Citrate Synthesis of Gold Nanoparticles

Full procedure can be found at: https://education.mrsec.wisc.edu/citr...

Properties of materials change at the nanoscale. In bulk at the macroscale, the element of gold is gold colored, but at the nanoscale, the element of gold is red to purple in color. The formation of gold nanoparticles can be therefore observed by a change in color since small nanoparticles of gold are red. The layer of absorbed citrate anions on the surface of the nanoparticles keep the nanoparticles separated, and the presence of this colloidal suspension can be detected by the reflection of a laser beam from the particles. Switching to a smaller anion allows the particles to approach more closely and another color change is observed.

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