TITLE

The Kinetics of Polyacrylamide Adsorption on Polycrystalline Gold

AUTHOR(S)
Chamovska, Dragica; Cvetkovska, Maja; Grchev, Toma
PUB. DATE
November 2008
SOURCE
Croatica Chemica Acta;Nov2008, Vol. 81 Issue 3, p461
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Fast potential step measurements (0.9 → 1.9 → 0.9 V, E vs. she) with simultaneous monitoring of the double layer capacity were applied in the study of the kinetics of PAA adsorption on gold from 0.5 M H2SO4, at 293 K. It was shown that the addition of PAA to the solution at 1.9 V (in the presence of a very thin oxide layer at the gold surface of ≈ 1 nm) does not affect the value of the capacity of the Au/Au2O3/PAA-solution interface, which was also confirmed by Electrochemical Impedance Spectroscopy. After the very fast cathodic reduction of the thin oxide layer (step 1.9 → 0.9 V) for several milliseconds, the initial adsorption of PAA molecules at the bare gold surface reappeared in ≈ 10 ms, causing exhaustion of the metal/solution boundary layer. The induction region (dθ/dt ≈ 0) as well as the diffusion controlled region (dθ/dt = const. = f M¯n((PAA); cPAA) are characteristic of low concentrations in the solution. According to the experimentally obtained linear parts of the (θ / logt)-dependences, values of the diffusion coefficient of PAA-molecules with different molecular weights were calculated. These values follow fairly well the empirical equation: DPAA = 7.03 × 10-4 M¯n-0.66 cm² s-1. Using the same procedure, the diffusion coefficient of 9 × 10-6 cm² s-1 for adsorption of »small« organic molecules, such as HMBT, was calculated.
ACCESSION #
36330428

 

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