Zeta Potential and Colloid Reaction Kinetics

Mulvaney, Paul

doi:10.1002/9783527612079.ch12

Cited by 15 publications

(7 citation statements)

References 34 publications

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“…Fawcett and co-workers have calculated the total differential capacitance of the metal−SAM−water interface and find that the SAM layer has a potential-dependent capacitance, whose origin appears to be the image charge on the metal induced by the ionization of the carboxyl groups at the SAM−water interface. , This image charge itself acts to retard ionization of the acid sites at high pH. We note that it is well-established that the overpotential for electron transfer on metal oxide surfaces is coupled directly to the solution pH, which, in turn, is the primary factor controlling the surface potential …”

Section: Discussionmentioning

confidence: 73%

“…We note that it is well-established that the overpotential for electron transfer on metal oxide surfaces is coupled directly to the solution pH, which, in turn, is the primary factor controlling the surface potential. 33 Conclusions ω-Substituted alkanethiol monolayers on gold appear to be model surfaces for double-layer studies. The doublelayer forces measured in this work are in reasonable accord with the wetting studies carried out by previous workers.…”

Section: Discussionmentioning

confidence: 99%

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Double-Layer Interactions between Self-Assembled Monolayers of ω-Mercaptoundecanoic Acid on Gold Surfaces

1998

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The atomic force microscope was used to investigate the interaction between 11-mercaptoundecanoic acid surfaces and 2-mercaptoethanesulfonic acid surfaces as a function of electrolyte and pH. The surface potential was found to peak at −80 mV at pH 6-8 in 0.1 mM 1:1 electrolyte. The Hamaker constant for the gold−gold interaction was found to be decreased from the value of 1 × 10-19 J in water to 4 × 10-20 J in ethanol. The dispersion interaction between gold surfaces following derivatization with 11-mercaptoundecanoic acid was drastically reduced. The terminal carboxyl groups did not ionize in ethanol. Even in water, extremely low degrees of ionization were observed, with just 1−2% of surface sites being ionized at pH 10. The force curves showed no jump-in nor adhesion above pH 7. We could not reconcile the ψafm−pH results with a simple diffuse layer model for the interface; however the ionization behavior could be explained with sodium ion binding to surface carboxyl groups with a binding constant pK Na = 6.3. The addition of micromolar amounts of Pb2+ caused almost complete neutralization of charged surface groups. These data could be modeled with K Pb = (1−4) × 10-10. An alternative modeling procedure based on incorporation of a zero-order Stern layer could only explain the experimental values if an extremely low value of the inner layer capacitance was assumed of 1−4 μF cm-2. However, this model may be able to explain the lack of jump-in in alkaline solution and the absence of adhesion at high pH.

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Double-Layer Interactions between Self-Assembled Monolayers of ω-Mercaptoundecanoic Acid on Gold Surfaces

1998

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“…Chemisorbed molecules provide a steric barrier and for particles below 10 nm this will be sufficient to offset van der Waals attraction if the surface potential is large enough to prevent the formation of loose agglomerates. 16 However, the particle volume fraction in such particle-ligand systems becomes very small due to their large surface to volume ratio. 17 Therefore, small, chemisorbed molecules should be used to functionalize NPs, 16 thereby preventing reagglomeration and generating long-term stable dispersions.…”

Section: Introductionmentioning

confidence: 99%

“…16 However, the particle volume fraction in such particle-ligand systems becomes very small due to their large surface to volume ratio. 17 Therefore, small, chemisorbed molecules should be used to functionalize NPs, 16 thereby preventing reagglomeration and generating long-term stable dispersions. Ultrasonic treatment or milling processes are often used to break agglomerates in liquids, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, the primary minimum becomes shallower and, therefore, already small functionalizing molecules can prevent coalescence and coagulation of NPs. Chemisorbed molecules provide a steric barrier and for particles below 10 nm this will be sufficient to offset van der Waals attraction if the surface potential is large enough to prevent the formation of loose agglomerates . However, the particle volume fraction in such particle-ligand systems becomes very small due to their large surface to volume ratio .…”

Section: Introductionmentioning

confidence: 99%

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Interaction of l-Cysteine with ZnO: Structure, Surface Chemistry, and Optical Properties

et al. 2015

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Zinc oxide (ZnO) nanoparticles (NPs) were stabilized in water using the amino acid l-cysteine. A transparent dispersion was obtained with an agglomerate size on the level of the primary particles. The dispersion was characterized by dynamic light scattering (DLS), pH dependent zeta potential measurements, scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray absorption fine structure (EXAFS, XANES) spectroscopy. Cysteine acts as a source for sulfur to form a ZnS shell around the ZnO core and as a stabilizer for these core-shell NPs. A large effect on the photoluminescent properties is observed: the intensity of the defect luminescence (DL) emission decreases by more than 2 orders of magnitude, the intensity of the near band edge (NBE) emission increases by 20%, and the NBE wavelength decreases with increasing cysteine concentration corresponding to a blue shift of about 35 nm due to the Burstein-Moss effect.

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