If the answer is yes, then does the charge acquisition mechanism change with respect to metallic, metal oxide, and carbon-based nanoparticles?
And would it also change between totally pure water and tap water?
Assume no coatings, surfactants, or any stabilizing agents, and pH = 7.
Carbon based nanoparticles may become oxidized by e.g. air at imperfections and in this way surface groups may be formed that in aquous solutions dissociate. As indicated by Lehtinen the actual charge density will depend on the pK of the groups and the ionic strength.
Yes, the nanoparticles will acquire charge if the surface groups dissociate at pH 7. This depends on the pKa-values of the surface groups. There is a difference between between pure water and tap water. Tap water may contain salt-ions that screen the charges.
Thanks a lot, Olli-Pekka Lehtinen.
For the case of carbon-based nanoparticles (e.g., graphite), will the surface group dissociate in pure water?
And are there any other mechanisms for nanoparticle charge acquisition in pure water?
I am not familiar with the surface functional groups of graphite. For my knowledge, there is no other mechanisms for a nanoparticle to acquire charges in pure water.
When electrolytes do not participate in the formation of an electrical double layer, the following rule can be used to determine the sign of the surface. Of the two matched phases, the phase with a higher dielectric constant is positively charged. The example with graphite in water is like this rule. Graphite charges positively . The dielectric constant of distilled water is about 1, graphite is 12-15.
For previous questions, see more answers.
https://www.researchgate.net/post/Should_Colloids_possess_pH_other_than_neutral
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