研究者詳細 - 中嶋　敦

論文 - 中嶋　敦

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Room-temperature isolation of V(benzene)₂ sandwich clusters via soft-landing into n-alkanethiol self-assembled monolayers

S. Nagaoka, T. Matsumoto, E. Okada, M. Mitsui, A. Nakajima

Journal of Physical Chemistry B （American Chemical Society） 110 （ 32 ） 16008 - 16017 2006年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 15206106

The adsorption state and thermal stability of V(benzene)2 sandwich clusters soft-landed onto a self-assembled monolayer of different chain-length n-alkanethiols (Cn-SAM, n -8, 12, 16, 18, and 22) were studied by means of infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD). The IRAS measurement confirmed that V(benzene)2 clusters are molecularly adsorbed and maintain a sandwich structure on all of the SAM substrates. In addition, the clusters supported on the SAM substrates are oriented with their molecular axes tilted 70-80° off the surface normal. An Arrhenius analysis of the TPD spectra reveals that the activation energy for the desorption of the supported clusters increases linearly with the chain length of the SAMs. For the longest chain C22-SAM, the activation energy reaches ∼150 kJ/mol, and the thermal desorption of the supported clusters can be considerably suppressed near room temperature. The clear chain-length-dependent thermal stability of the supported clusters observed here can be explained well in terms of the cluster penetration into the SAM matrixes. © 2006 American Chemical Society.

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Photoelectron spectroscopy of binary Au cluster anions with a doped metal atom: Au_nM^- (n = 2-7), M = Pd, Ni, Zn, Cu, and Mg

K. Koyasu, Y. Naono, M. Akutsu, M. Mitsui, A. Nakajima

Chemical Physics Letters （Elsevier Science BV） 422 （ 1-3 ） 62 - 66 2006年04月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 00092614

The electronic structures of binary gold cluster anions: AunM- (M = Pd, Ni, Zn, Cu, Mg) were investigated by anion photoelectron spectroscopy at the photon energy of 4.66 eV. The spectra exhibit even-odd alternation of electron affinities and characteristic spectral changes with n, which are accountable in terms of the interactions between the Au clusters and doped metal atoms. For the binary clusters containing Pd, Ni, and Cu, their valence electrons are shared with those of the Au clusters, whereas for Mg the doped atom is weakly bound to Au clusters. A size-dependent spectral change is clearly observed for AunPd- at n ≈ 5. © 2006 Elsevier B.V. All rights reserved.

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Electronic properties of Cs-atom doped aluminum and silicon clusters: Al_nCs_m and Si_nCs_m

K. Koyasu, M. Akutsu, J. Atobe, M. Mitsui, A. Nakajima

Chemical Physics Letters （Elsevier Science BV） 421 （ 4-6 ） 534 - 539 2006年04月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 00092614

The effect of Cs atom doping on metallic aluminum clusters and covalent silicon clusters, AlnCsm (n = 5-14, m = 0-3) and SinCsm (n = 5-16, m = 0-3), was examined by mass spectrometry and anion photoelectron spectroscopy. For clusters containing Cs atom(s), the electron affinities of both clusters are generally decreased and the following characteristic features are observed: for AlnCsm, Cs-atom doping causes (1) electron filling into the electronic shell structure of the Aln clusters and (2) geometrical packing of icosahedral 13-atoms, while for SinCsm Cs-atom doping enhances electronic stability to be ascribed to pure Sin clusters, particularly at (n, m) = (10, 3) and (13, 1). © 2006 Elsevier B.V. All rights reserved.

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Laser synthesis and magnetism of amorphous iron and cobalt carbide nanoparticles with carbon onion

S. H. Huh, A. Nakajima

Journal of Applied Physics （American Institute of Physics） 99 （ 6 ） 064302 - (5 pages) 2006年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 0021-8979

Amorphous iron or cobalt carbide nanoparticles with a carbon onion structure were produced using a pulsed laser ablation of metallocene powders at room temperature. While they are ferromagnetic at room temperature, they exhibit a drastic change in magnetic spin moments at 20-30 K. These magnetic properties are ascribed to a considerable magnetic contribution of superparamagnetism for the amorphous iron or cobalt carbide nanoparticles with a carbon onion and the origin of the magnetic properties is discussed. © 2006 American Institute of Physics.

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Classification and characterization of gold and nickel nanoparticles with a differential mobility analyzer

Y. Naono, S. Kawabata, S. H. Huh, A. Nakajima

Science and Technology of Advanced Materials （National Institute for Material Science） 7 （ 2 ） 209 - 215 2006年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 1468-6996

Ultrafine gold and nickel nanoparticles (NPs) were fabricated by pulsed laser ablation in helium gas, and the NPs 2-15 nm in diameter were selectively classified by an electrostatic size-selection technique employing a low-pressure differential mobility analyzer (LP-DMA). In the classification of the NPs, a chain of several gold NPs or doubly charged NPs were produced as well as singly charged spherical NPs. The morphological selection was performed with the LP-DMA, using a relationship in which the cross section of the spherical NP chains was governed by the product of the diameter and the length, instead of by the square of the diameter. Below a blocking temperature of about 100 K, the Ni NPs that were 3.1 nm in diameter exhibited ferromagnetism. © 2006 Elsevier Ltd. All rights reserved.

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Soft-landing isolation of vanadium-benzene sandwich clusters on a room-temperature substrate using n-alkanethiolate self-assembled monolayer matrixes

M. Mitsui, S. Nagaoka, T. Matsumoto, A. Nakajima

Journal of Physical Chemistry B （American Chemical Society） 110 （ 7 ） 2968 - 2971 2006年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 1520-6106

Gas-phase synthesized vanadium-benzene 1:2 (VBz2) sandwich clusters were size-selectively deposited onto bare gold and long-chain n-alkanethiolate [-S-(CH2)n-1-CH3; n = 16, 18, and 22] self-assembled monolayer (SAM)-coated gold substrates under ultrahigh vacuum (UHV) conditions. Investigation of the resulting deposited clusters was performed by infrared reflection absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). The IR frequencies of the soft-landed VBz 2 clusters show excellent agreement with the fundamentals reported in IR data of VBz2 in an argon matrix. The analysis of IRAS spectra reveals that while there was no orientational preference of the VBz2 clusters on a bare gold substrate, the VBz2 clusters deposited onto the SAM substrates were highly oriented with the molecular axis 70-80° tilted off the surface normal. In addition, analysis of TDS spectra revealed unusually large adsorption heats of the physisorbed VBz2 clusters. The present results are explained by cluster penetration into the long-chain alkanethiolate SAM and for the first time demonstrate the matrix isolation of gas-phase organometallic clusters around room temperature. © 2006 American Chemical Society.

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Determination of the excited-state structure of 7-azaindole-water cluster using a Franck-Condon analysis

R. Brause, D. Krügler, M. Schmitt, K. Kleinermanns, A. Nakajima, T. A. Miller

Journal of Chemical Physics （American Institute of Physics） 123 （ 22 ） 224311 2005年12月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0021-9606

The change of the 7-azaindole-water cluster structure upon electronic excitation was determined by a Franck-Condon analysis of the intensities in the fluorescence emission spectra obtained via excitation of five different vibronic bands. A total of 105 emission band intensities were fitted, together with the changes of rotational constants of one isotopomer. These rotational constants have been obtained from a fit to the rovibronic contour of the cluster. The geometry change upon electronic excitation to the π π* state can be described by a strong and asymmetric shortening of the hydrogen bonds and a deformation of both the pyridine and the pyrrole rings of 7-azaindole. The resulting geometry changes are interpreted on the basis of ab initio calculations. © 2005 American Institute of Physics.

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New world in soft-nano-materials

K. Kaya, A. Nakajima, M. Mitsui

Proceedings - 2005 International Conference on MEMS, NANO and Smart Systems, ICMENS 2005 （IEEE COMPUTER SOC） 231 - 232 2005年11月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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Magnetic properties of lanthanide organometallic sandwich complexes produced in a molecular beam

K. Miyajima, M. B. Knickelbein, A. Nakajima

Polyhedron （Pergamon-Elsevier Science Ltd.） 24 （ 16-17 ） 2341 - 2345 2005年11月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 0277-5387

The magnetic properties of gas-phase terbium-cyclooctatetraene multi-decker sandwich complexes, Tbn(C8H8)n+1 were measured using a Stern-Gerlach type magnetic deflection approach. Beams of Tbn(C8H8)n+1 complexes displayed one-sided deflection toward high field - indicating that fast spin relaxation occurs within the complexes as they pass through the magnetic field. The magnetic moment for Tbn(C8H8)n+1 (n = 1-5) was evaluated using the Langevin model. Evolution of magnetic moment with the complex size is discussed with electronic structures for oxidation states of Tb3+/2+ ions, implying the possibility of antiferromagnetic interaction of two adjacent Tb2+ ions. © 2005 Elsevier Ltd. All rights reserved.

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Preparation of a SERS substrate using vacuum-synthesized silver nanoparticles

N. Horimoto, N. Ishikawa, A. Nakajima

Chemical Physics Letters （Elsevier Science BV） 413 （ 1-3 ） 78 - 83 2005年09月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 0009-2614

Vacuum-synthesized Ag nanoparticles were dispersed and immobilized on an organosilane-functionalized glass surface in water. Nearly spherical particles with diameters of ≈ 200 nm were used for a substrate for surface enhanced Raman scattering (SERS). Molecules deposited on this substrate in both gas and liquid phases were detected by SERS. The SERS efficiency of this substrate was compared with that of Ag colloidal substrate and the morphological difference of these SERS substrates was studied by scanning electron microscopy. The aggregates of 5-10 Ag nanoparticles formed at the spread area exhibited prominent SERS activity. © 2005 Elsevier B.V. All rights reserved.

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Formation and photoelectron spectroscopy of nanoscale cluster anions of biphenyl, (BP)_n^- (n = 2-100)

M. Mitsui, Y. Matsumoto, N. Ando, A. Nakajima

Chemistry Letters （Chemical Society of Japan） 34 （ 9 ） 1244 - 1245 2005年08月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 03667022

Evolution of electronic structures of nanoscale biphenyl cluster anions, (BP) n- (n = 2-100), have been studied by photoelectron spectroscopy in a size-selective fashion. The energetics of vertical detachment energy (VDE) revealed negative electron affinity of a biphenyl molecule and substantial cluster reorganizations via electron attachment. Comparison of the VDE energetics with naphthalene cluster anions implied that the freezing (and/or melting) temperatures of the BP clusters may be much lower than those of naphthalene clusters. Copyright © 2005 The Chemical Society of Japan.

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Trapping of V(benzene)₂ sandwich clusters in a n-alkanethiol self-assembled monolayer matrix

S, Nagaoka, E. Okada, S. Doi, M. Mitsui, A. Nakajima

European Physical Journal D （Springer Nature） 34 （ 1-3 ） 239 - 242 2005年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 14346060

V(benzene)2 sandwich cluster cations produced in the gas phase were size-selectively deposited onto a self-assembled monolayer of n-hexadecanethiols (HDT-SAM) chemisorbed on a Au(111) surface as well as onto a bare Au(111) surface. The thermal chemistry of the neutralized clusters on each substrate was studied with temperature programmed desorption (TPD). From the analyses of the threshold in the TPD, the desorption activation energies of the clusters deposited were determined to be 64.4 ±12.8 kJ/mol for the Au(111) and 130 ±10 kJ/mol for the HDT-SAM. The remarkably large desorption activation energy from the SAM suggests that the deposited clusters are incorporated into the SAM matrix and firmly trapped inside the alkyl chains of the SAM. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2005.

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Stern-Gerlach studies of organometallic sandwich clusters

K. Miyajima, M. B. Knickelbein, A. Nakajima

European Physical Journal D （Springer Nature） 34 （ 1-3 ） 177 - 182 2005年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 1434-6060

Stern-Gerlach type magnetic deflection measurements were performed for two types of multiple sandwich clusters: vanadium-benzene Vn(C 6H6)n+1 and terbium-cyclooctatetraene Tb n(C8H8)n+1. Beams of V n(C6H6)n+1 clusters (n = 1-4) showed symmetric broadening induced by the inhomogeneous field, indicating free spin behavior similar to that displayed by isolated paramagnetic atoms. By contrast, beams of Tbn(C8H8)n+1 clusters displayed one-sided deflection, indicating that fast spin relaxation occurs within the clusters. The difference in the magnetic deflection behavior exhibited by these two systems is explained by their electronic structures, specifically the bonding characteristics between metal atoms and ligand molecules. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2005.

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Negative ion photoelectron spectroscopy of 2,2'-bithiophene cluster anions, (2T)_n^- (n = 1-100)

M. Mitsui, Y. Matsumoto, N. Ando, A. Nakajima

European Physical Journal D （Springer Nature） 34 （ 1-3 ） 169 - 172 2005年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 14346060

Cluster anions of 2,2'-bithiophene, (2T)n-, were produced up to n ∼ 500 in the gas-phase. The energetics of the excess electron in the (2T)n- clusters with n =1-100 were explored by negative ion photoelectron spectroscopy. When the vertical detachment energies (VDEs) obtained from the photoelectron spectra were analyzed by a plot against n-1/3, it has been revealed that the excess electron trapping level thus extrapolated is located at ∼0.8 eV below the conduction band minimum (i.e. LUMO) of the 2T thin film. The large slope of the VDEs vs. n-1/3 plot suggests that the neutral 2T molecules surrounding the anion core take non-planar twisted conformations with permanent dipole moments, resulting in the exceedingly deep trapping of the excess electron in the 2T cluster anions. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2005.

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Gold-nanoparticle-dispersed boron-doped diamond electrodes for electrochemical oxidation of oxalic acid

T. A. Ivandini, Y. Naono, A. Nakajima, Y. Einaga

Chemistry Letters （Chemical Society of Japan） 34 （ 8 ） 1086 - 1087 2005年07月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0366-7022

Electrochemical behavior of gold-nanoparticle-dispersed diamond electrodes have been studied for the oxidation of oxalic acid in phosphate buffer solution. Comparison is made with gold, as-deposited diamond and gold-implanted diamond. The electrodes combine the high catalytic activity of gold and the low background current of diamond electrodes. Moreover, the electrodes can overcome the problem of stability as it is found when using other electrodes. Copyright © 2005 The Chemical Society of Japan.

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Selective formation of MSi₁₆ (M = Sc, Ti, and V)

K. Koyasu, M. Akutsu, M. Mitsui, A. Nakajima

Journal of the American Chemical Society （American Chemical Society） 127 （ 14 ） 4998 - 4999 2005年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 00027863

Metal-encapsulated silicon cage clusters are a new class of clusters and are opening up new avenues for silicon-based nanoscale materials. We present experimental evidence for a highly stable cluster corresponding to M@Si16 (M = Sc, Ti, and V). Mass spectrometry and anion photoelectron spectroscopy show that the cluster features an electronically closed TiSi16 neutral core which undergoes a change in the number of valence electrons involving (i) substitution of neighboring metals with Sc and V, or (ii) addition of a halogen atom to the TiSi16 anion, and that VSi16F is predicted to form an ionically bound superatom complex. Copyright © 2005 American Chemical Society.

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Geometric and electronic structures of multiple-decker one-end open sandwich clusters: Eu_n(C₈H₈)_n^- (n = 1-4)

R. Takegami, N. Hosoya, J. Suzumura, A. Nakajima, S. Yabushita

Journal of Physical Chemistry A （American Chemical Society） 109 （ 11 ） 2476 - 2486 2005年02月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 10895639

We have measured the photoelectron spectra of the multiple-decker 1:1 sandwich clusters of Eun(COT)n- (n = 1-4; COT = 1,3,5,7-cyclooctatetraene), synthesized in the gas phase, and studied theoretically the bonding scheme, charge distribution, valence orbital energies, and photodetachment energies. We calculated the ground electronic state X - and the first excited electronic state A-, both of which have strong ionic bonding and a characteristic charge distribution. Moreover, we found that the valence orbital energies of Eu (6s) and COT (L δ) depend strongly on cluster size and their positions in the clusters. With the calculated vertical detachment energies for these valence orbitals, we assigned the peaks in the experimental photoelectron spectra and analyzed the origin of their interesting behavior by employing simple point charge models. From these analyses, it became clear that the characteristic behavior of the spectra is due to the strong ionic bonding and the charge distribution. In addition, using the point charge models, we estimated the vertical detachment energies of the one-dimensional polymer [Eu(COT)]. © 2005 American Chemical Society.

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Ionization energies and electron distributions of one-end open sandwich clusters: Eu_n(C₈H₈)_n (n = 1-4)

R. Takegami, N. Hosoya, J. Suzumura, K. Yada, A. Nakajima, S. Yabushita

Chemical Physics Letters （Elsevier Science BV） 403 （ 1-3 ） 169 - 174 2005年02月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00092614

The ionization energies of Eun(COT)n (n = 1-4) were found to decrease asymptotically with the cluster size. The low-spin state X and the high-spin state a were characterized with DFT calculations; their adiabatic energy difference was found to decrease with the cluster size. The calculated ionization energies of the X states reproduced the experimental size dependence. Those of the a states also agreed except for n = 1. These features were explained by the significant variation of the electrostatic potential at ionization sites. The state-specific permanent dipole moments were calculated to clarify the difference in the electronic states. © 2005 Elsevier B.V. All rights reserved.

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Electron-beam-induced surface quasimelting of Co granular nanowires

S. H. Huh, A. Nakajima

Applied Physics Letters （American Institute of Physics） 85 （ 25 ） 6149 - 6151 2004年12月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 0003-6951

Electron-beam-induced surface quasimelting of Co granular nanowires (GNWs) of 6-10 nm in diameter and ~30 nm in length has been studied using a high-resolution electron microscope. From the time evolution of electron microscope images as a function of the irradiation time, it has been revealed that the morphological change in the Co GNW is quite different from that in a Co nanocluster (NC) in terms of structures and phase transitions. For example, the allotropic Β→α transition, inhibited in the Co NC, can proceed in the Co GNW through the lattice softening of fcc (111) facets without dimensional collapse. © 2004 American Institute of Physics.

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Lanthanide organometallic sandwich nanowires: Formation mechanism

N. Hosoya, R. Takegami, J. Suzumura, K. Yada, K. Koyasu, K. Miyajima, M. Mitsui, M. B. Knickelbein, S. Yabushita, A. Nakajima

Journal of Physical Chemistry A （American Chemical Society） 109 （ 1 ） 9 - 12 2004年12月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 10895639

A molecular beam of europium-cyclooctatetraene sandwich nanowires Eu n(COT) m was produced by a laser vaporization synthesis method. The formation mechanism of the nanowires was quantitatively revealed by photoelectron and photoionization spectroscopies of the Eu-COT species, together with supporting theoretical calculations. From these results, it is confirmed that growth processes extending the length of Eu-COT nanowires involve a series of elementary reactions in which efficient charge transfer occurs at the terminal reaction sites. In every elementary step, the reaction proceeds between one reactant having low ionization energy and the other reactant having high electron affinity, probably via a "harpoon" mechanism.

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中嶋 敦

論文 - 中嶋 敦

中嶋　敦

論文 - 中嶋　敦