I synthesized CdSe and CdS nanoparticles using DiEthyleneTriamine as capping agent by chemical precipitation method at room temperature. I took the precursors in the ratio 1:1:2. In TEM characterisation I found nanoparticles were agglomerated and there was no dark spots in the saed pattern. What would be the reason for agglomeration? Will pH varying play any role in it?
We used glycerin and gelatin as capping agent. Nice SAED and separated nanoparticles less than 5 nm were obtained.
amine or sulfur terminated soft ligand (HSAB principle) will better for the synthesis of CdSe/CdS as Cd is soft. there are several reason behind agglomeration-a) surface modification is not efficient. b) chain length of the tail part is not sufficient to impart proper crowding around the nanoparticle.
again reaction temperature has also a significant role. a) it helps in arranging atoms to develop well defined crystalline particle. b) it will helps in proper surface modification.
amount of capping ligand also have role in designing size/ shape selective particle with proper surface modification.
i think, the amount of surfactant (DiEthyleneTriamine) is not sufficient.
what is your Sulfur/ selenium source and solvent ?
to get better SAED pattern in your procedure, its better to increase the temperature.
pH also have a role. it will depends upon all the reactants and solvent.
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