A metal ion nanocluster having a formula of X(OH)aYbZcMd(H2O)e. X, Y, Z, M, a, b, c, d, and e are defined herein. The nanocluster has a particle size of 2 to 500 nm and a molecular weight of 3500 to 1000000 Dalton. Also disclosed are a composition containing the nanocluster and a method of preparing the nanocluster.一具有X(OH)aYbZcMd(H2O)e化學式的金屬離子奈米簇。X、Y、Z、M、a、b、c、d,及e定義於此處。該奈米簇具有2至500nm的顆粒尺寸及3500至1000000道爾頓的分子量。包含該奈米簇的組成物及製備該奈米簇的方法亦被揭示。