The group has used its experience in modeling doped nanoclusters to tackle the challenge of predicting the optical properties of nitrogen-vacancy (NV) color centers in quantum-confined nanodiamonds. As NV-containing diamonds approach the nanosize (d≈5 nm), they show promise for many technological applications, such as quantum computing, ultra-sensitive magnetometry, and bio-labeling. Doping may introduce new sub-band gap levels, and diamond NV centers, in particular, introduce new dopant-centered sp3-sp3 mid-gap electronic transitions and charge-transfer excited states.
We provided a theoretical analysis of the electronic properties of a reduced isolated NV color center in nanodiamond clusters. We combine time-dependent DFT with a finite cluster approach, exploring simultaneously the effect of the local NV center symmetry on the electronic structure and the size dependence of the electronic transitions. Both the zero phonon line splitting and the full absorption UV-vis spectrum are investigated, validating a theoretical protocol that can be used in the future to study other defects and their dynamics, crucial to develop and improve the nanodiamond based technology. This work is published in Physical Review B and is available online here.