Nature (2013)

DNA is the carrier of life's genetic code and the field of DNA nanotechnology — making clever use of artificial nucleic acids — is booming. In particular, the well-defined nucleobase pairing rules, which govern the structure of double-stranded DNA, provide molecular-recognition opportunities that are being increasingly exploited for the self-assembly of nanoparticles.

Evelyn Auyeung and colleagues now report an experiment in which they attached pieces of DNA to gold nanoparticles, and then heated a solution of these DNA-functionalized nanoparticles to slightly above the assembly's melting temperature before allowing it to cool down slowly — a process taking two or three days to complete. What emerged from the solution were micrometre-sized crystals in the form of rhombic dodecahedra (the 12 faces of which are congruent rhombi).

The shape of crystallite for which the surface energy is a minimum is called a Wulff polyhedron, and for a body-centred cubic lattice (the type of lattice formed by the gold nanoparticles) the Wulff polyhedron is expected to be a rhombic dodecahedron — exactly as Auyeung and colleagues saw. For many other systems, the predicted Wulff polyhedron does not actually form — hence these experiments clearly underline the power of DNA as a mediator in the fabrication of high-quality 3D nanoparticle crystals.