Search Results (70)

A comprehensive first-principles investigation of bulk and surface Cu defects in Zn-based chalcogenides (ZnO, ZnS, and ZnSe) is presented, aimed at assessing the effect of Cu doping on the optoelectronic properties of these materials and at addressing the photocatalytic activity towards the hydrogen evolution reaction (HER). Defect formation energies, adiabatic and optical charge-transition levels of the bulk materials are determined, and their dependence on growth conditions and Fermi-level position is analysed. The results indicate that, whereas ZnO supports both donor- and acceptor-like Cu defects with pronounced Jahn-Teller distortions, ZnS and ZnSe predominantly stabilise substitutional Cu as a mid-gap acceptor with weaker electron-lattice coupling and similar absolute transition levels. Calculated vertical transition energies rationalise the characteristic emission of Cu-doped samples in terms of defect-mediated optical cycles. The focus is then placed on surface energetics, which differ markedly from bulk behaviour and critically influence photocatalytic performance. Explicit modelling of HER demonstrates that Cu substitution dramatically reduces the overpotential on ZnS and ZnSe by tuning hydrogen adsorption toward the Sabatier optimum, while in ZnO the beneficial effect of Cu doping is diminished by the excessive strengthening of the adsorbate-surface interactions. Finally, the measured HER activities are rationalised by proposing a defect-mediated mechanism involving electron trapping at the surface Cu site, cooperative proton adsorption, and hydride formation. These findings establish defect thermodynamics and surface charge localisation as key design parameters for optimising materials engineering strategies in photocatalytic applications. Full article

Magnesium antimonide (Mg₃Sb₂) has emerged as a promising high-performance thermoelectric material, yet its efficiency is fundamentally determined by intrinsic point defects. In this study, we present a comprehensive investigation of defects in the intermetallic compound Mg₃Sb₂ using first laws of thermodynamics and density functional theory (DFT) within the generalized gradient approximation (GGA). By calculating the energy of defect formation and the charge transition energy between energy levels, it was determined how the change in chemical potential associated with phase synthesis affects the phase stability and carrier concentrations. Calculations show that donor defects dominate in Mg-rich alloys, primarily antimony vacancies and magnesium atoms in interstitial positions. This means that in a phase with a slight magnesium excess, e.g., Mg_3.01Sb_1.99 at 1400 K, n-type conductivity dominates. In the opposite case, i.e., in an Sb-rich alloy, magnesium vacancies spontaneously form in the Wyckoff 1a position. These ionized acceptors induce strong self-compensation, blocking the Fermi level about 0.38 eV above the valence band maximum. As a result of this process, the Mg₃Sb₂ phase, at elevated temperatures, becomes the non-stoichiometric Mg_2.99Sb_2.01 phase, which causes the material to retain p-type conductivity and actively block doping-induced n-type conductivity. The conducted studies demonstrate that the homogeneity range of the Mg-Sb system, although traditionally considered narrow, has a significant impact on the semiconducting properties of the material. Furthermore, they also point to the need for continued research on high temperature in the area of synthetic defect engineering, interface engineering, and optimization of the thermoelectric properties of materials based on Mg-Sb alloys. Full article

Drought is a major environmental constraint that disrupts photosynthetic processes. This study investigated the effects of foliar-applied commercial humic acid (HA) at different concentrations (1, 3 and 5 mg/mL) on the photosynthetic apparatus of sweet basil (Ocimum basilicum L. Italiano classico) under PEG-induced stress. The responses of the photosynthetic machinery were evaluated using chlorophyll a fluorescence analyses (JIP-test and PAM), leaf pigment composition, and assessments of membrane integrity. Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired Q_A⁻ reoxidation, reduced open PSII reaction centers (qP), diminished electron transport (ETo/RC, REo/RC), and substantial declines in performance indices (PI_ABS, PItotal). Energy dissipation increased (DI₀/RC), with regulated energy losses (Φ_NPQ) rising more strongly than non-regulated losses (Φ_NO). Drought also elevated oxidative stress markers (MDA and H₂O₂), leading to enhanced membrane injury. Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress. This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides and increased the proportion of open reaction centers (qP). Improved PSII photochemistry corresponded with more efficient Q_A⁻ reoxidation, facilitated its interaction with plastoquinone, and caused the overall stabilization of photosynthetic functions under drought. The protective effects of HA were also evident for both PSI subpopulations. The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC). In contrast, lower HA concentrations (1 and 3 mg/mL) provided insufficient protection. This study clearly demonstrates that HA enhances drought tolerance in basil in a concentration-dependent manner by protecting the structural and functional integrity of the photosynthetic apparatus, supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions. Full article

In this study, potential fungicides were prepared following the principles of green chemistry. The compounds were synthesized in deep eutectic solvents as an alternative medium and compared with syntheses in traditional solvents such as ethanol. The efficiency of the reaction was improved by ultrasonic synthesis in both eutectic solvents and ethanol, resulting in higher yields while reducing reaction energy and time. For the first time, deep eutectic solvents (DES) were used for quaternisation reactions, with choline chloride as a hydrogen bond acceptor and urea, glycerol, malic acid, malonic acid, and levulinic acid as donors. DES, composed of biodegradable, non-toxic, and renewable components, represented a greener alternative to conventional solvents. However, reactions in DES by the conventional method generally resulted in lower yields, probably due to solubility and viscosity limitations inherent in the eutectic medium. The combination of ultrasound and deep eutectic solvents proved to be a good alternative to organic solvents for the quaternisation reaction, as higher yields were achieved in a shorter time compared to conventional methods. The antifungal activity of all 18 synthesized compounds was tested. The compounds exhibited significant antifungal activity against all four pathogens, with varying levels of mycelial growth inhibition. B. cinerea was the most sensitive species (up to 70.7% inhibition), while F. culmorum was the least sensitive (≤32%). Full article

TiO₂ films with a thickness of 20 nm were obtained by anodizing a titanium film with an aluminum sublayer on a glass substrate. The I–V characteristics were studied in a temperature range of 100–300 K. Three linear sections can be distinguished on the I–V curves in logarithmic coordinates with a bias voltage of up to 2.5 V. The first section is an ohmic section with a bias voltage sweep from 0 V. The second section is associated with the space-charge-limited currents. The third section is characterized by the flow of Poole–Frenkel currents. In the third section, the slope of the approximating line is greater than in the second one due to the flow of higher currents. This is explained by the transition of electrons from donor centers to trap levels, which leads to a decrease in the number of free traps available for capturing electrons injected from the contacts into the conduction band. The obtained values of the Fermi energy of 0.032 and 0.028 eV for temperatures from 100 to 300 K, respectively, indicate that the electron traps in the forbidden zone of TiO₂ are shallow. The value of the donor level energy E = 0.082 eV is close to the values of the activation energy of thermal conductivity. This indicates the formation of donor centers in anodic TiO₂ by the mechanism of donor vacancies. In anodic TiO₂ films, the concentration of electron traps is 10¹⁵ cm⁻³, which is approximately three orders of magnitude less than their concentration in anodic TiO₂ films obtained by vacuum deposition. Full article

This study presents a SCAPS-1D-based numerical optimization of an organic ultraviolet (UV) photodetector employing an FTO/PTB7/Spiro-OMeTAD/Au device architecture. The novelty of this work lies in a simulation-guided, UV-specific optimization strategy that combines thickness engineering, controlled doping, and contact work-function tuning to achieve intrinsic spectral selectivity without external optical filters. We systematically optimize material and device parameters, including active layer thicknesses, donor and acceptor densities, and the metal electrode work function, to enhance responsivity, detectivity, and spectral performance. Simulations identify optimal thicknesses of 1200 nm for PTB7 and 1000 nm for Spiro-OMeTAD, with donor concentrations of 1 × 10²⁰ cm⁻³ and 1 × 10¹⁸ cm⁻³, respectively. A comparative contact analysis demonstrates that replacing aluminum with gold (Au) forms a near-ohmic back contact, leading to improved hole extraction and suppressed dark current due to favorable energy-level alignment. The optimized device achieves a peak external quantum efficiency of approximately 80% in the 300–400 nm ultraviolet range, with a responsivity up to 0.4 A/W. The UV selectivity originates from the absorption characteristics of PTB7 combined with suppressed long-wavelength charge collection, resulting in a negligible response in the visible–near-infrared region. These results confirm the device’s strong potential for high-sensitivity, solar-blind UV photodetection. By integrating practical material selection with physically consistent SCAPS-1D optoelectronic modeling, this work provides a robust design framework to guide the development of next-generation organic UV photodetectors for environmental sensing, biomedical diagnostics, and wearable optoelectronics. Full article

The efficiency of organic solar cells is constantly improving thanks to more advanced materials. Electron donor polymers, such as PM6 and its derivatives, as well as non-fullerene acceptors (NFAs) Y6 and ITIC and their derivatives, have become the standard materials for organic solar cell studies. To broaden the absorption range of solar cells, so-called ternary organic solar cells have been developed, which add a third material to the active layer. In this work, two chromophores based on the derivatives of the Janus-dione (s-indacene-1,3,5,7(2H,6H)-tetraone) central acceptor fragment, namely TIIC-1 and TIIC-2, were synthesized. Materials were characterized using theoretical and experimental methods, including UV-Vis absorption measurements, cyclic voltammetry, photoemission yield spectroscopy, and photoconductivity. The materials were incorporated as ternary components in PM6:Y7 bulk heterojunction solar cells. The power conversion efficiency (PCE) of PM6:Y7:TIIC-1 ternary solar cells was improved compared to binary PM6:Y7 reference cells. The PCE increased from 11.9% in binary blends to 12.5% in ternary cells. This increase is attributed to the cascade-like energy level arrangement, which facilitates charge transfer in the photoactive layer. Full article

We report a notable enhancement in the performance of small-molecule-based organic photovoltaics (OPVs) through the use of a ternary blend comprising a small-molecule donor (DTS(FBTTh₂)₂), a polymer donor (PBDTTT-EFT), and a fullerene acceptor (PC₇₁BM). By optimizing the composition of this ternary active layer, we achieved a significant increase in power conversion efficiency from 7.99% to 9.08%. This improvement is attributed to the broader light absorption spectrum and enhanced charge transport pathways provided by the polymeric donor. PBDTTT-EFT optimizes the nanomorphology and ordering of the bulk heterojunction films and forms a cascade energy level that enhances charge carrier mobility. Our results demonstrate that semiconducting polymer donors can effectively control light absorption, charge transport, and exciton dissociation by optimizing morphology and crystallinity. This approach offers new possibilities for advancing the performance of various optoelectronic devices through strategic use of different semiconducting polymer donors. Full article

Hydrogen is frequently incorporated in alkaline-earth oxides during crystal growth or post-deposition annealing. For MgO, several studies in the past showed that interstitial monatomic hydrogen can also favourably bind with oxygen vacancies to form stable substitutional defect complexes (substitutional hydrogen or U-defect centers). The present study reports first-principles density-functional calculations of the formation energies of both interstitial and substitutional forms of the hydrogen impurity in MgO. Determination of the site-resolved densities of electronic states allowed for a detailed identification of the nature of the impurity-induced levels, both in the valence-energy region and inside the band gap of the host. The stability and diffusion mechanisms of both hydrogen defects was also studied with the aid of nudged elastic-band (NEB) calculations. Interstitial hydrogen was found to be an amphoteric defect with the lower formation energy for any realistic environment conditions (temperature and oxygen partial pressure). The NEB calculations showed that it is a fast-diffusing species when it is thermodynamically stable as a positively-charged state (bare proton). In contrast, the hydrogen-vacancy complex is a shallow donor, extremely stable against dissociation and virtually immobile as an isolated defect. Its formation is found to be favoured for a range of mid-gap Fermi-level positions where positively-charged interstitial hydrogen and neutral oxygen vacancies (F centers) are both thermodynamically stable low-energy defects. The present findings are consistent with the established consensus on the electrical activity of hydrogen in MgO as well as with experimental observations reporting the remarkable thermal stability of substitutional hydrogen defects and their ability to act as electron traps. Full article

Owing to the intramolecular push-pull electron effect between the electron donor (D) unit and electron acceptor (A) unit, the D-A type based polymer donors display outstanding device performance. However, the imperfect energy levels lead to the D-A-type-based polymer device exhibiting high voltage loss. In this study, an A1-A2-type copolymer M1 was developed with 1,3-bis(2-ethylhexyl)-5,7-di(thiophen-2-yl)benzo[1,2-c:4,5-c’]dithiophene-4,8-dione (BDD) as the A1 unit and dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) as the A2 unit. Compared with D-A-type-based polymer donor PM6, the A1-A2 type based M1 possesses lower energy levels, broader absorption, and stronger crystallinity. After introducing M1 to the PM6:L8-BO-based system as the guest material, the ternary blend films exhibited exceptional face-on molecular orientation and favorable active-layer morphology, which promotes exciton dissociation and suppresses charge recombination. Consequently, the PM6:M1(5%):L8-BO-based ternary device exhibited an impressive power conversion efficiency (PCE) of 19.70% with simultaneously enhanced photostability, which is superior to the PM6:L8-BO-based binary system. Our work offers an efficient approach to developing high-performance ternary devices by introducing a novel A1-A2 type polymer donors as the guest material. Full article

Reef restoration is the major way to compensate the loss of scleractinian corals, which requires huge amounts of transplantation donors. Previous study revealed that some species of corals can conduct polyp bailout and reattachment under environmental stress, which contributes to the living of coral communities and offer a novel way to produce numerous coral colonies for reef restoration. In the present study, physiological and transcriptomic approaches were conducted to illustrate the effects and molecular mechanisms of brine shrimp feeding on the newly attached polyps of coral Poccillopora damicornis. It was observed that brine shrimp feeding significantly prompted the growth of reattached polyps by elevating polyp diameter, number of new polyps, weight of the calcified skeleton, symbiont density, chlorophyll a + c₂ content and Ea values. Transcriptomic analysis also inferred that signaling pathways responsive for energy metabolism, cell growth and biomineralization were dramatically activated. Furthermore, brine shrimp feeding enhanced the immunity of the reattached polyps by suppressing caspase-3 activation level and elevating antioxidant capacity. These results collectively reveals the influence and detailed molecular mechanisms of brine shrimp feeding on the growth of newly reattached coral polyps, which shed light on the potential application of such methods in the cultivation of coral transplantation donors. Full article

Adventitious rooting is a key step for the clonal propagation of many economically important horticultural and woody species. Accumulating evidence suggests that nitric oxide (NO) serves as a key signaling molecule with key roles in root organogenesis. However, the role of NO in adventitious root development and its underlying mechanism in sweetpotato cuttings remain to be clarified. In this study, a pot experiment was conducted using hydroponically cultured sweetpotato cuttings (Ipomoea batatas cv. ‘Jin Ganshu No. 9’) treated with different concentrations of sodium nitroprusside (SNP, an NO donor) solution (0, 10, 50, 100, 200, and 500 μmol·L⁻¹). Three treatments were established: Control, SNP (the optimal concentration of SNP), and SNP + 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, an NO scavenger). The results showed that NO promoted adventitious rooting in a dose-dependent manner, with the maximal biological response observed at 100 μM SNP. At this concentration, the root number and length of adventitious roots increased by 1.22 and 2.36 times, respectively, compared to the control. SNP treatment increased fresh root weight, dry root weight, the content of soluble sugar, soluble protein, chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll (a + b) [Chl(a + b)], as well as the activities of peroxidase (POD), polyphenol oxidase (PPO), and indole acetic acid oxidase (IAAO). It also enhanced the levels of maximum fluorescence (Fm), maximum photochemical efficiency of photosystem II (Fv/Fm), absorbed light energy (ABS/RC), trapped energy flux (TRo/RC), and electron transport flux (ETo/RC), while decreasing starch content and initial fluorescence (Fo). On the 7th day, the SNP treatment significantly enhanced several biochemical parameters compared to the control. We observed an increase in many of the parameters: POD activity by 1.35 times, PPO activity by 0.55 times, chlorophyll content (Chl a by 0.66 times, Chl b by 0.22 times, and Chl a + b by 0.57 times), and photosynthesis parameters by 28–98%. Meanwhile, starch content and Fo in the SNP treatment decreased by 10.77% and 23.86%, respectively, compared to the control. Furthermore, the positive effects of NO on adventitious root development and associated biochemical parameters were reversed by the NO scavenger cPTIO. Additionally, significant and positive correlations were observed between morphological characteristics and most physiological indicators. Collectively, these results demonstrate that NO promotes adventitious root formation, which may be by enhancing rooting-related enzyme activities, improving photosynthetic performance in leaves, and accelerating the metabolism of soluble sugar, soluble protein, and starch. Full article

The strategic design of donor–acceptor (D-A) conjugated porous polymers has emerged as a pivotal methodology for advancing efficient photocatalytic hydrogen evolution. However, conventional D-A polymeric architectures face inherent limitations: excessively strong acceptor units may lower the LUMO energy level, compromising proton (H⁺) reduction capability, while weak D-A interactions result in inadequate light-harvesting capacity and insufficient photogenerated electrons, ultimately diminishing photocatalytic activity. To address these challenges, we developed a new D1-A-D2 conjugated porous polymer (CPP) system. The strategic incorporation of a secondary donor benzothiophene (DBBTh) unit enabled precise bandgap engineering in D₁-A-D₂ CPPs. Experimental results demonstrate that DBBTh integration significantly enhances both light absorption efficiency and proton reduction ability. Under visible-light irradiation (λ > 420 nm), the Py-BKh1 photocatalyst achieved a hydrogen evolution rate (HER) of 10.2 mmol h⁻¹ g⁻¹ with an apparent quantum yield (AQY) of 9.5% at 500 nm. This work provides a groundbreaking paradigm for designing high-performance organic photocatalysts. Full article

Cyanidin-3-O-glucoside (C3G) was used as a substrate for enzymatic acylation, and different compounds (methyl n-octanoate and methyl salicylate) were selected as acyl donors. Structural analysis (UV–Vis, FTIR, and HPLC) revealed the successful integration of methyl ester compounds into the structural units of C3G. The thermostability and photostability of acylated C3Gs, particularly those with methyl salicylate as the acyl donor, exhibited significant improvements. The molecular geometries of the different anthocyanins were optimized using computational chemistry, and energy level calculations were performed by using Density Functional Theory (DFT) to identify the antioxidant active site. Then, the antioxidant properties of C3G and acylated C3Gs (O-C3G and S-C3G) were studied in both aqueous and lipid systems. In aqueous systems, acylated C3Gs exhibited higher antioxidant properties than C3G in DPPH radical scavenging and hydroxyl radical scavenging assays, with cyanidin-3-O-glucoside salicyl acyl product (S-C3G) demonstrating the highest activity. However, the antioxidant properties varied in lipid systems. In lipid systems, acylated C3Gs displayed better antioxidant properties than C3G in POV and TBARS assays, with cyanidin-3-O-glucoside n-octanoate acid acyl product (O-C3G) showing better antioxidant properties compared to that in aqueous systems. Full article

The intricate relationship between hydrogen sulfide (H₂S), gut microbiota, and sirtuins (SIRTs) can be seen as a paradigm axis in maintaining cellular homeostasis, modulating oxidative stress, and promoting mitochondrial health, which together play a pivotal role in aging and neurodegenerative diseases. H₂S, a gasotransmitter synthesized endogenously and by specific gut microbiota, acts as a potent modulator of mitochondrial function and oxidative stress, protecting against cellular damage. Through sulfate-reducing bacteria, gut microbiota influences systemic H₂S levels, creating a link between gut health and metabolic processes. Dysbiosis, or an imbalance in microbial populations, can alter H₂S production, impair mitochondrial function, increase oxidative stress, and heighten inflammation, all contributing factors in neurodegenerative diseases such as Alzheimer’s and Parkinson’s. Sirtuins, particularly SIRT1 and SIRT3, are NAD⁺-dependent deacetylases that regulate mitochondrial biogenesis, antioxidant defense, and inflammation. H₂S enhances sirtuin activity through post-translational modifications, such as sulfhydration, which activate sirtuin pathways essential for mitigating oxidative damage, reducing inflammation, and promoting cellular longevity. SIRT1, for example, deacetylates NF-κB, reducing pro-inflammatory cytokine expression, while SIRT3 modulates key mitochondrial enzymes to improve energy metabolism and detoxify reactive oxygen species (ROS). This synergy between H₂S and sirtuins is profoundly influenced by the gut microbiota, which modulates systemic H₂S levels and, in turn, impacts sirtuin activation. The gut microbiota–H₂S–sirtuin axis is also essential in regulating neuroinflammation, which plays a central role in the pathogenesis of neurodegenerative diseases. Pharmacological interventions, including H₂S donors and sirtuin-activating compounds (STACs), promise to improve these pathways synergistically, providing a novel therapeutic approach for neurodegenerative conditions. This suggests that maintaining gut microbiota diversity and promoting optimal H₂S levels can have far-reaching effects on brain health. Full article