Temperature Matters: Bacterial Response to Temperature Change.

Temperature is one of the most important factors in all living organisms for survival. Being a unicellular organism, bacterium requires sensitive sensing and defense mechanisms to tolerate changes in temperature. During a temperature shift, the structure and composition of various cellular molecules including nucleic acids, proteins, and membranes are affected. In addition, numerous genes are induced during heat or cold shocks to overcome the cellular stresses, which are known as heat- and cold-shock proteins. In this review, we describe the cellular phenomena that occur with temperature change and bacterial responses from a molecular perspective, mainly in Escherichia coli.

A Method to Study α-Synuclein Toxicity and Aggregation Using a Humanized Yeast Model.

Parkinson's disease is the second most common neurodegenerative disorder and is characterized by progressive cell death caused by the formation of Lewy bodies containing misfolded and aggregated α-synuclein. α-synuclein is an abundant presynaptic protein that regulates synaptic vesicle trafficking, but the accumulation of its proteinaceous inclusions results in neurotoxicity. Recent studies have revealed that various genetic factors, including bacterial chaperones, could reduce the formation of α-synuclein aggregates in vitro. However, it is also important to monitor the anti-aggregation effect in the cell to apply this as a potential treatment for the patients. It would be ideal to use neuronal cells, but these cells are difficult to handle and take a long time to exhibit the anti-aggregation phenotype. Therefore, a quick and effective in vivo tool is required for the further evaluation of in vivo anti-aggregation activity. The method described here was used to monitor and analyze the anti-aggregation phenotype in the humanized yeast Saccharomyces cerevisiae, which expressed human α-synuclein. This protocol demonstrates in vivo tools that could be used for monitoring α-synuclein-induced cellular toxicity, as well as the formation of α-synuclein aggregates in cells.

Self-supported mesoscopic tin oxide nanofilms for electrocatalytic reduction of carbon dioxide to formate.

Here we report a self-supported SnO2 nanofilm prepared by a robust electrochemical process as an electrocatalyst for the CO2 reduction reaction. The SnO2 film had a large surface area originating from its nano-architecture and manifested high selectivity toward formate (over 60%), which resulted in CO2-to-formate current density up to 33.66 mA cm-2 that is among the state-of-the-art. We unveiled that the high performance of the SnO2 nanofilm is attributable to the presence of a metastable oxide under reductive conditions in addition to the abovementioned advantages.

Aggregation-free optical and colorimetric detection of Hg(II) with M13 bacteriophage-templated Au nanowires.

An optical and colorimetric biosensor comprising gold nanowires (Au NWs) templated with genetically engineered M13 bacteriophages expressing a specific Au binding peptides tyrosine-glutamic acid-glutamic acid-glutamic acid (Y3E) is fabricated by silver nitrate and surfactant-mediated biomineralization process. The diameter of the Y3E-Au NWs is around 10 nm and an oriented growth mechanism is identified for the continuous growth of the NWs by interconnecting M13 bacteriophages. The flexible Au NWs have formed an enriched Hg(II) binding sites on its surface and the surface-coated silver nanophase functions as a receptor for more efficient Hg(II) binding. Amalgamation-based colorimetric and optical Hg(II) biosensing of Au NWs are scrutinized in the presence of wild-type M13 bacteriophage-templated Au NWs and spherical Au nanoparticles. It is demonstrated that in comparison with the spherical Au nanoparticles, Y3E-Au NWs exhibits an aggregation-free optical and colorimetric sensor for Hg(II). Mechanistic investigation for the aggregation-free sensor and the Au-Hg amalgam crystals are carried out using TEM, STEM-EDX and XPS analyses.

Hematite/M (M = Au, Pd) Catalysts Derived from a Double-Hollow Prussian Blue Microstructure: Simultaneous Catalytic Reduction of o- and p-Nitrophenols.

Present study deals with hematite/M (M = Au, Pd) catalysts converted from a double-hollow Prussian blue microstructure (DHPM). The unique Prussian blue (PB) microstructure (MS) is prepared by a template-free solvothermal synthetic route in a single-step reaction. An amine-functionalized silicate sol-gel matrix (SSG) has served as the structure-directing agent cum stabilizer for making DHPM. Synthesized DHPM is having a unique structure: a hollow core and an in situ etched porous surface. Growth mechanism is explored and revealed by analyzing several experimental parameters such as HCl concentration, Fe source, effect of the added EtOH, silane concentration, and role of silanes' amine groups. It is identified that the superstructure consisted of well-aligned PB cubes growing radially from the core of the superstructure. Metal (Au and Pd) nanoparticles (NPs) are deposited on both interior and exterior of the PB MS through galvanic displacement reaction, and thus metal NP-loaded hematite phase iron oxide (α-Fe2O3) nanomaterials were derived by annealing them in air. Catalytic activities of the hematite/M(M = Au, Pd) MS are investigated toward simultaneous catalytic reduction of o-nitrophenol and p-nitrophenol. The resultant hematite/Pd MS showed high structural stability and catalytic active sites than the hematite/Au MS, which enhances the catalytic properties for the simultaneous catalytic reduction of both nitrophenols.

Solvothermal-Derived S-Doped Graphene as an Anode Material for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have attracted enormous attention in recent years due to the high abundance and low cost of sodium. However, in contrast to lithium-ion batteries, conventional graphite is unsuitable for SIB anodes because it is much more difficult to intercolate the larger Na ions into graphite layers. Therefore, it is critical to develop new anode materials for SIBs for practical use. Here, heteroatom-doped graphene with high doping levels and disordered structures is prepared using a simple and economical thermal process. The solvothermal-derived graphene shows excellent performance as an anode material for SIBs. It exhibits a high reversible capacity of 380 mAh g-1 after 300 cycles at 100 mA g-1, excellent rate performance 217 mAh g-1 at 3200 mA g-1, and superior cycling performance at 2.0 A g-1 during 1000 cycles with negligible capacity fade.

Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes.

Dye-sensitized solar cells (DSCs) are promising solar energy conversion devices with aesthetically favorable properties such as being colorful and having transparent features. They are also well-known for high and reliable performance even under ambient lighting, and these advantages distinguish DSCs for applications in window-type building-integrated photovoltaics (BIPVs) that utilize photons from both lamplight and sunlight. Therefore, investigations on bifacial DSCs have been done intensively, but further enhancement in performance under back-illumination is essential for practical window-BIPV applications. In this research, highly efficient bifacial DSCs were prepared by a combination of electropolymerized poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and cobalt bipyridine redox ([Co(bpy)3]3+/2+) electrolyte, both of which manifested superior transparency when compared with conventional Pt and iodide counterparts, respectively. Keen electrochemical analyses of PEDOT films verified that superior electrical properties were achievable when the thickness of the film was reduced, while their high electrocatalytic activities were unchanged. The combination of the PEDOT thin film and [Co(bpy)3]3+/2+ electrolyte led to an unprecedented power conversion efficiency among bifacial DSCs under back-illumination, which was also over 85% of that obtained under front-illumination. Furthermore, the advantage of the electropolymerization process, which does not require an elevation of temperature, was demonstrated by flexible bifacial DSC applications.

Electrochemically Synthesized Nanoporous Molybdenum Carbide as a Durable Electrocatalyst for Hydrogen Evolution Reaction.

Demands for sustainable production of hydrogen are rapidly increasing because of environmental considerations for fossil fuel consumption and development of fuel cell technologies. Thus, the development of high-performance and economical catalysts has been extensively investigated. In this study, a nanoporous Mo carbide electrode is prepared using a top-down electrochemical process and it is applied as an electrocatalyst for the hydrogen evolution reaction (HER). Anodic oxidation of Mo foil followed by heat treatment in a carbon monoxide (CO) atmosphere forms a nanostructured Mo carbide with excellent interconnections, and these structural characteristics lead to high activity and durability when applied to the HER. Additionally, characteristic behavior of Mo is observed; metallic Mo nanosheets form during electrochemical anodization by exfoliation along the (110) planes. These nanosheets are viable for chemical modification, indicating their feasibility in various applications. Moreover, the role of carbon shells is investigated on the surface of the electrocatalysts, whereby it is suggested that carbon shells serve as a mechanical barrier against the oxidative degradation of catalysts that accompanies unavoidable volume expansion.

Electrochemical synthesis of nanoporous tungsten carbide and its application as electrocatalysts for photoelectrochemical cells.

Photoelectrochemical (PEC) cells are promising tools for renewable and sustainable solar energy conversion. Currently, their inadequate performance and high cost of the noble metals used in the electrocatalytic counter electrode have postponed the practical use of PEC cells. In this study, we report the electrochemical synthesis of nanoporous tungsten carbide and its application as a reduction catalyst in PEC cells, namely, dye-sensitized solar cells (DSCs) and PEC water splitting cells, for the first time. The method employed in this study involves the anodization of tungsten foil followed by post heat treatment in a CO atmosphere to produce highly crystalline tungsten carbide film with an interconnected nanostructure. This exhibited high catalytic activity for the reduction of cobalt bipyridine species, which represent state-of-the-art redox couples for DSCs. The performance of tungsten carbide even surpassed that of Pt, and a substantial increase (∼25%) in energy conversion efficiency was achieved when Pt was substituted by tungsten carbide film as the counter electrode. In addition, tungsten carbide displayed decent activity as a catalyst for the hydrogen evolution reaction, suggesting the high feasibility for its utilization as a cathode material for PEC water splitting cells, which was also verified in a two-electrode water photoelectrolyzer.

Wrinkled silica/titania nanoparticles with tunable interwrinkle distances for efficient utilization of photons in dye-sensitized solar cells.

Efficient light harvesting is essential for the realization of high energy conversion efficiency in dye-sensitized solar cells (DSCs). State-of-the-art mesoporous TiO2 photoanodes fall short for collection of long-wavelength visible light photons, and thus there have been efforts on introduction of scattering nanoparticles. Herein, we report the synthesis of wrinkled silica/titania nanoparticles with tunable interwrinkle distances as scattering materials for enhanced light harvesting in DSCs. These particles with more than 20 times larger specific surface area (>400 m(2)/g) compared to the spherical scattering particles (<20 m(2)/g) of the similar sizes gave rise to the dye-loading amounts, causing significant improvements in photocurrent density and efficiency. Moreover, dependence of spectral scattering properties of wrinkled particles on interwrinkle distances, which was originated from difference in overall refractive indices, was observed.

Deployment shock attenuation of a solar array tape hinge by means of the Martensite detwinning of NiTi Shape Memory Alloy.

This paper presents a new tape hinge for attenuating the deployment shock of a satellite solar array. This hinge uses the Martensite detwinning of Shape Memory Alloy (SMA). To attenuate the deployment shock, a NiTi SMA strip is assembled between two curved steel strips. The attenuation performance of the hinge is analyzed using a SMA detwinning constitutive equation. A prototype of the hinge is manufactured and its characteristics are measured in a bending test and in a deployment test. Finally, the deployment performance of the prototype hinge is investigated on a satellite model. It is shown that the new SMA damped tape hinge can effectively minimize the deployment shock and dynamic perturbation while also maintaining suitable deployment performance.

Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells.

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.