I am looking at synthesis methods for upconversion nanoparticles. In some journal articles I've read, the authors mention the use of a vacuum to remove water and oxygen during the synthesis process while in other articles the authors don't mention it at all. Because these synthesis procedures are at such high temperatures, I imagine that water and oxygen would be removed anyway (with vigorous stirring while under nitrogen atmosphere) even without the use of a vacuum, but I might be wrong. Is using a vacuum preferable or essential for the synthesis of upconversion nanoparticles?
EDIT: I am interested in using a thermal decomposition method.
Thanks!
Actually it depends on what type of system you are preparing using thermal decomposition route. If you are interested in a very narrow size distribution (nearly mono dispersed) then it is must to use vacuum drying of precursors before starting the reaction. Use of vacuum drying remove the water content which helps to reduce the particle size distribution. However, If your precursors does not contain any water molecules then you can skip this step.
No, it is not necessary always. Its depend on which method are you following to synthesize the UCNPs. There are various processes like Thermal decomposition
method, Hydrothermal/ solvothermal method, Other methods like Co-precipitation method ,Sol–gel processing, Combustion synthesis, Flame synthesis etc.
I am interested in using a thermal decomposition method. Would that require a vacuum?
Here is an example from our work (enclosed). In practice we did not bother using vacuum and it did work quite well. Hope this helps.
Article Monodisperse upconversion GdF3:Yb, Er rhombi by microwave-as...
Article Size and shape evolution of upconverting nanoparticles using...
Article Monodisperse Upconverting Nanocrystals by Microwave-Assisted Synthesis
Actually it depends on what type of system you are preparing using thermal decomposition route. If you are interested in a very narrow size distribution (nearly mono dispersed) then it is must to use vacuum drying of precursors before starting the reaction. Use of vacuum drying remove the water content which helps to reduce the particle size distribution. However, If your precursors does not contain any water molecules then you can skip this step.
thats case dependent, you question does not have a concrete answer. 1st study the chemistry behind the reaction system and then make a decision.
It is not always necessary, which depends on your mehtod and the host.
Even using a thermal decomposition method，vacuum is not necessary, N2 flux isjust enough.
In the event of a vacuum, the finished product becomes completely oily and it is difficult to remove the powder But the use of the nitrogen gas system was easy to reach.
As a result of reversible reactions of thermal decomposition, low-molecular reaction products are isolated, water, carbon dioxide, ammonia ... To shift the equilibrium towards the formation of nanoparticles, the decomposition process must be carried out under vacuum or in feeding an inert gas into the reaction zone. Then you lower the partial pressure of low molecular weight products and get more nanoparticles.
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