Hello again. Welcome back to LuxeSci - a podcast to re-ignite your wonder by exploring the science behind luxury items. I’m Dr Lex, PhD, infectious disease expert and jewelry lover. I’m joined by my co-host Dr. Dimos, also a PhD, electrical engineer and materials science enthusiast.
So we’re continuing our theme of jewelry but moving away from the metals and into the gems! I’m very excited about this shift. Our Instagram account has been following some amazing independent jewelers and gemological societies, which means it’s full of sparkling gemstones and I love it. (follow us at luxescipod to see who we’re following and showcasing). So I mentioned my grandmothers wedding ring set in our previous episode on platinum and it has some relevance here as well. My engagement ring contains the center stone from my grandmother’s ring. One of the reasons I love it so much, aside from the strong sentimental value, is that it’s an unusual cut (at least for these modern times). It’s an old European cut diamond, which were prominent between 1890 - 1930. This cut is round and is a predecessor to the modern round, brilliant cut. Apparently this cut optimizing more weight, rather than optimizing appearance. This old cut results in more dispersion of the light within the diamond (referred to as fire) as opposed to the modern brilliant cut, which results in more sparkle, apparently. I say apparently because it’s been my experience that my engagement ring sparkles more than stones of a similar size. Perhaps it’s that fire that is a little bit different from the sparkle and thus catches the eye. Regardless, I love my antique diamond (even with its chip).
Dimos - what’s your experience been with diamonds?
So here’s a microbiologists and electrical engineer’s take on the science of diamonds.
Background:
There is so much to talk about with diamonds from their geology and formation to their mining and cutting to the marketing that made them the de rigeur choice for engagement rings. We’re not going to be able to cover everything in our short podcast so here’s a bit of an overview
Diamonds are made of carbon where the atoms are arranged in a crystal structure
Most commonly a diamond cubic formed of unit cells stacked together
Has the highest hardness and thermal conductivity of any natural material
Few impurities can exist with the rigid arrangements of carbon atoms in diamondsThe most common of these is replacing a carbon atom in the crystal lattice. Colored diamonds are called fancy diamonds
Boron and nitrogen - these account for some of the different colors of diamonds
Boron - blue
Nitrogen - yellow and brown
Defects - brown
Radiation exposure - green,
Plastic deformation (the ability of a solid material to undergo permanent deformation, non-reversible change of shape in response to applied forces) - pink, orange or red
Black diamonds are not truly black. They contain numerous inclusions that give them a dark appearance
Most natural diamonds are between 1 billion and 3.5 billion years old and were formed at the depths of 150 to 250 kilometers (93-155 mi) below the surface of the earth
Diamonds form when carbon-containing fluids dissolve minerals under high pressure and temperature
Synthetic diamonds are grown from high-purity carbon or hydrocarbon gases
Extremely rare - concentration of at most parts per billion in source rock.
Misconception - diamonds come from coal (formed from buried prehistoric plants)
Most diamonds are older than the first land plants
Most likely carbon source is carbonate rocks and organic carbon in sediments, not coal
20th century is when gemologists developed the 4 Cs to grade diamonds
Mass (carat)
Cut - graded according to proportions, symmetry and polish
Color - how close to white or colorless; or how intense the hue)
Clarity - how free from inclusions (any material that is trapped inside a mineral during formation)
Mid-20th century is also when De Beers revived the American diamond market with some clever advertising and created new markets in countries where no diamond tradition had existed previously
History
Evidence of diamonds being traded goes back as far as the 4th century BC in India - for the very wealthiest
Gradually those diamonds (through trade) found their was to Western Europe via Venice’s medieveal markets
By the 1400s, diamonds were fashionable accessories for the Europe’s elite
In the 1700s, Brazil took over as the top diamond producer worldwide and remained so for the next 150 years
1800s - explorers unearthed the first of the great South African diamond deposits and diamond demand broadened
Really hinges on the 1866 discovery of the deposits in Kimberley, SA by Cecil Rhodes and the establishment of the De Beers mines
Since then there have been deposits discovered in Democratic Republic of Congo, the former USSR, Botswana, Australia and CAnada
Science
Diamond thin films - potential coatings for implants
Paper by PA Nistor and PW May in Interface (royal society publication) from 2017
Two properties that make diamond a good candidate for biomedical applications
Inert - minimal immune response if used in the body
Electrical conductivity can be altered in a controlled manner
So how do you get a thin film of diamonds
Chemical vapour deposition (CVD)
Fundamentally - the material to be coated is put in a vacuum chamber.
The coating material is heated or the pressure around it is reduced until the material vaporizes
In the vacuum chamber the suspended material (vaporized stuff) begins to settle onto the material you want coated
Adjusting the temperature and duration controls the thickness of the coating
https://news.mit.edu/2015/explained-chemical-vapor-deposition-0619
Surprisingly, this isn’t that expensive. The authors of the article quote a plate of diamond 1 cm 2 and 0.5mm thick as costing $50, which if you know anything about lab materials, isn’t that expensive at all
Interestingly for a bioinert material, diamonds form a surface that cells with adhere to, making it a possible substrate for cell culture
There are of course limits on diamond’s biocompatibility
Diamond nanoparticles have been shown to be toxic to aquatic life and at very high concentrations they limit macrophages
Also - diamond nanoparticles and diamond films have shown bactericidal properties
The second advantage of controlling the electrical conductivity is cool
Doping - addition of tiny amounts of non-carbon elements that act as electron donors or acceptors
Conductivity can range from highly insulating to near-metallic
The cool thing here is that you could have a cell-supporting structure that can also allow electrical signals to be passed to and from the cells its supporting (very useful for research involving neurons)
An additional advantage of diamond thin films is that they can be patterned so that there are areas which can support cell growth and areas that cannot
Given the advantages of diamond nanoparticles or thin films, there are a range of biomedical application possibilities:
Coat blood vessel stents
Artifical joint components (diamond is super strong!)
Neural implants
Cool use of diamond’s conductivity properties: nanosensors for COVID-19
Changhao Li, et al in Nano Letters (American Chemical Society) in 2021
The team created a quantum sensor model using nitrogen-vacancy centers in diamond
Quantum sensor - detects variations in microgravity using the principles of quantum physics
Nitrogen vacancy center - point defect in a diamond (nearest-neighbor pair of a nitrogen atom and a vacancy in the crystal lattice)
Photoluminescent
NV center’s electron spin can be manipulated at RT and leading to shifts in the intensity of the photoluminescence.
Unit for quantum computing as well
The team built a theoretical model to see if the viral RNA from the COVID-19 virus could “set off” the sensor. The model was successful showing the limit of detection as low as several hundred viral RNA copies, less than what is currently available.
Lots of work still to be done to make this a reality but it’s fascinating work
Glossary
Plastic deformation (the ability of a solid material to undergo permanent deformation, non-reversible change of shape in response to applied
inclusions (any material that is trapped inside a mineral during formation)
Doping - addition of tiny amounts of non-carbon elements that act as electron donors or acceptors
Quantum sensor - detects variations in microgravity using the principles of quantum physics
Nitrogen vacancy center - point defect in a diamond (nearest-neighbor pair of a nitrogen atom and a vacancy in the crystal lattice)
Fun facts:
How old are most diamonds - between 1 billion and 3.5 billion years
Are diamonds made from coal - mostly no, they are made from other carbon sources
What impurity causes blue diamonds - boron
What impurity causes yellow diamonds - nitrogen
I hope you’ve enjoyed exploring diamonds with me and Dimos and I hope you remember a little fact from this episode the next time at your next party, maybe when complimenting someone’s diamond jewelry. Thanks for listening to this episode of LuxeSci. A very special thank you to my audio engineer and co-host, Dimos. Our theme music is Harlequin Moon by Burdy. We’re on Twitter and Instagram at luxescipod. Please subscribe and review where ever you listen. This episode we ask that you follow us on Instagram for both some interesting science content and some beautiful jewelry content.
References:
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