The effect of chloride on the point of zero charge of γ-Al2O3

Mieth, J.A.; Schwarz, John H.; Huang, Y.-J.; Fung, S.C.

doi:10.1016/0021-9517(90)90272-l

Cited by 19 publications

(2 citation statements)

References 11 publications

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“…Similar upward and downward shifts in PZC are typically observed when basic ions or halogens are added to inorganic solids. For example, it has been shown that small amounts of Na + and K + can significantly increase the PZC of silica. − Similarly, the presence of chloride on alumina has been seen to lower the PZC from 8 to 6 …”

Section: Resultsmentioning

confidence: 99%

“…[35][36][37] Similarly, the presence of chloride on alumina has been seen to lower the PZC from 8 to 6. 38 The PZC measurements were complemented by X-ray photoelectron spectroscopic (XPS) analysis to quantify the surface concentration of the different elements that may be left on the SWNT sample as a result of the particular pretreatment method. The XPS surface analysis results were in good agreement with the observed trends in PZC.…”

Section: Point Of Zero Chargementioning

confidence: 99%

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Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant NaDDBS

et al. 2003

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The insolubility of single-walled carbon nanotubes (SWNT) in either water or organic solvents has been a limitation for the practical application of this unique material. Recent studies have demonstrated that the suspendability of SWNT can be greatly enhanced by employing appropriate surfactants. Although the efficiency of anionic, cationic, and nonionic surfactants has been demonstrated to different extents, the exact mechanism by which carbon nanotubes and the different surfactants interact is still uncertain. To deepen the understanding of this interfacial phenomenon, we have investigated the effects of chemical modifications of the surface on the extent of nanotube−surfactant interaction. Such changes in the surface chemistry of the SWNT can be achieved by simply varying the pretreatment method, which can be acidic or basic. We have found that intrinsic surface properties such as the PZC (point of zero charge) are greatly affected by the purification method. That is, the electrical charge of the SWNT surface varies with the pH of the surrounding media. However, it has been found that during the adsorption of the anionic surfactant sodium dodecylbenzenesulfonate (NaDDBS) on SWNT Coulombic forces do not play a central role, but are overcome by the hydrophobic interactions between the surfactant tail and the nanotube walls. Only at pH values far from the PZC do the Coulombic forces become important. The hydrophobic forces between the surfactant tail and the nanotube determine the structure of the surfactant-stabilized nanotubes. In such a structure, each nanotube is covered by a monolayer of surfactant molecules in which the heads form a compact outer surface while the tails remain in contact with the nanotube walls. It is important to note that although the final configuration can be described as a cylindrical micelle with a nanotube in the center, the mechanism of formation of this structure does not proceed by incorporation of a nanotube into a micelle, but rather by a two-step adsorption that ends up in the formation of a surfactant monolayer.

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