Hydrogen Storage Capacity of Cobalt Cluster Ions.

The adsorption of H2 on gas-phase Con± (n = 5-12) clusters at 300 K and the desorption of H2 from ConHm± upon heating were studied experimentally by combining thermal desorption spectrometry and mass spectrometry to elucidate the hydrogen storage property of the Co clusters. Hydrogen atoms adsorbed well on Con+ (n = 5, 10-12) and Con- (n = 5-12) at 300 K to form ConHm±. The atomic ratios, m/n, for ConHm- (0.9-1.4) were higher than those for ConHm+ (0.2-1.1). According to density functional theory (DFT) calculations, the first few H2 molecules had a tendency to dissociatively adsorb onto the Co clusters. Further, the bonding nature of the H atoms was ionic, similar to the H atoms in the metallic hydrides. In contrast, H2, adsorbed molecularly, was explained in terms of σ complex formation. H2 molecules were desorbed from the clusters upon heating. The temperature dependences showed that ConHm- released H2 at a higher temperature (700-800 K) than ConHm+ (600-700 K), suggesting that Con- should have a higher affinity to hydrogen than Con+. The desorption temperatures were lower than those of VnHm+, which was consistent with the fact that the adsorption energies of H2 were lower for the Co clusters than those for the V clusters. The low adsorption energies were ascribed to their large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps in the Co clusters.

Hydrogen Storage Mechanism by Gas-Phase Vanadium Cluster Cations Revealed by Thermal Desorption Spectrometry.

The adsorption of hydrogen on gas-phase vanadium cluster cations, Vn+ (n = 3-14), at 300 K and desorption of hydrogen from hydride clusters, VnHm+, upon heating were observed experimentally by combined thermal desorption spectrometry and mass spectrometry analyses. The ratio m/n was approximately 1.3 for all n values at 300 K, which was reduced to approximately zero at 1000 K. For n = 4, stable cluster geometries of V4Hm+ (m = 0, 2, 4, and 6) were investigated by DFT calculations, revealing that V4 adopted a trigonal pyramidal structure and the H atoms adsorbed mainly on the µ2 bridge sites. The adsorption reaction pathway of one H2 molecule on V4+ was also investigated. The experimentally estimated desorption energies of the H2 molecules were consistent with their calculated binding energies. Among the observed hydride clusters, V6H8+ was found to be significantly thermally durable, probably because of its close-packed octahedral V6 core structure, with H atoms occupying all hollow sites.

Salvage Case of Corpus Cavernosum Necrosis and Urethral Perforation associated with Infection after Penile Prosthesis Insertion.

Penile prosthesis implantation can be considered in patients with unsuccessful treatment with phosphodiesterase type 5 inhibitors for erectile dysfunction. Its associated postoperative complications include infection and urethral injury. Nevertheless, only a few studies have reported the successful management of severe cases. Herein, we report a case of corpus cavernosum necrosis and distal urethral perforation caused by infection after penile prosthesis insertion, which had favorable outcomes. A 60-year-old man with multiple atherosclerotic risks underwent penile prosthesis implantation for erectile dysfunction at another hospital. Postoperatively, he developed infectious necrosis and underwent prosthesis removal. However, he presented at our department because of technical difficulties in the treatment at other hospitals. The initial examination revealed extensive necrosis of the corpus cavernosum and perforation of the peripheral urethra. A thin urethral catheter was inserted, and the necrotic corpus cavernosum was debrided to preserve the artery and urethra. Then, the perforated urethra was sutured. Subsequent negative pressure wound therapy resulted in sufficient granulation and closure of the perforated urethra. One month after the surgery, the scar was resected and sutured following the circumcision line. Despite experiencing this severe postoperative complication, good functional and cosmetic outcomes were achieved after minimal surgery with a blood-flow-conserving method.

Dissociative Adsorption of Water on CaMn4O5 Cationic Clusters.

Water splitting is catalyzed by photosystem II, which comprises an inorganic core (CaMn4O5) and protein ligands. To understand the evolution of CaMn4O5 after attaching water molecules, an isolated CaMn4O5+ cluster was investigated using vibrational spectroscopy and density functional theory calculations. Computational findings suggest that when a water molecule adsorbs on the Ca atom through the O atom of water, one of the OH bonds forms a hydrogen bond with a µ-oxo bridge, which dissociates into two OH groups. This is consistent with the fact that no isomers with molecularly adsorbed water were experimentally observed.

Adsorption Forms of NO on Iridium-Doped Rhodium Clusters in the Gas Phase Revealed by Infrared Multiple Photon Dissociation Spectroscopy.

The adsorption of an NO molecule on a cationic iridium-doped rhodium cluster, Rh5Ir+, was investigated by infrared multiple photon dissociation spectroscopy (IRMPD) of Rh5IrNO+·Arp complexes in the 300-2000 cm-1 spectral range, where the Ar atoms acted as a messenger signaling IR absorption. Complementary density functional theory (DFT) calculations predicted two near-isoenergetic structures as the putative global minimum: one with NO adsorbed in molecular form in the on-top configuration on the Ir atom in Rh5Ir+, and one where NO is dissociated with the O atom bound to the Ir atom in the on-top configuration and the N atom on a hollow site formed by three Rh atoms. A comparison between the experimental IRMPD spectrum of Rh5IrNO+ and calculated spectra indicated that NO mainly adsorbs molecularly on Rh5Ir+, but evidence was also found for structures with dissociatively adsorbed NO. The estimated fraction of Rh5IrNO+ structures with dissociatively adsorbed NO is approximately 10%, which was higher than that found for Rh6+, but lower than that for Ir6+. The DFT calculations indicated the existence of an energy barrier in the NO dissociation pathway that is exothermic with respect to the reactants, which was considered to prevent NO from dissociating readily on Rh5Ir+. The height of the barrier is lower than that for NO dissociation over Rh6+, which is attributed to the higher binding energy of atomic O to the Ir atom in Rh5Ir+ than to a Rh atom in Rh6+.

Substitution of O with a Single Au Atom as an Electron Acceptor in Al Oxide Clusters.

Al atoms generally adopt the +3 oxidation state and form stoichiometric oxides such as Al2O3 in the bulk phase. Among small cationic gas-phase clusters, near-stoichiometric clusters such as Al3O4+, Al3O5+, Al4O6+, Al4O7+, Al5O7+, and Al5O8+ have been readily generated in experimental studies. However, when a single Au atom was included in the clusters, oxygen-deficient clusters such as AuAl4O5+ were formed in high abundance; in these clusters, the Au atom accepted electron density from the Al atoms. The geometrical structures and atomic charges in the clusters suggest that a single Au atom can substitute for O atoms in Al oxide clusters. This propensity originates from the high electron and low oxygen affinities, which, together, constitute an unusual property of Au.

Oxophilicity as a Descriptor for NO Cleavage Efficiency over Group IX Metal Clusters.

Iridium and rhodium are group IX elements that can both catalytically reduce NO. To understand the difference in their reactivity toward NO, the adsorption forms of NO onto clusters of Ir and Rh are compared using vibrational spectra, recorded via infrared multiple-photon dissociation spectroscopy. The spectra give evidence for the existence of at least two specific adsorption forms. The main Ir6+NO isomer is one in which NO is dissociated, whereas one other is a local minimum structure in the reaction pathway leading to dissociative adsorption. In contrast to adsorption onto Rh6+, where less than 10% of the isomeric population was found in the global minimum associated with dissociative adsorption, a substantial fraction (about 50%) of NO dissociates on Ir6+. This higher efficiency is attributed to a considerably reduced activation barrier for dissociation on Ir6+. The key chemical property identified for dissociation efficiency is the cluster's affinity to atomic oxygen.

Effect of atomicity on the oxidation of cationic copper clusters studied using thermal desorption spectrometry.

The resistivity to oxidation of small copper clusters, Cun+ (n ≤ 5), in the gas phase with a precise atomicity at the molecular level was investigated using a combination of thermal desorption spectrometry and mass spectrometry. Oxide clusters, CunOm+, with more O atoms than those present with a stoichiometry of n : m = 1 : 1 were produced at room temperature in the presence of O2, and the weakly bound excess oxygen atoms involved in the clusters were removed by post heating. Non-oxidized Cu2+ and Cu3+ clusters were formed in the range of 323-923 K, whereas partially oxidized clusters, Cu4O2+ and Cu5O2+, were generated for n = 4 and 5. Considering the fact that CunOm+ (m = n/2 + 1) tends to be generated for n ≥ 6, the small copper clusters were concluded to be resistive to oxidation. The possible reaction paths for the oxidation of Cu2+ and Cu4+ clusters were obtained by density functional calculations, which were consistent with the experimental findings. The oxidation states of the Cu atoms in the clusters were discussed based on the natural charges of the atoms.

Usefulness of serum biopterin as a predictive biomarker for childhood asthma control: A prospective cohort study.

BACKGROUND: Pteridines are metabolites of tetrahydrobiopterin, which serves as co-enzyme of nitric oxide synthase. We sought to investigate the usefulness of pteridines as biomarkers for childhood asthma control. METHODS: We conducted a single-center prospective cohort study involving 168 asthmatic children aged 4-17 years who visited the periodical asthma checkup program. Serum neopterin and biopterin levels were measured as pteridines at each visit along with measurement of FeNO, respiratory function tests, nasal eosinophil test, blood eosinophil count, and IgE level. We calculated coefficients for relation between pteridines and asthma control, which was assessed by questionnaires (JPAC: Japanese Pediatric Asthma Control Program). RESULTS: A total of 168 participants aged 10.3 ± 3.39 years (mean ± SD) with asthma were recruited. The participants in this study contained 58 patients (34.5%) of complete-controlled based on JPAC, 132 patients (76.0%) of well-controlled group based on GINA. FeNO and serum neopterin level did not correlate with following period's JPAC scores. In contrast, serum biopterin level significantly correlated with following period's JPAC total score (Coefficients 0.398; 95% CI 0.164 to 0.632; p value 0.001) and frequency of wheezing during exercise (Coefficients 0.272; 95% CI 0.217 to 0.328; p value < 0.001). CONCLUSIONS: We found serum biopterin effected the following period's control status of asthmatic children, thus monitoring biopterin level will be a useful for management of asthma to adjust treatment.

Anharmonic calculations of frequencies and intensities of OH stretching vibrations of (R)-1,3-butanediol conformers in the fundamentals and first overtones by density functional theory.

The frequencies and absorption intensities of the five kinds of conformers of 1,3-butanediol with the same carbon skeleton (GG') were calculated by anharmonic calculation for the fundamentals and first overtones of OH stretching vibrations. The four kinds of conformers form intramolecular hydrogen bonds and one conformer did not. Intramolecular hydrogen bond formation shifted the frequency of fundamental and first overtone of H-bonding OH stretching vibration to the lower frequency. The absorption intensities of the fundamentals as well as the vibrational anharmonicities increased upon hydrogen bond formation, while the intensities of first overtones decreased. The differences of conformers were clearly seen in the frequencies of the first overtones of free OH.

Catalytic Decomposition of NO by Cationic Platinum Oxide Cluster Pt3O4.

The catalytic decomposition of NO by cationic platinum oxide cluster Pt3O4+ was investigated by mass spectrometry and thermal desorption spectrometry. Upon reaction with two NO molecules, molecular oxygen desorbed from the cluster at room temperature to form Pt3O4N2+. Then, at temperatures above 400 K, desorption of N2 from Pt3O4N2+ was observed. These processes were confirmed by isotope-labeling experiments, and the energetics of O2 and N2 release were determined by density functional calculations. The combination of these elementary steps resulted in the catalytic decomposition of NO by Pt3O4+.

Geometrical Structures of Partially Oxidized Rhodium Cluster Cations, Rh6Om+ (m = 4, 5, 6), Revealed by Infrared Multiple Photon Dissociation Spectroscopy.

Infrared multiple photon dissociation (IRMPD) spectra of Rh6Om+ (m = 4-10) are obtained in the 300-1000 cm-1 spectral range using the free electron laser for infrared experiments (FELIX) via dissociation of Rh6Om+ or Rh6Om+-Ar complexes. The spectra are compared with the calculated spectra of several stable geometries obtained by density functional theory (DFT) structural optimization. The spectrum for Rh6O4+ shows prominent bands at 620 and 690 cm-1 and is assigned to a capped-square pyramidal Rh atom geometry with three bridging O atoms and one O atom in a hollow site. Rh6O5+ displays bands at 460, 630, 690, and 860 cm-1 and has a prismatic Rh geometry with three bridging O atoms and two O atoms in a hollow site. Rh6O6+ shows three intense bands around 600-750 cm-1 and multiple weak bands in the range of 350-550 cm-1. This species has a prismatic Rh geometry with four bridging O atoms and two O atoms in a hollow site. Considering that Rh6Om+ (m ≤ 3) adopts tetragonal bipyramidal Rh6 structures, the change at m = 4 to capped bipyramidal and at m = 5 to prismatic geometries results in a reduction of the number of triangular hollow sites. Since NO preferentially binds on a triangular hollow site through the N atom, the geometry change lowers the possibility of NO dissociative adsorption.

Nitrogen Molecule Adsorption on Cationic Tantalum Clusters and Rhodium Clusters and Desorption from Their Nitride Clusters Studied by Thermal Desorption Spectrometry.

Adsorption and desorption of N2 molecules onto cationic Ta and Rh clusters in the gas phase were investigated in the temperature range of 300-1000 K by using thermal desorption spectrometry in combination with density functional theory (DFT) calculations. For Ta6(+), the first N2 molecule was found to adsorb dissociatively, and it remained adsorbed when Ta6(+)N2 was heated to 1000 K. In contrast, the second and the subsequent N2 molecules adsorbed weakly as a molecular form and were released into the gas phase when heated to 600 K. The difference can be explained in terms of the activation barrier between the molecular and dissociative forms. On the other hand, when Ta clusters were generated in the presence of N2 gas by the laser ablation of a Ta rod, isomeric clusters, TanNm(+), having heat resistivity were formed. For Rh6(+), N2 adsorbed molecularly at 300 K and desorbed totally at 450 K. These results were consistent with the DFT calculations, indicating that the dissociative adsorption of N2 is endothermic.

Rhodium Oxide Cluster Ions Studied by Thermal Desorption Spectrometry.

Gas-phase rhodium oxide clusters, RhnOm(+), were investigated by measuring the rate constants of oxidation and thermal desorption spectrometry. RhnOm(+) was suggested to be categorized into different states as m/n ≤ 1, 1 < m/n ≤ 1.5, and 1.5 < m/n in terms of energy and kinetics. For m/n ≤ 1, the O atoms readily adsorbed on the cluster with a large binding energy until RhO was formed. Under the O2-rich environment, oxidation proceeded until Rh2O3 was formed with a moderate binding energy. In addition, O2 molecules attached weakly to the cluster, and Rh2O3 formed RhnOm(+) (1.5 < m/n). The energetics and geometries of Rh6Om(+) (m = 6-12) were obtained using density functional theory calculations and were found to be consistent with the experimental results.

Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

Thermal Desorption Spectroscopy Study of the Adsorption and Reduction of NO by Cobalt Cluster Ions under Thermal Equilibrium Conditions at 300 K.

Adsorption of NO molecules on gas phase cobalt cluster ions, Con(+) (n = 4-9), was investigated in thermal equilibrium with He gas at 300 K. The Con(+) clusters, contrary to the isolated clusters in a vacuum, adsorbed NO without undergoing significant dissociation. Thermal desorption spectroscopy of Con(+)(NO)m indicated that Con(+) clusters with n = 4-6 and n = 7-9 can have four and six adatoms chemisorbed, respectively. Reduction of NO occurred, releasing N2 molecules, to form Con(+)Ok(NO)m-k (k = 2, 4, ...). The reaction mechanism involved the exchange of chemisorbed N atoms with the O atom in NO bound to the clusters. The reactivity of Con(+) (n = 4-9) exhibited periodic n dependence, and Co6(+) and Co9(+) was similar to the case of the isolated Co16(+) clusters holding up to eight adatoms reported by Anderson et al. ( J. Chem. Phys . 2009 , 130 , 10992 - 11000 ).

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy.

Cationic rhodium clusters, Rh(n)(+) (n = 4-8), were prepared in the gas phase by the laser ablation of a Rh rod. The Rh(n)(+) clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He, where they were subjected to collisions with NO and He in a thermal equilibrium at 300 K. The NO molecules were found to adsorb sequentially on the Rh(n)(+) clusters forming Rh(n)(+)(NO)m. To examine the adsorption form and the reaction of NO, we heated Rh(n)(+)(NO)m in an extension tube located after the reaction gas cell and the thermal response of the clusters, desorption of the fragments, was recorded as a function of temperature (300-1000 K). The desorption of NO molecules was predominantly observed below 500 K, giving either Rh(n)(+)(NO)n+1 or Rh(n)(+)(NO)n+2, which indicates that there were NO molecules loosely adsorbed on the Rhn(+) clusters. Further desorption was found to proceed at higher temperatures (500-1000 K), whereby NO was released from the smaller clusters, Rh(n)(+) (n ≤ 5). In contrast, for the larger clusters (n ≥ 6), N2 release was clearly observed at high temperatures (>800 K). Thus, the reduction of NO occurred for larger clusters at higher temperatures.

Stable Stoichiometry of Gas-Phase Manganese Oxide Cluster Ions Revealed by Temperature-Programmed Desorption.

Temperature-programmed desorption (TPD) experiments were performed on gas-phase manganese oxide cluster ions, namely, Mn(n)O(m)(+) (n = 3-20) and Mn(n)O(m)(-) (n = 3-18). These cluster ions were prepared by laser ablation of a manganese rod in the presence of oxygen gas, and their composition was investigated using mass spectrometry. The composition of Mn(n)O(m)(±) distribution lies above the m = (4/3)n line. When the cluster ions were heated to 1000 K, Mn(n)O(m)(+) (m = (4/3)n + δ, with δ = -1, 0) and Mn(n)O(m)(-) (m = (4/3)n + δ, with δ = 0, 1) was found to be the predominant species, formed by thermal dissociation. These experimental findings indicate that the nascent manganese oxide clusters comprise robust Mn(n)O(m)(±) (m/n ≈ 4/3) and weakly bound excess oxygen atoms. On the basis of the TPD experiments, the oxygen-molecule release was identified as the main dissociation channel. The temperature dependence of O2 desorption was found to be similar among the clusters with the same oxygen excess or deficiency regardless of the number of Mn atoms. The threshold energy of O2 desorption was estimated for Mn4O(m)(+) (m = 6-11) and compared with bond dissociation energies calculated by density functional theory.

Adsorption and Desorption of Hydrogen by Gas-Phase Palladium Clusters Revealed by In Situ Thermal Desorption Spectroscopy.

Adsorption and desorption of hydrogen by gas-phase Pd clusters, Pdn(+), were investigated by thermal desorption spectroscopy (TDS) experiments and density functional theory (DFT) calculations. The desorption processes were examined by heating the clusters that had adsorbed hydrogen at room temperature. The clusters remaining after heating were monitored by mass spectrometry as a function of temperature up to 1000 K, and the temperature-programmed desorption (TPD) curve was obtained for each Pdn(+). It was found that hydrogen molecules were released from the clusters into the gas phase with increasing temperature until bare Pdn(+) was formed. The threshold energy for desorption, estimated from the TPD curve, was compared to the desorption energy calculated by using DFT, indicating that smaller Pdn(+) clusters (n ≤ 6) tended to have weakly adsorbed hydrogen molecules, whereas larger Pdn(+) clusters (n ≥ 7) had dissociatively adsorbed hydrogen atoms on the surface. Highly likely, the nonmetallic nature of the small Pd clusters prevents hydrogen molecule from adsorbing dissociatively on the surface.