In co-precipitation or other wet chemical methods for preparing nanoparticles. The precipitates obtained are generally freeze-dried or vacuum dried, or heated at 100-120. This is followed by annealing at high temperature. Can I omit this drying step and anneal the precipitates directly. What changes will it have on the final nanoparticles? Is this freeze-drying step necessary? If so, why?
I am synthesizing BaSnO3 nanoparticles by using SnCl4, BaCl2, citric acid, and 30% H2O2, further to increase the pH I am using NH4OH. I wash the precipitates with DI water and ethanol and centrifuge them. In the literature, for this synthesis route, people freeze-dry these centrifuged precipitates. However, I am annealing them directly. I am not sure if that is the correct way and what changes it might incur in the final obtained nanoparticles.
Kindly check https://www.sciencedirect.com/science/article/pii/S1004954111602188/pdf?md5=5af6c4f6ddd615f20c440d2bb83c416f&pid=1-s2.0-S1004954111602188-main.pdf&_valck=1
Also check https://onlinelibrary.wiley.com/doi/full/10.1002/jps.23998
Hi Sushobhita Chawla you never made it clear what is the nature of your precipitates and what you are trying to achieve.
In my experience there are some materials such as rare-earth oxides or Ba-Zr systems which precipitate separately even in very dilute solutions such that at the nano level there is considerable chemical inhomogeneity. This is compounded by the fact that precipitate washing is often accompanied with centrifuging which leads to gravity separation of dense and light clusters.
Hence, when you eliminate the drying and pre-grinding step you are compounding your probability to have a large variation in both chemistry and size-dispersion of your particles, assuming that is indeed your aim. Hence, drying is preferred. It can usually be eliminated for simple systems such as single phase oxides. However, you still run the risk of producing polydisperse samples upon calcination.
I hope it helps.
General note. It is not enough to describe the methods, but also to specify what compounds this method relates to. Otherwise it's guesswork.
Thank you for your answers Chinaza Godswill Awuchi Aditya Chauhan and Mirosław Grzesik. I have modified the question to add the details of my experiment. Kindly help if there are additional comments
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