Nature of the improved raman-scattering from alpha-copper phthalocyanine particles on a compacted electrode

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Abstract

Electrodes consisting of a compacted mixture of powders of silver metal and alpha-copper phthalocyanine (CuPc) have been used to study small pigment particles bonded to the metal surface using resonance Raman spectroscopy as a probe of in situ changes. This system provides a different starting point for the study of the nature of the terms which give rise to improved Raman scattering at metal surfaces. An understanding of these processes is vital if Raman spectroscopy is to achieve its potential as an in situ method for the detection of reactions at metal/organic interfaces in aqueous solution. Resonance excitation profiles (REPs) indicate that the improved scattering is in the region of the phthalocyanine absorption (Q band) and resembles a CuPc multilayer. There is a significant electronic interaction between the particles and the metal surface with a downward shift in the O-O transition energy of the Q band of ca. 30 nm. The REPs from the electrode surface are more clearly resolved than for CuPc itself. There are fewer effective vibronic contributions especially at negative potentials and scattering is greater from higher vibronic levels. New bands not present in the spectrum of CuPc appear at negative potentials and the appearance coincides with changes in intensity of bands observed at all potentials. Two different mechanisms of enhancement are indicated: a resonance mechanism where increased scattering efficiency is achieved both by good sample presentation and by an electronic interaction between the particles and the metal, and a surface-enhanced resonance effect which competes with the resonance mechanism at negative potentials. Both the resonance effect and the surface-enhanced effect give rise to REPs attributable to phthalocyanine Q-band interactions. Both processes arise from a long-range 'charge-transfer' mechanisms between the CuPc particles and the metal rather than from short-range metal-monolayer interactions.
LanguageEnglish
Pages4065-4069
Number of pages4
JournalJournal of the Chemical Society, Faraday Transactions
Volume86
Issue number24
DOIs
Publication statusPublished - 21 Dec 1990

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Raman scattering
Metals
Raman spectra
copper
Electrodes
electrodes
metal surfaces
metals
Scattering
Raman spectroscopy
profiles
scattering
interactions
excitation
copper phthalocyanine
pigments
Silver
electronics
Pigments
Powders

Keywords

  • cobalt phthalocyanine
  • spectra
  • silver

Cite this

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title = "Nature of the improved raman-scattering from alpha-copper phthalocyanine particles on a compacted electrode",
abstract = "Electrodes consisting of a compacted mixture of powders of silver metal and alpha-copper phthalocyanine (CuPc) have been used to study small pigment particles bonded to the metal surface using resonance Raman spectroscopy as a probe of in situ changes. This system provides a different starting point for the study of the nature of the terms which give rise to improved Raman scattering at metal surfaces. An understanding of these processes is vital if Raman spectroscopy is to achieve its potential as an in situ method for the detection of reactions at metal/organic interfaces in aqueous solution. Resonance excitation profiles (REPs) indicate that the improved scattering is in the region of the phthalocyanine absorption (Q band) and resembles a CuPc multilayer. There is a significant electronic interaction between the particles and the metal surface with a downward shift in the O-O transition energy of the Q band of ca. 30 nm. The REPs from the electrode surface are more clearly resolved than for CuPc itself. There are fewer effective vibronic contributions especially at negative potentials and scattering is greater from higher vibronic levels. New bands not present in the spectrum of CuPc appear at negative potentials and the appearance coincides with changes in intensity of bands observed at all potentials. Two different mechanisms of enhancement are indicated: a resonance mechanism where increased scattering efficiency is achieved both by good sample presentation and by an electronic interaction between the particles and the metal, and a surface-enhanced resonance effect which competes with the resonance mechanism at negative potentials. Both the resonance effect and the surface-enhanced effect give rise to REPs attributable to phthalocyanine Q-band interactions. Both processes arise from a long-range 'charge-transfer' mechanisms between the CuPc particles and the metal rather than from short-range metal-monolayer interactions.",
keywords = "cobalt phthalocyanine, spectra, silver",
author = "A.J. Bovill and A.A. McConnell and W.E. Smith",
year = "1990",
month = "12",
day = "21",
doi = "10.1039/FT9908604065",
language = "English",
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journal = "Journal of the Chemical Society, Faraday Transactions",
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T1 - Nature of the improved raman-scattering from alpha-copper phthalocyanine particles on a compacted electrode

AU - Bovill, A.J.

AU - McConnell, A.A.

AU - Smith, W.E.

PY - 1990/12/21

Y1 - 1990/12/21

N2 - Electrodes consisting of a compacted mixture of powders of silver metal and alpha-copper phthalocyanine (CuPc) have been used to study small pigment particles bonded to the metal surface using resonance Raman spectroscopy as a probe of in situ changes. This system provides a different starting point for the study of the nature of the terms which give rise to improved Raman scattering at metal surfaces. An understanding of these processes is vital if Raman spectroscopy is to achieve its potential as an in situ method for the detection of reactions at metal/organic interfaces in aqueous solution. Resonance excitation profiles (REPs) indicate that the improved scattering is in the region of the phthalocyanine absorption (Q band) and resembles a CuPc multilayer. There is a significant electronic interaction between the particles and the metal surface with a downward shift in the O-O transition energy of the Q band of ca. 30 nm. The REPs from the electrode surface are more clearly resolved than for CuPc itself. There are fewer effective vibronic contributions especially at negative potentials and scattering is greater from higher vibronic levels. New bands not present in the spectrum of CuPc appear at negative potentials and the appearance coincides with changes in intensity of bands observed at all potentials. Two different mechanisms of enhancement are indicated: a resonance mechanism where increased scattering efficiency is achieved both by good sample presentation and by an electronic interaction between the particles and the metal, and a surface-enhanced resonance effect which competes with the resonance mechanism at negative potentials. Both the resonance effect and the surface-enhanced effect give rise to REPs attributable to phthalocyanine Q-band interactions. Both processes arise from a long-range 'charge-transfer' mechanisms between the CuPc particles and the metal rather than from short-range metal-monolayer interactions.

AB - Electrodes consisting of a compacted mixture of powders of silver metal and alpha-copper phthalocyanine (CuPc) have been used to study small pigment particles bonded to the metal surface using resonance Raman spectroscopy as a probe of in situ changes. This system provides a different starting point for the study of the nature of the terms which give rise to improved Raman scattering at metal surfaces. An understanding of these processes is vital if Raman spectroscopy is to achieve its potential as an in situ method for the detection of reactions at metal/organic interfaces in aqueous solution. Resonance excitation profiles (REPs) indicate that the improved scattering is in the region of the phthalocyanine absorption (Q band) and resembles a CuPc multilayer. There is a significant electronic interaction between the particles and the metal surface with a downward shift in the O-O transition energy of the Q band of ca. 30 nm. The REPs from the electrode surface are more clearly resolved than for CuPc itself. There are fewer effective vibronic contributions especially at negative potentials and scattering is greater from higher vibronic levels. New bands not present in the spectrum of CuPc appear at negative potentials and the appearance coincides with changes in intensity of bands observed at all potentials. Two different mechanisms of enhancement are indicated: a resonance mechanism where increased scattering efficiency is achieved both by good sample presentation and by an electronic interaction between the particles and the metal, and a surface-enhanced resonance effect which competes with the resonance mechanism at negative potentials. Both the resonance effect and the surface-enhanced effect give rise to REPs attributable to phthalocyanine Q-band interactions. Both processes arise from a long-range 'charge-transfer' mechanisms between the CuPc particles and the metal rather than from short-range metal-monolayer interactions.

KW - cobalt phthalocyanine

KW - spectra

KW - silver

UR - http://dx.doi.org/10.1039/FT9908604065

U2 - 10.1039/FT9908604065

DO - 10.1039/FT9908604065

M3 - Article

VL - 86

SP - 4065

EP - 4069

JO - Journal of the Chemical Society, Faraday Transactions

T2 - Journal of the Chemical Society, Faraday Transactions

JF - Journal of the Chemical Society, Faraday Transactions

SN - 0956-5000

IS - 24

ER -