Method for preparation of magic-sized nano-crystalline substance

A method for preparing a magic-sized nano-crystalline substance, comprising:

• preparing a reaction mixture comprising a metal element selected from organic acid salts or inorganic acid salts of Cd, Pb, Zn, In, and Ga and a non-metal element selected from S, Se, Te, P, and As, wherein a molar ratio of said metal element and said non-metal element is (4-8):1;
• heating the reaction mixture to a reaction temperature of 120° C. to 240° C.;
• maintaining the reaction temperature for 5 min to 30 min;
• adding a diluent and an additive into the reaction mixture;
• cooling the resulting reaction mixture to a temperature that is 50% or lower than the reaction temperature;
• and
• obtaining the magic-sized nano-crystalline substance after standing, wherein the diluent is toluene or cyclohexane, and the additive is selected from butylamine, octylamine, dodecylamine, oleyl amine, methanol, ethanol, isopropanol, hexanol, decanol, tetrahydrofuran, and carboxylic acids, and
• wherein a volume ratio of additive and the diluent is 1:(60-150).