Hello all,
I've recently been attempting to synthesize monodisperse diameter gold nanoparticles (approx 2.5nm) based on the work of Levi-Kalisman (2019). In short, particles are synthesized directly using HAucl4, 4-MBA as thiolate protection and NaBH4 as the reducing agent at room temperature. Particles are precipitated after synthesis with 80% MeOH and 10mM NaCl, centrifuged and resuspended in ddH20.
I'm happy with the particle size as measured by TEM (2.3nm +- 0.4nm) however I would like to prevent aggregation as much as possible - I haven't been able to prevent the particles bunching up under TEM. I have tried dilutions of the suspension and filtering with a 20nm inorganic membrane.
Any ideas and discussion welcome and can post example images if needed!
Thanks!
Charlie Beales
You write 4-MBA as thiolate protection. 4-MVA prevents the aggregation of your particles. Then you delete it and aggregation appears. Therefore, try to leave 4-MVA on the surface of the nanoparticles, for example, washing with water instead of alcohol or with a more dilute alkali solution.
Yuri Mirgorod
Dear Prof Mirgorod,
Thank you for your suggestion. I should clarify - the "aggregation" is strange, the particles almost self arrange into a 2D layer on the carbon coated grid rather than a 3D aggregation as you might expect if this happened in solution. Please see the image attached as an example. I'm beginning to believe that there is some kind of interaction with the carbon coat itself that is causing this arrangement or this is some kind of "drying" effect.
What are your thoughts on this?
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