I have read that ligands are needed to stabilise perovskite quantum dots through passivation of their surface defects and trapping sites.
People generally use oleic acid and oleylamine, I am not sure why two different ligands are always employed?
10.1073/pnas.1607471113 (page 11698 right side)
Some insight on this would be appreciated.
Hi John,
In my opinion you can use one type ligand OA or OAm. But it also depends on the quantum material that you want to synthesis. Some atom like Cu is reactive with acid ligand so we prefer use OAm instead. Both OA and OAm can work well As ligand. Typical OA is easier to replace with shorter ligand than OAm.
Best!
For more detail. I recommend you to read this below article following the link.
http://pubs.acs.org/doi/abs/10.1021/cm4000476?journalCode=cmatex
good luck!
While I think some of this is simply a hold-over from the typical synthetic route used to make traditional inorganic Quantum Dots like CdSe, there is another obvious reason. You need two different ligands as there are two different surface sites. To maximize the Quantum Yield and to prevent oxidative degradation you need both ligands, otherwise one site will be susceptible to attack from the environment. However, as the other commenters have alluded to, there is no reason you have to stick to oleic acid and oleylamine (ligand transfer as much as you like) - just make sure you are passivating both surface sites!
I have found another article with experimental derivation of the role of each of these types of ligands and several other similar ligands on the QD nanoparticle synthesis using contrast experiments. It supports the answers that both of you have suggested.
Article Brightly Luminescent and Color-Tunable Colloidal CH 3 NH 3 P...
To quote from the article:
"Without n-octylamine, precursors undergo fast crystallisation and aggregated into large particles that precipitated out of solution. Other longer chain alkyl amines can be used such as dodecylamine, hexadecylamine and hexylamine can be used to control the crystallisation process and form a colloidal QD NP solution. N-octylamine controls recrystallisation kinetics and particle size.
Without oleic acid, a luminescent colloidal QD solution can still be obtained, but the solution will become cloudy after 24 hours. Other alkyl acids such as octanoic or butyric acid can stabilise the colloid. So oleic acid suppresses QD aggregation and contributes to colloidal stability. Due to the high surface-to-volume ratio of the nanoparticles, oleic acid stabilisation may be explained by the charge equilibrium."
Thank you for your insight. Both of your answers were very helpful.