Could anyone share their experience on applicable methods and best practices? We perform zeta-potential measurements on powders, but how can we find out at least the sign of the charge on the surface of extended objects like metallic or ceramic substrates?
You may use an AFM for this yet just in case you dont have such equipment you may use surfactant consumption (this just came to my mind and have no idea whether it works or not). Were I you I would add anionic and cationic surfactants in certain concentrations. Then by measuring the concentrations again after a while I would be able to determine the charge sign (just sign).
agree with Stefan Weber , Kelvin Probe, or (XPS) would be my prime choice in this experiment. You might be able to see the change of sign if you place the water of Si+ pr Si- substrates. Note that in such measurements the accumulated charge should be proportional to strength of molecular dipoles and interface
The best method is to take a small amount of the sample and to crush it, then dispersed in water and then measuring the zeta potential.
Amane Jade sir, I am new to this field..could clarify my doubts
i) if zeta potential is -ve, what is the surface charge present on the particle?
ii) if zeta potential is +ve, what is the surface charge present on the particle?
iii)if zeta potential is zero, what is the surface charge present on the particle?
Hi Roman,
AFM colloidal probe technique (CPT)—detecting forces between surfaces and a mircon-sized sphere attached to the cantilever—is a mature technique for charging studies of solid-liquid interfaces, pioneered by H. Butt and W. Ducker. Here are several useful links, you may find more by googling with "colloidal probe technique ":
1. Wiki on CPT: http://en.wikipedia.org/wiki/Colloidal_probe_technique;
2. A nice review by Kappl and Butt, The Colloidal Probe Technique and its Application to Adhesion Force Measurements. Part. Part. Syst. Charact., 19: (2002), 129–143. doi: 10.1002/1521-4117(200207)19:33.0.CO;2-G. http://onlinelibrary.wiley.com/doi/10.1002/1521-4117(200207)19:3%3C129::AID-PPSC129%3E3.0.CO;2-G/abstract
3. Our Langmuir paper on charging properties of gibbsite using CPT is a solid example of application of CPT and explanation of results. Gan Y, Franks G V. Charging behavior of the gibbsite basal (001) surface in NaCl solution investigated by AFM colloidal probe technique[J]. Langmuir, 2006, 22(14): 6087-6092. You may download it from my RG homepage. http://pubs.acs.org/doi/abs/10.1021/la053391%2B
Hope this helps.
Yang
Hi,
Better late than sorry :-) There is a possibility to use standard instruments (with special cells) for this, like e.g. here:
http://www.ebatco.com/solid_surface.html
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