In red, purple and blue

Invisible specks of gold promise new scientific advances—fighting cancer and faster computers. Elixir or fool’s gold?
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First Published: Thu, Jul 11 2013. 04 52 PM IST
Could the growing human hunger for gold adversely affect its scientific applications? Photo: Reuters
Could the growing human hunger for gold adversely affect its scientific applications? Photo: Reuters
Hernán Cortés, the 16th century Spanish conquistador who ended the Aztec empire, spoke of a sickness of the heart “that only gold can cure”. Christopher Columbus, the Italian explorer who discovered the new world instead of India, said people who possess gold could help “souls into paradise”.
No country on earth has a greater sickness of the heart or feels more the call of that golden paradise than India. Gold is No. 2 on India’s import bill, after petroleum. Its price has doubled in five years; since 2000, it’s up more than 500%. Globally, prices are actually down, but physical demand is soaring (dominated by individual buyers from India and China). “Gold’s allure is timeless and we continue to treat it with an almost religious reverence,” writes John Browne, a former chief executive of oil giant BP, in his new book, Seven Elements That Have Changed the World. “No currency is tied to it and no trade is facilitated by it but still we want more and more of it.”
This unprecedented, seemingly insatiable gold-lust obscures the increasingly vital role that gold plays in furthering the frontiers of science and technology. Although the Egyptians consumed gold for medical purposes more than 5,000 years ago—they believed it was a mystical metal that healed the body and extended life—and various civilizations have used it for specific ailments, such as arthritis or dental decay, or as an elixir, it has really come to prominence with the advent of nanotechnology, with engineering, medical, electronic and chemical applications.
The science of very small things has revealed that gold at a molecular or atomic level is quite different from the smooth, shiny stuff we know. In the world we cannot see, materials do not behave quite as they do in the world we can. We are now at the nanoscale, approximately encompassing things from 1-100 nanometres. A human hair, in comparison, is more than 80,000 nanometres thick.
At this level, science works with individual atoms and molecules. In this world, gold has no fixed colour, varying from light blue, bright purple to a deep red, depending on how it interacts with light. The gold we see is dense; it reflects light. The gold we cannot lets in light, its electrons absorb varying wavelengths. Different wavelengths, different colours of gold.
Nanoscale gold is far more reactive than visible gold, which is known as a metal that does not corrode or fade. The smaller the gold nanoparticle, the more excitable its atoms, which tend to gather in larger numbers at its surface. Gold at the nanoscale as a catalyst has provided for advances in fields as diverse as paints, textiles and water purification. Traditionally used in electronics, gold in its nano avatar is now emerging as an important material in the development of faster computer chips and communication devices.
In the medical sciences, gold nanoparticles create great excitement in diagnostics, imaging and—in particular—cancer treatment. Research teams have demonstrated how gold nanoparticles can attack cancers in many ways, from identifying and destroying them in a more selective, benign fashion. For instance, gold nanoparticles tend to gather in cancerous tumours. So, these cells can be targeted for destruction, avoiding harm to healthy cells.
The interaction of gold nanoparticles and DNA is another emerging area of interest. Last year, researchers at the University of Illinois demonstrated how segments of human DNA can direct the shape of gold nanoparticles. If perfected, such nanoparticles could be tailored for specific purposes.
The advances involving nanoscale gold come thick and fast:
Last month, scientists from the University of Notre Dame, US, showed how dengue in mosquitoes could be detected cheaply and quickly using invisible gold.
In May, research papers described how such nanoparticles could help fight ovarian cancer, or be used as catalysts to produce clean hydrogen, the fuel of the future.
In April, there were advances in the stability of the nanoparticles, the ability to observe individual particles in action and, for the first time, their self-assembly in real time—the last an attempt to use lessons from nature to create new materials.
It is important to note that gold at the nanoscale is far from being an elixir of life, as the ancients once believed of regular gold, as many still do. The toxicity and stability of these nanoparticles are an ongoing concern, and their manufacture requires very poisonous chemicals (One solution comes from the kitchen cabinet: replace the nasty stuff with cinnamon).
As the frontier near, many hurdles will be overcome, and new ones will emerge. The future lies somewhere between the claims of elixir and fool’s gold.
Could the growing human hunger for gold adversely affect its scientific applications? Industrial and medical applications consume roughly one-tenth of global gold production. At the nanoscale, the amounts involved are—currently—small. The human hunger for gold might not matter.
Samar Halarnkar is a Bangalore-based journalist. This is a fortnightly column that explores the cutting edge of science and technology. Comments are welcome at frontiermail@livemint.com. To read Samar Halarnkar’s previous columns, go to www.livemint.com/frontiermail
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First Published: Thu, Jul 11 2013. 04 52 PM IST
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