Search Results (2,681)

Climate change and the global energy crisis have led to an increasing need for greenhouse gas remediation and clean energy sources. The electrochemical CO₂ reduction reaction (CO₂RR) is a promising solution for both issues as it harvests waste CO₂ and chemically reduces it to more useful forms. However, the high overpotential required for the reaction makes it electrochemically unfavorable. Here, we fabricate a novel electrode composed of TiO₂ nanoparticles grown in situ on MXene charge acceptor 2D sheets with excellent CO₂RR characteristics. A straightforward solvothermal method was used to grow the nanoparticles on the Ti₃C₂T_x MXene flakes. The electrochemical performance of the TiO₂/MXene electrodes was analyzed. The Faradaic efficiencies of the TiO₂/MXene electrodes were determined, with a value of 99.41% at −1.9 V (vs. Ag/AgCl). Density functional theory mechanistic analysis was used to reveal the most likely mechanism resulting in the production of one CO molecule along with a carbonate anion through ∗CO, ∗O, and activated CO₂²⁻ intermediates. Bader charge analysis corroborated this pathway, showing that CO₂ gains a greater negative charge when TiO₂/MXene serves as a catalyst compared to MXene or TiO₂ alone. These results show that TiO₂/MXene nanocomposite electrodes may be very useful in the conversion of CO₂ while still being efficient in both time and cost. Full article

This study reports on the direct electron transfer (DET) ability of the enzyme spermidine dehydrogenase (SpDH) and its use in a DET-type enzymatic sensor for detecting spermine. SpDH was found to exhibit internal electron transfer from its cofactor, flavin adenine dinucleotide (FAD), to heme b. This was confirmed by observing the heme b-derived reduction peak at 560 nm in the presence of spermine, the substrate. SpDH was immobilized on a gold electrode via a dithiobis (succinimidyl hexanoate) self-assembled monolayer. The cyclic voltammetry analysis of the SpDH-immobilized gold electrode revealed an increased oxidation current in the presence of 0.1 mM spermine with an onset potential of −0.14 V vs. Ag/AgCl in the absence of an additional external electron acceptor. This result confirmed that SpDH is capable of DET. Chronoamperometric analyses were conducted using an SpDH-immobilized gold electrode with spermine as the substrate under a 0 V oxidation potential vs. Ag/AgCl using an artificial saliva matrix containing 10 µM ascorbic acid and 100 µM uric acid. The sensor exhibited good linear correlation between the current increase and spermine concentration from 0.2 to 2.0 µM, with a limit of detection of 0.084 µM, which encompasses the physiologically relevant spermine concentration found in the saliva. Primary structure alignments and 3D structure predictions revealed that all SpDH homologs possess two conserved histidine residues in the same location on the surface as the heme b ligand of SpDH. This indicates their potential for DET-ability with an electrode. Full article

This work presents the HX-responsiveness of the following heteroleptic donor–M–acceptor dithiolene complexes: Bu4N[MII(L1)(L2)] [M = Ni(1), Pd(2), Pt(3)], where L1 is the chiral acceptor ligand [(R)-α-MBAdto = chiral (R)-(+)α-methylbenzyldithio-oxamidate] and L2 is the donor ligand (tdas = 1,2,5-thiadiazole-3,4-dithiolato). Addition of hydrohalic acids induces a strong bathochromic shift and visible color change, which is fully reversed by ammonia (NH₃). Moreover, the sensing capability of 1 was further evaluated by deposition on a cellulose substrate. Exposure to HCl vapors induces an evident color change from purple to green, whereas successive exposure to NH₃ vapors fully restores the purple color. Remarkably, cellulose films of 1 were revealed to be excellent optical sensors against the response to triethylamine, which is a toxic volatile amine. Moreover, the HCl-responsiveness of the nonlinear optical properties of complexes 1, 2, and 3 embedded into a poly(methyl methacrylate) poled matrix was demonstrated. Reversible chemical second harmonic generation (SHG) switching is achieved by exposing the poled films to HCl vapors and then to NH₃ vapors. The SHG response ratio HCl–adduct/complex is significant (around 1.5). Remarkably, the coefficients of the susceptibility tensor for the HCl–adduct films are always larger than those of the respective free-complex films. Density Functional Theory (DFT) and time-dependent DFT calculations help in highlighting the structure–properties relationship. Full article

This work thoroughly investigated the compound 4-(2,5-Dimethoxyphenyl)-3,4-dihydrobenzo[g]chromene-2,5,10-trione (DMDCT) using molecular docking, quantum chemical analysis, and vibrational spectroscopy methodology. The medicinal chemistry group has been particularly interested in chromene and benzochromene derivatives due to their wide range of pharmacological actions, including anticancer, antibacterial, anti-inflammatory, antioxidant, antiviral, and neuroprotective capabilities. In this connection, DMDCT has been explored to evaluate its biological, electrical, and structural properties. DFT using the B3LYP functional and 6–31G basis was established to conduct theoretical computations with the Gaussian 09 program. The findings from these computations provide insight into the following topics: NBO interactions, optimal molecular geometry, Mulliken charge distribution, frontier molecular orbitals, and MEP. Second-order perturbation theory has been used to assess stabilization energies arising from donor–acceptor interactions. Furthermore, general features such as chemical hardness, softness, and electronegativity were studied. The results suggest that DMDCT has stable electronic configurations and biologically relevant active sites. This integrated experimental and theoretical study supports the potential of DMDCT as a practical scaffold for future therapeutic applications and contributes valuable information regarding its vibrational and electronic behavior. Full article

Thick active layers are crucial for scalable production of organic photodetectors (OPDs). However, most OPDs with active layers thicker than 200 nm typically exhibit decreased photocurrents and responsivities due to exciton diffusion and prolonged charge transport pathways. To address these limitations, we designed and synthesized PFBDT-8ttTPD, a fluorinated polymer donor. The strategic incorporation of fluorine effectively enhanced the charge carrier mobility, enabling more efficient charge transport, even in thicker films. OPDs combining PFBDT−8ttTPD with IT−4F or Y6 non-fullerene acceptors showed a substantially lower dark current density (J_d) for active layer thicknesses of 250−450 nm. Notably, J_d in the IT-4F-based devices declined from 8.74 × 10⁻⁹ to 4.08 × 10⁻¹⁰ A cm⁻² under a reverse bias of −2 V, resulting in a maximum specific detectivity of 3.78 × 10¹³ Jones. Meanwhile, Y6 integration provided near-infrared sensitivity, with the devices achieving responsivity above 0.48 A W⁻¹ at 850 nm and detectivity over 10¹³ Jones up to 900 nm, supporting broadband imaging. Importantly, high-quality thick films (≥400 nm) free of pinholes or defects were fabricated, enabling scalable production without performance loss. This advancement ensures robust photodetection in thick uniform layers and marks a significant step toward the development of industrially viable OPDs. Full article

Cobalt-doped iron disulfide (FeS₂) thin films were synthesized via chemical bath deposition (CBD) followed by annealing at 450 °C, yielding phase-pure pyrite structures with multifunctional properties. A deposition temperature of 95 °C is critical for promoting Co incorporation, suppressing sulphur vacancies, and achieving structural stabilization of the film. After annealing, the dendritic morphologies transformed into compact quasi-spherical nanoparticles (~100 nm), which enhanced the crystallinity and optoelectronic performance of the films. The films exhibited strong absorption (>50%) in the visible and near-infrared regions and tunable direct bandgaps (1.14 to 0.96 eV, within the optimal range for single-junction solar cells. Electrical characterization revealed a fourth-order increase in conductivity after annealing (up to 4.78 Ω⁻¹ cm⁻¹) and confirmed stable p-type behavior associated with Co²⁺-induced acceptor states and defect passivation. These results demonstrate that CBD enabled the fabrication of Co-doped FeS₂ thin films with synergistic structural, electrical, and optical properties. The integration of earth-abundant elements and tunable electronic properties makes these films promising absorber materials for the next-generation photovoltaic devices. Full article

The Z-isomer of N,N’-diammoniopropyl derivative of di(3-pyridyl)ethylene was synthesized. The structure and stability of complexes between this non-planar weak acceptor (A, (Z)-2) and a planar strong donor, the E-isomer of bis(18-crown-6)stilbene (D, (E)-1), were studied using X-ray diffraction, ¹H NMR spectroscopy, and optical spectroscopy, including ¹H NMR and spectrofluorimetric titrations. In MeCN, the components form a very stable pseudocyclic bimolecular complex (logK_D·A = 8.48) due to homoditopic coordination of the ammonium groups of the acceptor to the crown moieties of the donor through numerous hydrogen bonds. Intrasupramolecular photo-driven electron transfer (ET) in the isomeric complexes of (E)-1 with (E)- and (Z)-2 was studied using steady-state absorption and fluorescence spectroscopy with time-resolved pulse absorption spectroscopy. It was found that back ET is approximately two times faster in complex (E)-1·(Z)-2 than in closely related (E)-1·(E)-2. Meanwhile, it is ~67 times slower in complex (E)-1·(E)-2 than in the isomeric complex based on N,N’-diammoniopropyl derivative of (E)-di(4-pyridyl)ethylene. Quantum chemical (DFT, TD-DFT) calculations suggest the actual photorelaxation pathway for the complexes under study. Full article

Background/Objectives: SARS-CoV-2 pandemic led to the identification of peptide-based main protease (M^pro) inhibitors. The overwhelming majority of them carry an electrophilic warhead and a γ-lactam at the P1 position. During the selectivity assessment of an in-house Michael acceptors targeting SARS-CoV-2 M^pro, we unexpectedly observed a significant inhibition of human cathepsin S (hCatS). Methods: The biological investigation of three compounds (i.e., SPR38, SPR39, and SPR41) against hCatS was performed. The binding mode of SPRs was investigated by docking and molecular dynamics simulations. Results: Biological investigation has corroborated that hCatS is sensitive to peptide-based analogues harbouring γ-lactam at the P1 position and a vinyl methyl ketone warhead. In silico studies revealed that despite being solvent exposed, the γ-lactam at P1 might be involved in water-mediated H-bonds that could be optimized to gain inhibition potency and selectivity. Conclusions: The molecules repurposing of peptide-based SARS-CoV-2 M^pro inhibitors carrying the γ-lactam at the P1 site could pave the way for the identification of novel potent and selective hCatS ligands. Full article

This study presents a computational investigation into the design of triphenylamine-based donor chromophores incorporating 2-(1,1-dicyanomethylene)rhodanine as the acceptor unit. Three molecular architectures (System-1 to System-3) were developed by introducing distinct thiophene-derived $\pi$-bridges to modulate their electronic and optical characteristics for potential application in bulk heterojunction organic solar cells (OSCs). Geometrical optimizations were performed at the B3LYP/6-31+G(d,p) level, while excited-state and absorption properties were evaluated using TD-DFT with the CAM-B3LYP functional. Frontier orbital analysis revealed efficient charge transfer from donor to acceptor moieties, with System-3 showing the narrowest HOMO–LUMO gap (1.96 eV) and the lowest excitation energy (2.968 eV). Charge transport properties, estimated from reorganization energies, indicated that System-2 exhibited the most favorable balance for ambipolar transport, featuring the lowest electron reorganization energy (0.317 eV) and competitive hole mobility. Photovoltaic parameters calculated with PC₆₁BM as acceptor predicted superior $V_{oc}$, $J_{sc}$, and fill factor values for System-2, resulting in the highest theoretical power conversion efficiency (10.95%). These findings suggest that $\pi$-bridge engineering in triphenylamine-based systems can significantly enhance optoelectronic performance, offering promising donor materials for next-generation OSC devices. Full article

This study investigates the impacts of the gas environment, water matrix, and reactive species on the TiO₂-mediated photocatalytic degradation of safranin O (SO), a dye commonly found in wastewater. A slurry reactor (UVA, 365 nm) was used to quantify SO oxidation while systematically varying the SO concentration (5–40 mg/L), the TiO₂ loading (0–3 g/L), the temperature (15–45 °C), and the pH (2–12). The dissolved gases (air, nitrogen, and argon) and matrices (deionized water, mineral water, and seawater) were also examined. Eight mechanistic probes (ascorbic acid, methanol, azide, nitrite, benzoquinone, oxalate, sucrose, and phenol) were used to identify active oxidants. UVA/TiO₂ achieved rapid decolorization in approximately 90 min at 10 mg/L of SO and 0.4 g/L of TiO₂. Decolorization rates decreased with increasing SO concentration due to active-site competition and inner-filter effects. Rates also exhibited a bell-shaped dependence on TiO₂ loading due to light scattering and aggregation at high solids concentrations. Temperature exhibited a non-monotonic profile with an optimum around 25 °C, and the pH displayed an optimum range with maximal removal occurring around pH 10 and declining at pH 12. Air saturation outperformed N₂ and Ar, indicating that O₂ is the terminal electron acceptor. Photocatalytic performance decreased in the order deionized water > mineral water > seawater, owing to bicarbonate/chloride scavenging and ionic-strength effects. Scavenger tests converged on ^•OH dominance, with measurable contributions from superoxide/hydrogen peroxide (O₂^•−/H₂O₂) and valence-band holes (h⁺); singlet oxygen (¹O₂) played a minor role. These findings underscore the critical interplay between operational and environmental factors and offer a practical framework for scaling TiO₂-based SO abatement in real waters. Full article

Enhanced Natural Attenuation (ENA) can accelerate pollutant degradation by adding electron acceptors or nutrients. However, its impact on carbon-fixing microorganisms, which are widely found in the natural attenuation process, remains unclear. In this study, four types of ENA materials were added in batch experiments. Chemical analysis and metagenomic sequencing were employed to analyze the degradation kinetics of petroleum hydrocarbons, the consumption pattern of nitrate, as well as the functional genes and population evolution characteristics of carbon-fixing microorganisms. Results showed that nitrate-based enhancement materials significantly improved the petroleum hydrocarbon degradation rate but suppressed the expression of some carbon fixation genes, such as those involved in the Calvin–Benson–Bassham cycle. Nevertheless, the overall abundance of carbon fixation genes did not show a notable decline. Dominant bacterial genera such as Pseudomonas and Achromobacter possessed both hydrocarbon degradation and carbon fixation capabilities. Although the calcium peroxide treatment group only achieved a 40% petroleum hydrocarbon degradation rate, it significantly promoted the abundance of carbon fixation genes involved in the reductive tricarboxylic acid cycle pathway. Therefore, ENA alters carbon fixation pathways but does not diminish carbon fixation potential, indicating its potential for synergistically achieving pollution remediation and carbon fixation. Full article

Donor–acceptor (D–A) cyclopropanes are important precursors in the synthesis of complex molecules due to their bidentate character and high reactivity. Among them, cyclopropane-1,1-dicarbonitriles are less commonly reported in modern literature, primarily because of the high reactivity of the nitrile groups and their limited compatibility with metal-catalyzed processes, which is caused by the geometrical constraints imposed by the linear cyano substituents. While the cyano groups can be seen as a limitation, they also offer synthetic versatility by serving as handles for further functionalization. In this work, we performed a cycloaddition reaction with mercaptoacetaldehyde, leading to a new class of DA cyclopropanes bearing a thiazole moiety. This one-pot, two-step transformation requires only a single purification step. The resulting thiazolyl-substituted cyclopropanes were subjected to ring strain-release reactions, showing reactivity comparable to the parent cyclopropane-1,1-dicarbonitriles. Full article

This theoretical work investigates the linear (absorption and emission) and nonlinear (first hyperpolarizability and TPA) optical properties of donor–$\pi$–acceptor (D–$\pi$–A) molecular architectures based on functionalized benzoxazoles, with potential applications in optoelectronic technologies such as OLEDs and solar cells. Four $\pi$-conjugated compounds were studied in the gas phase and in polar (methanol) and nonpolar (toluene) solvents, employing DFT with the B3LYP and CAM-B3LYP functionals and the 6-311++G(d,p) basis set, as implemented in Gaussian and Dalton. The results reveal that the chemical environment induces spectral shifts and modulates the intensity of electronic transitions. In particular, the compound 2-((4-((5-nitro-2-oxo-1,3-benzoxazol-3(2H)-yl)amino)phenyl)methyl)-1,3-benzoxazole exhibited outstanding behavior in methanol, with a significant increase in dipole moment, polarizability, and first hyperpolarizability (static and dynamic at 1064 nm), reaching a TPA cross-section close to 150 GM. These findings highlight the key role of ionic substituents in tuning the optical response of $\pi$-conjugated systems and underscore their potential as functional materials for high-performance light-emitting and energy-conversion devices. Full article

Neutral and protonated histamine tautomers, mono-substituted with twelve functional groups, were studied theoretically as isolated molecules and complexes with the H₁ receptor. Geometry and energy of tautomers were optimized using the DFT method with the B3LYP functional and the aug-cc-pVTZ basis set. The approach was based on the charge of the substituent active region (cSAR) parameters and the Harmonic Oscillator Model of Aromaticity (HOMA) indices. The cSAR parameters characterized the electron density better than the conventional Hammett’s constants σ. In general, the cSAR parameters correlate with other characteristics of the charge distribution, particularly those for substituents at the carbon atom in the ring adjacent to the side chain. Substituents at this atom affected the aromaticity less strongly than those located between two nitrogen atoms, which confirmed recent reports. Our results suggest that the 3H tautomer isomerizes into the 1H one after binding to the H₁ receptor. Moreover, the electron structure of the molecule hydrogen-bonded to the receptor may significantly depend on the electron donor-acceptor properties of the substituent. The strong electron-accepting substituents, e.g., NO₂, favor the imidazole configuration of the ring in the bonded molecule, while the strong electron-donating ones, e.g., NH₂, promote the imidazolium one. Full article

Deep eutectic solvents (DESs) have emerged as sustainable and tunable alternatives to conventional solvents for the extraction of polysaccharides. This review presents a structure-informed framework linking DES composition to polysaccharide solubility, emphasizing the differential responsiveness of amorphous, interfacial, and crystalline domains. Amorphous polysaccharides are efficiently extracted under mild DES conditions, while crystalline polymers often require stronger hydrogen bond acceptors or thermal/mechanical activation. Beyond dissolution, DESs modulate key properties of the extracted polysaccharides, including molecular weight, monomer composition, and bioactivity. Comparative analysis highlights how acidic, basic, or metal-coordinating DESs selectively target distinct polymer classes. Emerging innovations, such as in situ DES formation, mechanochemical systems, and switchable solvents, enhance efficiency and reduce downstream processing demands. Furthermore, the integration of machine learning and COSMO-RS modeling enables predictive solvent design, reducing reliance on empirical screening. By combining mechanistic insight, compositional tailoring, and computational tools, this review provides a scientifically grounded perspective for advancing DES-mediated extraction processes and enabling structure-preserving, application-oriented recovery of polysaccharides in food, pharmaceutical, and biorefinery domains. Full article