What is Striking rare gold: Researchers unveil new material infused with gold in an exotic chemical state

 

Stanford researchers created and stabilised Au2+, a rare type of gold, for the first time. This elusive variant of the prized element is stabilised by a halide perovskite, a family of crystalline materials with considerable potential for solar cells, light sources, and electrical components. Using off-the-shelf components at room temperature, Au2+ perovskite is also easy to produce. "It was a real surprise that we were able to synthesise a stable material containing Au2+—I didn't even believe it at first," said Stanford School of Humanities and Sciences associate professor of chemistry Hemamala Karunadasa, senior author of the Nature Chemistry study published Aug. 28. "Creating the first Au2+ perovskite is exciting. Perovskite gold atoms are analogous to copper atoms in high-temperature superconductors, and heavy atoms with unpaired electrons, like Au2+, have cool magnetic effects." "Halide perovskites possess really attractive properties for many everyday applications, so we've been looking to expand this family of materials," said study lead author Kurt Lindquist, a Stanford doctoral student and Princeton University postdoctoral scholar in inorganic chemistry. "An unprecedented Au2+ perovskite could lead to intriguing new discoveries."

Gold's heavy electrons

Gold has traditionally been appreciated for its scarcity, malleability, and chemical inertness, allowing it to be easily moulded into jewellery and coins that do not tarnish. Gold's name suggests that no other metal has such a rich colour in its pure state, adding to its worth. Karunadasa emphasised that gold's beauty and rarity stem from its physics. The cause is relativistic effects, first proposed in Albert Einstein's theory of relativity. „Einstein showed us that objects get heavier when their velocity approaches a large percentage of the speed of light," Karunadasa remarked. This applies to particles and has major implications for "massive" heavy elements like gold, whose atomic nuclei include many protons. These particles exert massive positive charge, causing negatively charged electrons to spin rapidly around the nucleus. Electrons become heavy and densely surround the nucleus, blunting its charge and allowing outside electrons to drift farther than in ordinary metals. Gold absorbs blue light and appears yellow due to electron energy rearrangement. Read More!