Silver nanoparticles can be positively, negatively or neutrally charged depending on the method of synthesis. However, I used commercial silver nitrate. How can I know the charge of silver nanoparticles?
Any idea or suggestions?
Thank you:)
There are several methods that can be used to determine the charge of silver nanoparticles. Some of the most common methods include:
-Zeta potential measurement
- Surface charge measurement
- X-ray photoelectron spectroscopy (XPS)
- Electrokinetic measurements.
It is also important to note that the charge of silver nanoparticles can be affected by the presence of other ions in the solution, as well as the pH of the solution.
Deepa Suresh Ilham Ben Amor Badr-Edine Sadoq
Zeta potential is measured using electrophoresis and is expressed in units of Volts. However, using electrophoresis, it is possible to determine qualitatively what charge silver nanoparticles have in dispersion. If they move towards the negative electrode, then they have a + charge, and vice versa, if they move towards the positive electrode, then they have a - charge. Quantitatively, in Coulomb units, the charge of nanoparticles cannot be determined by this method.
If you don't have access to instrumentation and you have a concentrated enough dispersion that seems stable, you can flocculate it with non-symmetric electrolytes such as CaCl2 and Na2SO4. For each one, you add an increasing concentration of electrolyte until you see flocculation. If the silver particles are -ve, you will need a lower concentration of the CaCl2 than Na2SO4 and vice versa for +ve.
Because this is an old school macroscopic technique (i.e., visual observation), you need the dispersion to be sufficiently concentrated with respect to particles so that you can actually see something happen.
In general, though, most simple nanoparticles are -ve unless you are at notably low pH.
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