I have produced silver Nonparticles from Bacteria , but I cant get the Nonoparticles to use it in farther applications .
How can i get it from the solution ? I have tried cooling centfugation at 4c for 15 mins but it just gave me a brown color on the wall of the eppendorf, and the weight of the eppendorf doesn't change( before and after ) . what should i do and how can i get large amount from the Nanoparticles ?
Increase the concentration of silver nitrate. Then washed your nanoparticles wit ethanol 2 times.
Thank you Mina
if you don't mind please tell me more information because i haven't used any of these methods before .
If i used ultracentrifugation for how long time shod i keep the sample ? and does it need any treatment before ?
You may use a simple purification/separation method with two phase solvent system, i.e, water:organic solvent(toluene). If your particles are organic soluble, it will be collective at the solvent phase, if not, vice versa.
You can use high speed ultracentrifugation followed by a freeze drying to obtain dry powder of nanoparticles.
I am not sure if bacteria are still present in your solution or not. You did something with centrifugation if you have brown color on the wall of the tube. The fact that you did not realize weight changes means you have small amount of precipitate (below of the detection limit) or you did not measure it properly. Most of balances are more sensitive for the differences than the absolute weight.
I think that if you have bacteria in your solution they are precipitate more easily than your nanoparticles. It is means that you can precipitate most of the bacteria at lower rpm and you have NP solution (of course you lost some particles also). Than you can try precipitate your particle at higher speed or you can try some other method, example playing with the solubility. evaporation etc.
As far as I know, most of the bacteria can be filtered with commercial 0.2 um siring filter. If it is true in your case, it is the simplest method.
The methods you can use for precipitation are depend on the composition of your solution. If you use buffer, antibiotic or any salt. you need remove your particle from the solution without solvent evaporation and you have to be careful with solvent changes also.
Centrifugation redispersion centrifugation is good method for cleaning and collecting your particles But if you have small quantity, making "free" powder is tricky. You can dry your particles on any grid after you washed them (it could be good for raman, IR, TEM, AFM ...) . it is most easier than making powder.
The brown color may be due to the aggregation of SNP. When the SNP aggregate and forms larger particles the color shitfs and this could be one reason according to me.
Hi Dina,
you have synthesized silver Nonoparticles from Bacteria, right. It is synthesized extracellular and intracellular. So just sonicate the reaction soln with bacteria. Bacteria will be lysed and you will get max bio-synthesized of Np. ..firstly remove cell debris..and then Np by ultracentrifugation.
Centrifuge speed should be high atleast 15000 rpm for harvesting your nanoparticles, wash three times with double distilled water after harvesting that. If your nanoparticles are present on the wall of falcon or eppendorff then you can scratch that with the help of spatula.
Increase the concentration of silver nitrate. Then washed your nanoparticles wit ethanol 2 times.
The best method to purify your nanoparticles really depends on how they are stabilized (monolayer, charge-charge repulsions, ...).
In my work, I have prepared silver nanoparticles, protected by dodecanethiol in toluene. I purified the nanoparticles by adding ethanol, which caused the nonpolar nanoparticles to precipitate. (Dodecanethiol has a nonpolar tail, resulting in nonpolar nanoparticles). unbound dodecanethiol, and surfactant, left over from the synthesis remained in solution. I then easily centrifuged the precipitated nanoparticles, and decanted off the supernatant, and leftover reagent. I added more toluene to dissolve the nanoparticles, and repeated several times to purify the nanoparticles.
This could be a valuable technique to separate your nanoparticles from the remains of your bacteria, although you will need to use different solvents, based on your synthesis.
Once you have your nanoparticles purified, you can use a rotovap, or N2 to dry them if you want to keep them in the same bottle.
Also, remember that you can try sonicating your nanoparticles if they don't want to re-suspend easily.
But overall, precipitate your nanoparticles before centrifugation, and you will find it much easier. Also, be careful, because some nanoparticles can irreversibly aggregate.
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