Hello.
I am trying to immobilize a Ru complex which has a carboxylic acid anchoring group on TiO2 surface. I need the dye to be grafted in its deprotonated form, but I see that the adsorption is very weak. Does anyone have any idea?
I dissolve the complex in 5mM TBAOH/ACN solution, but I get no adsorption from this solution, though its pH is not higher than 7!!
Thank you.
How we can help you if you do not specify what is your Ru-complex? There are tons of publications in this area
What kind of information do you need?
It's a new Ru-complex with a ligand analogous to the terpyridine and has a phenyl spacer and one carboxylic acid group.
Immobilization of Ru-polypyridine complexes on TiO2 surface is a tricky process described in literature. It might be thousands reasons why the complex does not bind to the surface. The concentration of TBAOH might be too low, acetonitrile could be a wrong solvent (try alcohol), TiO2 should have a high surface area, etc. Keep in mind that pKa in AN and water are very different. The definition of pH in AN is a separate question.
Dear Professor Yurii,
Thank you for your answers.
I used AN with the protonated form of the complexes and the adsorption was very good. The question is why deprotonation affects the adsorption?! If we increase the conc. of TBAOH the medium will be highly basic, and in literature they usually desorb the dyes in basic media.
It might be related to the point of zero charge (pzc) of TiO2.
https://en.wikipedia.org/wiki/Point_of_zero_charge
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