Organic-soluble Ag nanocrystals(NCs) with tunable sizes in the range from 5.4 to 22.1 nm were synthesized by a facile, reproducible and easily scaled up route using water as solvent in the presence of oleic acid and an alkylamine.The synthetic Ag NCs exhibits excellent hydrophobicity and can be well re-dispersed in various non- or weak-polar media.The tunable sizes of the Ag NCs were achieved by simply adjusting the initial precursor AgNO_3 concentration.Large-scale synthesis of the Ag NCs was realized at a high AgNO_3 concentration(0.4 mol/L).As much as 16.2 g highly uniform organic-soluble Ag NCs with 5 nm average diameter can be readily synthesized at low cost in a single reaction only using 400 mL water as solvent,which is adaptable to the industrial scale production.The structure of the obtained Ag NCs was investigated in detail by X-ray diffractometry,transmission electron microscopy,Fourier transform infrared and thermal gravimetric analysis measurements.The results reveal that the surface of the organic-soluble Ag NCs is coated with the monolayer surfactants consisting of oleic acid and the alkylamine.In addition,on the basis of the sufficient evidences,a proposed mechanism based on the “bilayer surfactant-controlled reaction” successfully demonstrates the formation of high quality organic-soluble Ag NCs in the aqueous solution. Organic-soluble Ag nanocrystals (NCs) with tunable sizes in the range from 5.4 to 22.1 nm were synthesized by a facile, reproducible and easily scaled up route using water as solvent in the presence of oleic acid and an alkylamine. excellent hydrophobicity and can be well re-dispersed in various non- or weak-polar media. The tunable sizes of the Ag NCs were achieved by simply adjusting the initial precursor AgNO 3 concentration. Large-scale synthesis of the Ag NCs was realized at a high AgNO 3 concentration (0.4 mol / L). As much as 16.2 g highly uniform organic-soluble Ag NCs with 5 nm average diameter can be prepared synthesized at low cost in a single reaction only using 400 mL water as solvent, which is adaptable to the industrial scale production. The structure of the obtained Ag NCs was investigated in detail by X-ray diffractometry, transmission electron microscopy, Fourier transform infrared and thermal gravimetric analysis measurements. The results reveal that the surface of the organic-soluble Ag NCs is coated with the monolayer surfactants consisting of oleic acid and the alkylamine. In addition, on the basis of the sufficient evidences, a proposed mechanism based on the “bilayer surfactant-controlled reaction” successfully demonstrates the formation of high quality organic-soluble Ag NCs in the aqueous solution.