Large-scale electrochemical synthesis of SnO₂ nanoparticles

Tin oxide nanoparticles were synthesized by electrochemical oxidation of a tin metal sheet in a non-aqueous electrolyte containing NH₄F. The as-prepared nanoparticles were then thermally annealed at 700 °C for 6 h. The resulting particles were characterized by a variety of experimental techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Raman, UV-visible, and photoluminescence (PL) spectroscopy. The XRD patterns clearly showed that the amorphous phase of the as-synthesized SnO₂ particles was transformed into a rutile-type crystalline structure after thermal treatment; and from the line broadening of the XRD peaks, the average size of the annealed particles was found to be 15.4, 12.5, 11.8 nm for the particles initially synthesized at 20, 30, and 40 V, respectively. Consistent results were also observed in HRTEM measurements which showed clear crystalline lattice fringes of the calcined nanoparticles, as compared to the featureless profiles of the as-produced counterparts. In Raman spectroscopic studies, three dominant peaks were observed at 480, 640, and 780 cm⁻¹ which were ascribed to the E_1g, A_1g, and B_2g Raman active vibration modes, respectively, and the wavenumbers of these peaks blue-shifted with decreasing particle size. Additionally, a broad strong emission band was observed in room-temperature photoluminescence measurements.