Bleach makes for great bio-imaging

That it holds promise for quantum computing is a bonus

A little bit of bleach and sunlight may be all it takes to dope carbon nanotubes with oxygen, thus making them fluoresce in ways that will improve both bio-imaging and quantum computing. Pic, Pixabay

The T. C. team

Those famous quantum computers we have all heard about have rather frugal needs – a source that produces one photon at a time at frequencies about which telecom systems operate. And yes, everything at about room temperature.

Once these requirements are addressed, of course, speeds of some computing operations, including cryptography, can leave their traditional counterparts in the dust.

For the present, only expensive carbon nanotubes with a fluorescent quantum defect meet those requirements. It calls for special reactants and relies on methods that are difficult to control. It also proceeds slowly, generates defects that affect light emission, and is hard to scale.

Researchers Angela Belcher and Ching-Wei Lin
Researchers Angela Belcher and Ching-Wei Lin of the Belcher Lab at MIT

But researchers who were actually looking at a biomedical application have found that one household product can generate the right kind of carbon nanotube: bleach.

“We can now quickly synthesize these fluorescent quantum defects within a minute,” says researcher and post-doc Ching-Wei Lin at the Massachusetts Institute of Technology. “We can produce them at large scale easily.” And to think that the team’s primary concern was not even quantum computers but biomedical imaging.

A solution containing the singe-walled carbon nanotubes (SWCNT) and the bleach (NaClO) come together and are irradiated by light at 300 nm for about a minute to produce oxygen-doped nanotubes.

Some background may be needed here on quantum computing, at least.

Quantum systems have an advantage over the ones on your laps or in your pockets. The latter are limited to a on-off/one-zero language of the classical computer as envisaged by Alan Turing. Yes, yes, the protagonist of The Imitation Game.

Translated in to this two-letter alphabet of the computer, each bit of information can be ‘off’ (0) or ‘on’ (1) – two unambiguous states, like the two sides of a coin.

But quantum computers can allow for both at the same time, like a coin spinning on a table, which is both heads and tails, at least until it stops. When spinning, it can be seen as more heads or more tails, depending on when it is observed. Having heads, tails, both and proportions of each as options in each ‘qubit’ increases the number of ‘letters’ available. Thus, there is more information in a qubit than the traditional bit. Each additional qubit increases computational power exponentially. By comparison, each extra bit in a traditional system only doubles the information.

Images of mice leg using O-doped carbon nanotubes
When mice were injected with the oxygen-doped, fluorescent nanotubes in solution, the resulting images clearly showed arteries and veins (A&V) and lymph nodes (LN)

To get single photons for the job is hard. Most light we see comes from heated objects that give off light (consider hated iron glowig red, then white) or lasers.

Lin and others found that ultraviolet light caused the bleach – otherwise called sodium hypochlorite or NaClO – to release oxygen, which acted as a bridge between the carbon atoms in the nanotubes. The resulting structure was fluorescent. It sent out short infrared light a little over 1100 nm in wavelength. The icing – the process took less than a minute.

The research was done in the lab of Angela Belcher, head of the MIT Department of Biological Engineering. Her lab aims to develop probes that are just right to find very small tumors, primarily ovarian and brain cancers.

The oxygen (in red) forming an ester with other carbon atoms (black) on the nanotube.

So even before worrying about quantum computers, the researchers tested out the modified nanotubes’ bio-imaging applications. They pumped tiny quantities of it into mice and got pretty, infrared images of blood vessels and lymphathic structures.

“We have demonstrated a clear visualization of vasculature structure and lymphatic systems using 150 times [fewer] probes compared to previous generations of imaging systems,” Belcher says, “This indicates that we have moved a step forward closer to early cancer detection.”

That it holds promise for quantum computing is a welcome bonus.

The research was published in Nature Communications.

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