Structure, Composition and Morphology of Self-Assembled 2D Nanostructures Based on SnO2 Nanoparticles Observed in Unannealed Mn Doped Hydrated Form of Tin Oxide (II) or (IV) Synthesized by Co-precipitation Method

Background: 2D nanostructures are greatly interested in different technological applications, particularly optoelectronics. Tin oxide 2D nanostructures have shown great transparency and ideal charge carrier transport properties. Objective: The current study aims to evaluate the main characteristics of 2D-nanostructures observed during the synthesis of hydrated forms of tin oxide (II) or (IV) doped with Mn. Methods: A chemical co-precipitation method was used for the synthesis of the hydrated forms of tin oxide (II) or (IV) with different conditions on time (1 and 1.5 h) and temperature (60ºC and 90ºC), using MnCl2 as the manganese source. Results: X-ray diffraction and XPS results revealed the formation of the hydroromarchite phase (Sn6O4(OH)4) as the main product of the synthesis reaction. Scanning electron microscopy images were used to identify and measure, in a first approach, the 2D nanostructures observed as a result of the synthesis. Morphological characterization using different transmission electron microscopy techniques revealed the presence of nanoparticles that were observed to self-assemble to form the 2D nanostructures observed (nanorods and nanosheets). Nonetheless, selected-area electron diffraction suggested the presence of the cassiterite phase (SnO2) in the nanoparticles forming the 2D nanostructures. Furthermore, chemical analyses using energy-dispersive X-ray spectroscopy supported the observations made by the diffraction studies regarding the presence of cassiterite phase (SnO2) in the 2D nanostructures. The number of 2D nanostructures observed in the analyzed samples increased as the Mn concentration increased in the synthesis reaction. Conclusions: The addition of Mn as an intended doping element increased the crystallite size and the polycrystallinity of the synthesized hydrated forms of tin oxide (II) or (IV). Additionally, it also promoted the formation of 2D nanostructures made of SnO2 nanoparticles.