Phosphorus-Ligand Redox Cooperative Catalysis: Unraveling Four-Electron Dioxygen Reduction Pathways and Reactive Intermediates.

The reduction of dioxygen to water is crucial in biology and energy technologies, but it is challenging due to the inertness of triplet oxygen and complex mechanisms. Nature leverages high-spin transition metal complexes for this, whereas main-group compounds with their singlet state and limited redox capabilities exhibit subdued reactivity. We present a novel phosphorus complex capable of four-electron dioxygen reduction, facilitated by unique phosphorus-ligand redox cooperativity. Spectroscopic and computational investigations attribute this cooperative reactivity to the unique electronic structure arising from the geometry of the phosphorus complex bestowed by the ligand. Mechanistic study via spectroscopic and kinetic experiments revealed the involvement of elusive phosphorus intermediates resembling those in metalloenzymes. Our result highlights the multielectron reactivity of phosphorus compound emerging from a carefully designed ligand platform with redox cooperativity. We anticipate that the work described expands the strategies in developing main-group catalytic reactions, especially in small molecule fixations demanding multielectron redox processes.

SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries.

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.

Melting domain size and recrystallization dynamics of ice revealed by time-resolved x-ray scattering.

The phase transition between water and ice is ubiquitous and one of the most important phenomena in nature. Here, we performed time-resolved x-ray scattering experiments capturing the melting and recrystallization dynamics of ice. The ultrafast heating of ice I is induced by an IR laser pulse and probed with an intense x-ray pulse which provided us with direct structural information on different length scales. From the wide-angle x-ray scattering (WAXS) patterns, the molten fraction, as well as the corresponding temperature at each delay, were determined. The small-angle x-ray scattering (SAXS) patterns, together with the information extracted from the WAXS analysis, provided the time-dependent change of the size and the number of liquid domains. The results show partial melting (~13%) and superheating of ice occurring at around 20 ns. After 100 ns, the average size of the liquid domains grows from about 2.5 nm to 4.5 nm by the coalescence of approximately six adjacent domains. Subsequently, we capture the recrystallization of the liquid domains, which occurs on microsecond timescales due to the cooling by heat dissipation and results to a decrease of the average liquid domain size.

Ultrafast photoisomerization mechanism of azaborine revealed by nonadiabatic molecular dynamics simulations.

1,2-Dihydro-1,2-azaborine is an isoelectronic analog of benzene with a B-N substitution, and its unique photoisomerization behavior, which is distinct from that of benzene, has drawn significant attention. To understand the detailed mechanism of azaborine photochemistry considering the dynamical effect and gain a comprehensive understanding of photochemical reactions, we investigated the photoisomerization dynamics of azaborine using nonadiabatic molecular dynamics simulations with Tully's surface hopping algorithm. Herein, the structural and energetic analyses of the trajectories revealed three different paths: direct relaxation (path 1), relaxation via a prefulvene-like intermediate (path 2), and formation of the Dewar isomer as a photoproduct (path 3). Our results confirmed that the photoisomerization of azaborine follows the energetically favored pathway predicted by the previous minimum energy path (MEP) calculations, exclusively forming the Dewar isomer, which is consistent with the experimental observations. Additionally, despite the low quantum yield found in our simulations, the high-level excitation energy calculations support the complete conversion observed in the experiments.

Liquid-liquid phase separation in supercooled water from ultrafast heating of low-density amorphous ice.

Recent experiments continue to find evidence for a liquid-liquid phase transition (LLPT) in supercooled water, which would unify our understanding of the anomalous properties of liquid water and amorphous ice. These experiments are challenging because the proposed LLPT occurs under extreme metastable conditions where the liquid freezes to a crystal on a very short time scale. Here, we analyze models for the LLPT to show that coexistence of distinct high-density and low-density liquid phases may be observed by subjecting low-density amorphous (LDA) ice to ultrafast heating. We then describe experiments in which we heat LDA ice to near the predicted critical point of the LLPT by an ultrafast infrared laser pulse, following which we measure the structure factor using femtosecond x-ray laser pulses. Consistent with our predictions, we observe a LLPT occurring on a time scale < 100 ns and widely separated from ice formation, which begins at times >1 µs.

Analysis of VOCs Emitted from Small Laundry Facilities: Contributions to Ozone and Secondary Aerosol Formation and Human Risk Assessment.

Volatile organic compounds (VOCs) emitted to the atmosphere form ozone and secondary organic aerosols (SOA) by photochemical reactions. As they contain numerous harmful compounds such as carcinogens, it is necessary to analyze them from a health perspective. Given the petroleum-based organic solvents used during the drying process, large amounts of VOCs are emitted from small laundry facilities. In this study, a laundry facility located in a residential area was selected, while VOCs data emitted during the drying process were collected and analyzed using a thermal desorption-gas chromatography/mass spectrometer (TD-GC/MS). We compared the results of the solvent composition, human risk assessment, contribution of photochemical ozone creation potential (POCP), and secondary organic aerosol formation potential (SOAP) to evaluate the chemical species. Alkane-based compounds; the main components of petroleum organic solvents, were dominant. The differences in evaporation with respect to the boiling point were also discerned. The POCP contribution exhibited the same trend as the emission concentration ratios for nonane (41%), decane (34%), and undecane (14%). However, the SOAP contribution accounted for o-xylene (28%), decane (27%), undecane (25%), and nonane (9%), thus confirming the high contribution of o-xylene to SOA formation. The risk assessment showed that acrylonitrile, carbon tetrachloride, nitrobenzene, bromodichloromethane, and chloromethane among carcinogenic compounds, and bromomethane, chlorobenzene, o-xylene, and hexachloro-1, 3-butadiene were found to be hazardous, thereby excessing the standard value. Overall these results facilitate the selection and control of highly reactive and harmful VOCs emitted from the dry-cleaning process.

Li-Compound Anodes: A Classification for High-Performance Li-Ion Battery Anodes.

Four main anode types are generally considered as typical anodes for Li-ion batteries (LIBs): Li-metal, carbon-based, alloy-based, and oxide-based anodes. Although they exhibit satisfactory electrochemical performance as LIB anodes, they cannot simultaneously satisfy all key requirements for LIB anodes: high reversible capacity, high initial Coulombic efficiency (ICE), long cycle life, fast rate capability, structural stability, and no safety concerns. Here, we suggest Li-compound anodes as a promising class of high-performance LIB anodes. Three binary (LiSn, Li2Sb, and LiBi) and three ternary (Li2ZnSb, Li5GeP3, and Li5SnP3) Li compounds were introduced as Li-compound anodes. LiSn and Li5SnP3 were selected and further modified into their nanocomposites by solid-state synthetic routes using carbon sources for high-performance LIB anodes. The Li-compound nanocomposite anodes exhibited excellent performance and simultaneously fulfilled all the key requirements for high-performance LIB anodes. Therefore, Li-compound anodes are expected to be a promising and innovative category of high-performance LIB anodes.

Following the Crystallization of Amorphous Ice after Ultrafast Laser Heating.

Using time-resolved wide-angle X-ray scattering, we investigated the early stages (10 µs-1 ms) of crystallization of supercooled water, obtained by the ultrafast heating of high- and low-density amorphous ice (HDA and LDA) up to a temperature T = 205 K ± 10 K. We have determined that the crystallizing phase is stacking disordered ice (Isd), with a maximum cubicity of χ = 0.6, in agreement with predictions from molecular dynamics simulations at similar temperatures. However, we note that a growing small portion of hexagonal ice (Ih) was also observed, suggesting that within our timeframe, Isd starts annealing into Ih. The onset of crystallization, in both amorphous ice, occurs at a similar temperature, but the observed final crystalline fraction in the LDA sample is considerably lower than that in the HDA sample. We attribute this discrepancy to the thickness difference between the two samples.

Self-Healing Graphene-Templated Platinum-Nickel Oxide Heterostructures for Overall Water Splitting.

Electrocatalysts with dramatically enhanced water splitting efficiency, derived from controlled structures, phase transitions, functional activation, etc., have been developed recently. Herein, we report an in situ observation of graphene-based self-healing, in which this functional activation is induced by a redox reaction. Specifically, graphene on stainless steel (SUS) switches between graphene (C-C) and graphene oxide (C-O) coordination via an electrical redox reaction to activate water splitting. A heterostructure comprising Pt-NiO thin films on single-layer graphene directly grown on a SUS substrate (Pt-NiO/Gr-SUS) was also synthesized by electrodeposition. Pt-NiO/Gr-SUS exhibited water splitting activity with low Pt loading (<1 wt %). The findings provide valuable insight for designing robust electrodes based on reversible redox-induced self-healable graphene to develop more efficient catalysts.

Quantification of tire wear particles in road dust from industrial and residential areas in Seoul, Korea.

In this study, we examined tire and road wear microparticles (TRWMPs) in road dust along the Seoul metropolitan area, from industrial and residential areas. The road dust samples were collected via vacuum sweep methods and then filtered to obtain particles with diameters less than 75 µm. To quantify the TRWMPs in road dust, we used the raw materials of tire components, natural rubber (NR), and styrene-butadiene rubber (SBR), as standard materials. We evaluated the usability of the pyrolyzer-gas chromatography/mass spectrometry py-GC/MS method introduced in ISO/TS 20593 by confirming the decomposition temperatures of the NR and SBR by thermogravimetric (TG) and evolved gas analysis (EGA)-MS. The average of TRWMPs in industrial and residential area road dust were 22,581 and 9818 µg/g, respectively, indicating that the industrial area has 2.5 times higher TRWMPs concentration. Further, the NR, the main component of truck bus radial, to SBR, the main component of passenger car radial, ratio was slightly higher in the industrial area than in the residential area. This presumably means that the high traffic volume, including heavy duty vehicles in industrial areas, affected the higher concentration of TRWMPs. This study reveals the growing evidence of the importance of TRWMPs in road dust and how TRWMPs quantity can impact the air quality of the Seoul metropolitan area.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing.

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS2 and Pd nanoclusters (Pd/MoS2) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS2 produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS2 can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS2 is enhanced three-fold under visible light illumination (17% for 140 ppm of H2) in comparison with dark light (5% for 140 ppm of H2). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS2 can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Experimental observation of the liquid-liquid transition in bulk supercooled water under pressure.

We prepared bulk samples of supercooled liquid water under pressure by isochoric heating of high-density amorphous ice to temperatures of 205 ± 10 kelvin, using an infrared femtosecond laser. Because the sample density is preserved during the ultrafast heating, we could estimate an initial internal pressure of 2.5 to 3.5 kilobar in the high-density liquid phase. After heating, the sample expanded rapidly, and we captured the resulting decompression process with femtosecond x-ray laser pulses at different pump-probe delay times. A discontinuous structural change occurred in which low-density liquid domains appeared and grew on time scales between 20 nanoseconds to 3 microseconds, whereas crystallization occurs on time scales of 3 to 50 microseconds. The dynamics of the two processes being separated by more than one order of magnitude provides support for a liquid-liquid transition in bulk supercooled water.

Characteristics of hydrogen production by photocatalytic water splitting using liquid phase plasma over Ag-doped TiO2 photocatalysts.

Hydrogen production from water was investigated by applying liquid plasma (LPP) to photocatalytic splitting of water. The optical properties of LPP due to water emission were also evaluated. The correlation between the optical properties of plasma and the formation of active species in water was investigated with the photocatalytic activity of hydrogen production. TiO2 was also doped with Ag to evaluate the effect of enhancing photocatalytic activity. The photocatalytic activity was evaluated by the rate of hydrogen production, and the effect of hydrogen formation was also investigated by injecting methanol as an additive. As a result of examining the luminescence properties of LPP, it showed high luminescence in the 309 nm UV region and the 656 nm visible region. The hydrogen doping rate was increased in the Ag-doped TiO2 photocatalyst. Ag-doped TiO2 has wider light absorption into the visible region and narrower band gap. Due to these properties, the rate of hydrogen generation is superior to TiO2 photocatalysts. The photochemical reaction with LPP and photocatalyst in aqueous solution with CH3OH showed a significant increase in hydrogen production rate. The increase in hydrogen production by injection of additives is because the optical properties of generating OH radicals are improved and CH3OH is decomposed to act as an electron donor to improve hydrogen production.

Epiduroscopic decompression of a symptomatic perineural cyst: A case report.

RATIONALE: Perineural cysts in the spinal canal are usually asymptomatic. However, symptoms can occur when the cyst becomes large enough to compress a nerve root. There are still no established treatment options for this disease. In this report, we describe a case of successful decompression of the large symptomatic perineural cyst using epiduroscope. PATIENT CONCERNS: A 42-year-old male patient visited our pain center complaining of discomfort and pain in his right posterior thigh. Magnetic resonance imaging of the patient showed a large perineural cyst (53 × 31 × 21 mm) compressing the right S1 nerve. No other abnormalities that would explain the patient's symptoms were identified. DIAGNOSIS: Perineural cyst at the right S1 nerve. INTERVENTIONS: We performed an epiduroscopic decompression of the perineural cyst. After advancing the epiduroscope and locating the cyst, we used the laser to make a hole in the cyst wall. Then, the epiduroscope was advanced into the cyst, and the cystic fluid was aspirated. OUTCOMES: The symptoms of the patient were relieved after the procedure, without any complications. There was no recurrence of symptoms until 6 months after the procedure. LESSONS: The epiduroscope is a minimally invasive method which can be used safely for decompression of symptomatic perineural cysts in the spinal canal.

Kambin's Triangle Approach versus Traditional Safe Triangle Approach for Percutaneous Transforaminal Epidural Adhesiolysis Using an Inflatable Balloon Catheter: A Pilot Study.

Spinal stenosis is a common condition in elderly individuals. Many patients are unresponsive to the conventional treatment. If the transforaminal epidural block does not exert a sufficient treatment effect, percutaneous transforaminal epidural adhesiolysis (PTFA) through the safe-triangle approach using an inflatable balloon catheter can reduce the patients' pain and improve their functional capacity. We aimed to evaluate the safety and efficacy of the Kambin's-triangle approach for PTFA using an inflatable balloon catheter and compare this approach to the traditional safe-triangle approach. Thirty patients with chronic unilateral L5 radiculopathy were divided into two groups: the safe-triangle-approach and Kambin's-triangle-approach groups, with 15 patients each. The success rate of the procedure was assessed. Pain and dysfunction were assessed using the Numerical Rating Scale and Oswestry Disability Index, respectively, before the procedure and at 1 and 3 months after the procedure. The success rate of the procedure was high in both the groups, with no significant difference between the groups. The Numerical Rating Scale and Oswestry Disability Index scores significantly decreased 3 months after the procedure in both the groups, with no significant difference between the groups. For patients in whom the safe-triangle approach for PTFA is difficult, the Kambin's-triangle approach could be an alternative.

Study of stainless steel electrodes after electrochemical analysis in sea water condition.

For water electrolysis, a rare earth material (eg., platinum) is often used as an electrode, but because of the high cost and toxicity of chemicals, researchers are searching for cost effective and eco-friendly alternative materials. Various alloys and metals have been long explored for use as electrode materials in different media. Stainless steel (SS 304) electrodes are cost effective and have a large surface area; further their catalytic performance is comparable to that of carbon coated noble metals cathodes. Stainless steel has good mechanical properties and durability so it is widely used in desalination plants, oil and gas industries, ship building, etc. However, over a period of time it corrodes very quickly in saline water. To improve the stability and durability of the electrodes (i.e., to minimize corrosion), we anneal the samples under two different sets of conditions and test the electrodes in 3.5% NaCl solution. The anodic peak (-0.25 V) observed for bare stainless steel result from the formation of iron (II) hydroxide [Fe(OH)2]. The Raman bands observed at 210 and 274 cm-1 for bare stainless steel result from the formation of α-Fe2O3 owing to partial, anodic, and cathodic reactions occurring on the electrode which disrupts the surface layers. High intensity X-ray diffraction (XRD) and Raman peaks of Cr2O3 and MnCr2O4 observed in argon and hydrogen annealed sample after cyclic voltammetry reveal that this sample is more stable than bare and air annealed samples. XRD reveals mixed oxide phases in addition to eskolaite and magnetite phases. Scanning electron microscope (SEM) images show that although the air-annealed sample has a soft, spongy structure, Na and Cl ions are adsorbed in the voids on the outer surface of the electrode leading to quick degradation. For the air-annealed sample the oxide appears to adhere poorly to the stainless steel. Oxygen (ie., oxide composition) may play a key role in adherence and growth of Cr2O3 formed at high temperature. X-ray photoelectron spectroscopy (XPS) reveals that large amounts of Cr and Mn are dissolved/corroded into the electrolyte for air annealed sample which is in good agreement with the Raman and SEM results.

The Lineage-Defining Transcription Factors SOX2 and NKX2-1 Determine Lung Cancer Cell Fate and Shape the Tumor Immune Microenvironment.

The major types of non-small-cell lung cancer (NSCLC)-squamous cell carcinoma and adenocarcinoma-have distinct immune microenvironments. We developed a genetic model of squamous NSCLC on the basis of overexpression of the transcription factor Sox2, which specifies lung basal cell fate, and loss of the tumor suppressor Lkb1 (SL mice). SL tumors recapitulated gene-expression and immune-infiltrate features of human squamous NSCLC; such features included enrichment of tumor-associated neutrophils (TANs) and decreased expression of NKX2-1, a transcriptional regulator that specifies alveolar cell fate. In Kras-driven adenocarcinomas, mis-expression of Sox2 or loss of Nkx2-1 led to TAN recruitment. TAN recruitment involved SOX2-mediated production of the chemokine CXCL5. Deletion of Nkx2-1 in SL mice (SNL) revealed that NKX2-1 suppresses SOX2-driven squamous tumorigenesis by repressing adeno-to-squamous transdifferentiation. Depletion of TANs in SNL mice reduced squamous tumors, suggesting that TANs foster squamous cell fate. Thus, lineage-defining transcription factors determine the tumor immune microenvironment, which in turn might impact the nature of the tumor.

Precipitation of Nickel Oxide on TiO2 Photocatalysts for Enhanced Visible Degradation Activity.

The liquid phase plasma (LPP) synthetic process has been exploited to synthesize nickel oxide nanoparticles doped TiO2 photocatalyst (NOTP) that can respond to visible light. The physicochemical properties of NOTPs were studied by several analysis instruments. The nickel oxide nanoparticles precipitated uniformly on the TiO2 powder are mostly NiO. The band gap energy of the NOTP measured was 2.99 eV, which was smaller than that of bare TiO2, 3.12 eV. The NOTP synthesized in this work showed high photoactivity under visible blue light.

Assembling a supercapacitor electrode with dual metal oxides and activated carbon using a liquid phase plasma.

Developing supercapacitor electrodes at an affordable cost while improving their energy and/or power density values is still a challenging task. This study introduced a recipe which assembled a novel electrode composite using a liquid phase plasma that was applied to a reactant solution containing an activated carbon (AC) powder with dual metal precursors of iron and manganese. A comparison was made between the composites doped with single and dual metal components as well as among those synthesized under different precursor concentrations and plasma durations. The results showed that increasing the precursor concentration and plasma duration raised the content of both metal oxides in the composites, whereas the deposition conditions were more favorable to iron oxide than manganese oxide, due to its higher standard potential. The composite treated with the longest plasma duration and highest manganese concentration was superior to the others in terms of cyclic stability and equivalent series resistance. In addition, the new composite selected out of them showed better electrochemical performance than the raw AC material only and even two types of single metal-based composites, owing largely to the synergistic effect of the two metal oxides. Therefore, the proposed methodology can be used to modify existing and future composite electrodes to improve their performance with relatively cheap host and guest materials.

Transcriptomic analysis of genes modulated by cyclo(L-phenylalanine-L-proline) in Vibrio vulnificus.

Diketopiperazine is produced by various organisms, including bacteria, fungi, and animals, and has been suggested as a novel signal molecule involved in the modulation of genes with various biological functions. Vibrio vulnificus, which causes septicemia in humans, produces cyclo(L-phenylalanine-L-proline) (cFP). To understand the biological roles of cFP, the effect of the compound on the expression of the total mRNA in V. vulnificus was assessed by nextgeneration sequencing. Based on the transcriptomic analysis, we classified the cFP-regulated genes into functional categories and clustered them according to the expression patterns resulted from treatment with cFP. From a total of 4,673 genes, excepting the genes encoding tRNA in V. vulnificus, 356 genes were up-regulated and 602 genes were down-regulated with an RPKM (reads per kilobase per million) value above 3. The genes most highly induced by cFP comprised those associated with the transport and metabolism of inorganic molecules, particularly iron. The genes negatively regulated by cFP included those associated with energy production and conversion, as well as carbohydrate metabolism. Noticeably, numerous genes related with biofilm formation were modulated by cFP. We demonstrated that cFP interferes significantly with the biofilm formation of V. vulnificus.