**2.1. Structural and physical properties of nanoclays**

Nanoclays are fine-grained crystalline materials. A layer is the basic structural unit of nanoclays, and these layers are prone to arrange themselves over one another like pages of a book. Individual layers are composed of the tetrahedral and/or octahedral sheets, and this arrangement of sheets plays a vital role in defining and distinguishing these clay minerals. In tetrahedral sheet, the silicon-oxygen tetrahedra are linked to neighboring tetrahedra by sharing three corners while the fourth corner of each tetrahedron forms a part to the adjacent octahedral sheet. The octahedral sheet is usually composed of aluminum or magnesium in a sixfold coordination with oxygen from the tetrahedral sheet and with hydroxyl.
