Gemini imidazolium salts comprising Cl−, BF4−, PF6−, AuCl4− counterions: Synthesis, thermotropic liquid crystal study and use of AuCl4− salt precursor to AuNPs

Abstract

The synthesis and thermotropic liquid crystal (LC) properties of gemini imidazolium salts comprising Cl−, BF4−, PF6−, AuCl4− counteranions, varied alkenyl spacer lengths and terminal alkyl chains are described. LC properties are investigated by differential scanning calorimetry, polarizing optical microscopy, and powder X-ray diffraction studies. It should be noted that, salts of short spacers favor the formation of mesophase. A SmA with wide mesophase range and high thermal stability are identified. The Cl− salts have shown an odd-even effect on phase transition temperatures as the length and parity of the spacer is varied. The use of [(CH2)4(C18-Im)2][AuCl4]2 salt as precursor for the fabrication of Au nano/micro particles via chemical reduction, photo irradiation, and thermolysis methods is presented. A clear vision of morphology change is observed in Au structures by varying the reduction method, however the mesophase does not control over the size and morphology of Au particles in the thermolysis method. The colloidal AuNPs prepared in this study showed remarkable stability for over six months. These results offer great insight into the counter anion and spacer effects on LC nature of gemini Im salts, which broadens the scientific understanding to develop advanced soft materials.