To make Fe3O4 nanoparticles in powder form, a co-precipitation method can be employed. First, mix iron salt precursors (such as FeCl3 and FeCl2) in a solvent under controlled conditions. Then, add a reducing agent like NaOH to induce co-precipitation. The mixture is stirred and heated until nanoparticles form. After washing and drying, Fe3O4 nanoparticles in powder form can be obtained, suitable for various applications in medicine, electronics, and more.

Agra Yuba Bachtiar If you want to have your material in a truly nano state (100% < 100 nm) then you should leave it in (stable) colloidal suspension and not dry or filter. If you dry or filter you'll end up with a fused collection of (tight) aggregated and (looser) agglomerates.

Take a look at:

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

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

And this webinar (free registration required):

Dispersion and nanotechnology

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat

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 particle… ‘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

"Add a reducing agent like NaOH"? Always trust in answers from people like Alan F Rawle . Drying will destroy the nanosystem.

Dear Asma Iqbal

Fe3O4 NPs were fabricated according to previously reported works.34,35 Typically, approximately 13.7 mmol of FeCl2.4H2O and 29.5 mmol of FeCl3.6H2O were dissolved in 200 mL of deionized water under N2 atmosphere in a round bottom flask. Then, the mixed solution was stirred in an oil bath at 60 C. While heating the solution, 7.5 mL NH3 was added. The product was washed with deionized water after 1 h and was dried in an oven at 60 C degrees.

Fereshteh Javidfar, Manoochehr Fadaeian & Javad Safaie Ghomi (2021): Synthesis of Fe3O4@GO Nanocomposites Modified with La2O3 Nanoparticles as an Efficient Catalyst for Selective Oxidation of Aromatic Alcohols to Aldehydes, Polycyclic Aromatic Compounds, DOI: 10.1080/10406638.2021.1948874 To link to this article: https://doi.org/10.1080/10406638.2021.1948874

Alan F Rawle then how do I do characterization like sem, tem and xrd? all of these characterizations need to be in solid form. my city don't have a characterization equipments so I need to send it to another city

Agra Yuba Bachtiar The aim of producing a material is not to characterize it. It must be produced for a purpose. Take a look at this cynical article:

https://www.materials-talks.com/characterization-is-a-number-42-not-a-goal/

What are the properties of the material that are the reason for producing it? Catalysis? Here the testing would be by the appropriate chemical reactivity in the wet.

In terms of your techniques then XRD can be carried out in the wet although for nano-sized material you'll expect broad peaks that can be evaluated using Scherrer for crystallite size. If you're looking simply to confirm the phase (Fe3O4) then dry powder XRD would be fine. Electron microscopy would tend to show aggregated material (what you 'see' is an artifact of the sample preparation for electron microscopy) but you'd still get a handle on the morphology of the system. Note than thin sections are required for TEM and thus everything you observe under TEM is an artifact. Take a look at this old drawing for confirmation of the fact.

I totally agree with Alan F Rawle For your desired application you must retain your particles in the colloidal state. I recommend taking part of your sample and drying it for conventional characterization. You can use a magnetic separation process for this purpose, neodymium commercial magnets can be useful.

Another important debate question is how do you know that you have correctly synthesized pure nanomagnetite?

Juan Adrian Ramos Guivar regarding your question how do I know or not, i still don't know if this is pure nanomagnetite. Thats why I want to do some characterization such as XRD,SEM,TEM etc so I could know what characteristics of my sample. So I need my sample in dry phase. Regarding your recommendation, what do you mean conventional characterization? Could you give me examples?

Alan F Rawle My purpose is modification the surface of Fe3O4 in nanoparticles state. I am confused how I can modify Fe3O4 if not in solid state? I can't measure the weight if not in dry state. I also need characterization in order to know if my sample already modified or

Hi Agra Yuba Bachtiar By conventional characterization I mean the use of X-ray diffraction, SEM, TEM, and Raman that can offer information about structural, vibrational, and morphological properties. To confirm the magnetic properties it is mandatory to employ 57Fe Mossbauer spectrometry, XPS, and VSM techniques, they need to be evaluated all together and at the same time. They will give you details about stoichiometry, Fe oxidation states, and global magnetization properties. Misunderstanding of the magnetic properties can arise when analyzing the samples by this technique at different times due to the aging effect. If you are planning to use these NPs for biomedical applications, it would not be suitable due to common agglomeration and broad particle distribution. Of course, you need zeta potential to ensure the colloidal or dispersion stability.

I let you here two nice reviews about the difference between nanoFe3O4 and gamma-Fe2O3, please you can also see my participation in the LACAME 2022 Conference at Vitória Brazil, where I discuss this important issue:

Article Differentiating Nanomaghemite and Nanomagnetite and Discussi...

-Da Costa, G.M.; Blanco-Andujar, C.; De Grave, E.; Pankhurst, Q.A. Magnetic Nanoparticles for in vivo use: A critical assessment of their composition. J. Phys. Chem. B 2014, 118, 11738–11746.

LACAME 2022

-https://www.youtube.com/watch?v=YWa65dEhLCo&t=1493s&ab_channel=N%C3%BAcleodeNovosMateriais-UFES

I am constantly open to collaboration and answering aspects of Nanotechnology. My best!

Thank you for your answer Juan Adrian Ramos Guivar . Regarding characterization, how i can do characterization such as XRD, SEM, TEM, VSM or etc if I can't dried it? Could you give me detail about it? I'm confused in this part because the characterization need in dry state and I want my samples in nanoparticles

SEM and TEM will give information about particle size distribution. About XRD..this technique analyzes nanocrystallites contained in a powder state, non-particles. The extracted information is different. The surface modification is often called functionalization and is carried out in a liquid state, it is not necessary to dry the sample. If you dry them then you have an aggregate of nanoparticles (common current term), a redispersion of these particles will need the assistance of ultrasonication and stabilization with other organic agents, which will end with a totally different nanoparticle system. Hence, I recommend separating your samples for characterization and your desired application (liquid). I hope this message helps, some papers for nano-characterization are:

https://pubs.rsc.org/en/content/articlehtml/2016/ce/c6ce00198j

https://pubs.rsc.org/en/content/articlehtml/2018/nr/c8nr02278j

Fe3O4 NPs were fabricated according to previously reported works.34,35 Typically, approximately 13.7 mmol of FeCl24H2O and 29.5 mmol of FeCl36H2O were dissolved in 200 mL of deionized water under N2 atmosphere in a round bottom flask. Then, the mixed solution was stirred in an oil bath at 60 C. While heating the solution, 7.5 mL NH3 was added. The product was washed with deionized water after 1 h and was dried in an oven at 60 C degrees.

Agra Yuba Bachtiar of course you can dry your sample for characterization, but you cannot expect to further use dried material. It is destroyed as a nanoentity.