Dear All, I have a doubt in preparing InP/ZnS QDs water soluble with higher stability.
I had synthesized InP/ZnS QDs using Octadecane, Dodecanethiol, and P(TMS)3 as precursors and Surfactants.
I got the green fluorescence and yellow fluorescence still. Now I am supposed to make it as water soluble QDs, for that, I used 3-Mercaptopropionic acid (MPA) and TMAH, but I didn't get the water soluble QDs, instead it denaturized the emission under UV light.
If anyone has the procedure to make QDs water soluble, Let me know.
Thank you in advance
In my experience, the ligand exchange methods for the phase transfer of QDs (like what you've attempted with MPA) are difficult to perform well, such that they don't quench the fluorescence emission. You need to get the conditions just right and even then these exchange reactions often don't work 100% of the time.
My suggestion would be to look into ligand encapsulation methods instead, where a amphiphilic polymer or similar is used to give colloidal stability in water. This retains the organic capping ligands and often retains the initial fluorescence intensity. One downside though is that this can often lead to much larger nanoparticle sizes so it really depends on what your applications are going to be.
If you're set on ligand exchange then try changing the concentration of TMAH and using an excess of MPA. Otherwise look at the use of polymers for QD encapsulation - polystyrene maleic anhydride for example.
Hi Manga have you tried coating with aminosilanes or mercaptosilanes?
Hi Manga,
I hope the attached publication can help you resolve this issue.
Thank you.
Article Design and fabrication of covalently linked PEGylated nanohy...
In my experience, the ligand exchange methods for the phase transfer of QDs (like what you've attempted with MPA) are difficult to perform well, such that they don't quench the fluorescence emission. You need to get the conditions just right and even then these exchange reactions often don't work 100% of the time.
My suggestion would be to look into ligand encapsulation methods instead, where a amphiphilic polymer or similar is used to give colloidal stability in water. This retains the organic capping ligands and often retains the initial fluorescence intensity. One downside though is that this can often lead to much larger nanoparticle sizes so it really depends on what your applications are going to be.
If you're set on ligand exchange then try changing the concentration of TMAH and using an excess of MPA. Otherwise look at the use of polymers for QD encapsulation - polystyrene maleic anhydride for example.
@Steingrimur Stefansson: Professor, Will you please tell me the procedure. Is it same as MPA coating on QDs.
Hi friend,
You just try to prepare QD in DMSO or DMF as solvent. Just check it as a trial experiment.
Hai Niveditha,
I will check the response of your idea also.
Thank you
I synthesized water soluble InP/ZnS with mercaptoacetic acid (MAA) as a ligand. At that time I used triethylamine (TEA) as the base instead of TMAH, because TEA can activate the SH group of MAA, and also because TEA is soluble in most non-polar solvent. I used CH2Cl2 as the solvent at the beginning, but toluene or hexane could be used as well. And, TMAH seems to be strong base enough to decompose ZnS shell.
The procedure I did is as following:
1. disperse the QD in CH2Cl2
2. add MAA. -> precipitate could be observed.
3. add TEA as dropwise until precipitate diappears. -> reaction heat could be felt.
4. add excess acetone to obtain precipitate of ligand exchanged InP/ZnS
5. centrifugate to recover the InP/ZnS. Repeat this washing ~3 times until the smell of MAA disappears.
6. add water to obtain uniform dispersion.
If the precipitation could not observed at 4, a drop of NH3 aq may be added to dissociate the ligand MAA to COO-.
Both MAA and TEA seem to etch the ZnS slightly, so ZnS shell should be formd a little bit thicker than ideal thickness.
Thank you Dr.Shuzo Tokumitsu. I will try your procedure today.
I made a ligand exchange from a carboxilic acid in PbS nanoparticles surface to L-Cysteine and it works, the problem is to find the adequate conditions to get high stability of the nanoparticles in aqueous media.
I hope this article can help you, I based on it.
likely you will want to make it only water dispersible, not soluble. The latter implies that you have individual molecules or ions 'dispersed' in solvent.
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