TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The temperature for ultrasonication is -13 degrees C to 200 degrees C and is carried out for 1-24 hours. In the method, the temperature of heat treatment is 350-600 degrees C. Preferred Components: The group I element is copper or copper compounds. The group III element is indium or indium compounds, and gallium or gallium compounds. The group VI element is selenium or selenium compounds, and sulfur or sulfur compounds. The I-III-VI2 nanoparticles are copper indium gallium selenium sulfur complex of formula (Cu(InxGa1-x) (SeyS1-y)2) (102) (where x, y are 0-1), copper indium gallium selenium complex of formula (CuInxGa1-xSe2) (where x is 0-1), copper indium gallium sulfur complex of formula (CuInxGa1-xS2 (where x is 0-1)), copper indium selenium sulfur complex of formula (CuIn(SeyS1-y)2 (where y is 0-1)) or copper gallium selenium silicon complex of formula (CuGa(SeySi1-y)2) (where y is 0-1) nanoparticles, preferably copper gallium selenide, copper gallium sulfide, copper indium selenide or copper indium sulfide nanoparticles. The copper compounds comprise one or two or more species, which are copper oxide, copper dioxide, copper(I)hydroxide, copper(II)hydroxide, copper acetate, copper diacetate, copper(II)fluoride, copper(I)chloride, copper(II)chloride, copper(I)bromide, copper(II)bromide, copper(I)iodide, copper(II)perchlorate, copper(II)nitrate, copper sulfate, copper selenide, copper selenium complex of formula (Cu2-xSe) (where x is 0-2), dicopper selenide or their hydrates. The indium compounds comprise one or two or more species, which is indium(III)oxide, indium(III)hydroxide, indium(III)triacetate, indium(III)trifluoride, indium(I)chloride, indium(III)chloride, carbon indium complex of formula (CInBr), indium(III)bromide, indium(I)iodide, indium(III)iodide, indium(III)perchlorate, indium(III)nitrate, indium sulfate, indium selenide, indium gallium selenide or their hydrates. The gallium compounds comprise one or two or more species, which are gallium(III)oxide, gallium(III)hydroxide, gallium(III)acetate, gallium(III)fluoride, gallium(I)chloride, gallium(III)chloride, gallium(I)bromide, gallium(III)tribromide, gallium(I)iodide, gallium(III)iodide, gallium(III)perchlorate, gallium(III)nitrate, gallium(III)sulfate, gallium selenide, indium gallium selenide or their hydrates. The selenium compounds comprise one or two or more species, which is selenium, hydrogen selenide, disodium selenide, dipotassium selenide, dicalcium selenide, dimethylselenide, copper selenide, copper selenium complex of formula (Cu2-xSe) (where x is 0-2), dicopper selenide and/or indium selenide. The sulfur compounds comprise one or two or more species, which are thioacetamide, thiourea, thioacetic acid, alkyl thiol or sodium sulfide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The solvent comprises N-chelants and water or alcoholic solvents. The solvent further comprises ionic liquids. The N-chelants comprise one or two or more species, which are amine compounds including diethyl amine, triethylamine, diethylene diamine, diethylene triamine, toluene diamine, meta-phenylenediamine, diphenyl methane diamine, hexamethylene diamine, triethylene tetramine, tetraethylenepentamine, hexamethylene tetramine and 4,4-diaminodiphenyl methane, hydrazine, hydrazide, thioacetamide, urea or thiourea. The alcoholic solvents comprise one or two or more species, which are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 3-methyl-3-methoxy butanol, tridecyl alcohol, pentanol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, hexylene glycol, butylene glycol, sucrose, sorbitol or glycerin. The ionic liquids comprise cationic compounds, which are alkyl ammonium, N-alkyl pyridinium, N-alkyl pyridazinium, N-alkyl pyrimidinium, N-alkyl pyrazinium, N,N-alkyl imidazolium, N-alkyl pyrazolium, N-alkyl thiazolium, N-alkyl oxazolium, N-alkyl triazolium, N-alkyl phosphonium and N-alkyl pyrolidinium or their derivatives and anions, which are hexafluoroantimonate, hexafluorophosphate, tetrafluoroborate, bis(trifluoromethylsulfonyl)amide, trifluoromethanesulfonate, acetate or nitrate. EXAMPLE - Copper(II)diacetate, indium(III)triacetate and selenium powders were placed into a reactor with the molar ratio of 1:1:2. The reactor was charged with triethylene tetramine, 1-butyl-3-methylimidazolinium trifluoromethanesulfonate and an alcoholic solvent. The mixture was subjected to ultrasonication for 4 hours at 100 degrees C and then allowed to cool in the air. The resulted product was centrifuged to remove the solvent, washed several times with distilled water and ethanol, and then dried for 4 hours at 80 degrees C under the atmospheric pressure to give copper indium selenide nanoparticles.