Rapid synthesis of nanoparticles of hexagonal type In₂O ₃ and spherical type Tl₂O₃ by microwave irradiation

Semiconducting nanoparticles of indium and thallium oxides (In ₂O₃ and Tl₂O₃) have been successfully synthesized in high yield (> 95%) by microwave irradiation. The oxides are synthesized in a simple domestic microwave oven (DMO) by adding an aqueous ammonia solution to the aqueous solutions of indium chloride (InCl ₃) and thallium chloride (TlCl₃), respectively. The structures, morphologies, compositions and physical properties of the products have been characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), selected area electron diffraction (SAED), etc. The XRD and SAED analysis indicate that the as-synthesized product, obtained after microwave (MW) heating of the indium chloride solution, is crystalline In(OH)₃, but its calcined form is a crystalline body-centered cubic (bcc) phase of In₂O₃. On the other hand, in the case of thallium chloride, the as-synthesized material is a crystalline body-centered cubic (bcc) phase of Tl₂O₃. The particles are of uniform size, being about 16 nm and 24 nm for Tl ₂O₃ and In₂O₃, respectively. A possible mechanism for the formation of the In₂O₃ and Tl₂O₃ nanoparticles is discussed briefly.