In a groundbreaking study, researchers from Stanford University have successfully created and stabilized an extremely rare form of gold known as Au2+. This unique and elusive version of gold is a halide perovskite, a crystalline material that shows great potential for various applications, including solar cells, light sources, and electronics components. This discovery is particularly significant because the Au2+ perovskite can be easily synthesized using common ingredients at room temperature, making it an accessible and exciting breakthrough in the field of materials science.
Lead author Kurt Lindquist, a former Stanford doctoral student and current postdoctoral scholar at Princeton University, explains that the creation of an Au2+ perovskite was an unexpected surprise. The gold atoms in this perovskite exhibit similar characteristics to the copper atoms found in high-temperature superconductors. Additionally, heavy atoms with unpaired electrons, like Au2+, display unique magnetic effects not observed in lighter atoms. These findings open up new possibilities for exploring the properties and potential applications of this rare form of gold.
Gold has long been revered for its scarcity, malleability, and chemical inertness. These properties make it valuable for jewelry and coins that do not tarnish over time. One of the key reasons for gold’s distinctiveness is its color, which is unmatched by any other metal in its pure form. The physics behind gold’s appearance also explains the rarity of Au2+. Due to relativistic effects, gold atoms with a high number of protons have heavy nuclei, resulting in a rearrangement of electrons and energy levels. This rearrangement causes gold to absorb blue light, giving it its characteristic yellow color. As a consequence of this rearrangement, gold primarily occurs as Au1+ and Au3+, losing one or three electrons respectively and avoiding the formation of Au2+.
Remarkably, the Stanford researchers found a way to create and stabilize Au2+ in a perovskite. Lindquist made this groundbreaking discovery while working on a project involving magnetic semiconductors for electronic devices. By mixing cesium chloride with Au3+-chloride in water and adding hydrochloric acid along with vitamin C, Lindquist was able to produce Au2+. The Au2+ remained stable in the solid perovskite but not in solution. This synthesis process, using simple ingredients and taking only five minutes at room temperature, yielded a dark green, almost black powder. Further tests confirmed the presence of Au2+ and shed light on its light absorption and crystal structure.
The Stanford researchers’ findings add a new chapter to the century-old story of chemistry and physics involving Linus Pauling, a Nobel laureate. Pauling had previously worked on gold perovskites that contained the more common forms of gold, Au1+ and Au3+. Interestingly, Pauling also studied the structure of vitamin C, which is one of the ingredients used to stabilize the elusive Au2+ in the perovskite. The connection between Pauling’s work and this new discovery adds to the significance and intrigue surrounding the synthesis of this unique material.
Moving forward, the researchers intend to further study and manipulate the chemistry of the Au2+ perovskite. The hope is that this material can be utilized in applications requiring magnetism and conductivity, as electrons move between Au2+ and Au3+ within the perovskite. This exciting breakthrough paves the way for exploring the potential of Au2+ perovskites and their various applications. The researchers are eager to unlock the possibilities and continue expanding the field of materials science with this rare form of gold.
The discovery of a stable Au2+ perovskite by Stanford researchers is a significant milestone in the field of materials science. The surprising synthesis of this rare form of gold using off-the-shelf ingredients at room temperature opens up new avenues for research and applications in a range of fields, including solar energy, electronics, and magnetism. This breakthrough showcases the power of scientific exploration and the potential for unexpected discoveries that can shape our understanding of the natural world. The researchers’ contributions add to the legacy of scientific pioneers like Linus Pauling, further enriching the history of chemistry and physics. As scientists continue to study and refine the chemistry of Au2+ perovskites, the possibilities for their use in innovative technologies and materials are boundless.
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