Hello,
I'm coating silver nanoparticles (on a substrate of aluminosilicates) with dodecanethiol, for dispersion in polyethylene through melt processing in an injection machine.
During one of my tests I sonicated the Ag in a mixture of toluene and dodecanethiol, and heated it to evaporate the solvent. While heating, it turned into a semi-viscous stuff, the color of the mixture changing from dark orange to white. I centrifugated it to separate the nps and they changed from orange to white as well.
Does anyone have any ideia about what might be happening? I expected the dodecanethiol to bond with the nps and stay stable, but now i`m afraid it might be reacting with the silver.
Thank you!
From first principles, I'd say it's very likely that Ag is reactiing with the S. Ag has a strong affinity for S, and the fine particle size would enhance the process. If you expose the viscous stuff to sunlight, or if you let it sit for a while, does it turn darker?
From first principles, I'd say it's very likely that Ag is reactiing with the S. Ag has a strong affinity for S, and the fine particle size would enhance the process. If you expose the viscous stuff to sunlight, or if you let it sit for a while, does it turn darker?
As you might know thiol groups produce a dative bond with silver. If too much thiol is added you can expect that silver is stripped from the nanoparticles.
It is not a good idea to heat Ag or Ag+ with thiols materials, it can be complicated. As Prof. Omar mentioned Ag has high tendency for S donating molecules. One of the methods usually used for the removal of heavy metals, such as Hg or Ag, from solutions is functionalization of the adsorbents with thiols because of the soft-soft high interaction.
Peofessor Pavlov, the samples are not turning black under sunlight nor after few days of resting. I think you guys are right, I reacted the silver with the Thiol.
Thank you all, Your answers were very helpfull!
Your silver particles are normally covered with a thin oxide layer (especially, if they were synthesized a long time ago).
For instance, in this article (DOI: 10.1021/nn503644v) we can't make the mirror with AgNPs and tetrathiafulvalene.
So, you need to eliminate it. Sunlight or some light, as proposed by Julus, can be an option.
Heating will kill your NPs colloid with 99.99% probability.
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