Hydrogen-terminated carbon nanoparticles - diamondoids - are expected to have several properties which could make them technologically useful. The optical gap of diamond is in the UV range, and the effect of quantum confinement is expected to push diamondoid optical gaps to even higher energies, enabling a unique set of sensing applications. Furthermore, it has been demonstrated that some hydrogen-terminated diamond surfaces exhibit negative electron affinities, suggesting that diamondoids could also have this property. This would open up the possibility of coating surfaces with diamondoids to produce new low-voltage electron-emission devices.

Measuring the optical gaps of diamondoids has proved to be challenging, due to the difficulty in isolating and characterising particular molecules. Drummond et al. have carried out diffusion quantum Monte Carlo (DMC) calculations designed to resolve the experimental controversies over the optoelectronic properties of diamondoids. The DMC results show that quantum confinement effects disappear in diamondoids larger than one nanometre, which actually turn out to have gaps below that of bulk diamond. In addition, the DMC calculations predict a negative electron affinity for diamondoids up to one nanometre, resulting from the delocalised nature of the lowest unoccupied molecular orbital. These calculations illustrate the usefulness of computer simulation in cases where experimental results are sparse or even absent.