I tried the round trip exchange method (by first exchanging the CTAB with dodecanethiol and further by mercaptoundecanoic acid), but my particles aggregated. The direct addition of mercaptoundecanoic acid in DMF also leads to partial aggregation, as revealed by UV-Vis spectroscopy.
Also, I would like to avoid dispersing them in ethanol as I would like to keep the carboxylic acids free and not form esters.
Any help is greatly appreciated.
Hi,
CTAB is a very good ligand and hard to remove because there is a bilayer on the nanoparticle surface. Some poeple tried with PEG, and then thiol (J. Mater. Chem., 2011, 21, 16453). To help you, there's plenty of citrate-stabilized gold nanosphere synthesis reported in the litterature avoiding the use of CTAB (which is the main problem).
Dear Rifat, I agree with Philippe -
CTAB is often hard to exchange, even for thiol ligands. Moreover, if you have CTAB-stabilized NP, they have positive charge, and any attempts to exchange CTAB to negative-charged ligands would lead to agglomeration. SO the possible workouts are 1) to try the synthesis of citrate-stabilized NP; 2) to exchange CTAB for positive-charged ligands (e.g., HS-PEG-NH2).
Thank you Philippe and Andrei for your answers. I agree that CTAB is a very tricky ligand to get rid off.
Regarding the thiol capping of citrate ligands, how can one characterize the thiol exchange (mercaptocarboxylic acids) ;as I reckon in simple techniques like gel electrophoresis both the functionalized and unfunctionalized would move to the positive electrode.
Thanks!
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