Small molecule-controlled spontaneous growth of rose-like Se crystals at room temperature

The spontaneous growth of rose-like Se crystals in aqueous solutions at room temperature is reported. The formation of rose-like Se crystals is based on the oxidation of Na2Se in the presence of thioglycerol solution at pH = 11 in a dark ambient atmosphere. In alkaline solutions, the growth evolution of rose-like Se crystals with aging time was followed by scanning electron microscopy (SEM), and an interesting formation process from initial Se monomers to amorphous Se (a-Se) spheres, and to the final rose-like complex structures of Se crystals was observed. Seven kinds of small molecules with different structures, including 1-thioglycerol (TG), mercaptamine (MA), L-cysteine (L-cys), 3-mercaptopropionic acid (MPA), thioglycolic acid (TGA), glycerol (GLY), and L-serine (L-ser), were used to manipulate the growth of Se crystals. The experimental results show that the structures of the small molecules play a key role in the growth of the Se crystals. The presence of thiols in the structure of the small molecules is favorable for the formation of the aggregates of Se crystals, and other termini, such as -NH2, -OH, or -COO-, will determine whether the aggregates of Se crystals are made up of Se slices or Se prisms. These observations suggest that the ligand molecules have a crucial effect on the nucleation, monomers, and growth of nanocrystals. The selection of ligands can be extended to other important materials for further preparation of nanocrystals with desired shapes. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).