Tohoku University · Materials Science
Professor Takahiro Kondo's research lab specializes in the synthesis, characterization, and application of two-dimensional nanomaterials, particularly boron-based and nitrogen-doped carbon systems. The lab focuses on understanding the atomic-scale electronic structures and catalytic properties of these materials using advanced spectroscopic and microscopic techniques combined with first-principles calculations. Key research directions include the development of novel 2D materials like hydrogenated borophene (HB sheets) and nitrogen-doped graphite for catalytic and electronic applications, as well as exploring exotic quantum phenomena such as strain-induced Landau levels in 2D systems.
Figures are computed from collected data and may differ slightly.
We report on the local atomic and electronic structures of a nitrogen-doped graphite surface by scanning tunneling microscopy, scanning tunneling spectroscopy, x-ray photoelectron spectroscopy, and first-principles calculations. The nitrogen-doped graphite was prepared by nitrogen ion bombardment followed by thermal annealing. Two types of nitrogen species were identified at the atomic level: pyridinic-N (N bonded to two C nearest neighbors) and graphitic-N (N bonded to three C nearest neighbors
Hydrogen boride nanosheets (HB sheets) are facilely synthesized via ion-exchange treatment on magnesium diboride (MgB<sub>2</sub>) in an acetonitrile solution. Optical absorption and fluorescence spectra of HB sheets indicate that their bandgap energy is 2.8 eV. According to first-principles calculations, optical absorption seen at 2.8 eV is assigned to the electron transition between the σ-bonding states of B and H orbitals. In addition, density functional theory (DFT) calculations suggest the
Various types of zero, one, and two-dimensional boron nanomaterials such as nanoclusters, nanowires, nanotubes, nanobelts, nanoribbons, nanosheets, and monolayer crystalline sheets named borophene have been experimentally synthesized and identified in the last 20 years. Owing to their low dimensionality, boron nanomaterials have different bonding configurations from those of three-dimensional bulk boron crystals composed of icosahedra or icosahedral fragments. The resulting intriguing physical a
Hydrogen boride (HB) or hydrogenated borophene sheets are recently realized two-dimensional materials that are composed of only two light elements, boron and hydrogen. However, their catalytic activity has not been experimentally analyzed. Herein, we report the catalytic activity of HB sheets in ethanol reforming. HB sheets catalyze the conversion of ethanol to ethylene and water above 493 K with high selectivity, independent of the contact time, and with an apparent activation energy of 102.8 ±
Nitrogen doping of a graphite surface by ion bombardment has been found to enhance the durability of deposited Pt clusters for H2−D2 exchange reaction. Scanning tunneling microscopy suggests that this high durability is originated from the stabilized monolayer morphology of the Pt clusters. From the comparison with the case of argon ion bombardment, stabilized morphology has been ascribed to the nitrogen-doping effect such as an electron doping, which enhances the interface interaction between t
Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped gra
We report nonuniform and long-range electronic perturbation of graphite near the Fermi level by the point defect based on the measurements with scanning tunneling spectroscopy. The states propagate with threefold symmetry perpendicular to the zigzag edges at the point defect, indicating the formation of the nonbonding states. The propagation continues for 3--4 nm from the defect and is accompanied by oscillations in the state energy and state intensity with a periodicity of $(\sqrt{3}\ifmmode\ti
Combined liquid chromatography and electrospray mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) were used for the characterization of the conjugated metabolites (glucuronides) of a new angiotensin II receptor antagonist, candesartan cilexetil (TCV-116; (+/-)-1-(cyclohexyloxycarbonyloxy)ethyl 2-ethoxy-1-¿[2'-(1H-tetrazol-5-yl)biphenyl- 4-yl]methyl¿-1H-benzimidazole-7-carboxylate) in the plasma and bile of rats given the drug. The glucuronides of the active component, M-I (cande
We have investigated the local free volume and its thermal fluctuation in an amorphous polymethylsilsesquioxane (PMSQ) consisting only of T3 (CH3SiO3/2) and T2 (CH3Si(OH)O2/2) units using photoisomerization of azobenzene molecularly dispersed in the PMSQ films as a photoprobe over a wide temperature range (4−300 K). Photoisomerization profiles are discussed on the basis of three parameters, i.e., first-order plots, final cis fractions, and three-component analysis, for uncured and silanol-conden
The deposition and the isothermal crystallization kinetics of thin amorphous solid water (ASW) films on both Ru(0001) and CO-precovered Ru(0001) have been investigated in real time by simultaneously employing helium atom scattering, infrared reflection absorption spectroscopy, and isothermal temperature-programmed desorption. During ASW deposition, the interaction between water and the substrate depends critically on the amount of preadsorbed CO. However, the mechanism and kinetics of the crysta
The electronic states of the graphite surface with platinum clusters have been investigated at the atomic scale by scanning tunneling spectroscopy. The distinct local density of states were observed near the Fermi level for carbon atoms around the Pt clusters, which has been ascribed as nonbonding $\ensuremath{\pi}$ electronic states of graphite due to Pt-C hybridization. This is consistent with the experimentally observed weaker phonon energies of graphite near the Pt cluster as well as the res
Two-dimensional hydrogen boride (HB) sheets were recently demonstrated to act as a solid acid catalyst in their hydrogen-deficient state. However, both the active sites and the mechanism of the catalytic process require further elucidation. In this study, we analyzed the conversion of ethanol adsorbed on HB sheets under vacuum during heating using in situ Fourier transform infrared (FT-IR) absorption spectroscopy with isotope labelling. Up to 450 K, the FT-IR peak associated with the OH group of
Two-dimensional boron monosulfide nanosheets are realized by physical exfoliation of rhombohedral boron monosulfide.
We have clarified the dynamics and mechanism of CH4 dissociative chemisorption processes on a cesiated Pt(111) surface by means of molecular beam scattering techniques. A comparison is made of similar processes on a Pt(111) surface. It is found that the CH4 molecules with enough energy to overcome the activation barrier for dissociation can no longer dissociate on a cesiated surface of Pt(111). Time-of-flight and angular intensity distribution measurements of the reflected CH4 molecules have rev
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