Cheon Lab

While interesting and unprecedented material characteristics of two dimensionality (2-D) layered nanomaterials are emerging, their reliable synthetic methodologies are not well developed. In this study we demonstrate general applicability of synthetic protocols to a wide range of colloidal 2-D layered transition-metal chalcogenide (TMC) nanocrystals. As distinctly different from other nanocrystals, we discovered that 2-D layered TMC nanocrystals are unstable in the presence of reactive radicals from elemental chalcogen during the crystal formation. We first introduce the synthesis of titanium sulfide and selenide where well-defined single crystallinity and lateral size controllability are verified, and then such synthetic protocols are extended to all of group IV and V transition-metal sulfide (TiS₂, ZrS₂, HfS₂, VS₂, NbS₂, and TaS₂) and selenide (TiSe₂, ZrSe₃, HfSe₃, VSe₂, NbSe₂, and TaSe₂) nanocrystals. The use of appropriate chalcogen source is found to be critical for the successful synthesis of 2-D layered TMC nanocrystals. CS₂ is an efficient chalcogen precursor for metal sulfide nanocrystals, whereas elemental Se is appropriate for metal selenide nanocrystals. We briefly discuss the effects of reactive radical characteristics of elemental S and Se on the formation of 2-D layered TMC nanocrystals.