Melika Afshar

Please provide a picture of your 'suspension' so we know what you're talking about. Such problems have been previously discussed. For example:

https://www.researchgate.net/post/What_is_an_appropriate_solvent_for_dispersing_copper_nanoparticles_in_PSA

Use Probe sonicator or ultrasonicator for dispersion of NP. but when you stop the sonication, it may again agglomerate.

Dear Melika Afshar ;

The agglomeration behavior depends on several parameters:

Ratios of electric charges.

Particle sizes.

Temperature.

Concentrations of the particles.

As detailed in the following reference;

https://arxiv.org/ftp/cond-mat/papers/0210/0210187.pdf

1. Add a little electrolyte (e.g., 0.1 to 1.0mM KCl) - this will help define the double layer around the particles. Depending on how the surface of the particles behave, this can also increase the magnitude of the zeta potential (by reducing the double layer thickness in a constant surface charge system)

2. Add a surfactant - you don't indicate if you are allowed to add anything else

John Francis Miller

The extent of the problem is apparent in the SEM picture toward the end of the thread:

https://www.researchgate.net/post/Hi_I_would_like_to_know_what_is_a_proper_way_of_preparing_a_sample_corresponding_to_a_solution_of_Nano_particles_for_SEM_imaging

I don't think that simple treatments will be effective here...

Alan F Rawle Yes, I see what you mean :)

Alan F Rawle John Francis Miller Mahmood H. M. Kishore Kumar Sriramoju

!Hi thanks , for your response. is that possible that My NPs are not just conductive copper but also copper oxide among them as well? And the poor quality of image may be due to the charging effect?! I have attached the picture of my suspension as well. One thing that happen to them was that my suspension after a while turned to dark green which may be due to oxidation.

Melika Afshar The image is not good, but it appears that all your material is sitting on the bottom of the Pettri dish in the middle picture. Do you have a closer picture to confirm? If so, then you have no nano material (< 100 nm by ISO and ASTM definition). A Stokes' Law calculation will confirm this.

Alan F Rawle During SEM I measure spherical particle, which were about 40 nm, if I have not mistaken. However I'm not so sure how to use stokes law for this.

Bests,

Melika

Melika Afshar

I'd like to see a closer picture of your copper 'suspension'. Stokes' Law refers to spherical particles.... You can calculate settling rates for different sizes. Cu has a high density.... Material would need to be

Alan F Rawle Dear professor sorry for the late reply here is a closer image. I do not see settlements in my solution or if there is, it is not too much. Some of them has a color change some not.

Melika Afshar I'm still struggling to see what you have in your system so probably I'm not explaining myself well enough. In such systems visual inspection tells you a lot. Ideally, you'd have a picture taken from the side in say a 10 or 20 mL vial (could be smaller) rather than a Petri dish. Then we'd be able to look at the color of the supernatant, any settled/settling particles and so on. If you have a transparent colored solution (e.g. like wine or de-gassed beer) without sediment then we can be confident that you have a small, certainly nano (< 100 nm), system. It's a simple visual examination that should be the first thing to do. Turbidity would suggest larger material (perhaps sub-micron, 100 - 1000 nm) and settled material (> 1 up to 100 microns). This is why visualization is important. If you have such a small system then the SEM image you showed (with almost complete aggregation) is an artefact of preparing the sample for SEM and we can work on that. If your sample is already aggregated (much settling) then there's much less hope.