Effects of alkanethiols chain length on the synthesis of Cu2−xS nanocrystals: phase, morphology, plasmonic properties and electrical conductivity

Cu2−xS nanocrystals with different morphologies and crystal phases have been synthesized by using a simple one-pot and phosphine-free colloidal method, in which different alkanethiols (CnH2n+1SH, n = 8, 12, 18) have been selected as sulfur sources and capping ligands. The crystal phase can be transformed from monoclinic Cu1.94S to tetragonal Cu1.81S by varying the alkyl chain length of alkanethiols, and the morphology changes from nanospheres to nanodisks during the phase transformation. Strong localized surface plasmon resonance (LSPR) absorbance in the near-infrared (NIR) region has been observed in these Cu2−xS nanocrystals, which originates from excess holes in the valence band due to copper deficiencies. The alkyl chain length of alkanethiols plays an important role in the crystal phase, morphology and plasmonic properties of the as-obtained Cu2−xS nanocrystals.