1D Narrow-Bandgap Tin Oxide Materials: Systematic High-Resolution TEM and Raman Analysis

We demonstrate for the first time the structure identification and narrow-bandgap property of 1D hybridized SnO/SnO(2) nanoparticles derived from the calcination of a single-source precursor, i.e., tin(II) oxalate. Systematic Raman analysis together with high-resolution TEM (HR-TEM) measurements of the tin oxide samples were carried out by changing the calcination temperatures. These data revealed the simultaneous formation of 1D SnO/SnO(2) in the rod particles that grew in air. It was also found that Sn(II) can be introduced by changing the concentration of Sn(II) salt in the precursor synthesis and the maximum temperature in calcination. Particles measuring 20~30 nm were sintered to produce tin oxide nanorods including tin monoxide, SnO. Photoabsorption properties associated with the formation of the SnO/SnO(2) nanocomposites were also investigated. Tauc plots indicate that the obtained tin oxide samples had a lower bandgap of 2.9~3.0 eV originating from SnO in addition to a higher bandgap of around 3.5~3.7 eV commonly observed for SnO(2). Such 1D SnO(x)/SnO(2) hybrids via tin oxalate synthesis with this optical property would benefit new materials design for photoenergy conversion systems, such as photocatalysts.