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| Gold nanocrystals and the size-color relationship. The picture is from Wikipedia |
If you are a nanochemist, and your friend is interested in scientific trivia related to what you research, size dependence of gold nanocrystal color would one of the easiest examples. Gold and silver nanocrystals can change their color by changing their shape, just like when you are skinny, you look red; when you are fat, you look blue.
There are a lot of interesting things going on with nanosized metals and the basic physical events that lead to super-good nanotechnologies. However, the history is pretty long; the emergence of nanosized gold was back to the 1857 paper by Michael Faraday. He used phosphorus to reduce a solution of gold chloride to make nanosized gold (he called it ‘gold leaf’ in the paper). He found the color was different from bulk gold.
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| One of the oldest research papers in my laptop. |
Another important breakthrough was made by Turkevich, as you can guess, the originator of the famous Turkevich method, where he made gold nanoparticles by reducing HAuCl4 by citrate (aka Vitamine C). This method is still used in the lab to create water-soluble particles (yes, good scientific discovery is immortal!).
Frens was one of the first researchers to study the nucleation and growth of nanocrystal synthesis, leading to a very famous theory, the LaMar theory. The most monumental work was published in Nature Physical Science (another trivia: The journal Nature was Nature Physical Science before!) in 1973.
This historical research spurred the flourish of the metal nanocrystal synthesis protocols, notably contributed by C. Murphy, Y. Xia, K. Klaubunde, G. Stucky, and so on. Today, we can make a lot of gold nanocrystals in terms of size, shape (rod shape, spherical shape, a lot of polyhedra shape), and solubility (water-soluble, or oil-soluble). Gold nanocrystals are cool because they can change the physical properties by synthesis that can be useful in the field of medical materials or materials science such as for special sensing techniques or imaging agents through its coloration, Raman response, and the plasmonic features.
Good luck with your “golden” research!
