Precipitated nano particles just showed change in color but not showing magnetic property. Is there any need to add some chemical. If so how it would be green approach ?
First you should check whether the particles are made of magnetite (Fe3O4) or maghemite (gamma-Fe2O3). Other phases (like hematite) would not be magnetic in the sense you seem to need. Also, very small size (less than 4-5 nm) of the particles could be responsible for the lack of response with a small magnet.
Hope this helps.
Hi,
Building further on the comments of Prof. Goya, the two most important parameters to note are:
1) The mineralogy (magnetiite, hematite, maghemite). i.e, either they are characterized as ferromagnetic, antiferromagnetic, or canted antiferromagnetic. This would determine the primary ability of the material to demonstrate desired magnetic property.
2) The size of the nanoparticle is important. It determines if the particles are super-paramagentic, stable single domain, pseudo-single domain or multi-domain. Each mineral, depending upon the size of the unit cell, has specific size range for each of these domains.
Please let us know about the exact magnetic property you are looking for.
Cheers
Sir I am looking for super para-magnetic behavior of nanoparticles @ Amar Agarwal sir
I can think of a possibility. If the particles are very small, thermal excitation may be sufficient to spontaneously and frequently change the direction of magnetization in super para-magnetic particles in weak external fields.
Better look of articles from Michael James Jackson, University of Minnesota. The link is attached. They are working especially on magnetic properties of nano particles including biogenic magnetic nano particles.
https://www.scopus.com/authid/detail.uri?authorId=24606584900
My dear Prashant,
You have got good suggestions above. Do you know the crystal structure from XRD or TEM work? Do you know what ions are in the mineral? For example, iron, oxygen, hydrogen. These are first order questions.
If you have an instrument (like Magnetic Property Measurement System) to measure magnetic susceptibilty in a low (~10 mT) field in a shielded superconducting magnet from 300 down to 10 K, suprparamagnetic particles will become thermally blocked at their blocking temperature leading to a peak in susceptibility.
magnetic NPs synthesised by plant extracts should be in specific range for magnetism retention and proper surfactants should be used.
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