• Question: How do you make gold nanoparticles?

    Asked by sianfreeman to Nicola on 8 Mar 2014.
    • Photo: Nicola Rogers

      Nicola Rogers answered on 8 Mar 2014:

      Making gold nanoparticles is actually quite easy as chemstry goes!

      We take a gold salt; HAuCl4. which contains Au (III) ions, i.e. Au 3+ ions, and we dissolve this in water. Therefore in the solution we have H+ ions, lots of Cl- ions and some Au3+ ions. we boil the solution and whilst it is rapidly stirring we add a reducing agent called sodium citrate – which contains lots of citrate anions. The citrate anions reduce the Au3+ ions to Au(0) ions, and the Au(0) centres begin to group together to form particles. Usually the particles are about 10 nm in diameter, and that is about 100,000 gold atoms which have stuck together to form a particle…… To give you an idea of how big the nanoparticles are, if we lined up 100,000 nanoparticles in a row, they would be 1 mm in length!

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