An Easy Recipe For Quantum Dots

An anonymous reader writes "Semiconductor nanocrystals, better known as quantum dots, might find their way into solar cells, cancer tests, and all sorts of other products. Making them is surprisingly easy, if you have the right equipment, but it's not cheap. A team of reporters from Chemical and Engineering News visited Johns Hopkins and learned how to make the pricey particles (YouTube video). They have produced a slick video that explains the whole process."

Re:What's So Expensive?

[JustinOpinion]

So how much more expensive is the second, "smoothing" phase than the original production phase?

It's another wet-chemistry phase. It's no more expensive than the first synthesis step. But each step of course adds to costs (in terms of manpower, chemicals needed, etc.).

Similarly, adding the lipid layer is just a a ligand exchange: you mix the quantum dots with ligand in the right solvent mixture and they become coated. Simple in principle, not too complicated in practice, but it adds another step to the process.

how much do the products of each of those phases currently cost

Quantum dots are fairly expensive, but they are similar in cost to speciality chemicals that don't have industrial uses and thus don't benefit from economies of scale. Some examples from companies that currently sell quantum dots:
Invitrogen [invitrogen.com] 4 ml of 1 micro-molar QD solution (~15 mg of qdot solids) for $335 ~ $22 million/kg
Sigma-Aldrich [sigmaaldrich.com] CdSe QD, 5mg/mL, 10mL solution for $399 ~ $8 million / kg
SpectrEcology [spectrecology.com] 50 mg CdSe/ZnS QDs for $449.00 ~ $9 million / kg

For comparison, ubiquitous chemicals like gasoline are ~$1/kg, common chemicals like acetone (reagent grade) are ~$30/kg, high-purity semi-rare materials (e.g. pure selenium) are ~$1,000/kg, and speciality chemicals (for which there is no industrial need) are typically $100-$1,000 for a 500 mg quantity, which means $1 million / kg. As you can see, it is much more expensive to synthesise a speciality chemical (basically requires a trained chemist to manually do a small-scale lab synthesis for each batch), as compared to industrial-scale manufacturing.

There's no doubt that quantum dots could be made more cheaply if there were a real need for them. There are huge challenges in terms of how to scale-up the synthesis, but nothing that couldn't be addressed with clever chemical engineering and automation.