Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. Thanks to the enorm...Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. Thanks to the enormously large enhancement factor on the order of 106～10 15, one can readily acquire the vibrational spectra from adsorbates on roughened surfaces of Ag, Au, and Cu. However, SERS has not developed to be as powerful a surface technique as many people had hoped initially because of two specific obstacles. One obstacle is that only three noble metals Au, Ag, and Cu can provide large enhancement, severely limiting the widespread applications involving other metallic materials of both fundamental and practical importance. The other major obstacle is that even for the noble metals, surface morphology with roughness scale of 50～200 nm is crucial to exhibiting a large enhancement factor. The atomically flat surfaces, commonly used in fundamental as well as application research in surface science and nano technology, are not suitable for SERS investigation.展开更多
A major task in molecular electronics is the precise determination of the molecule-metal interface characteristics. This is particularly because metals and single molecules have intrinsically unavoidable electrical mi...A major task in molecular electronics is the precise determination of the molecule-metal interface characteristics. This is particularly because metals and single molecules have intrinsically unavoidable electrical mismatches but there is not yet an established way to evaluate them systematically. At present the most attracting molecule is deemed to be aromatic thiol because it can readily form stable metal-sulfur bond together with the provision of the delocalized ring orbitals. Considering that the electrical transport property is susceptible to the angle made by the metal atom and the molecule, the metal-sulfur bond may not be as effective as the metal-isocyanide bond, however, since linear angles formed in the latter will favor conduction. On the other hand, metal nanoparticles are attracting greatly in recent years since they can be used as passive components in molecular electronics. The surface property of nanoparticles is quite different from their bulk property due to the inevitable presence of dangling bonds at the surface sites. For alloy nanoparticles, surface chemical composition may also be substantially different from their interior composition. Even using the state-of-art surface analyzing tools such as XPS and EDAX, quantification of such a difference is extremely difficult due to the finite penetration depth of the probing beams. In this symposium, we clearly demonstrate using surface-enhanced Raman scattering (SERS) spectroscopy that Au/Ag alloy nanoparticles, for instance, are enriched with Ag atoms at the very outer part of the nanoparticles. The definitive proof is provided on the grounds that (1) organoisocyanides readily adsorb on metals such as Ag and Au by forming a M-C bond, (2) the intrinsic isocyanide stretching frequency, ν(-N≡C), observable at 2100-2300 cm -1 is substantially different from the usual group frequencies of organic compounds, and (3) the exact isocyanide stretching frequency is very susceptible to the kind of metals attached, thereby a minute metallic difference in composition can readily be detected by SERS.展开更多
Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. To use SERS in rout...Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. To use SERS in routine, on-line studies for analytical purposes, the substrates should be stable, reproducibly prepared, inexpensive, and easy to make. We report in this symposium that optically tunable, SERS-active Ag films can be reproducibly fabricated on dielectric substrates by the thermal decomposition of silver carboxylate. The nanostructured Ag films prepared in this way are expected to provide a new type of substrate materials for developing SERS as an ultrasensitive analytical tool.展开更多
Chordae tendineae rupture(CTR),mostly occurred posterior,was identified in 16.1%of dogs with mitral valve disease(MVD).We form a hypothesis that selective transect of posterior chordae tendineae(CT)would alter the car...Chordae tendineae rupture(CTR),mostly occurred posterior,was identified in 16.1%of dogs with mitral valve disease(MVD).We form a hypothesis that selective transect of posterior chordae tendineae(CT)would alter the cardiac functions in dogs.An objective of this study was to observe alterations of cardiac function to make a canine MR model from CTR.1 Materials and methods Nine healthy beagles weighed were used.Dogs had normal heart function from echocardiography.A left thoracotomy was performed through the 6thor 7thintercostal space.A specific hook was inserted into the left ventricle(LV)展开更多
文摘Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. Thanks to the enormously large enhancement factor on the order of 106～10 15, one can readily acquire the vibrational spectra from adsorbates on roughened surfaces of Ag, Au, and Cu. However, SERS has not developed to be as powerful a surface technique as many people had hoped initially because of two specific obstacles. One obstacle is that only three noble metals Au, Ag, and Cu can provide large enhancement, severely limiting the widespread applications involving other metallic materials of both fundamental and practical importance. The other major obstacle is that even for the noble metals, surface morphology with roughness scale of 50～200 nm is crucial to exhibiting a large enhancement factor. The atomically flat surfaces, commonly used in fundamental as well as application research in surface science and nano technology, are not suitable for SERS investigation.
文摘A major task in molecular electronics is the precise determination of the molecule-metal interface characteristics. This is particularly because metals and single molecules have intrinsically unavoidable electrical mismatches but there is not yet an established way to evaluate them systematically. At present the most attracting molecule is deemed to be aromatic thiol because it can readily form stable metal-sulfur bond together with the provision of the delocalized ring orbitals. Considering that the electrical transport property is susceptible to the angle made by the metal atom and the molecule, the metal-sulfur bond may not be as effective as the metal-isocyanide bond, however, since linear angles formed in the latter will favor conduction. On the other hand, metal nanoparticles are attracting greatly in recent years since they can be used as passive components in molecular electronics. The surface property of nanoparticles is quite different from their bulk property due to the inevitable presence of dangling bonds at the surface sites. For alloy nanoparticles, surface chemical composition may also be substantially different from their interior composition. Even using the state-of-art surface analyzing tools such as XPS and EDAX, quantification of such a difference is extremely difficult due to the finite penetration depth of the probing beams. In this symposium, we clearly demonstrate using surface-enhanced Raman scattering (SERS) spectroscopy that Au/Ag alloy nanoparticles, for instance, are enriched with Ag atoms at the very outer part of the nanoparticles. The definitive proof is provided on the grounds that (1) organoisocyanides readily adsorb on metals such as Ag and Au by forming a M-C bond, (2) the intrinsic isocyanide stretching frequency, ν(-N≡C), observable at 2100-2300 cm -1 is substantially different from the usual group frequencies of organic compounds, and (3) the exact isocyanide stretching frequency is very susceptible to the kind of metals attached, thereby a minute metallic difference in composition can readily be detected by SERS.
文摘Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. To use SERS in routine, on-line studies for analytical purposes, the substrates should be stable, reproducibly prepared, inexpensive, and easy to make. We report in this symposium that optically tunable, SERS-active Ag films can be reproducibly fabricated on dielectric substrates by the thermal decomposition of silver carboxylate. The nanostructured Ag films prepared in this way are expected to provide a new type of substrate materials for developing SERS as an ultrasensitive analytical tool.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science and Technology(2012-004052)
文摘Chordae tendineae rupture(CTR),mostly occurred posterior,was identified in 16.1%of dogs with mitral valve disease(MVD).We form a hypothesis that selective transect of posterior chordae tendineae(CT)would alter the cardiac functions in dogs.An objective of this study was to observe alterations of cardiac function to make a canine MR model from CTR.1 Materials and methods Nine healthy beagles weighed were used.Dogs had normal heart function from echocardiography.A left thoracotomy was performed through the 6thor 7thintercostal space.A specific hook was inserted into the left ventricle(LV)
