Adsorption of cetyltrimethylammonium bromide and/or cetyldimethylbenzylammonium chloride on partly covered hanging mercury drop electrode

Koniari, Argyri; Avranas, Antonis

doi:10.1016/j.jcis.2011.06.026

Cited by 4 publications

(1 citation statement)

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“…The nature of neither the inorganic nor the organic adsorbate layer is readily evident in this region of the isotherms but the low coverage of bromide implies a disordered, gaslike state. Avranas and co-workers have previously described the adsorption of quaternary ammonium bromide surfactants on mercury electrodes − and reported that short-chained species do not form condensed layers which is consistent with the low-coverage OTA + isotherms reported in this study. Interestingly, when the surface excess of bromide exceeds 7 × 10 –10 moles cm –2 (corresponding to approximately 1/3 of a monolayer), the amount of cationic surfactant at the interface begins to decrease but does not fall to zero as might be expected for a cation at a highly positive charged surface.…”

Section: Resultssupporting

confidence: 91%

Quaternary Ammonium Bromide Surfactant Adsorption on Low-Index Surfaces of Gold. 2. Au(100) and the Role of Crystallographic-Dependent Adsorption in the Formation of Anisotropic Nanoparticles

Vivek

Burgess

2012

Langmuir

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A qualitative and quantitative description of the coadsorption of a quaternary ammonium bromide surfactant on Au(100) has been determined using electrochemical techniques. Cyclic voltammetry reveals that both the cationic surfactant ion and its halide counterion are adsorbed on the surface of unreconstructed Au(100) over a wide range of electrode potentials or charge densities. The relative Gibbs excesses of the cationic and anionic components of octyltrimethylammonium (OTA(+)) bromide have been determined using the thermodynamics of ideally polarized electrodes. Coadsorbed OTA(+) does not strongly affect the behavior of bromide layers on Au(100) with low-coverage films being replaced by commensurate overlayers at positive electrode charge densities. The presence of surface bromide allows for the stabilization of adsorbed OTA(+) at positive polarizations. Furthermore, charge-induced phase changes in the bromide layer lead to subtle but appreciable changes in the surface excesses of OTA(+) ions which is consistent with a hierarchical model of surfactant adsorbed upon a halide-modified Au(100) surface. A comparison of the OTA(+) adsorption isotherms on Au(100) and Au(111) reveals that the presence of coadsorbed bromide does not lead to preferential accumulation of cationic surfactant ions on a particular crystal facet. These results are inconsistent with explanations of anisotropic nanoparticle formation that invoke a thermodynamic argument of preferred surfactant adsorption on different crystal facets of an embryonic nanoparticle seed crystal.

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