In my experience, nothing beats repeated centrifugation. If the material is well ligand-stabilized there should be no risk of aggregation. Centrifugal filtration is also good but often leads to losses by particles sticking to the filter. Of course, you have the whole range of chromatographies you can try, but this is also quite time consuming. In some selected cases you can also flocculate the particles by addition of a non-solvent (or non-dispersant, to be pedantic) and, if you are lucky, can wash away all impurities before re-dispersion of the particles. If you want to purify charge-stabilized colloids, remember that this is not routinely possible. Even dialysis will often compromise their colloidal stability and lead to aggregation. This is in the nature of colloids and cannot be avoided since their stability as a dispersion depends on the presence of other factors in the system, for example ionic charge.

Please go through the following link, I hope it may help you out.

http://www.ncbi.nlm.nih.gov/pubmed/20039604

Depending on hydrophobicity/hydrophilicity of the head group, the functionalized nanoparticle could be phase transferred to a different solvent system. Check this paper for details. PNAS 2008, 105, 9886–9891

Magnetic gold nanoparticles.

Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...

In my experience, nothing beats repeated centrifugation. If the material is well ligand-stabilized there should be no risk of aggregation. Centrifugal filtration is also good but often leads to losses by particles sticking to the filter. Of course, you have the whole range of chromatographies you can try, but this is also quite time consuming. In some selected cases you can also flocculate the particles by addition of a non-solvent (or non-dispersant, to be pedantic) and, if you are lucky, can wash away all impurities before re-dispersion of the particles. If you want to purify charge-stabilized colloids, remember that this is not routinely possible. Even dialysis will often compromise their colloidal stability and lead to aggregation. This is in the nature of colloids and cannot be avoided since their stability as a dispersion depends on the presence of other factors in the system, for example ionic charge.

M also wondering for this. But i can't use centrifugaion...any other method?

Tangential flow filtration works well

Best way is to prepare pure nanoparticles, with minimum additives. An example on preparation of conducting polymer based nanoparticles is attached.

Article Polymerization Model for Hydrogen Peroxide Initiated Synthes...

patience is a virtue!

Can we use a series of nano seives?

i am also having a problem by using centrifugation so is there any specific and easy and less time consuming way?

I have the same problem with the purification of gold/MUA nanoparticles. After second centrifugation there was an irreversible aggregate

I also tried to dialize but the nanoparticles were also aggregate. 

Hi everyone, When you are interested in the purification, concentration and isolation of drug-laden nanoparticles and nanocarriers by ultrafiltration, you can refer to the following application review to find the right ultrafiltration device for your application:

https://www.sartorius.com/_ui/images/h4e/h45/8858221772830.pdf

I hope this is helpful.

Which centrifuge speed should be used to purify nanoparticles. I am preparing Gelatin nanoparticles and purify it by centrifugation (10,000g , 10 min) 3 times. However, I lost the nanoparticles with low particles size (less than 100 nm). Does the centrifuge speed have any impact on this?

Hi Hien, I would first vary the time at 10000 g, starting at 1 min and going upwards. Perform DLS on the pellets that you isolate.