Stabilization of gold and silver nanowires inside cyclo[8]thiophene nanoaggregates: a theoretical study

The stability and electronic properties of gold and silver nanowires (NWs) containing up to 12 atoms trapped inside cyclo[8]thiophenes (CT8) nanoaggregates have been modeled using M06 functional, 3-21G* basis set for nonmetallic atoms; LANL2DZ pseudopotential basis set for metals were applied for optimization; and 6-31G* and LANL2DZ basis sets for single point calculations, respectively. It has been found that the formation of (NW) inside CT8 nanoaggregates is a thermodynamically favorable process and it could be a potentially useful method of metal NW stabilization. The inclusion of metal NW inside CT8 nanoaggregates increases significantly the binding energy between macrocycles and changes the geometry of NW compared to that of free-standing clusters due to the size restriction imposed by the nanoaggregate cavity. The binding energies per metal atom reach a maximum for three metal atoms and then start decreasing with a possible stabilization for large NW. It was found that the binding energies between silver NW and CT8 nanoaggregate are lower than those of gold NW and that in the case of gold NW containing more than four metal atoms the S0 → S1 excitation involves almost exclusively electrons of metal NW. On the other hand, in the case of silver NW the excitation involves the electron transfer from the NW to the CT8 nanoaggregate.