New route in the synthesis of Tin(II) oxide micro-sheets and its thermal transformation

•The pure tin(II) oxide have been successfully prepared using new route hydrothermal-alkaline solution method.•Tin(II) oxide starts to oxidize at 400 °C and completely transform into tin(IV) oxide at 600 °C.•The transformation route is a direct oxidation without forming the intermediate phase of tin oxide (SnxOx+1).•The thermal treatment can control the nucleation process, crystal morphology, particle sie, and properties of tin(II) oxide. The micro-sheets tin(II) oxide (SnO) has been synthesized using hydrothermal-alkaline solution at 95 °C (low temperature) under the ambient atmosphere. The as-prepared material showed a romarchite tetragonal structure without impurities. Furthermore, the study of SnO transformation has been carried out by thermal treatment ranging from 400 °C to 700 °C. The result shows that the transformation was a direct oxidation without forming any intermediate phases. The SnO started to oxidize at 400 °C and fully transformed into tin(IV) oxide (SnO2) at 600 °C. The thermal treatment has also changed the morphology and particle size of SnO from micro-sheets-structure to amorphous-flowerlike nanostructure and shifted the absorption spectra resulting in shorter UV wavelength and higher calculated-band gap.