Mana Toma

Publications (2)7.15 Total impact

• Source

  Available from: plasmonic.net

  Article: Collective plasmon modes excited on a silver nanoparticle 2D crystalline sheet.

  Mana Toma, Koji Toma, Kanae Michioka, Yasuhiro Ikezoe, Daiki Obara, Koichi Okamoto, Kaoru Tamada
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  ABSTRACT: This paper describes unique plasmonic characteristics of two dimensional (2D) crystalline sheets composed of homogeneous Ag nanoparticles (AgNPs) fabricated by the Langmuir-Schaefer method at an air-water interface. The localized surface plasmon resonance (LSPR) band of the Ag nanosheet was tuned by changing the interparticle distance of AgNPs via the length of the organic capping molecules. Red shift of the LSPR band of the AgNPs sheet followed an exponential law against the interparticle distance in a similar manner to the previous reports of metal nanodisc pairs. However, the shift was much larger and less dependent on the interparticle separation gap. This phenomenon is reasonably interpreted as the long-range interaction of LSPR in the 2D sheet ('delocalized' LSPR) confirmed by simulation using the finite difference time domain (FDTD) method. The FDTD simulation also revealed additional enhancement of local electric fields on the 2D sheet compared to those on the single or paired particles.
  Physical Chemistry Chemical Physics 03/2011; 13(16):7459-66. · 3.57 Impact Factor
• Article: Nanoscale coupling of photons to vibrational excitation of Ag nanoparticle 2D array studied by scanning tunneling microscope light emission spectroscopy.

  Satoshi Katano, Koji Toma, Mana Toma, Kaoru Tamada, Yoichi Uehara
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  ABSTRACT: Scanning tunneling microscope light emission (STM-LE) spectroscopy has been utilized to elucidate the luminescence phenomena of Ag nanoparticles capped with myristate (myristate-capped AgNP) and 2-methyl-1-propanethiolate (C(4)S-capped AgNP) on the dodecanethiol-precovered Au substrate. The STM imaging revealed that myristate-capped AgNPs form an ordered hexagonal array whereas C(4)S-capped AgNPs show imperfect ordering, indicating that a shorter alkyl chain of C(4)S-capped AgNP is not sufficient to form rigid interdigitation. It should be noted that such a nanoparticle ordering affects the luminescence properties of the Ag nanoparticle. We found that the STM-LE is only detected from the Ag nanoparticles forming the two-dimensional superlattice. This indicates that the STM-LE of the Ag nanoparticle is radiated via the collective excitation of the local surface plasmon resonance (LSPR) spread over the Ag nanoparticles. Note that the STM-LE spectra of the Ag nanoparticles exhibit spike-like peaks superimposed on the broad light emission peak. Using Raman spectroscopy, we concluded that the spike-like structure appearing in the STM-LE spectra is associated with the vibrational excitation of the molecule embedded between Ag nanoparticles.
  Physical Chemistry Chemical Physics 10/2010; 12(44):14749-53. · 3.57 Impact Factor