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

Owing to their unique properties, hollow nanoparticles have attracted tremendous atten-tion in various research fields. However, it is a still challenge to prepare hollow nanoparticles with -out 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 morpho-logical and optical properties of the fabricated nanospheres were investigated via different analyt-ical 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. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.