Decreasing Hydrogen Content within Zirconium Using Au and Pd Nanoparticles as Sacrificial Agents under Pressurized Water at High Temperature.

Decreasing hydride-induced embrittlement of zirconium-based cladding is a significant challenge for the successful dry storage of spent nuclear fuel. Herein, to radically minimize hydride-induced embrittlement, we used nanoparticles as sacrificial agents with a greater affinity than zirconium for hydrogen. Corrosion experiments in the presence of gold (Au) and palladium (Pd) nanoparticles under simulated pressurized water reactor (PWR) conditions revealed that the hydrogen content of the zirconium samples was remarkably reduced, with a maximum decrease efficiency of 53.9% using 65 nm Au and 53.8% using 50 nm Pd nanoparticles. This approach provides an effective strategy for preventing hydride-induced embrittlement of zirconium-based cladding.

Adsorption behavior of furan at Ge(100) surface.

The adsorption behavior of furan on the Ge(100) surface was studied using a combination of high-resolution photoemission spectroscopy (HRPES) and density functional theory (DFT) calculations. We identified the two adsorption species produced by the [4 + 2] cycloaddition and deoxygenation reactions of furan with the Ge(100) surface in a ratio of approximately 76:24 at the surveyed coverages, via an analysis of the binding energies and relative area proportions of all the peaks in the C 1s and O 1s core-level spectra. The DFT simulation results revealed that the [4 + 2] cycloaddition and deoxygenation adducts are thermodynamically preferred by the reaction of furan with the Ge(100) surface compared with others, which is consistent with the HRPES results. The findings will further our understanding of the surface reactions of five-membered heterocyclic molecules.

Verifying the relationships of defect site and enhanced photocatalytic properties of modified ZrO2 nanoparticles evaluated by in-situ spectroscopy and STEM-EELS.

Base treatment and metal doping were evaluated as means of enhancing the photocatalytic activity of ZrO2 nanoparticles (NPs) via the generation of oxygen vacancies (OvS), and the sites responsible for this enhancement were identified and characterized by spectroscopic and microscopic techniques. We confirmed that OvS produced by base treatment engaged in photocatalytic activity for organic pollutant degradation, whereas surface defects introduced by Cr-ion doping engaged in oxidative catalysis of molecules. Moreover, we verified that base-treated ZrO2 NPs outperformed their Cr-ion doped counterparts as photocatalysts using in situ X-ray photoelectron spectroscopy and scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS). Thus, our study provides valuable information on the origin of the enhanced photocatalytic activity of modified ZrO2 NPs and demonstrates the practicality of in situ spectroscopy and STEM-EELS for the evaluation of highly efficient metal oxide photocatalysts.

Photocatalysis of Cr- and Fe-Doped CeO2 Nanoparticles to Selective Oxidation of 5-Hydroxymethylfurfural.

Oxygen vacancies (Vo) present in CeO2 nanoparticles (NPs) can effectively boost their photocatalytic activity under ultraviolet (UV) light. To improve photocatalytic performance, Cr- and Fe-doped CeO2 NPs with increased Vo were prepared using a simple method of doping Cr and Fe ions into CeO2 NPs, which was confirmed by an in-depth analysis of the structural and electronic changes. Through photocatalytic degradation (PCD) experiments with 5-hydroxymethylfurfural (HMF), we found that the PCD rates of the two doped CeO2 NPs were faster than that of the CeO2 NPs. In addition, the conversion of HMF to 2,5-furandicarboxylic acid (FDCA) using the doped CeO2 NPs occurred only through the mechanism of the selective oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), exhibiting better efficiency than using CeO2 NPs.

Crystal Phase Transition Creates a Highly Active and Stable RuCX Nanosurface for Hydrogen Evolution Reaction in Alkaline Media.

Although metastable crystal structures have received much attention owing to their utilization in various fields, their phase-transition to a thermodynamic structure has attracted comparably little interest. In the case of nanoscale crystals, such an exothermic phase-transition releases high energy within a confined surface area and reconstructs surface atomic arrangement in a short time. Thus, this high-energy nanosurface may create novel crystal structures when some elements are supplied. In this work, the creation of a ruthenium carbide (RuCX , X < 1) phase on the surface of the Ru nanocrystal is discovered during phase-transition from cubic-close-packed to hexagonal-close-packed structure. When the electrocatalytic hydrogen evolution reaction (HER) is tested in alkaline media, the RuCX exhibits a much lower overpotential and good stability relative to the counterpart Ru-based catalysts and the state-of-the-art Pt/C catalyst. Density functional theory calculations predict that the local heterogeneity of the outermost RuCX surface promotes the bifunctional HER mechanism by providing catalytic sites for both H adsorption and facile water dissociation.

Reaction Behaviors of S-, O-, and N-containing Aliphatic Molecules with a Propyl Moiety on Ge(100) Surface.

The reaction pathways of 1-propanethiol, 1-propanol, and propylamine molecules, containing a propyl moiety, on a Ge(100) surface were investigated using high-resolution photoemission spectroscopy (HRPES) experiments and density functional theory (DFT) calculations. Upon analysis of the HRPES data, the adsorption of 1-propanethiol and 1-propanol was found to occur through a dissociation reaction, whereas that of propylamine took place via N dative bonding at room temperature. On the basis of our DFT results, adsorption geometries and transition states for each of these molecules on the Ge(100) surface were confirmed. Systematic studies of S-, O-, and N-containing molecules, composed of an identical propyl moiety, on the Ge(100) surface provide insight into the adsorption mechanism of aliphatic molecules containing alkyl chains on the Ge(100) surface.

Platform- and label-free detection of lead ions in environmental and laboratory samples using G-quadraplex probes by circular dichroism spectroscopy.

Guanine-rich quadruplex (G-QD) are formed by conversion of nucleotides with specific sequences by stabilization of positively charged K+ or Na+. These G-QD structures differentially absorb two-directional (right- and left-handed) circularly polarized light, which can discriminate the parallel or anti-parallel structures of G-QDs. In this study, G-QDs stabilized by Pb2+ were analyzed by a circular dichroism (CD) spectroscopy to determine Pb2+ concentration in water samples. Thrombin aptamer (TBA), PS2.M, human telomeric DNA (HTG), AGRO 100, and telomeric related sequence (T2) were studied to verify their applicability as probes for platform- and label-free detection of Pb2+ in environmental as well as laboratory samples. Among these nucleotides, TBA and PS2.M exhibited higher binding constants for Pb2+, 1.20-2.04 × 106/M at and 4.58 × 104-1.09 × 105/M at 100 micromolar and 100 mM K+ concentration, respectively. They also exhibited excellent selectivity for Pb2+ than for Al3+, Cu2+, Ni2+, Fe3+, Co2+, and Cr2+. When Pb2+ was spiked into an effluent sample from a wastewater treatment plant (WWTP), its existence was detected by CD spectroscopy following a simple addition of TBA or PS2.M. By the addition of TBA and PS2.M, the Pb2+ signals were observed in effluent samples over 0.5 micromolar (100 ppb) concentration. Furthermore, PS2.M caused a Pb2+-specific absorption band in the effluent sample without spiking of Pb2+, and could be induced to G-QD structure by the background Pb2+ concentration in the effluent, 0.159 micromolar concentration (3.30 ppb). Taken together, we propose that TBA and PS2.M are applicable as platform- and label-free detection probes for monitoring Pb2+ in environmental samples such as discharged effluent from local WWTPs, using CD spectroscopy.

Enhanced Electrochemical Properties and OER Performances by Cu Substitution in NiCo2O4 Spinel Structure.

In order to improve the electrochemical performance of the NiCo2O4 material, Ni ions were partially substituted with Cu2+ ions having excellent reducing ability. All of the electrodes were fabricated by growing the Ni1-xCuxCo2O4 electrode spinel-structural active materials onto the graphite felt (GF). Five types of electrodes, NiCo2O4/GF, Ni0.875Cu0.125Co2O4/GF, Ni0.75Cu0.25Co2O4/GF, Ni0.625Cu0.375Co2O4/GF, and Ni0.5Cu0.5Co2O4/GF, were prepared for application to the oxygen evolution reaction (OER). As Cu2+ ions were substituted, the electrochemical performances of the NiCo2O4-based structures were improved, and eventually the OER activities were also greatly increased. In particular, the Ni0.75Cu0.25Co2O4/GF electrode exhibited the best OER activity in a 1.0 M KOH alkaline electrolyte: the cell voltage required to reach a current density of 10 mA cm-2 was only 1.74 V (η = 509 mV), and a low Tafel slope of 119 mV dec-1 was obtained. X-ray photoelectron spectroscopy (XPS) analysis of Ni1-xCuxCo2O4/GF before and after OER revealed that oxygen vacancies are formed around active metals by the insertion of Cu ions, which act as OH-adsorption sites, resulting in high OER activity. Additionally, the stability of the Ni0.75Cu0.25Co2O4/GF electrode was demonstrated through 1000th repeated OER acceleration stability tests with a high faradaic efficiency of 94.3%.

Ring-Opening Reaction of Tetrahydrofuran on Ge(100) Surface.

The adsorption structures and reaction mechanism of tetrahydrofuran on a Ge(100) surface were investigated through high-resolution photoemission spectroscopy (HRPES) and density functional theory (DFT) calculations. On the basis of our analysis of the HRPES spectra, two adsorption species consisting of a major Ge-(CH2)4-O-Ge structure formed via a ring-opening reaction and a minor molecularly adsorbed structure formed via O dative bonding were identified. Our DFT results provided not only the optimized adsorption structures and their corresponding adsorption energies but also the level of the transition state for the pathway from the molecularly adsorbed species to the major adsorption structure. The results confirmed that the adsorption of tetrahydrofuran on the Ge(100) surface is under both kinetic and thermodynamic controls. Our discovery of the ring-opening reaction is an unprecedented result in the field of Ge(100) surface chemistry.

The Effect of Deposition Time on the Surface Coverage of Sublimation Deposited Solid-Phase Glycine and Proline Molecules Measured by Scanning Tunneling Microscopy.

The effect of deposition time on the surface coverage of sublimation deposited solid-phase glycine and proline molecules onto a Ge(100) surface was studied at room temperature using scanning tunneling microscopy (STM). The STM images obtained at various coverages of glycine and proline adsorbed on the Ge(100) surface showed that (i) the adsorption rate for both molecules gradually decreased with increasing deposition time, obeying the Langmuir adsorption model, and (ii) the coverage of glycine on the Ge(100) surface is higher than that of proline under the same deposition conditions, which may be due to the differences in their molecular weight or molecular sticking probability.

Synchrotron-based high-resolution photoemission spectroscopy study of ZIRLO cladding with H2O adsorption: Coverage and temperature dependence.

The coverage and temperature dependence of ZIRLO cladding with H2O adsorption are studied using synchrotron-based high-resolution photoemission spectroscopy (HRPES). Based on the analytical results of the Zr 3d, O 1 s, C 1 s, and Sn 3d HRPES profiles prior to H2O adsorption, we determine the surface compositions of O2-, hydroxyl OH-, chemisorbed H2O, zirconium carbide, adventitious carbon, Sn metal, and SnO2 in ZIRLO. When ZIRLO is exposed to H2O molecules, the relative proportion of zirconium metal decreases, whereas that of the total zirconium oxides increases, suggesting the reaction between H2O and the zirconium metal in ZIRLO. On annealing a sample with 1000 L H2O on ZIRLO at 300 °C, Zr2O3 and ZrO2 decompose, and oxygen diffuses into the bulk, thereby reducing the oxidation states of zirconium on the surface. Moreover, at this temperature, the excess H2O molecules on ZIRLO are thoroughly desorbed and tin element is diffused into the bulk in ZIRLO.

Molecular tuning of amino acids to form two-dimensional molecular networks driven by conformational preorganization.

We investigated the self-assembly of rationally designed γ-Phe on Au(111) using scanning tunneling microscopy with density functional theory calculations. In contrast to α-Phe, γ-Phe self-assembled into ring-shaped clusters (RSCs) and two-dimensional (2D) molecular domains. The better self-association tendency was attributed to conformational preorganization through intramolecular interaction between ammonium and carboxylate functionalities.

Hydrolysis of trivalent plutonium and solubility of Pu(OH)3 (am) under electrolytic reducing conditions.

The aim of this work is to determine the solubility product of plutonium hydroxide under reducing conditions and to ascertain the stability of Pu(OH)3 (am) in water. Hydrolysis of Pu(iii) and solubility of Pu(OH)3 (am) were investigated at a constant ionic strength of 0.1 M NaClO4. Coulometric titration was adopted to adjust the pH of plutonium solutions, during which the electrolytic reducing conditions maintained the oxidation state of Pu(iii). Chemical speciation for dissolved plutonium was investigated using sensitive spectrophotometry coupled with a liquid waveguide capillary cell. The spectroscopic investigations indicated that dissolved Pu(iv), Pu(v), and Pu(vi) species were ignorable under these experimental conditions. The absorbance of Pu3+ ions decreased due to hydrolysis of Pu(iii) but the absorbance of Pu(iii) hydrolysis species was not distinguishable. The formation constant for the first hydrolysis species (log *ß'1) determined in the present study is -6.62 ± 0.25. The non-crystalline structure of the plutonium precipitate was observed through X-ray diffraction. The solubility product of Pu(OH)3 (am), log *K's,0 is determined to be 15.23 ± 0.50. These results indicate a stronger tendency for the hydrolysis of Pu(iii) and higher stability (lower solubility) of Pu(OH)3 (am) compared to Am(iii).

Dissociative adsorption of guanine on Ge(100).

Adsorption of guanine on Ge(100) was investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Guanine appears dark in STM images, indicating that its adsorption occurs through N-H dissociation. DFT calculations revealed that "N(1)-H dissociation through an O dative bonded structure" is the most favorable configuration.

Bacillus coreaensis sp. nov.: a xylan-hydrolyzing bacterium isolated from the soil of Jeju Island, Republic of Korea.

A xylan-degrading bacterium, designated as MS5(T) strain, was isolated from soil collected from the Jeju Island, Republic of Korea. Strain MS5(T) was Gram-stain-positive, aerobic, and motile by polar flagellum. The major fatty acids identified in this bacterium were iso-C15:0 (32.3%), C16:0 (27.3%), and anteiso-C15:0 (10.2%). A similarity search based on the 16S rRNA gene sequence revealed that the strain belongs to the class Bacilli and shared the highest similarity with the type strains Bacillus beringensis BR035(T) (98.7%) and Bacillus korlensis ZLC-26(T) (98.6%) which form a coherent cluster in a neighbor-joining phylogenetic tree. The DNA G+C content of strain MS5(T) was 43.0 mol%. The major menaquinone was MK-7 and the diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The DNADNA relatedness values between strain MS5(T) and two closely related species, B. beringensis BR035(T) and B. korlensis ZLC-26(T), were less than 70%. DNA-DNA relatedness analysis and 16S rRNA sequence similarity, as well as phenotypic and chemotaxonomic characteristics suggest that the strain MS5(T) constitutes a novel Bacillus species, for which the name Bacillus coreaensis sp. nov. is proposed. The type strain is MS5(T) (=DSM25506(T) =KCTC13895(T)).

STM tip catalyzed adsorption of thiol molecules at the nanometer scale.

The tungsten oxide covered tungsten (W) tip of a scanning tunneling microscope was found to act as a catalyst to catalyze the S-H dissociative adsorption of phenylthiol and 1-octanethiol molecules onto a Ge(100) surface. By varying the distance between the tip and the surface, the area of the tip-catalyzed adsorption could be controlled. We have found that the thiol headgroup is the critical functional group for this catalysis and the catalytic material is the tungsten oxide layer of the tip. This local tip-catalyzed adsorption may be used in positive lithographic methods to produce nanoscale patterning on semiconductor substrates.

Coverage dependence of the adsorption structure of alanine on Ge(100).

The variations with coverage and annealing temperature in the adsorption structure of alanine on Ge(100) have been investigated using high-resolution core-level photoemission spectroscopy (HRCLPES). The C 1s, N 1s, and O 1s core-level spectra at a low initial coverage show that both the carboxyl and amine groups of the alanine molecules participate in bonding with the Ge(100) surface in an "intrarow O-H dissociated and N dative bonded structure". However, at higher coverage we found that in addition to this structure an "O-H dissociation structure" is present. Moreover, we systematically monitored the variation of the bonding features of alanine adsorbed on Ge(100) with annealing temperature and thus were able to track the desorption processes. By analyzing the C 1s, N 1s, and O 1s spectra at 420 K, we conclude that the principal adsorption structure at this temperature is the "O-H dissociation structure" because of the disconnection of Ge-N dative bonding. At higher temperatures, the "O-H dissociation structure" is converted into various fragments such as Ge oxide (or Ge-CO), Ge nitride (Ge cyanide), and Ge carbide.

Intrarow adsorption structure of glycine on Ge(100).

The adsorption structure of glycine on Ge(100) was investigated using scanning tunneling microscopy (STM), density functional theory (DFT) calculations, and high-resolution core-level photoemission spectroscopy (HRCLPES). We found a major adsorption feature of glycine on Ge(100) in the STM images. This feature appeared as a bright protrusion between two dimer rows with a dark adjacent dimer. The position of the bright protrusion located in the middle of the two dimer rows indicates a multibonding adsorption structure. The results of the theoretical calculations confirm that the adsorption structure of glycine on Ge(100) (between two possible multibonding adsorption structures) is an "intrarow O-H dissociated and N dative bonded structure". In the HRCLPES experiments, we found an N 1s peak (at 399.5 eV) and two O 1s peaks (at 531.1 and 532.0 eV), which represent strong evidence that the adsorption configuration of glycine on Ge(100) is composed of both O-H dissociation and N dative bonding. All our STM, DFT, and HRCLPES results suggest that the adsorption structure of glycine molecules on Ge(100) is an "intrarow O-H dissociated and N dative bonded structure".