Gold – Useful on Earth and in Space

 
Gold has spurred humanity’s economic development. We decorate ourselves with it. What is less well known is that gold facilitates much of our modern world, including electronics, space flight, science, and medicine.
 

Medieval artists didn't know they were working with plasmons when they used colloid gold to color this window in Notre Dame Cathedral.  Source

Medieval artists didn’t know they were working with plasmons when they used colloidal gold to color this window in Notre Dame Cathedral. Source

Electronics

Last week we saw that gold electrons don’t orbit the nucleus – they oscillate at very high frequencies. This electron plasma permeates the entire atom, making gold an excellent conductor.

Gold isn’t the only metal with this property (although gold and cesium are the only metals in which relativity effects allow us to sense this oscillation as a golden shimmer). In fact, copper and silver are better conductors; however, they tarnish.

Gold is preferred for electronics not because it’s a good conductor but because of its chemical stability – it has a longer useful life. This is is especially useful in high-energy applications or in something where failure is a very expensive option.

In spacecraft, for instance, gold is used for wiring, solder alloys, and electrical contacts.

Space flight

Its chemical and other physical properties also make gold an ideal protective coating for the harsh space environment.

Yes, it’s harsh. You would think spacecraft have it made once they get above the atmosphere’s moisture and wind, but corrosion is quite a problem up there.

Besides the almost constant bombardment from micrometeorites and the solar wind, ionized oxygen reacts with aluminum – an otherwise ideal metal for flight because it’s inexpensive and very lightweight.

Gold is almost totally chemically inert and doesn’t react with ionized oxygen. Many spacecraft are wrapped in gold foil to fight corrosion and also because gold reflects heat (infrared radiation).
 

Not pictured:  Moon bling.  This Apollo 16 landing module wore gold for all the right reasons.  Source

Not pictured: Moon bling. This Apollo 16 landing module wore gold for all the right reasons. Source

Gold can also be pressed into sheets so thin they’re transparent. This is ideal for spacesuit visors that need to reflect both the heat and glare of sunlight.

Electron microscopy: (A) Gold particles  mark DNA near the mitochondria. (B) DNA is marked with gold particles after extraction.  Source

Electron microscopy: (A) Gold particles mark DNA near the mitochondria. (B) DNA is marked with gold particles after extraction. Source

Scientific uses for gold

Anyone who has ever tried to photograph the outdoors knows how difficult it is to get something small to hold still. What about really small things that you want to see in a scanning electron microscope?

Gold is used to coat nonconducting specimens – plastic, glass or biological – but this isn’t done to hold them still.

Gold is very dense and it keeps the electron beam from going right through the object being studied. As a conductor, gold makes a very good ground (an electron beam is, well, electrical). It also produces low-energy secondary electrons that the scanner uses as a signal source.

When you break down gold into tiny particles, this otherwise inert element becomes extremely reactive. This is why David Faraday called his gold colloid solution “activated gold” in 1857.

This reactivity makes gold nanoparticles a very good catalyst for chemical reactions. Gold could eventually replace the environmentally harmful mercury catalyst that’s now used to make polyvinyl chloride (PVC).

Various solutions of gold nanoparticles.  Source

Various solutions of gold nanoparticles. Source

Gold nanoparticles also work at lower temperatures than the catalysts currently used in auto emission control systems. These aren’t activated until the engine is hot. Perhaps one day we will see “cold start” emission controls, thanks to gold.

Medical uses of gold

Gold is one of humanity’s oldest medicines, although its chemical inertness means gold metal just passes through the body. The old treatments weren’t toxic – they just didn’t work.

morguefile.com/clarita

morguefile.com/clarita

Today there is evidence that some gold salts reduce inflammation, although no one is sure exactly how this works. They relieve the pain of joint swelling and may also prevent further inflammation, although they doesn’t repair the damage arthritis has already caused.

Gold injections are most often used to treat rheumatoid arthritis. They have been shown to help about half of patients who have been treated early in the disease course.

The Etruscans, back in 700-600 BC, were perhaps the first to use gold in dentistry to secure teeth as well as to display gold socially. Today, depending on where you are, you might earn disapproval or favor for showing a prominent gold tooth, but gold’s chemical inertness means it is widely used in dentistry, as well as for medical implants and other equipment.

Gold seeds are used in some radiation therapy treatments, while gold isotopes are themselves used to treat some forms of cancer.

Researchers are also exploring many medical uses for gold nanoparticles.
 

Gold nanoparticle used for targeted drug delivery.  Source

Gold nanoparticle used for targeted drug delivery. Source

It’s still in the experimental stage, but gold nanoparticles show promise as drug delivery systems, tumor targeting, and body scanning.

Almost 90% of a year’s supply of gold is used for either jewelry or in financial transactions. The rest goes into practical uses in electronics, medicine and space flight. Shimmering gold is precious to us, but so is all that is gold and yet does not necessarily glitter.

Tomorrow, we’ll take a look at where gold comes from.
 
 
 


 
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