Synthesis of crystalline chalcogenide arsenates in surfactants via a low temperature route
Eashwer Umesh Athresh
Date of Issue2014
School of Materials Science and Engineering
The synthesis of novel materials drives forward the engine that is material science. The discovery of new materials is important not just from the standpoint of new applications, but is also important for the study of the fundamental forces that guide the reaction mechanism. Ever since Flanigen et. al. first reported the synthesis of zeolite like open framework in 1982, this field has grown exponentially. Nearly 25 elements of the periodic table have open framework structures attributed to them. Metal – chalcogenides have been a very important part of this Solid State chemistry. They have a wide range of applications like ion conductivity, magnetism and non – linear optical response. The larger size of chalcogen atoms allows them to have larger coordination numbers, thus increasing the number of ways they can form open frameworks. This offers a very good opportunity to study the area of open frameworks from different reactions. Solvent thermal synthesis has garnered much attention lately for its ability to produce diverse open framework topologies. By varying the reaction media and the structure directing agent, the desired properties expected of the final product can be finely tuned. Recently, using Ionic Liquids as reaction media, a number of new chalcogenide open frameworks have been reported. The high cost and limited commercial availability of Ionic Liquids has been a great obstacle to the exploitation of their properties as reaction media. Surfactants have long been used to influence the structure of open frameworks. In this investigation, surfactants are used as reaction media, in place of Ionic Liquids. The advantages of this approach is the cheaper costs of the surfactants and their vast varieties available, like acidic, basic, neutral, ionic, etc. This offers great scope for many different interactions between the reagents and the surfactants to form novel open frameworks. In this report, a series of chalcogenidoarsenates is used to demonstrate the excellent qualities of using Surfactants as reaction media. A homologous series of chalcogenidoarsenates is synthesised with dimensionalities varying from 0D clusters to 3D framework. The crystals exhibit semi conductor behaviour, with band gaps of 1.91eV to 2.46eV, which corresponds to the colour of the crystals. The crystals also exhibit magnetic properties, which are tested. Thus, this method offers new possibilities in the field of open framework syntheses of crystalline materials with diverse range of structures and properties.