A metal sulfide nanocrystal manufactured by a method of reacting a metal precursor and an alkyl thiol in a solvent, wherein the alkyl thiol reacts with the metal precursor to form the metal sulfide nanocrystals, wherein the alkyl thiol is present on the surface of the metal sulfide nanocrystal, wherein the alkyl thiol is bonded to the sulfur crystal lattice. A metal sulfide nanocrystal manufactured with a core-shell structure by a method of reacting a metal precursor and an alkyl thiol in a solvent to form a metal sulfide layer on the surface of a core, wherein the alkyl thiol is present on the surface of the metal sulfide nanocrystal, wherein the alkyl thiol is bonded to the sulfur crystal lattice. These metal sulfide nanocrystals can have a uniform particle size at the nanometer-scale level, selective and desired crystal structures, and various shapes.