I use a polymer with COOH on the one end and thiol on the other(11-mercaptoindecanoic acid) to exchange with the native ligands of a cadmium based nanoparticle. In one of the literatures it's been mentioned that the polymer should be dissolved in water and the pH was adjusted to be 11 using tetramethylammonium hydroxide pentahydrate(TMAH). My question is, how does the base make a difference for this purpose? Can we use other bases such as NaOH ? or TMAH has been chosen for a especial reason?
Dear Mohammad Javad Afshari, pH is driven to basic range to ensure the complete dissociation of the COOH groups (weak acids dissociation is pH dependent). It is possible to adjust the pH with NaOH but contrary to TMAH, it has no hydrophobic counter part to ensure the stability of the complexes with the metal to be exchanged. This is the reason why TMAH is used for both purposes : pH rising, and complex formation and stability. My Regards
Dear Mohammad,
it's somewhat difficult to give you a qualified answer to your interesting technical question without knowing the original literature. If the purpose of the base is just the deprotonation of the 11-mercaptoundecanoic acid my guess would be that NaOH will also do the job. Perhaps you should run two experiments with NaOH and TMAH and see what comes out. 11-Mercaptoundecanoic acid is well-established as a capping agent for e.g. cadmium selenide (CdSe) nanoparticles. See e.g. the following relevant literature reference:
Dilution Destabilizes Engineered Ligand-Coated Nanoparticles in Aqueous Suspensions
https://escholarship.org/content/qt2pb8n34j/qt2pb8n34j.pdf?t=pdv5fv
Good luck with your work!
Dear all, the following documents are examples showing the role of TMAH (or TMAOH) that is beyond a simple pH adjustment (as NaOH do) in nanoparticles preparation. My Regards
https://www.researchgate.net/publication/258384578_Effect_of_Tetramethylammonium_Hydroxide_on_Nucleation_Surface_Modification_and_Growth_of_Magnetic_Nanoparticles
https://www.researchgate.net/publication/291720600_Effect_of_TMAH_on_dispersion_behavior_of_TiN_nanoparticles
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