Controllable synthesis and optical properties of SnO ₂ core‐shell microspheres

SnO ₂ core‐shell microspheres were synthesised via a hydrothermal method with hexamethylenetetramine as a surfactant. The structure and the morphology of the products were characterised by X‐ray diffraction, field‐emission scanning electron microscopy and transmission electron microscopy. The results indicated that the overall dimension of the core‐shell microspheres and the diameter of the spherical nuclei could be adjusted by changing the concentration of NaOH and hexamethylenetetramine or the reaction time. Based on the time dependent reactions, a possible growth mechanism is proposed. It is believed that the Kirkendall effect plays an important role in the formation of the core‐shell structure. The optical properties of the core‐shell structure microspheres were also studied through the photoluminescence and the Raman spectra.