From single to multiple atomic layers: a unique approach to the systematic tuning of structures and properties of inorganic-organic hybrid nanostructured semiconductors.

In order to systematically tailor the structures and properties of a unique family of inorganic-organic hybrid nanostructured materials based on II-VI semiconductors, we have designed and engineered a new group of two-dimensional crystalline [(M2Q2)(L)] nanostreuctures (where M = Zn, Cd; Q = S, Se; and L = ethylamine, n-propylamine, n-butylamine, n-amylamine, n-hexylamine). These compounds are composed of double atomic layers of M2Q2 separated by organic monoamines. The crystal structures of 2D-[(M2Q2)(L)] are characterized by powder X-ray diffraction (PXRD) analysis. The crystal structures of these compounds are similar to the 2D-[(MQ)(L)] series that we reported earlier, in that they also contain II-VI slabs sandwiched by organic monoamines. The main difference is in the thickness of the II-VI slabs, where they are single-layer (n = 1) in 2D-[(MQ)(L)] but double-layer (n = 2) in 2D-[(M2Q2)(L)]. Optical absorption experiments show that all double-layer compounds exhibit a blue shift in their absorption edge (0.6-1.2 eV), due to the quantum confinement effect (QCE). However, the extent of such a blue shift is significantly less than that of the single-layer 2D-[(MQ)(L)] systems (1.0-2.0 eV) as a result of the difference in their layer thickness. Thermogravimetric (TG) analysis has revealed nanosized II-VI (MQ) particles as the post-TG product of all double-layer hybrids.