152 research outputs found
Model Building of Metal Oxide Surfaces and Vibronic Coupling Density as a Reactivity Index: Regioselectivity of CO Adsorption on Ag-loaded GaO
The step-by-step hydrogen-terminated (SSHT) model is proposed as a model for
the surfaces of metal oxides. Using this model, it is found that the vibronic
coupling density (VCD) can be employed as a reactivity index for surface
reactions. As an example, the regioselectivity of CO adsorption on the
Ag-loaded GaO photocatalyst surface is investigated based on VCD
analysis. The cluster model constructed by the SSHT approach reasonably
reflects the electronic structures of the GaO surface. The geometry of
CO adsorbed on the Ag-loaded GaO cluster has a bent structure,
which is favorable for its photocatalytic reduction to CO.Comment: 18 pages, 11 figure
Mg-doped SrTiO₃ photocatalyst with Ag-Co cocatalyst for enhanced selective conversion of CO₂ to CO using H₂O as the electron donor
Photocatalytic conversion of CO₂ by H₂O is a promising method for solving energy and environmental problems. In this context, efficient photocatalysts that facilitate the selective conversion of CO₂ to the value-added chemical CO are essential. In this study, for the first time in the literature, we used an Mg-doped SrTiO₃ photocatalyst (Mg–SrTiO₃) for the photocatalytic conversion of CO₂ to CO using H₂O as the electron donor under monochromatic UV-light irradiation at 365 nm. Compared to pristine SrTiO₃, Mg–SrTiO₃, which was prepared via a flux method, exhibited dramatically enhanced conversion of CO₂ to CO in the presence of an Ag–Co cocatalyst. Moreover, the selectivity toward CO evolution was >99%, which indicates suppression of the unnecessary and competitive H₂ evolution. Scanning electron microscopy of Mg–SrTiO₃ revealed edge-shaved cubic particles, which were correlated to the anisotropic distribution of photogenerated electrons and holes and the consequent enhancement of photocatalytic activity. Furthermore, the Mg-doping temperature and amount used to prepare Mg–SrTiO₃ influenced the substitution of Ti⁴⁺ sites by Mg²⁺ in the bulk of SrTiO₃, thereby affecting the CO evolution. The apparent quantum efficiency of optimal Mg–SrTiO₃ in the photocatalytic conversion of CO₂ was determined to be 0.05%
Visible-light-assisted selective catalytic reduction of NO with NH[3] on porphyrin derivative-modified TiO[2] photocatalysts
Accepted 16 Sep 2014.Porphyrin-derivative-modified TiO[2] photocatalysts showed high photocatalytic activity for the selective catalytic reduction of NO with NH[3] in the presence of O[2] under visible-light irradiation. Tetra(p-carboxyphenyl)porphyrin (TCPP) was the most effective photosensitizer among the five porphyrin derivatives investigated. NO conversion and N[2] selectivity of 79.0% and 100%, respectively, were achieved at a gas hourly space velocity of 50 000 h[−1]. UV–Vis and photoluminescence spectroscopies revealed the presence of two species of TCPP on the TiO2surface; one was a TCPP monomer and the other was an H-aggregate of the TCPP molecules. It was concluded that the TCPP monomer is an active species for the photo-assisted selective catalytic reduction (photo-SCR). Moreover, an increase in the fraction of H-aggregates with increasing TCPP loading amount resulted in a decrease in the photocatalytic activity of the photo-SCR
Role of Catalyst Support and Regioselectivity of Molecular Adsorption on a Metal Oxide Surface: NO Reduction on Cu/{\gamma}-alumina
The role of catalyst support and regioselectivity of molecular adsorption on
a metal oxide surface is investigated for the NO reduction on a
Cu/{\gamma}-alumina heterogeneous catalyst. For the solid surface,
computational models of the {\gamma}-alumina surface are constructed based on
the Step-by-Step Hydrogen Termination (SSHT) approach. Dangling bonds, which
appear by cutting the crystal structure of a model, are terminated stepwise
with H atoms until the model has an appropriate energy gap. The obtained SSHT
models exhibit the realistic infrared (IR) and ultraviolet-visible (UV/Vis)
spectra. Vibronic coupling density (VCD), as a reactivity index, is employed to
elucidate the regioselectivity of the Cu adsorption on the {\gamma}-alumina and
that of the NO adsorption on the Cu/{\gamma}-alumina in place of the frontier
orbital theory that could not provide clear results. We discovered that the
highly dispersed Cu atoms are loaded on Lewis-basic O atoms, which is known as
anchoring effect, located in the tetrahedral sites of the {\gamma}-alumina
surface. The role of the {\gamma}-alumina support is to raise the frontier
orbital of the Cu catalyst, which in turn gives rise to the electron
back-donation from the Cu/{\gamma}-alumina to NO. In addition, the penetration
of the VCD distribution of the Cu/{\gamma}-alumina into the {\gamma}-alumina
support indicates that the excessive reaction energies dissipate into the
support after the NO adsorption and reduction. In other words, the support
plays the role of a heat bath. The NO reduction on the Cu/{\gamma}-alumina
proceeds even in an oxidative atmosphere because the Cu-NO bond is strongly
bounded compared to the Cu-O2 bond
Enhanced CO evolution for photocatalytic conversion of CO2 by H2O over Ca modified Ga2O3
高効率で二酸化炭素を再資源化する光触媒の合成に成功 --CO2を「ひかり」と「みず」でリサイクル--. 京都大学プレスリリース. 2020-10-14.Artificial photosynthesis is a desirable critical technology for the conversion of CO2 and H2O, which are abundant raw materials, into fuels and chemical feedstocks. Similar to plant photosynthesis, artificial photosynthesis can produce CO, CH3OH, CH4, and preferably higher hydrocarbons from CO2 using H2O as an electron donor and solar light. At present, only insufficient amounts of CO2-reduction products such as CO, CH3OH, and CH4 have been obtained using such a photocatalytic and photoelectrochemical conversion process. Here, we demonstrate that photocatalytic CO2 conversion with a Ag@Cr-decorated mixture of CaGa4O7-loaded Ga2O3 and the CaO photocatalyst leads to a satisfactory CO formation rate (>835 µmol h−1) and excellent selectivity toward CO evolution (95%), with O2 as the stoichiometric oxidation product of H2O. Our photocatalytic system can convert CO2 gas into CO at >1% CO2 conversion (>11531 ppm CO) at ambient temperatures and pressures
Dual Ag/Co cocatalyst synergism for the highly effective photocatalytic conversion of CO2 by H2O over Al-SrTiO3
金属ナノ粒子で光触媒のモチベーションを上げることに成功 --人工光合成で二酸化炭素(CO2)の再資源化の新展開--. 京都大学プレスリリース. 2021-03-11.Loading Ag and Co dual cocatalysts on Al-doped SrTiO3 (AgCo/Al-SrTiO3) led to a significantly improved CO-formation rate and extremely high selectivity toward CO evolution (99.8%) using H2O as an electron donor when irradiated with light at wavelengths above 300 nm. Furthermore, the CO-formation rate over AgCo/Al-SrTiO3 (52.7 μmol h−1) was a dozen times higher than that over Ag/Al-SrTiO3 (4.7 μmol h−1). The apparent quantum efficiency for CO evolution over AgCo/Al-SrTiO3 was about 0.03% when photoirradiated at a wavelength at 365 nm, with a CO-evolution selectivity of 98.6% (7.4 μmol h−1). The Ag and Co cocatalysts were found to function as reduction and oxidation sites for promoting the generation of CO and O2, respectively, on the Al-SrTiO3 surface
Long-Term Remission of Primary Bone Marrow Diffuse Large B-Cell Lymphoma Treated with High-Dose Chemotherapy Rescued by In Vivo
Primary bone marrow diffuse large B-cell lymphoma (DLBCL) is a rare type of extranodal lymphoma with poor prognosis. Here, we report a case of primary bone marrow DLBCL successfully treated with high-dose chemotherapy and rescued by in vivo rituximab-purged autologous stem cells. A 39-year-old woman visited our hospital because of anemia. Bone marrow examination revealed a large B-cell lymphoma invasion. An 18F-fluorodeoxyglucose positron emission tomography scan revealed disseminated bone marrow uptake without evidence of dissemination at other sites. These findings led to a diagnosis of primary bone marrow DLBCL. Our patient underwent R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) chemotherapy and achieved complete remission. Subsequently, she received high-dose chemotherapy with an in vivo rituximab-purged autologous stem cell transplant. Seven years have passed since the transplantation, and she remains in remission. This suggests that transplantation of an in vivo rituximab-purged autograft is a promising strategy for primary bone marrow DLBCL
Imparting CO₂ reduction selectivity to ZnGa₂O₄ photocatalysts by crystallization from hetero nano assembly of amorphous-like metal hydroxides
Imparting an enhanced CO₂ reduction selectivity to ZnGa₂O₄ photocatalysts has been demonstrated by controlled crystallization from interdispersed nanoparticles of zinc and gallium hydroxides. The hydroxide precursor in which Zn(II) and Ga(III) are homogeneously interdispersed was prepared through an epoxide-driven sol–gel reaction. ZnGa₂O₄ obtained by a heat-treatment exhibits a higher surface basicity and an enhanced affinity for CO₂ molecules than previously-reported standard ZnGa₂O₄. The enhanced affinity for CO₂ molecules of the resultant ZnGa₂O₄ leads to highly-selective CO evolution in CO₂ photo-reduction with H₂O reductants. The present scheme is promising to achieve desirable surface chemistry on metal oxide photocatalysts
Development of diffuse large B-cell lymphoma in a patient with Waldenström's macroglobulinemia/lymphoplasmacytic lymphoma: clonal identity between two B-cell neoplasms
Waldenström's macroglobulinemia (WM)/ lymphoplasmacytic lymphoma (LPL) is an indolent mature B-cell neoplasm. In rare cases of WM/LPL, diffuse large B-cell lymphoma (DLBCL) develops as a result of histologic transformation. In this report, we present a case of DLBCL developing in a patient with WM/LPL. Combination chemotherapy for DLBCL was effective and complete remission was eventually achieved. We attempted to determine the clonal relatedness between WM/LPL and DLBCL in the patient by analyzing complementarity-determining region 3 (CDR3) in the immunoglobulin heavy chain gene. A common CDR3 sequence was found in tumor cells of DLBCL and those of WM/LPL, indicating that tumor cells of DLBCL are clonally identical to those of WM/LPL. Therefore, in the present case, DLBCL is developed from WM/LPL cells by clonal evolution
Bifunctionality of Rh3+ Modifier on TiO2 and Working Mechanism of Rh3+/TiO2 Photocatalyst under Irradiation of Visible Light
A rhodium(III) ion (Rh3+)-modified TiO2 (Rh3+/TiO2) photocatalyst, prepared by a simple adsorption method and exhibiting high levels of photocatalytic activity in degradation of organic compounds, was investigated by using X-ray absorption fine structure (XAFS) measurements, (photo)electrochemical measurements, double-beam photoacoustic (DB-PA) spectroscopic measurements, and photoluminescence measurements. Based on the results, the features of the Rh3+ modifier and the working mechanism of the Rh3+/TiO2 photocatalyst are discussed. XAFS measurements revealed that the Rh3+ species were highly dispersed and almost atomically isolated on TiO2. The (photo)electrochemical measurements, DB-PA spectroscopic measurements, and photoluminescence showed a unique bifunction of the Rh3+ modifier as a promoter for O2 reductions and an electron injector to the conduction band of TiO2 for response to visible light. The reasons for the Rh3+/TiO2 photocatalyst exhibiting higher levels of photocatalytic activity than those of TiO2 photocatalysts modified with other metal ions are also discussed on the basis of obtained results
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