&lt;title&gt;Energy relaxation peculiarities in VO phthallocyanine film&lt;/title&gt;

Butvilas, V.; Gulbinas, Vidmantas; Urbas, Augustine; Vertsimakha, Ya.

doi:10.1117/12.131856

Cited by 2 publications

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“…8 Molecular aggregation of chlorophylls, porphyrins, and their structural analogues (the phthalocyanines) has been examined extensively by timeresolved spectroscopy, a direct and sensitive technique. 4,7,[9][10][11][12][13][14][15] Typically, fluorescence quantum yields decrease on pigment aggregation. By contrast, the fluorescence quantum yield of bacteriochlorophyll c increases on aggregation.…”

Section: Introductionmentioning

confidence: 99%

“…The ability of chlorophylls, porphyrins, cyanine dyes, and other such compounds to form molecular aggregates in solution is well established. − Molecular aggregation of pigments can lead to blue- or red-shifted absorption bands and to the broadening of Soret and Q-bands; in other cases, narrowing of the Soret band may occur on aggregation . Molecular aggregation of chlorophylls, porphyrins, and their structural analogues (the phthalocyanines) has been examined extensively by time-resolved spectroscopy, a direct and sensitive technique. ,,− Typically, fluorescence quantum yields decrease on pigment aggregation. By contrast, the fluorescence quantum yield of bacteriochlorophyll c increases on aggregation .…”

Section: Introductionmentioning

confidence: 99%

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Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

1999

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Solutions of free base meso-tetraphenylporphyrin (H 2 TPP), meso-tetra(4-carboxyphenyl)porphyrin (H 2 TPPC), and meso-tetra(4-pyridyl)porphyrin (H 2 TPyP) under various conditions generate aggregates whose absorption spectra are characterized by invariant Soret bands with bandwidths that are independent of the preparative method. One of the Soret bands is blue-shifted (H-aggregate) relative to the monomeric porphyrin band; other Soret bands are red-shifted (J-aggregates). The aggregates are characterized by different nonradiative rate constants for excited singlet-state decay and by different efficiencies of singlet-singlet annihilation at the high energies of laser excitation. The quantum yields of fluorescence vary between 10 -5 and 10 -2 , and the corresponding fluorescence lifetimes vary in the range from 10 -12 to 10 -9 s; they are more than 1 order of magnitude smaller than those of the corresponding monomeric porphyrins. Lifetimes (τ) correlate with the characteristic ground-state absorption recovery times of the aggregates. The sizes of the H-aggregate and aggregates that are characterized by a minimal blue shift of the Soret band range from 15 to 27 Å.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

1999

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“…Because of their diverse applications, the optical absorption and emission properties of these molecules in solutions have been extensively studied mainly with frequency-resolved techniques, while their thin films have been investigated both spectroscopically and electrochemically . The excited states of phthalocyanines are expected to play an important role in various applications, but still little is known about the excited-state dynamics of this important class of compounds on the subnanosecond time scales …”

Section: Introductionmentioning

confidence: 99%

Ultrafast Studies of Excited-State Dynamics of Phthalocyanine and Zinc Phthalocyanine Tetrasulfonate in Solution

1997

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Femtosecond measurements of transient absorption, bleach, and stimulated emission are used to study the excited-state dynamics of phthalocyanine tetrasulfonate (PcS4) and zinc phthalocyanine tetrasulfonate (ZnPcS4) in solution. In water the excited-state decay process is fast and dominated by energy relaxation due to intermolecular aggregation. In dimethyl sulfoxide (DMSO) both PcS4 and ZnPcS4 exist predominantly in the monomeric form and exhibit very different dynamics from that of the aggregates. The decays are much slower and the observed processes are strongly dependent on the probe wavelength. For PcS4 in DMSO, when probed at 790 nm, the dynamics are dominated by stimulated emission which is observed for the first time in solution. At other wavelengths either transient absorption or bleach dominates the signal. All the observed dynamics can be well fit using a double-exponential function with a fast and slow component. The fast decay has a time constant of 10 ± 4 ps for both phthalocyanines while the slow decay has a time constant of 370 ps for PcS4 and 460 ps for ZnPcS4, respectively. The overall excited-state decay dynamics correlate well with the recovery of the ground electronic state, indicating that the recovery is the predominant process on this time scale. On the basis of a simple three-state kinetic model, the fast decay (10 ps) is attributed primarily to a conversion from the second to the first excited singlet state, possibly involving vibrational relaxation in S1. There might also be a small contribution from aggregates. The first excited-state S1 subsequently decays with a time constant of 130 ps for PcS4 and 160 ps for ZnPcS4, respectively. This decay is due to a combination of radiative and nonradiative relaxation from S1 to S0 and intersystem crossing from S1 to the triplet state.

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<title>Energy relaxation peculiarities in VO phthallocyanine film</title>

Cited by 2 publications

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Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

Ultrafast Studies of Excited-State Dynamics of Phthalocyanine and Zinc Phthalocyanine Tetrasulfonate in Solution

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