Template-free single-step preparation of hollow CoO nanospheres using pulsed laser ablation in liquid enviromen

Owing to their unique properties, hollow nanoparticles have attracted tremendous attention in various research fields. However, it is a still challenge to prepare hollow nanoparticles without hard or soft template. In this study, high purity cobalt oxide (CoO) hollow nanosphere was experimentally obtained using pulsed laser ablation (PLA) in ethanol–water mixture. The morphological and optical properties of the fabricated nanospheres were investigated via different analytical techniques, including scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and ultraviolet–visible spectroscopy. Selected area electron diffraction, and energy-dispersive X-ray spectroscopy were utilized to evaluate the crystalline structure as well as the chemical composition of the fabricated materials, respectively, The ethanol/water mixture was varied during the ablation process from 0 to 70 % v/v and found to have a significant impact on the size, shape, and structure of the produced nanoparticles. The average size was found to be about 100 nm for the 0–30% v/v of ethanol and around 200 nm for the 50 and 70% v/v of ethanol. It was also shown that the optimum ratio of ethanol–water mixture for the formation of hollow nanoparticles is between 5 and 30% v/v as the formation the hollow structures is directly associated with the saturation of the gas in the medium. A possible mechanism for the formation of hollow structure CoO using pulsed laser ablation in ethanol/mixture media is discussed. This study paves the way for fabrication of template-free hollow nanosphere materials for several applications.