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STM-induced light emission from thin films of perylene derivatives on the HOPG and Au substrates.

Fujiki A, Miyake Y, Oshikane Y, Akai-Kasaya M, Saito A, Kuwahara Y - Nanoscale Res Lett (2011)

Bottom Line: A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules.The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes.The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Precision Science & Technology, Graduate school of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan. fujiki@ss.prec.eng.osaka-u.ac.jp.

ABSTRACT
We have investigated the emission properties of N,N'-diheptyl-3,4,9,10-perylenetetracarboxylic diimide thin films by the tunneling-electron-induced light emission technique. A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules. The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes. The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

No MeSH data available.


Related in: MedlinePlus

Absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml) (solid line) and of PTCDI-C7 thin film fabricated using the spin coating method on ITO (dashed line), whose intensities are normalized at 520 nm wavelength.
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Figure 3: Absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml) (solid line) and of PTCDI-C7 thin film fabricated using the spin coating method on ITO (dashed line), whose intensities are normalized at 520 nm wavelength.

Mentions: Figure 3 shows the absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml, solid line) and of the PTCDI-C7 thin film fabricated on an indium-tin oxide (ITO) substrate using the spin coating method (dashed line), in which the same method of sample preparation as that for the PTCDI-C7 thin film on the HOPG substrate was employed. In the spectrum of PTCDI-C7 solution, we found three distinct peaks at 455, 485, and 520 nm. These peaks are attributed to the S1(0-0) transition (S1 is a first singlet excited state of PTCDI-C7, numbers in parentheses denote the vibronic levels in the initial and final states) and its vibronic progressions with an energetic distance between the peaks of approximately 0.18 eV. The excitation energy from the ground (S0) state to the S1 state of PTCDI and its derivatives is 2.36 eV [22], and the energy intervals of the peaks correspond to the energy of the benzene-ring stretch oscillation of perylene (0.15 eV [23]). The obtained absorption spectrum of PTCDI-C7 solution was in good agreement with those in a previous report on perylene derivatives such as N,N'-dimethyl-PTCDI and N,N'-bis(2,6-xylyl)-PTCDI in dilute solutions by Schouwink et al. [24]. It is considered that the spectrum of PTCDI-C7 solution in Figure 3 is governed by monomer absorption and not ascribed to dimers or larger aggregates [25], which could be a result of the relatively long alkane substituents of PTCDI-C7 that prevent their aggregation through their steric effect. For the PTCDI-C7 thin film, in contrast, the spectrum became highly broadened with an additional small peak at 565 nm compared with that of PTCDI-C7 solution. The peak broadening and the emergence of the new peak are caused by the strong π-π interaction within molecular aggregates, and by the formation of dimers [22,24] or a crystal phase [24,25] due to the strong molecular stacking between PTCDI skeletons, respectively.


STM-induced light emission from thin films of perylene derivatives on the HOPG and Au substrates.

Fujiki A, Miyake Y, Oshikane Y, Akai-Kasaya M, Saito A, Kuwahara Y - Nanoscale Res Lett (2011)

Absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml) (solid line) and of PTCDI-C7 thin film fabricated using the spin coating method on ITO (dashed line), whose intensities are normalized at 520 nm wavelength.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211436&req=5

Figure 3: Absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml) (solid line) and of PTCDI-C7 thin film fabricated using the spin coating method on ITO (dashed line), whose intensities are normalized at 520 nm wavelength.
Mentions: Figure 3 shows the absorption spectra of PTCDI-C7 dissolved in 1-tetradecene (0.4 mg/ml, solid line) and of the PTCDI-C7 thin film fabricated on an indium-tin oxide (ITO) substrate using the spin coating method (dashed line), in which the same method of sample preparation as that for the PTCDI-C7 thin film on the HOPG substrate was employed. In the spectrum of PTCDI-C7 solution, we found three distinct peaks at 455, 485, and 520 nm. These peaks are attributed to the S1(0-0) transition (S1 is a first singlet excited state of PTCDI-C7, numbers in parentheses denote the vibronic levels in the initial and final states) and its vibronic progressions with an energetic distance between the peaks of approximately 0.18 eV. The excitation energy from the ground (S0) state to the S1 state of PTCDI and its derivatives is 2.36 eV [22], and the energy intervals of the peaks correspond to the energy of the benzene-ring stretch oscillation of perylene (0.15 eV [23]). The obtained absorption spectrum of PTCDI-C7 solution was in good agreement with those in a previous report on perylene derivatives such as N,N'-dimethyl-PTCDI and N,N'-bis(2,6-xylyl)-PTCDI in dilute solutions by Schouwink et al. [24]. It is considered that the spectrum of PTCDI-C7 solution in Figure 3 is governed by monomer absorption and not ascribed to dimers or larger aggregates [25], which could be a result of the relatively long alkane substituents of PTCDI-C7 that prevent their aggregation through their steric effect. For the PTCDI-C7 thin film, in contrast, the spectrum became highly broadened with an additional small peak at 565 nm compared with that of PTCDI-C7 solution. The peak broadening and the emergence of the new peak are caused by the strong π-π interaction within molecular aggregates, and by the formation of dimers [22,24] or a crystal phase [24,25] due to the strong molecular stacking between PTCDI skeletons, respectively.

Bottom Line: A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules.The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes.The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Precision Science & Technology, Graduate school of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan. fujiki@ss.prec.eng.osaka-u.ac.jp.

ABSTRACT
We have investigated the emission properties of N,N'-diheptyl-3,4,9,10-perylenetetracarboxylic diimide thin films by the tunneling-electron-induced light emission technique. A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules. The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes. The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

No MeSH data available.


Related in: MedlinePlus