STOCK markets may be crashing, but one thing remains a safe bet for anyone wondering how to invest their money: gold. Recently, the price of gold has risen to its highest level in more than six years. In times of uncertainty, the yellow metal is the safest haven around.
People have been putting their faith in gold since long before stock markets were invented. Why do we value it so? Part of the allure is its immutability. Gold stays gold. Shake the dirt from a pair of earrings worn in a Mycenaean citadel 4000 years ago and they shine as though made yesterday. Gold wedding rings are a potent symbol of constancy and endurance.
So what is the secret of this durability? It鈥檚 not entirely clear why gold is so unreactive. One reason is that gold atoms hang onto their electrons very tightly. But a key factor in the chemistry of gold is aurophilicity: the propensity of gold atoms to bond to each other. Gold, it turns out, is deeply attracted to itself. Since this discovery was made a few years ago, researchers have opened up a treasure-trove of weird chemistry.
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What鈥檚 going on here? Conventional wisdom tells us that gold atoms held in a molecular complex with other atoms should be in a stable state; they should not be available to bond with anything else. But it turns out that gold atoms also bond to each other. Though considerably weaker than the bonds that hold molecules together, such gold-gold bonds appear comparable in strength to hydrogen bonds.
Can we achieve anything useful with this aurophilicity? Chemists are trying to do just that. The bonds between gold atoms in a molecular complex are strong enough to tug it out of shape, and researchers are exploiting this property to build new molecular structures. At the molecular level, gold forms 鈥渘anoclusters鈥� of up to 40 gold atoms that arrange themselves in left and right-handed spirals like the stripes on a barber鈥檚 pole. Researchers believe they might be able to modify gold complexes to create photoluminescent materials, or 鈥渓iquid crystal鈥� structures that hover in that strange state between liquid and solid. Gold compounds also make surprisingly good catalysts: gold atoms can pull a molecule into convenient 鈥渄ocking鈥� structures that speed a chemical reaction.
Of course, the thing that makes gold a good financial investment is its scarcity, and the difficulty and expense of getting hold of it. The gold prospectors of ancient times used to peg out a fleece in a river to catch the nuggets that were washed out of gravel on the river bed. Today鈥檚 prospectors often have to dig 3000 metres underground to retrieve it. All for the love of a metal that is always drawn to itself.