Atoms & Molecules: Chemists Make The Tightest Knot Ever

Researchers in Manchester, UK have made the tightest knot ever. The knot uses a strand of 192 atoms which curls around in a triple loop and crosses itself eight times. Two-millionths of millimeter wide, this molecular knot breaks an obscure world record and may open up a new world for the material science for us. The material science breakthrough was published in the journal Science.

According to The Guardian, a human hair is about 200,000 times wider than this knot. Weaving strands of atoms require precise control by chemists in manipulating objects at the atomic scale. David Leigh, Professor of Chemistry at the University of Manchester and the one to lead this project, said, "Knotting and weaving helped the people of the Stone Age to invent clothes, tools and fishing nets. Now, working with molecular strands may help us to reap much greater rewards later."

The tightness of the knot is determined by the distance between two points on the strand at the crossing point. Each crossing point in the circular triple helix is just 24 atoms apart, which makes it the most tightly knotted physical structure ever known.

According to the NPR, David Leigh and his team broke the world record set by them four years ago, when they had created a pentafoil knot from a strand of 160 atoms. Before that, they had created a trefoil knot which had three crossing points. The new knot is an octofoil knot and is 20 nanometers long. We find billions of different knots in mathematics which chemists might try to replicate at the atomic or molecular level.

The new knot assembles itself from a solution that contains four strands of carbon, nitrogen and oxygen atoms. This solution is mixed with iron and chloride ions in a heated solvent so that the knot can take its shape. It takes about a day to form the shape of the knot. The ends of all strands are then fused together to a continuous loop of atoms. Later, the metal and chloride ions are washed away and only the knot remains.

This chemical process is called self-assembly. In this process, organic building blocks are mixed with ions so that they make crossing points in the right places. The beautiful structure was viewed with the images captures through x-ray crystallography. The properties of different kinds of knots are not known yet, and scientists are still wondering how weaving and knotting can be used to come up with new material science breakthroughs.