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@ARTICLE{Pronkin:10502,
author = {Pron'kin, S. and Wandlowski, Th.},
title = {{T}ime-resolved in-situ {ATR}-{SEIRAS} {S}tudy of
{A}dsorption and {P}hase {F}ormation of {U}racil on {G}old
{E}lectrodes},
journal = {Journal of electroanalytical chemistry},
volume = {550-551},
issn = {0022-0728},
address = {New York, NY [u.a.]},
publisher = {Elsevier},
reportid = {PreJuSER-10502},
pages = {131 - 147},
year = {2003},
note = {Record converted from VDB: 12.11.2012},
abstract = {The adsorption and phase formation of uracil on massive
Au[n(111)-(110)] single crystal and Au(111-20 nm) film
electrodes in 0.1 M H2SO4 was studied by electrochemical
measurements and ATR surface enhanced infrared reflection
absorption spectroscopy (ATR-SEIRAS). At E < 0.15 V uracil
molecules are disordered and planar oriented, co-adsorbed
with weakly hydrogen-bonded interfacial water (region I).
Around the potential of zero charge a 2D condensed,
physisorbed film of planar oriented molecules,
interconnected by directional hydrogen bonds is formed
(region II). At more positive potentials the carbonyl
combination bands, upsilon(C2O) and upsilon(C4O) increase
significantly in intensity and exhibit a large negative
shift, characteristic to uracil co-ordinated to metal ions
(region III). Band intensities and peak positions reach
rather constant values at E > 0.80 V (region IV). Uracil
undergoes an orientational change from planar to
perpendicular accompanied by the formation of a chemisorbed
adlayer composed of molecular islands. The organic molecule
is co-ordinated to the positively charged electrode surface
via O2-N3-O4. The chemisorbed uracil adlayer (first layer)
facilitates also the co-adsorption of hydrogen bonded water
and sulphate species in the second layer. The kinetics of
dissolution of uracil chemisorbed on Au[n(111)-(110)] or
Au(111-20 nm) electrodes (region IV) was studied by
chronoamperometry and time-resolved ATR-SEIRAS employing
either the rapid-scan or the step-scan regime. The
macrokinetics of the i-t transients could be described by
two processes: (i) hole nucleation according to an
exponential law coupled with detachment-controlled growth
(final potentials in region III) or surface diffusion
controlled growth (final potentials in region II) and (ii)
Langmuir-type desorption of disordered species from defect
sites. Time-resolved ATR-SEIRAS experiments demonstrate that
the transformation of chemisorbed uracil into lower coverage
adlayers proceeds according to the following scenario: (i)
Perpendicularly oriented uracil molecules change their
orientation toward a tilted or planar arrangement depending
on the final potential. (ii) Desorption of strongly
hydrogen-bonded second-layer water and sulphate species.
(iii) Adsorption of weakly hydrogen-bonded water. The
spectroscopic transient responses of these three processes
can be approximated by first order rate equations.
Macroscopic signals, such as i, q(M) or C, do not reflect
the entire complexity of the phase formation kinetics of the
system investigated. Simultaneously recorded
structure-sensitive transient data are of ultimate
importance to develop a 'real system understanding'. (C)
2003 Elsevier Science B.V. All rights reserved.},
keywords = {J (WoSType)},
cin = {ISG-3},
ddc = {540},
cid = {I:(DE-Juel1)VDB43},
pnm = {Materialien, Prozesse und Bauelemente für die Mikro- und
Nanoelektronik},
pid = {G:(DE-Juel1)FUEK252},
shelfmark = {Chemistry, Analytical / Electrochemistry},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000184724600013},
doi = {10.1016/S0022-0728(02)01472-9},
url = {https://juser.fz-juelich.de/record/10502},
}