Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy

Andrew R. Attar, Daniel E. Blumling, Kenneth L. Knappenberger

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (-S-CH2-COO-) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the π*CO ← nO transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.

Original languageEnglish (US)
Article number024514
JournalJournal of Chemical Physics
Volume134
Issue number2
DOIs
StatePublished - Jan 14 2011

Fingerprint

Photodissociation
Absorption spectroscopy
photodissociation
absorption spectroscopy
acids
dissociation
Carbon Monoxide
Excited states
excitation
decay
2-mercaptoacetate
Ultraviolet spectroscopy
Sulfhydryl Compounds
thiols
Light absorption
time constant
Absorption spectra
cleavage
Nanostructures
optical absorption

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

@article{0faf02d365d14af8bb885172ddc58c9d,
title = "Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy",
abstract = "Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (-S-CH2-COO-) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the π*CO ← nO transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.",
author = "Attar, {Andrew R.} and Blumling, {Daniel E.} and Knappenberger, {Kenneth L.}",
year = "2011",
month = "1",
day = "14",
doi = "10.1063/1.3526746",
language = "English (US)",
volume = "134",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "2",

}

Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy. / Attar, Andrew R.; Blumling, Daniel E.; Knappenberger, Kenneth L.

In: Journal of Chemical Physics, Vol. 134, No. 2, 024514, 14.01.2011.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy

AU - Attar, Andrew R.

AU - Blumling, Daniel E.

AU - Knappenberger, Kenneth L.

PY - 2011/1/14

Y1 - 2011/1/14

N2 - Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (-S-CH2-COO-) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the π*CO ← nO transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.

AB - Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (-S-CH2-COO-) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the π*CO ← nO transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.

UR - http://www.scopus.com/inward/record.url?scp=78751481497&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78751481497&partnerID=8YFLogxK

U2 - 10.1063/1.3526746

DO - 10.1063/1.3526746

M3 - Article

C2 - 21241127

AN - SCOPUS:78751481497

VL - 134

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 2

M1 - 024514

ER -