I have synthesised magnetite nanoparticles by co-precipitation method. But it is not stable, which is settling within 10 minutes. How can I increase the stability of magnetite nanoparticle?
Magnetite is magnetic (hence the name) and the long range magnetic forces will always overcome short range charge (or electrostatic) mechanisms attempted to confer stability. Only route is steric stabilization with a polymer such as PEG or say a 50 kDa PEI. This will prevent the magnetite particles from coming in contact - however, the penalty is that the size of the particle can increase markedly with the adsorbed steric layer.
Sir, Thank you for your reply. The size of the nanoparticle was 7-9nm. But I didn't do any coating? Is it without coating, it cannot be stabilised?
At those small sizes the particles should be superparamagnetic at room temperature, so long range interactions are averaged to zero. Your particles should be stable. Are you positive that your particles are 7-9 nm? In any case, adding a polymer as mentioned is, if not the only, the simplest way to stabilize them.
Yes sir, from TEM analysis it is inferred that size of the nanoparticle was 7-9nm. Even though it is in nanosize, it is settling down.
"1. ......from TEM analysis it is inferred that size of the nanoparticle was 7-9nm
2. Even though it is in nanosize, it is settling down"
Statements 1 and 2 are incompatible. A simple Stokes' Law calculation will easily show this.
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