I don’t often plug Nature Nanotechnology papers here on the blog, but I couldn’t resist this one… (mostly because of the title I get to use!)
A couple of days ago we published a paper on our website by Naoki Komatsu and co-workers, entitled, “Optically active single-walled carbon nanotubes”. As we all know, however you go about cooking up a batch of nanotubes, you get a mixture – different diameters, different lengths and different chiralities. Now, what is meant by ‘different chiralities’ in this context, is different degrees of twist when you roll up your graphene sheet – not really ‘chirality’ as the chemist knows it. Methods have been developed to sort carbon nanotubes by length and diameter (and also by degree of twist to some extent – see this free paper here and associated News & Views article here).
What is largely ignored/forgotten, is that chiral nanotubes are, wait for it…, chiral! They come as left- and right-handed forms, depending on which may you roll your graphene sheet, i.e., you can either curl the edges up and over to form a tube, or down and under. (If you want to try this at home, take a couple of overhead transparencies – for those of you under 25 years of age, you may want to look up what one of those is – and draw a hexagonal lattice on each one and roll them up in opposite directions – hey presto, enantiomeric nanotubes!).
Now, Pasteur, all those years ago, separated the enantiomers of tartaric acid by painstakingly sorting through mirror-image crystals, presumably with a microscope and a pair of tweezers. What Komatsu and colleagues have done is to make what they call ‘nano-tweezers’ – chiral gable-type diporphyrins that can discriminate between left- and right-handed nanotubes. One enantiomer of the nano-tweezers forms a stronger complex with either the left- or right-handed nanotubes and these diastereoisomers have different solubility properties, which means that they can be separated by centrifugation. You can then wash away the tweezers and record a CD spectrum of your resolved nanotubes!
Stuart
Stuart Cantrill (Associate Editor, Nature Nanotechnology)
Report this comment
This is great news! Something that the nanotube community has been waiting for since long!
Report this comment
Every time ‘something that the xxx community has been waiting for since long’ has been cracked out by someone, I wonder how many people besides him/her have also been working on this issue and why they failed.
Report this comment
I’ve been wondering when the analytical chemists are going to start playing around with nanotubes. Seems like there isn’t much you can do in the way of characterization for those. I don’t work on them, though, so I might be wrong.