Preparation of free-standing SiO2 nanobowl with an electrospraying technique

In this investigation, the electrospraying technique was applied to fabricate free-standing SiO2 nanoparticle with bowl-like morphology and controllable particle size. We investigated the influence from the properties of precursor SiO2 sol and electrospraying parameters to the size and morphological variation of the bowl-shaped SiO2 nanoparticles. Our results indicated that a relatively short reaction time of the SiO2 sol is required for the formation of the bowl-like morphology, while a relatively low applied voltage during the electrospraying is beneficial to achieve a uniform size distribution of the SiO2 nanoparticles. We made a primary analysis to the formation mechanism of the bowl-like morphology of the SiO2 nanoparticles, and found that it should be closely related to delayed evaporation of solvent and final structural collapse at the top part of the particles after crashing with the collector. Such bowl-shaped SiO2 nanoparticles may have great potential in various applications, including shape-dependent optics, nanoparticle selection, biomedical and nanofluidic devices, and template for the preparation of nanomaterials, etc.