Dynamic Photoelectrochemical Device Using an Electrolyte-Permeable NiO_<i>x</i>/SiO₂/Si Photocathode with an Open-Circuit Potential of 0.75 V

As a thermodynamic driving force obtained from sunlight, the open-circuit potential (OCP) in photoelectrochemical cells is typically limited by the photovoltage (<i>V</i>_ph). In this work, we establish that the OCP can exceed the value of <i>V</i>_ph when an electrolyte-permeable NiO_<i>x</i> thin film is employed as an electrocatalyst in a Si photocathode. The built-in potential developed at the NiO_<i>x</i>/Si junction is adjusted in situ according to the progress of the NiO_<i>x</i> hydration for the hydrogen evolution reaction (HER). As a result of decoupling of the OCP from <i>V</i>_ph, a high OCP value of 0.75 V (vs reversible hydrogen electrode) is obtained after 1 h operation of HER in an alkaline electrolyte (pH = 14), thus outperforming the highest value (0.64 V) reported to date with conventional Si photoelectrodes. This finding might offer insight into novel photocathode designs such as those based on tandem water-splitting systems

Scalable 3‑D Carbon Nitride Sponge as an Efficient Metal-Free Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal–air batteries. Here, we developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO₂, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn–air batteries. The resulting primary Zn–air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm^–2, a specific capacity of 830 mA h g^–1, and better durability for 210 h after mechanical recharging. An extraordinary small charge–discharge voltage polarization (∼0.80 V at 25 mA cm^–2), superior reversibility, and stability exceeding prolonged charge–discharge cycles have been attained in rechargeable Zn–air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn–air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles

Scalable 3‑D Carbon Nitride Sponge as an Efficient Metal-Free Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal–air batteries. Here, we developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO₂, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn–air batteries. The resulting primary Zn–air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm^–2, a specific capacity of 830 mA h g^–1, and better durability for 210 h after mechanical recharging. An extraordinary small charge–discharge voltage polarization (∼0.80 V at 25 mA cm^–2), superior reversibility, and stability exceeding prolonged charge–discharge cycles have been attained in rechargeable Zn–air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn–air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles

Hierarchically Designed 3D Holey C₂N Aerogels as Bifunctional Oxygen Electrodes for Flexible and Rechargeable Zn-Air Batteries

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey C₂N aerogels (S-C₂NA) as bifunctional catalysts for Zn-air and Li-O₂ batteries. The S-C₂NA exhibited ultrahigh surface area (∼1943 m² g^–1) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO₂) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C–N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-C₂NA air cathodes exhibit superb energy densities (958 and 862 Wh kg^–1), low charge–discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO₂ catalysts, respectively. Notably, Li-O₂ batteries with S-C₂NA demonstrated an outstanding specific capacity of ∼648.7 mA h g^–1 and reversible charge–discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics

Diazaquinomycin Biosynthetic Gene Clusters from Marine and Freshwater Actinomycetes

Tuberculosis is an infectious disease of global concern. Members of the diazaquinomycin (DAQ) class of natural products have shown potent and selective activity against drug-resistant Mycobacterium tuberculosis. However, poor solubility has prevented further development of this compound class. Understanding DAQ biosynthesis may provide a viable route for the generation of derivatives with improved properties. We have sequenced the genomes of two actinomycete bacteria that produce distinct DAQ derivatives. While software tools for automated biosynthetic gene cluster (BGC) prediction failed to detect DAQ BGCs, comparative genomics using MAUVE alignment led to the identification of putative BGCs in the marine Streptomyces sp. F001 and in the freshwater Micromonospora sp. B006. Deletion of the identified daq BGC in strain B006 using CRISPR-Cas9 genome editing abolished DAQ production, providing experimental evidence for BGC assignment. A complete model for DAQ biosynthesis is proposed based on the genes identified. Insufficient knowledge of natural product biosynthesis is one of the major challenges of productive, genome mining approaches. The results reported here fill a gap in knowledge regarding the genetic basis for the biosynthesis of DAQ antibiotics. Moreover, identification of the daq BGC shall enable future generations of improved derivatives using biosynthetic methods

Silver-Nanowire-Embedded Transparent Metal-Oxide Heterojunction Schottky Photodetector

We report a self-biased and transparent Cu₄O₃/TiO₂ heterojunction for ultraviolet photodetection. The dynamic photoresponse improved 8.5 × 10⁴% by adding silver nanowires (AgNWs) Schottky contact and maintaining 39% transparency. The current density–voltage characteristics revealed a strong interfacial electric field, responsible for zero-bias operation. In addition, the dynamic photoresponse measurement endorsed the effective holes collection by embedded-AgNWs network, leading to fast rise and fall time of 0.439 and 0.423 ms, respectively. Similarly, a drastic improvement in responsivity and detectivity of 187.5 mAW^–1 and of 5.13 × 10⁹ Jones, is observed, respectively. The AgNWs employed as contact electrode can ensure high-performance for transparent and flexible optoelectronic applications

Characterization of the RAF-forming oligomeric species of α-synuclein.

<p>(<b>A</b>) The fibrillation kinetics of α-synuclein was monitored with ThT binding fluorescence following the incubation of α-synuclein at 1 mg/ml in 20 mM Mes, pH 6.5, at 37°C with shaking at 200 rpm. (<b>B</b>) TEM images showing the RAF formation on the surface of PC-liposomes. The liposomes (1.25 mg/ml) were treated with various states of α-synuclein (0.5 mg/ml) collected during the fibrillation kinetics at the times indicated with arrow heads in panel (A). (<b>C</b>) CD spectra of the α-synuclein collected at various time points during the fibrillation process (0 hr, red; 4 hr, orange; 8 hr, yellow; 12 hr, green; 16 hr, cyan; 18.5 hr, light blue; 24 hr, blue; 28 hr, violet; 37.5 hr, black; 44 hr, dark gray; 50 hr, gray; 60 hr, white color). (<b>D</b>) Plot of negative ratios of the differences in molar ellipticities obtained at 193 nm and 220 nm (-Δθ_{193 nm}/Δθ_{220 nm}) for the various states of α-synuclein in comparison with those of the monomeric form. The inset shows the oligomeric state of α-synuclein visualized with TEM giving rise to the maximum value of - Δθ_{193 nm}/Δθ_{220 nm}.</p

Disruption of lipid membranes upon the surface-dependent amyloid fibril formation.

<p>(<b>A</b>) PC-liposomes (1.25 mg/ml, 0.2 ml) revealed with TEM following a brief incubation in 20 mM Mes, pH 6.5, for 5 min at 25°C under a quiescent condition with the oligomeric α-synuclein at 220 µg (left panel) and 330 µg (right panel). (<b>B</b>) Thermodynamic assessment with isothermal titration calorimetry (ITC) for the molecular assembly-disassembly process of the PC-liposomes as treated with either the oligomers (red line) or the monomers (black line) of α-synuclein. The PC-liposomes (2.5 mg/ml, 1.7 ml) in 62.5 mM Mes, pH 6.5 were sequentially combined with α-synuclein in either form at 54.7 µg per addition for 20 sec at 5 min-interval. Negative value of y-axis represents exothermic reaction. (<b>C</b>) Disruption of the liposome containing magnetic nanoparticles (MNPs). The PC-liposomes enclosing the Fe₃O₄ magnetic nanoparticles were examined with TEM before (left) and after (right) the treatment of oligomeric α-synuclein at 0.5 mg/ml in 20 mM Mes, pH 6.5, for 5 min at 25°C. Arrows in the right panel indicate MNPs localized on the fibrils. (<b>D</b>) Calcium release from the Ca²⁺-entrapped PC-liposomes in the presence of monomers, oligomers, and amyloid fibrils of α-synuclein. The PC-liposomes containing 1 mM CaCl₂ were incubated with monomers, oligomers, and fibrils of α-synuclein at 0.11 mg/ml in 20 mM Mes, pH 6.5, for 2 hr at 25°C. The release of Ca²⁺ ions was monitored with the Ca²⁺ ion-indicative fluorescent dye of BTC by detecting light emitting at 529 nm with an excitation at 401 nm. (<b>E and F</b>) Disruption of mitochondria (E) and lysosomes (F) with the oligomer treatment of α-synuclein. Mitochondria and lysosomes were visualized with TEM before (inset in a) and after (a) the oligomer treatment (0.5 mg/ml) in 20 mM Mes at pH 6.5 for 2 hr at 37°C. Presence of α-synuclein in the fibrils was confirmed with immunogold labeling with rabbit anti-α-synuclein antibody as indicated with arrows. Releases of lactate dehydrogenase (LDH) and cathepsin D were separately monitored upon the addition of oligomers with chromogenic substrates as a measure of disruption of mitochondria and lysosomes, respectively (b). Values are shown in means±s.d. (n = 2).</p

Radiating Amyloid Fibril Formation on the Surface of Lipid Membranes through Unit-Assembly of Oligomeric Species of α-Synuclein

<div><h3>Background</h3><p>Lewy body in the substantia nigra is a cardinal pathological feature of Parkinson's disease. Despite enormous efforts, the cause-and-effect relationship between Lewy body formation and the disorder is yet to be explicitly unveiled.</p> <h3>Methodology/Principal Findings</h3><p>Here, we showed that radiating amyloid fibrils (RAFs) were instantly developed on the surface of synthetic lipid membranes from the β-sheet free oligomeric species of α-synuclein through a unit-assembly process. The burgeoning RAFs were successfully matured by feeding them with additional oligomers, which led to concomitant dramatic shrinkage and disintegration of the membranes by pulling off lipid molecules to the extending fibrils. Mitochondria and lysosomes were demonstrated to be disrupted by the oligomeric α-synuclein via membrane-dependent fibril formation.</p> <h3>Conclusion</h3><p>The physical structure formation of amyloid fibrils, therefore, could be considered as detrimental to the cells by affecting membrane integrity of the intracellular organelles, which might be a molecular cause for the neuronal degeneration observed in Parkinson's disease.</p> </div

Radiating amyloid fibril (RAF) formation on the surface of lipid membranes.

<p>(<b>A</b>) Transmission electron microscopy (TEM) image of radiating fibrils that were developed on the surface of liposomes. (<b>B</b>) With congo red staining, birefringency of the radiating fibrils on PC-liposomes has been monitored with fluorescence microscope under polarized light. The corresponding image revealed with light microscope of differential interference contrast (DIC) is also shown in the inset. (<b>C</b>) Thioflavin-T (ThT) binding fluorescence of the PC-liposomes (0.57 mg/ml) treated with either the oligomers (open dots) or the monomers (closed dots) of α-synuclein at their protein concentrations indicated was monitored at 482 nm with an excitation at 450 nm. (<b>D</b>) Circular dichroism (CD) spectra obtained for the PC-liposomes (1.25 mg/ml) incubated with either the oligomers (red dots) or the monomers (black dots) of α-synuclein at 0.5 mg/ml after an extended period of quiescent incubation for 18 hours at 37°C.</p