I have synthesized Ag nanoparticles in DI water. Now I want to use the Ag nanoparticles with a flexible polymer to make a thin film. I tried centrifuging at 5000 rpm for 10 mins. However, the particles have settled down and on the tube walls.
Please help me how do I successfully obtain Ag NPs in dry form.
You might try dialysis and then vacuum evaporation of the remaining water.
Another option can be to try to destabilize them and wait overnight for their deposition without centrifugation.
Parul Thapa 'Nano powder' is an oxymoron. There are no free, discrete, independent particles < 100 nm in a powder. There are plenty of RG questions and answers dealing with this very topic. Keep the system wet and do not dry it to preserve the nano nature of the particulate system. How are your Ag nano particles stable in DI water? Look at:
https://www.researchgate.net/post/How_can_I_overcome_dispersion_issues_faced_while_re-suspending_powder_nanoparticles
https://www.researchgate.net/post/How_the_agglomerated_green_nanoparticles_can_restored_into_nano_size_particles
One overall webinar (registration needed) is this one:
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
'The micron scale is volumetrically 109 times larger than the nanoscale. Confusing microtechnology with molecular technology is like confusing an elephant with a ladybug' K Eric Drexler quoted in Ed Regis Nano: the emerging science of nanotechnology' Little, Brown and Company, 1st Edition pp 207 - 208 (1995)
2 quotes from those much greater than I:
'I think dry nanotechnology is probably a dead-end' Rudy Rucker Transhumanity Magazine (August 2002)
‘If the particles are agglomerated and sub-micron it may be impossible to adequately disperse the particles……‘The energy barrier to redispersion is greater if the particles have been dried. Therefore the primary particles must remain dispersed in water….’ J H Adair, E. Suvaci, J Sindel, “Surface and Colloid Chemistry” Encyclopedia of materials: Science and Technology pp 8996 - 9006 Elsevier Science Ltd. 2001 ISBN 0-08-0431526
This happens all the time. If NP are not (or poorly/inconveniently) capped, they can exhibit enhanced affinity towards various surfaces. So first, try to improve capping. Or you can try centrifugation in a different material (such as in a glass tube). Eventually, if your NP are not too small, you can try and let gravity work for you. Just leave the tube for some time and observe whether (at least some) NP are gathering at the bottom. In some cases this works, only note that after long time your NP would be matured - ie almost definitely not in the same condition as directly after synthesis.
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