Two-dimensional growth mode of thiolate-protected gold nanoclusters Au28+4n(SR)20+2n (n = 0-8): compared with their one-dimensional growth mode.

In this paper, six new atomic structures of thiolate-protected gold nanoclusters, i.e. Au32(SR)20, Au40(SR)26, Au48(SR)30, two Au56(SR)34, and Au60(SR)36, are predicted. Considering these six newly predicted structures and six previously predicted or crystallized Au28(SR)20, Au36(SR)24, Au44(SR)28, Au52(SR)32, and Au60(SR)36 altogether, the two-dimensional (2D) growth mode of Au28+4n(SR)20+2n (n = 0-8) nanoclusters is completely presented to compare with their one-dimensional (1D) growth mode. In Au28+4n(SR)20+2n (n = 0-8) nanoclusters with both 1D and 2D growth modes, the same number of gold-core atoms with different morphologies can be seen. Furthermore, the growth of the gold cores occurs via sequential fusion of one tetrahedral Au4 unit by sharing one gold atom. In addition, density functional theory calculations show that these six newly predicted gold nanoclusters following the 2D growth mode have relative energies very close to those of their isomeric structures following the 1D growth mode, large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, and all-positive harmonic vibration frequencies, indicating their high stabilities. Therefore, the complete presentation of the 2D growth mode of Au28+4n(SR)20+2n (n = 0-8) is beneficial not only for a better understanding of the structural growth of gold nanoclusters, but also for a theoretical guidance on the prediction of new stable structures for experimental confirmation.