TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In the method (M1), metal oxide or salt and acid or amine reacting with each other in a noncoordinating solvent at 100-350 degrees C for 5 minutes to 1 hour, where the molar ratio of the metal to the acid is 1:2 to 20; the Se precursor is prepared by reacting Se or selenium oxide (SeO2) with acids or amines in a noncoordinating solvent for preparing Se precursor at 100-300 degrees C for 5 minutes to 20 hours, where a molar ratio of the Se to the acid or amine is 1:1-20, where the tellurium (Te) precursor is prepared by dissolving tellurium (Te) or tellurium oxide (TeO2) in tri-n-octylphosphine sulfide (TOPS) or di-n-octylphosphine oxide (DOPO) at 100-400 degrees C for 5 minutes to 20 hours; the phosphine-free precursor is an alternative precursor when the preset reaction temperature is over 100 degrees C and reaction time last over 1 second which is sufficient to carry out the reaction to obtain the core, core/shell, and core/multi-shell metal chalcogenides nanocrystals; the phosphine-free precursor is added by injection with a solvent, where the solvent for Se and SeO2 is 1-octadecene (ODE) or paraffin oil and the solvent for Te and TeO2 is TOPO or DOPO, where when more than one phosphine-free precursors are added by injection, the phosphine-free precursors are added at the same time or separately; and the first composition is prepared by injection method including metal precursor injection or chalcogenide precursor injection or non-injection method which is one-spot reaction method. The method (M1) further involves providing a molecular metal chalcogenide complex as the ligand and the chalcogenide precursor, where the molecular metal chalcogenide complex is Sn-X:(Sn2S6)4- or (Sn2Se6)4- made from Sn(acac)2Cl2 or SnCl4. In the method (M2), the mixed solution is stirred for 2-30 hour under 600-2000 rotation per minute (rpm) through magnetic stirring so as to speeding up the evaporation and removal of the organic solvent in excess; a molar ratio of oligomer to nanocrystal is 10:1-200:1, and a volume ratio of water to organic solvent is 3:1 to 9:1; and the organic solvent-soluble nanocrystal is selected from monodisperse metal chalcogenides, metal oxides, and noble metals. The amphiphilic oligomer is selected from carboxyl, amine, and hydroxyl oligomer. The amphiphilic oligomer has 4-16C alkyl chain. The molar ratio of hydrophobic to hydrophilic is 1:1 to 1:10. Preferred Components: The final product is a nanocrystal selected from CdS, ZnS, Cu2S, PbS, CdSe, ZnSe, Cu2-xSe, PbSe, MnSe, CdTe, SnSe, HgSe, AgSe, InSe, GaSe, MgSe, Al2Se3, ZnTe, HgTe, CuInSe2, and CuInTe2; nanocrystal selected from CdS, ZnS, Cu2S, PbS, CdSe, ZnSe, Cu2-xSe, PbSe, MnSe, CdTe, SnSe, HgSe, AgSe, InSe, GaSe, MgSe, Al2Se3, ZnTe, HgTe, CuInSe2, and CuInTe2; core/shell or core/multi-shell nanocrystal selected from CdSe/ZnS, CdSe/CdS/ZnS, ZnSe/ZnS, PbSe/ZnS, MnSe/ZnSe, Cu2-xSe/CdS, Cu2-xSe/CdSe, Cu2-xSe/CdTe, Cu2-xSe/SnSe, CdTe/CdSe, ZnSe/ZnSexS1-x/ZnS, CdS/Zn1-xCdxS, CdSe/ZnSe/ZnSexS1-x/ZnS, Zn1-xCdxSe/ZnSe/ZnSexS1-x/ZnS, Zn1-xCdxSe/ZnS, Zn1-xCdxSe/CdS/Zn1-xCdxS/ZnS, CuInSe2/ZnS, CuInSxSe2-x/ZnS, CuInSexTe2-x/ZnS, CuInSxTe2-x/ZnS, CuInSe2/ZnSe/ZnS, CuInSxSe2-x/ZnSe/ZnS, CuInSexTe2-x/ZnSe/ZnS, and CuInSxTe2-x/ZnSe/ZnS nanocrystals; and a core/shell or core/multi-shell nanocrystal selected from the group consisting of CdS/ZnS, ZnS/SnS, Cu2S/SnS, PbS/SnS, CdSe/ZnS, CdSe/CdS/ZnS, ZnSe/ZnS, PbSe/ZnS, MnSe/ZnSe, Cu2-xSe/CdS, Cu2-xSe/CdSe, Cu2-xSe/CdTe, Cu2-xSe/SnSe, CdTe/CdSe, ZnSe/ZnSexS1-x/ZnS, CdS/Zn1-xCdxS, CdSe/ZnSe/ZnSexS1-x/ZnS, Zn1-xCdxSe/ZnSe/ZnSexS1-x/ZnS, Zn1-xCdxSe/ZnS, Zn1-xCdxSe/CdS/Zn1-xCdxS/ZnS, CuInSe2/ZnS, CuInSxSe2-x/ZnS, CuInSexTe2-x/ZnS, CuInSxTe2-x/ZnS, CuInSe2/ZnSe/ZnS, CuInSxSe2-x/ZnSe/ZnS, CuInSexTe2-x/ZnSe/ZnS, and CuInSxTe2-x/ZnSe/ZnS nanocrystals. The metal oxide is selected from Fe3O4, gamma-Fe2O3, FeO, and MnO. The metal of the monodisperse metal chalcogenides nanocrystal is selected from Au, Ag, alloyed AuAg and PtAu. The bifunctional nanocrystal is selected from Fe3O4-CdSe/ZnS; Fe3O4-Zn1-xCdxSe/ZnS, Fe3O4-Zn1-xCdxSe/ZnSe/ZnSexS1-x/ZnS, Fe3O4-CuInSe2/ZnS, Fe3O4-CuInSxSe2-x/ZnS, Fe3O4-CuInSe2/ZnSe/ZnS, Fe3O4-Au, Fe3O4-Ag, Au-CdSe/ZnS; Au-Zn1-xCdxSe/ZnS, Au-Zn1-xCdxSe/ZnSe/ZnSexS1-x/ZnS, Au-CuInSe2/ZnS, Au-CuInSxSe2-x/ZnS, and Au-CuInSe2/ZnSe/ZnS.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The final product is alloy nanocrystal selected from alloyed Zn1-xCdxSe, CdSxSe1-x, CdSexTe1-x, CdSxTe1-x, ZnSxSe1-x, ZnSexTe1-x, ZnSxTe1-x, Zn1-xCdxTe, Hg1-xCdxTe, Zn1-xCdxSeyS1-y, Zn1-xCdxTeyS1-y, Zn1-xCdxSeyTe1-y, CuInSxSe2-x, CuInSexTe2-x, and CuInSxTe2-x nanocrystals; an alloy nanocrystal selected from alloyed Zn1-xCdxSe, CdSxSe1-x, CdSexTe1-x, CdSxTe1-x, ZnSxSe1-x, ZnSexTe1-x, ZnSxTe1-x, Zn1-xCdxTe, Hg1-xCdxTe, Zn1-xCdxSeyS1-y, Zn1-xCdxTeyS1-y, Zn1-nCdxSeyTe1-y, CuInSxSe2-x, CuInSexTe2-x, and CuInSxTe2-x nanocrystals.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The air-sensitive phosphine-free precursor is S, Se and Te precursors. The S precursor is selected from S and thiols in 1-octadecene (ODE) or paraffin oil, where the thiols include hexanethiol, dodecanethiol and octadecanethiol. The second noncoordinating solvent is selected from ODE, 1-eicosene, tetracosane, paraffin oil, paraffin wax, and mineral oil. The metal precursor is selected from metal oxide, metal halides, metal carbonates, metal perchlorate, metal nitrate, metal chloride, metal acetates, and metal carboxylates. The ligand is selected from dodecylamine, hexadecylamine, octadecylamine, stearic acid, lauric acid, hexanethiol, dodecanethiol, octadecanethiol, hexylphosphonic acid, tetradecylphosphonic acid, octadecylphosphonic acid, and trioctylphosphine oxide. The additive composition is selected from hexanoic acid, octanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid. The organic solvent is selected from dichloromethane, chloroform, and hexanes, where the pH value of the solution B is adjusted by sodium hydroxide or sodium carbonate. EXAMPLE - A zinc-selenide (ZnSe)nanocrystals in hexanes (3x 10-7 mol) were added, and the system is kept at 100 degrees C under N2-flow for 30 minutes to remove the hexanes and other undesired materials of low vapor pressure. Subsequently, the solution was heated up to 240 degrees C under N2-flow where the shell growth was performed to form ZnSe/ZnS core-shell nanocrystal.