CO₂ insufflation was associated with lower VAS scores for abdominal distention at 1h after ESD, but not at 24h after ESD. However, no significant differences were observed with respect to postoperative transcutaneous partial pressure carbon dioxide (PtcCO₂), arterial blood carbon dioxide partial pressure (PaCO₂), oxygen saturation (SpO₂%), abdominal circumference, hospital stay, white blood cell (WBC) counts, C-Reactive protein (CRP) level, dosage of sedatives used, incidence of dysphagia and other complications.</p><p>Conclusion</p><p>Use of CO₂ insufflation for ESD was safe and effective with regard to abdominal discomfort, procedure time, and the residual gas volume. However, there appeared no significant differences with respect to other parameters namely, PtcCO₂, PaCO₂, SpO₂%, abdominal circumference, hospital stay, sedation dosage, complications, WBC, CRP, and dysphagia.</p></div