Electron-donating Properties Research Articles

Power Output Enhancement of Natural Rubber Based Triboelectric Nanogenerator with Cellulose Nanofibers and Activated Carbon.

The growing demand for energy and environmental concern are crucial driving forces for the development of green and sustainable energy. The triboelectric nanogenerator (TENG) has emerged as a promising solution for harvesting mechanical energy from the environment. In this research, a natural rubber (NR)-based TENG has been developed with an enhanced power output from the incorporation of cellulose nanofibers (CNF) and activated carbon (AC) nanoparticles. The highest voltage output of 137 V, a current of 12.1 µA, and power density of 2.74 W/m2 were achieved from the fabricated NR-CNF-AC TENG. This is attributed to the synergistic effect of the electron-donating properties of cellulose material and the large specific surface area of AC materials. The enhancement of TENG performance paves the way for the application of natural-based materials to convert mechanical energy into electricity, as a clean and sustainable energy source.

Preparation and Physicochemical Characterization of Gelatin-Aldehyde Derivatives.

The present study aimed at preparing novel free-radical scavenging and water-soluble compounds derived from gelatin. Specifically, gelatin–syringaldehyde, gelatin–anisaldehyde, and gelatin–vanillin were synthesized and thoroughly studied for their physicochemical properties. In particular, the compounds were characterized by UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Notably, as demonstrated by thermogravimetry and differential scanning calorimetry, all three derivatives exhibited higher thermal stability than gelatin itself. Free-radical scavenging activities of the examined compounds were explored by (i) a standard spectrophotometric ABTS assay and (ii) an assay of oxidative degradation of hyaluronic acid monitored by rotational viscometry. We found that gelatin and gelatin–syringaldehyde demonstrated the highest efficacy in scavenging •OH radicals, whereas gelatin–anisaldehyde was the least effective. The efficacy of scavenging alkyloxy- and alkylperoxy-type free radicals via hydrogen-atom-transferring property was in the following order: gelatin > gelatin–vanillin > gelatin–syringaldehyde > gelatin–anisaldehyde. Electron-donor properties determined using the ABTS assay revealed the following order in one-electron reduction of ABTS•+: gelatin > gelatin–anisaldehyde > gelatin–vanillin > gelatin–syringaldehyde.

Reversible Supramolecular Noncovalent Self-Assembly Determines the Optical Properties and the Formation of Melanin-like Nanoparticles.

The role of noncovalent supramolecular self-assembly in the formation of melanin-like NP, as well as the nature of the electronic transition at the basis of their unique optical properties, is strongly debated. Here we demonstrate that, during the first stage of formation of synthetic melanin, polydopamine (PDA), a small fraction of the molecular precursor dopamine (DA) is oxidized to quinone (Q) and a simple supramolecular charge-transfer (CT) adduct is formed thanks to the electron donor and electron acceptor properties of DA and Q, respectively. This adduct, also detectable by HPLC-MS, presents the broad absorption band in the red-NIR region typical of melanin-like materials. Importantly, its disaggregation upon dilution can be easily detected since it leads to the disappearance of the CT band, indicating the reversibility of the process. Moreover, the stability constant K of the CT adduct could be obtained using a simple association model.

Favorable and strain-tunable sensing property of chalcogenide-defected Janus SnSSe monolayer towards thermal runaway fault gases in a lithium-ion battery

This paper based on the first-principles simulations sheds light on the chalcogenide-defected behavior of the Janus SnSSe monolayer and the sensing property of the defected-SnSSe monolayer upon three typical thermal runaway fault gases, namely H2, CO and C2H2. Results indicate that the Se-vacancy is more likely to be formed in a SnSSe monolayer, and the Se–SnSSe monolayer performs physisorption, with adsorption energies of −0.14, −0.61 and −0.37 eV for three systems, and electron-donating property, contributing 0.047, 0.087 and 0.070 e to such three gases. The band structure and work function analyses reveal the desirable potential of Se–SnSSe monolayer as a resistance-type or WF-based sensor for CO detection. Also, the recovery property is analyzed to consider the reusability of such sensing material. Besides, the applied biaxial strains reveal that Se–SnSSe monolayer performs high and tunable sensitivity for these gas species, especially for H2 and C2H2 detections. This work paves the way to explore SnSSe-based material for gas sensing application in many typical fields involving H2, CO and C2H2 detection, which is also guidable to explore the sensing potential of many other Janus 2D materials.

3R-TaS2as an Intercalation-Dependent Electrified Interface for Hydrogen Reduction and Oxidation Reactions

Hydrogen technology, as a future breakthrough for the energy industry, has been defined as an environmentally friendly, renewable, and high-power energy carrier. The green production of hydrogen, which mainly relies on electrocatalysts, is limited by the high cost and/or the performance of the catalytic system. Recently, studies have been conducted in search of bifunctional electrocatalysts accelerating both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). Herein, we report the investigation of the high efficiency bifunctional electrocatalyst TaS2 for both the HER and the HOR along with the asymmetric effect of inhibition by organic intercalation. The linear organic agent, to boost the electron donor property and to ease the process of intercalation, provides a higher interlayer gap in the tandem structure of utilized nanosheets. XRD and XPS data reveal an increase in the interlayer distance of 22%. The HER and the HOR were characterized in a Pt group metal-free electrochemical system. The pristine sample shows a low overpotential of −0.016 V at the onset. The intercalated sample demonstrates a large shift in its performance for the HER. It is revealed that the intercalation is a potential key strategy for tuning the performance of this family of catalysts. The inhibition of the HER by intercalation is considered as the increase in the operational window of a water-based electrolyte on a negative electrode, which is relevant to technologies of electrochemical energy storage.

The charge-transfer states and excitation energy transfers of halogen-free organic molecules from first-principles many-body Green’s function theory

The organic solar cells based on halogen-free components, have been the new favorites to develop green and renewable energy. PBDB-T and its derivatives are considered the superior electron donors to construct the solar cells. Although there are plenty of researches about them, the charge-transfer mechanisms and excitation energy transfers of relative organic solar cells are still unclear, the developments of photovoltaic devices are restricted consequently. In this work, we calculate the electronic structures and excited-state properties of PBDB-T, PBT1-C, PBT1-O and PBT1-S donors in the gas phase from the many-body Green's function theory. With BTP-IC and BTP-IS as the acceptors, we consider the Förster, Dexter, and overlap electronic couplings to compute the excitation energy transfers of the dimers. The ionization energies and excited-state energies of the four donors calculated by GW + BSE are in good agreement with experiments, and they are sensitive to the functionals in the computation. We find two charge transfer schemes. The thienyl of PBDB-T molecule makes its charge-transfer state at the lowest energy, and the total electronic coupling of PBDB-T based dimer is the strongest. The Dexter, and overlap types electronic couplings are significant to study the excitation energy transfer of organic heterojunctions. We provide a theoretical guide in the design and synthesis of higher-performance halogen-free donors.

Modulation of the oxygen sensing properties of iridium (III) complexes by changing their substitution groups

In this study, new bis-cyclometalated iridium (III) complexes bearing different ligated groups (–H, –OCH3, –F, –CH3) at the aryl moiety (Ir-1, Ir-2, Ir-3 and Ir-4) were synthesized and characterized. Then oxygen sensing properties of corresponding complexes were investigated in EC film. The complexes showed room temperature phosphorescence spectra in the range of 562–590 nm in THF and 546–554 nm in ethyl cellulose (EC) matrix. When they were incorporated in an ethyl cellulose matrix, the probes showed optimal dynamics of luminescence for oxygen monitoring in the range from 0 % to 100 % air saturation. The I0/I100 values of Ir-1, Ir-2, Ir-3 and Ir-4 in EC thin film were calculated as 10.9, 5.0, 7.3 and 22.7, respectively. The results showed that the oxygen sensitivity accomplishment of the complex core can be fine-tuned by varying these ligated groups, and the weak electron-donating properties of the methyl groups at the aryl moiety improve remarkably the optical oxygen sensing abilities of the Iridium (III) complexes.

Roles of amorphous and crystalline regions in determining the optical and electronic properties of donor:acceptor systems comprising poly(3-hexylthiophene) embedded with nitrogen/sulfur-doped graphene quantum dots

Roles of amorphous and crystalline regions in determining the optical and electronic properties of donor:acceptor systems comprising poly(3-hexylthiophene) embedded with nitrogen/sulfur-doped graphene quantum dots

Caught in the act: Monitoring O[sbnd]O bond cleavage in Acylperoxoferric cytochrome P450cam to form compound I in real time

While monitoring the reaction of ferric cytochrome P450cam (Cyp101) with substituted peroxybenzoic acids using rapid-scanning, stopped-flow (RSSF) spectroscopy, an intermediate appears en route to formation of the high-valent moiety known as Compound I [Fe(IV)=O/porphyrin radical cation] that is thought to be the key catalytic species for O-atom transfer to substrate. We have previously suggested (Spolitak, T., Dawson, J.H., Ballou, D.P., J. Biol. Chem.2005, 280, 20,300–20,309) that this species is an acylperoxo-ferric heme adduct that subsequently undergoes OO bond cleavage to generate Compound I. Singular value decomposition analysis of the RSSF data for formation of this intermediate shows that the energy of its Soret absorption peak is sensitive to the electron donor properties of the aryl substituents on the peracid. A linear Hammett correlation plot is seen for the energy of the Soret absorption peak vs. the Hammett σ constant. This correlation requires that the aryl substituents remain as part of the ligand bound to the heme iron, providing direct evidence that the adduct is indeed a ferric acylperoxo derivative. Linear Hammett correlation plots are also seen for both the rate of formation of the intermediate as well as for its conversion to Compound I. It is proposed that the electron donating/withdrawing properties of the aryl-bound substituents affect the electrophilic nature for binding substrate, changing the observed rate of formation for the acylperoxo intermediate, as well as the propensity and stability of the substituted benzoic acid to serve as the leaving group during OO bond cleavage yielding Compound I.

Vitamin C supplementation rescued meiotic arrest of spermatocytes in Balb/c mice exposed to BDE-209

Deca-brominated diphenyl ether (BDE-209) is a ubiquitous industrial chemical as brominated flame retardant (BFRs). Exposure to BDE-209 has been clearly associated with male reproductive disorders. However, the meiotic arrest mechanism of spermatocytes exposed to BDE-209 is still unclear. The present work aimed to explore the protective effect of vitamin C on BDE-209-induced meiotic arrest of spermatocytes and its possible mechanism. Vitamin C (100 mg/kg BW) was administered to BDE-209-exposed (80 mg/kg BW) male Balb/c mice once daily by intraperitoneal injection for 2 weeks. Our results showed that vitamin C played male reproductive protection effects as showed by attenuated BDE-209-induced testicular damage, and reduced sperm abnormality rate. Vitamin C also attenuated BDE-209-induced increase in SOD and MDA in testes and GC-2 spd cells. Moreover, vitamin C promoted meiotic prophase in BDE-209-induced mice, with suppressed γ-H2AX, restored DMC1, RAD51, and crossover marker MLH1 levels, and prevented BDE-209-induced DNA impairment. In addition, vitamin C supplementation also interfered with BDE-209-induced upregulation of testicular H3K4me3 through inhibition of KDM5s capacity and decreasing ferrous ion concentration. Furthermore, ferrous sulfate pretreatment could partially restore the expression of H3K4me3 via maintaining the concentration of ferrous ions. Taken together, vitamin C exerts a potential therapeutic agent for preventing BDE-209-induced reproductive toxicity with meiotic arrest, which is attributed to its antioxidant and electron donor properties, as well as, modulation of ferrous ion levels and demethylation of H3K4me3.

Rhodium-Catalyzed Asymmetric Hydrogenation of All-Carbon Aromatic Rings.

Compared with heteroarenes, homogeneous asymmetric hydrogenation of all-carbon aromatic rings is a longstanding challenge in organic synthesis due to the strong aromaticity and difficult enantioselective control. Herein, we report the rhodium/diphosphine-catalyzed asymmetric hydrogenation of all-carbon aromatic rings, affording a series of axially chiral cyclic compounds with high enantioselectivity through desymmetrization or kinetic resolution. In addition, the central-chiral cyclic compounds were also obtained by asymmetric hydrogenation of phenanthrenes bearing a directing group. The key to success is the introduction of chiral diphosphine ligands with steric hindrance and strong electron-donating properties. The axially chiral monophosphine ligands could be obtained by simple conversion of the hydrogenation products bearing the phosphine atom.

Experimental and DFT investigations on enhanced stability found on Re-, Rh-, and Nb-promoted Pt/WOx/γ-Al2O3 catalyst during aqueous-phase glycerol hydrogenolysis

The aqueous-phase glycerol hydrogenolysis is one of the catalytic methods used to convert the glycerol by-product from biodiesel production to highly valuable chemicals, especially 1,3–propanediol (1,3PDO). The density functional theory (DFT) and experiments were used to study the promotional effects of third metals promoters: Re, Rh, and Nb in WOx doped Pt-based catalysts that withstand deactivation via metal leaching, sintering, and coking. The third metal promoter improves catalytic activity and 1,3PDO selectivity due to increased electron density at the Pt active site confirmed by DFT. However, improved stability was found only on re- and Rh-promoted systems, evident from sustained activity and selectivity of spent catalysts. The deactivation study revealed that Pt leaching was negligible in all cases. Still, W leaching is more concerned and can be reduced only by Re and Nb promoters, whereas Pt sintering can be prevented only in the case of Re promoter. Mitigation of coking can be realized from DFT that only the Re promoter has comparable electron donor property to Pt and can prevent active site blockage by shifting the preferable coke adsorption site from Pt to a promoter atom, as also confirmed by the lowest amount of type I coke measured by the thermal gravimetric analysis leading to a high product yield.

A Distinctive Pattern for Substituent Effects on Transition Metal Centers: Enhanced Electron-Donating Capacity of Cationic Palladium Species

A Distinctive Pattern for Substituent Effects on Transition Metal Centers: Enhanced Electron-Donating Capacity of Cationic Palladium Species

Nature-derived highly tribopositive ϰ-carrageenan-agar composite-based fully biodegradable triboelectric nanogenerators

Biodegradable triboelectric nanogenerators (TENGs) have been studied for powering biotransient electronics in past years. For stable powering, developing biodegradable materials which have high tribopositive properties as well as high biocompatibility is crucially required. Here, we investigate a nature-derived ϰ-carrageenan-agar (ϰC-Agar) composite as high-performing triboelectric friction material for biodegradable TENG. We found that the composite shows greatly enhanced electron-donating property. At an optimized ϰC concentration of 80 wt%, the surface potential at most 57.5% increases compared to bare materials. We validated that the enhancement was caused by increased charge trapping sites consisting of Ca2+ cations and sulfate ester groups in the composite. In addition, we found that the ϰC-Agar composite has high intrinsic biocompatibility as it shows high cell viability in MTT assay and subdermal implant causes little noticeable inflammation, contributed by the high hydrophilicity of the composite. We further demonstrate a fully biodegradable TENG using an optimized ϰC-Agar composite. Very thin (0.3 mm) and flexible our device generates high output root-mean-square (RMS) current of 0.45 mA·m−2 and output RMS power of 0.15 mW·m−2 at optimized impedance. Our work provides a basis for the development of high-performance biodegradable TENGs for self-powered transient electronics.

Molecular engineering and activity improvement of acetylcholinesterase inhibitors: Insights from 3D-QSAR, docking, and molecular dynamics simulation studies

The carbamate molecule rivastigmine was found to possess promising anti-acetylcholinesterase activity, enabling to target and occupy choline binding sites, and as a result, widely used to improve the treatment of Alzheimer's disease (AD). Higher dose of rivastigmine indicates rapid onset but more adverse effects, such as the large fluctuations in plasma concentration level and frequent incidence of gastrointestinal side effect. To solve the dilemma, we developed a three-dimensional quantitative structure-activity relationship (3D-QSAR), docking and molecular dynamics (MD) simulation strategy to construct a dismountable nanoplatform of inhibitor engineering, verification and application for improving the inhibitory activity per unit concentration. With the aid of 3D-QSAR method, we constructed a model by using 25 molecules reported, and verified well the rationality of these QSAR models by non-cross validation coefficient (r2 = 0.902). Docking and MD results show that rivastigmine, as a control, does target exactly the binding sites of acetylcholinesterase, those already observed experimentally, in turn, confirming the reliability of the present 3D-QSAR results. The method suggests that groups with electron-donating chemical property can improve the inhibitory activity, and screens out two novel inhibitors L-1 and L-2 with more activity from database (about 8000 compounds). Moreover, L-1 and L-2 not only target exactly the same binding sites of acetylcholinesterase as the rivastigmine does, but also hold stronger binding energy, showing a more powerful inhibitory ability. More broadly, this work showcases an approach in the engineering of carbamate inhibitors to enhance their inhibitory activity using electron-donating groups, which simplifies the design process of complex bioactive molecules.

Mössbauer studies of the ferryl, ferrous and ferric states of dehaloperoxidase from A. ornata

Dehaloperoxidase (DHP) is a multi-functional catalytic globin from the marine worm A. ornata, whose physiological functions include oxygen transport and oxidation of toxic substrates present in its habitat. In the Fe(III) state, DHPA has an isomer shift of 0.42 mm/s, characteristic for high-spin heme proteins. Changes in pH have subtle effects on the electronic structure of DHP in the Fe(III) state detectable in the high-field spectra, which show a pH-dependent mixture of species with different zero-field splittings between 5 and 18 cm−1. The short-lived intermediate obtained by direct reaction of the Fe(III) enzyme with H2O2 has an isomer shift of 0.10 mm/s, indicative of an Fe(IV)-oxo state and of an S = 1 electronic ground state confirmed by variable field studies. The O2-bound state of DHP has an isomer shift of 0.28 mm/s and a high-field spectrum characteristic for diamagnetic heme complexes, similarly to other haemoglobins.Overall, the isomer shift and quadrupole splitting of DHP in the four states studied are expectedly similar to both peroxidases and to myoglobin. The differences in electronic structure between DHP and other heme proteins and enzyme are observed in the high-field Mössbauer spectra of the ferric state, which show pH-dependent zero-field splittings suggesting a heme site in which the ligand field strength at the iron ion is tuned by pH. This tunability is correlated with variable electron-donating properties of the iron, which can perform multiple functions.

Conformation-Dependent Electron Donation of Nido-Carborane Substituents and Its Influence on Phosphorescence of Tris(2,2′-bipyridyl)ruthenium(II) Complex

In this work, we report the synthesis of the nido-carborane-substituted ruthenium complexes and the substituent effects of nido-carboranes on the optical properties. Initially, from the optical measurements, it is shown that deep-red phosphorescence was obtained from the synthesized molecule, and the phosphorescent quantum yields were significantly improved by loading onto a polyethylene glycol film. This result represents that nido-carborane can work as a strong electron donor and should be an effective unit for enhancing the solid-state phosphorescence of ruthenium complexes. Further, it is suggested that the electron-donating properties of the nido-carborane units and subsequently the optical properties can be tuned by controlling the conformation of the nido-carborane units with the steric substituents. We demonstrate in this study the potential of nido-carborane as a building block for constructing optical materials as well as fundamental information regarding electronic interactions with π-conjugated systems.

Electrochromic Polymers Based on 1,4-Bis((9H-carbazol-9-yl)methyl)benzene and 3,4-Ethylenedioxythiophene Derivatives as Promising Electrodes for Flexible Electrochromic Devices

A 1,4-bis((9H-carbazol-9-yl)methyl)benzene (DCB)-containing homopolymer (P(DCB)) and four DCB- and ED-derivative (3,4-ethylenedioxythiophene (EDOT) and 3,4-ethylenedioxythiophene-methanol (EDm))-containing copolymers (P(DCB-co-ED), P(2DCB-co-ED), P(DCB-co-EDm), and P(2DCB-co-EDm)) were electropolymerized on ITO-polyethylene terephthalate (PET) substrates and their electrochromic performances were studied. DCB displays a lower Eonset than that of EDOT and EDm, conjecturing that the biscarbazole-containing DCB group shows a stronger electron-donating property than that of the ED derivatives. The P(2DCB-co-ED) film presents slate grey, dark khaki, and dark olive green at 0.0, 1.0, and 1.2 V. Bleaching-to-coloring switching studies of polymers show that P(2DCB-co-EDm) shows a high ΔT (31.0% at 725 nm) in solutions. Five dual-layer flexible electrochromic devices (ECDs) based on P(DCB), P(DCB-co-ED), P(2DCB-co-ED), P(DCB-co-EDm), and P(2DCB-co-EDm) as the anodic materials and PEDOT-PSS as the cathodic material are constructed. The P(2DCB-co-ED)/PEDOT-PSS flexible ECD shows a high ΔT (40.3% at 690 nm) and long-term electrochemical cycling stability, while the P(DCB-co-EDm)/PEDOT-PSS ECD shows a high ΔT (39.1% at 640 nm) and short response time (≤1.5 s). These findings offer us a new structural insight for the valuable design of conjugated polymers in high-contrast, flexible ECDs.

Thiazol-2-ylidenes as N-Heterocyclic carbene ligands with enhanced electrophilicity for transition metal catalysis.

Over the last 20 years, N-heterocyclic carbenes (NHCs) have emerged as a dominant direction in ligand development in transition metal catalysis. In particular, strong σ-donation in combination with tunable steric environment make NHCs to be among the most common ligands used for C-C and C-heteroatom bond formation. Herein, we report the study on steric and electronic properties of thiazol-2-ylidenes. We demonstrate that the thiazole heterocycle and enhanced π-electrophilicity result in a class of highly active carbene ligands for electrophilic cyclization reactions to form valuable oxazoline heterocycles. The evaluation of steric, electron-donating and π-accepting properties as well as structural characterization and coordination chemistry is presented. This mode of catalysis can be applied to late-stage drug functionalization to furnish attractive building blocks for medicinal chemistry. Considering the key role of N-heterocyclic ligands, we anticipate that N-aryl thiazol-2-ylidenes will be of broad interest as ligands in modern chemical synthesis.

Design and Development of Ruthenium-Based Catalysts for Enabling Hydrogen Storage

For past decades, hydrocarbon-based fuels have been the primary source of energy as a necessity for modern machines and automotive vehicles. Despite use in combustion engines and power plants, fossil fuels reserves are unpredictable and the associated CO2 emissions are now causing terrible effects on the environment and human health. Researchers have realized H2 as a potentially safe and efficient energy source, with an energy density of 33.3 kWh per kg. Moreover, H2 is significantly more environmentally friendly as H2O is the only by-product. Currently, the development of on-board storage technology is progress for use in the transportation industry. The chemical storage of hydrogen, in which H2 is bound to a carrier molecule, provides a more practical and safer method to store and release immense amounts of H2. Ammonia Borane (H3N-BH3, AB) is a useful material for storing up to 19.6 wt% of and 0.145kg L-1 of H2 with the ability to release H2 under mild ambient conditions through exposure to a suitable catalyst. This project investigates the use of pyrazole-based compounds as ligands for η6-arene Ru-complexes in order to formulate efficient catalysts for AB dehydrogenation. Pyrazoles are interesting diaza-five member heterocycles and have strong electron-donating properties. Mono- and di-coordinating substituted pyrazole complexes and an unusual Cl-bridging dimeric Ru complex were successfully synthesized and characterized (NMR, ESI-MS and X-ray diffraction crystallography) before undergoing evaluation for AB dehydrogenation studies in a high-pressure stainless steel reactor. The dimeric Ru Cl-bridging catalyst released the largest H2 equivalent per mol of AB with 1.45 with a total of 7.82 bar of H2 pressure, proving to be the most successful catalyst in the series. However, from the H2 release profiles, it appears that catalysts undergo slow transformation where it is possible that the pyrazole ligands are lost. Further mechanistic studies are required to determine the decomposition process.