A macrocycle-assisted nanoparticlization process for bulk AgS.

We report herein a new nanoparticlization process for the bulk-to-nano transformation of AgS by incorporating both top-down and bottom-up approaches. Bulk AgS was dissolved in solution with the assistance of a macrocyclic ligand, hexamethylazacalix[6]pyridine (), to produce polynuclear silver sulfide cluster aggregates. All Ag-S cluster aggregates obtained in three crystalline complexes were protected by macrocycles. Removing the protective macrocycles by protonation led to the generation of unconventional Ag-S nanoparticles with a large energy gap. Theoretical calculations by a hybrid DFT method demonstrated that the silver sulfide clusters with high Ag/S ratio exhibited more localized HOMO-LUMO orbitals, which consequently enlarged their band gap energies. These experimental and theoretical studies broaden our understanding of the fabrication of nanomaterials by virtue of the advantages of both bottom-up and top-down methods and meanwhile provide a viable means of adjusting the band gap of binary nanomaterials independent of their size.