A novel class of organic-inorganic hybrid nanostructures based on II-VI semiconductors.

摘要

A novel class of organic-inorganic hybrid nanostructures based on II--VI semiconductors, namely, (MQ)n(L)x (M = Zn, Cd, Mn; Q = Te, Se, S; L = alkylamine or hydrazine; n = 1, 2; x = 0.5, 1) were synthesized via solvothermal and/or room temperature solution reactions. In all reactions, L had two functions, as solvent and as ligand. Three-dimensional (3D) MQ(L)1/2 were formed when applying alkyl-diamines as solvents as well as organic linkers. In solutions of alkyl-monoamines or hydrazine, two types of structures were obtained, two-dimensional (2D) MQ(L) and (M 2Q2)(L) (Q = Se, S). In a mixture of hydrazine and 1,3-propanediamine (pda), one-dimensional (1D) ZnQ(pda) (Q = Te, Se) were produced. Single-crystal or powder X-ray diffraction revealed that these nanostructures were composed of periodic arrays of II--VI fragments separated by organic spacers. In 3D-MQ(L)1/2, the monoatomic layered 2D-[MQ] slabs are interconnected by bifunctional diamine molecules via coordinate bonds to form three-dimensional networks. In 2D-MQ(L), the monoatomic [MQ] layers are separated by the terminal monoamine molecules which also form coordinate (dative) bonds with them. 1D-ZnQ(pda) consists of 1D-[ZnQ] chains with pda molecules forming chelating bonds to the zinc metals. The structures of 2D-(M2Q2)(L) were predicted to have the double-layered [M2Q2] slabs separated by terminal monoamines through coordinate bonds.; All compounds exhibit a large blue shift (or shift to higher energy) in their optical absorption edges with respect to their parent II--VI bulk materials, as a consequence of quantum confinement effect (QCE) induced in these hybrid structures. A systematic study showed that, the length of the organic molecules has negligible effect on the extent of the blue shift; neither the overall structural dimensionality. It is the inorganic fragments that account for this. The most significant features of these hybrids are that not only they are capable in modifying the electronic and optical properties of II--VI semiconductors at a large scale, but also they possess perfectly ordered structures that are highly desirable for optoelectronic applications requiring high intensity, sharp line width and high conductivity.; The thermal stability of these compounds was studied by thermogravimetric analysis (TGA). Thermolysis products were identified as the parent II--VI binary compounds.