I prepared a fluorescent nanoparticle solution from organic compound and salts by thermal decomposition. fluorophore/Particles size range : (a few Å to 100nm). Dialysis removes salts but also takes away the small sized fluorophore/nanoparticles. Need some method to retain all the fluorophore/nanoparticles.
Try filtering through specified pore sized filtering system or simple filter paper.
But the nanoparticles are very soluble in water and pass through ordinary filter paper and 1kDa dialysis bag
You could consider using an even smaller MWCO some tubing goes down to 100Da but at this MW are you sure the nanoparticles are on the outside of the membrane or are then simply getting stuck on the inside? In which case you might consider washing the membrane/gentle sonication to re-suspend them. Depending on the nature of the nanoparticles you could also consider a desalting column but again you would need to check your molecular weight cut off. I think dialysis is probably your best bet though.
Another question though is you mention that you prepared the nanoparticles from salts? What type of particles did you form? It's quite possible that the particles you formed will be in equilibrium with the solution which might mean when you remove the salts smaller nanoparticles will simply dissolve.
Dear Kye Robinson
I am not certain of the exact composition of my nanoparticles.
I obtained them after thermal oxidation of an organic source with inorganic salts, in air. I am interested in the fluorescence properties of these nanoparticles, I can confirm that after dialysis the smaller nanoparticles come into dialysate (since the dialysate gives fluorescence).
Also the particles show pH dependent behaviour in: solubility/dispersibility and fluorescence, i.e. on increasing the pH fluorescence intensity increases along with their soubility.
The retentate obtained after dialysis (which i assume is devoid of all inorganic salts) is highly soluble/dispersible in water.
The problem i wish to solve is that: I lose my more quantum efficient smaller nanoparticles during dialysis, and also it is a bit time consuming process. Is there a better technique?
You could try with a lower molecular weight cut off membrane many c-dot syntheses use 500Da if you go to 100Da sometimes not even NaCl goes through when dialysing against distilled water. It sounds like you might be losing some smaller fluorescent molecules that I would hesitate to describe as nano particles. If you wanted to separate your smaller products an extraction or precipitation would be much faster if you could find some suitable conditions (you could even use a spin column before hand to remove your larger components), but this would require some characterization/knowledge of your organic component.
Dear all, why not removing the nanoparticles instead of the salt. Centrifuge may help. My Regards
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