Currently been working with nano plate type structures and having issues with surface effects so we want to move away from this and try to make larger crystals to try and avoid some of the issues from surface effects. Currently run in a solvothermal synthesis in solution.
Interested in various methods I should look into. Right now they are in the nano range. So anything larger where I can look into more bulk properties would be helpful
Larger crystal can be grown by increasing the reaction time. 7-10 days are generally enough to grow single crystal for the diffraction by solvothermal synthesis in autoclave.
I usually run it at 2 hours. So easy to add more time. Do you generally have to add more precursors as the time goes on? Or does the reaction just use more of the precursors and get closer to 100% consumed? Think I average right around 82% right now.
Increase the time is a good strategy, if you are in the nanoscale (5-20 mm) and want to go to 100nm or higher you probably will need more than 3 days (as Arindam Indra says). Obviously the way the nanocrystals grow will depend of the type of oxide. Take a look at this work, about growing of TiO2
http://pubs.acs.org/doi/abs/10.1021/cg300473u
Increase the amount of precursor can help, but remember that there is a limit on the solubility and surpass it would be adverse for the synthesis. Which kind of solvent was used? (Oleic acid, e.g.). What are the nanoparticles? Are they functionalized with a organic layer?
If they are formed with a organic layer, they will not grow if the organic layer is not removed.
Using an organic solvent right now (Oleylamine). They are in that 5-20 nm range right now. How can you remove an organic layer if you are making them in an organic solvent?
Solubility shouldn't be a problem though since I have small amount of precursors in my solvent. But I will keep an eye on it. Looks like just more time is the first step to look at. Thanks.
What I mean is that if the particles are formed with a organic layer, is not worth it to add those particles to the synthesis together with the precursor in the solvent, since the layer will not be removed and the particles will not grow.
You need to start a new synthesis from zero; and as shown in the article of TiO2 previously shared, the TiO2 nanoparticles of different synthesis times from 15 minutes to 64 hours vary from 5 nm to less than 20 nm, and the growth appears to be stabilized so even after several days the nanoparticles might not exceed the 50 nm.
If you need larger particles, you could look at the literature for another synthesis that has already obtained the sized you need, while doing your synthesis.
This book is very good and have many synthesis: Metal Oxide Nanoparticles in Organic Solvents - Markus Niederberger
Aging of the synthesized compound in mother liquid for 5-10 days should increase the particle size.
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