Fast synthesis and optical property of SnO nanoparticles from choline chloride-based ionic liquid

A fast, environmentally friendly, and reproducible method is proposed to synthesize SnO nanoparticles in an ionic liquid which consists of choline chloride, urea, and SnCl 2 ·2H 2 O. The nano-sized SnO particles with a size of about 20–30 nm can be synthesized in 1 min without any further treatment and complicated infrastructures. When prolonging the reaction time, the SnO nanoparticles can be self-assembled into micro-sized balls with the hydrangea geometry. High-resolution transmission electron microscopy shows that the SnO nanoparticle consists of tetragonal structured crystals with the grain size of about 4–6 nm. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy further certify the composition, chemical state, and chemical band of the prepared SnO samples. Moreover, the direct band gap of the SnO samples is highly dependent on the particle architectures. A larger band gap value of about 3.80 eV is obtained in the nano-sized SnO which may be due to the quantum size effect.