I am about to freeze dry carbon nano dots that have a hydrodynamic diameter profile of 2.5nm, I’m afraid they will dissipate with the water as it evaporates. Is this a legitimate concern and if so is there a safe way to do this or is my concern unfounded? (freeze drying is lyophilization)
@Robert Michael Miller Your system will aggregate when you lyophilize your system. You will destroy the inherent nano nature of the system by evaporation. See, for example, May 28th, 2019 Dispersion and nanotechnology https://tinyurl.com/y2wfzed7
Robert Micheal Miller
I'm not a nanotech expert, so share some general information and extrapolation from pharmaceutical freeze drying, which may help.
Freeze drying is not evaporation, it's freezing and sublimation of the ice or frozen solvent.
Freeze drying removes something like 99% of the moisture, leaving the remaining 1% which typically binds chemically to the product, assuming an organic system. This 1% or so, may act as adhesive to keep the product "stuck" to the substrate.
The speed of freeze drying is a concern, as is the ice crystal size. Small ice crystals mean the product is a fine powder with small channels (the ice) through which the vapor escapes as the sample sublimes. This can lead to "blowout" if the freeze drying cycle is too aggressive, this carries powder away. Solutions are to dry slowly, and / or to induce large ice crystals during freezing, which provide big channels though the product structure for the vapor to escape.
What I'm not able to provide is a definite yes or no. Sorry.
Kind regards,
Rob
Robert Micheal Miller One question to ask you. Do you know what the diameter of a hydrogen atom is?
Robert Micheal Miller
If carbon dots have a graphite structure, then they can sublimate in the form of graphene leaves. Between graphene leaves a weak intermolecular bond.
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