Hello,

I will give you a few examples of how to make them in the easiest way possible (or the cheapest one), answering from my own experience:

1) About the choice of base, I would say NaOH, ascorbic acid or citric acid, as something that always will work (try a concentration of 0.1M). However you can use natural reducing agents, such as some plant extracts (that you can either buy or prepare just boiling), such as green tea, black tea, coffee extract or aloe vera. ere are a few reports of papers that used these techniques and. Can tell you from experience that they work pretty well (and quickly).

2) I would use a calibration line using small volumes (something like 20 mL final volume) and a proportion of reducing agent:metallic salt of 1:1. I would recommend to start from 100 mM and going down to 10 mM, with a few points in the middle. Then you can easily track down characteristics as absorbance (to see the production rate) nad size and morphology, with either DLS or TEM measurements.

3) The easiest way possible is using stirring at RT. However, if you use the natural compounds I told you before, I truly recommend microwave for 10-15 seconds (it will depend on the power and the final volume of your solution, mainly). Then you will see a change of color and density.

4) At RT and stirring, something like 30 min to 1 hour (less time if you use a water bath), and for microwave, 15 seconds should be enough (maybe, a cycle, RT for 3-5 minutes and then another cycle).

5) Centrifugation always work. If you use the natural compounds, use sonication for 10 minutes and then centrifuge at 6000 rpm for 10 minutes to separate the debris from the raw material from the nanoparticles in solution. Then collect the supernatant and centrifuge at aggresive conditions with water to wash the pellet for a couple of times. Then collect the nanoparticles in pellet, re-suspend with water and lyophilize the liquid to get a final powder that you can re-suspend to the desired concentration.

6) You should see different tonalities (but the same color) within the concentration calibration line that. Mentioned before, due to the change in parameters such as size, monodispersity and density of nanoparticles within the volume.

Hope this helps you a bit. F you have more questions or need more detail, do not hesistate in contact me.

Best

Dear David,

Thank you for the good explanation.

Won't sonication of the nanoparticles destroy the magnetic particles and result in fine suspension with all most no magnetic property?

Dear Ali,

It depends on the sonicator power. The regular ones that are combined with a water bath will not destroy the nanoparticles most of the cases. However, it will help the destruction of the natural debris presented in case of using natural products, releasing the nanoparticles and making a monodispersed solution -at least this happens most of the times-

Of course, if you use a sonication probe, it will probably disrupt the external core of the nanoparticles if it is used for a long period of time, plus considering the thermal agitation caused by the ultrasounds within the volume.

In conclusion, a regular sonicator for a short period of time will not alter the nanoparticles’ magnetic properties.

Thanks for sharing your concern.