Large-scale synthesis of fractal silica nanoparticles: understanding the impact of solvents

Fractal silica nanoparticles (FSN) have just emerged as a new type of nanoporous materials with high branching self-similarity and sharp tips. FSN are synthesized in ethanol-water mixed solvent at a reaction temperature well above the flash point, thus large-scale and safe synthesis of FSN remains challenging. In this work, two strategies were combined for scalable, safe and cost-effective synthesis of FSN. Firstly, by decreasing ethanol/water volume ratio, the yield of FSN per unit volume of synthesis solution was increased and the production cost was reduced. Secondly, by introducing ethylene glycol (EG) as a cosolvent, the flash point of the reaction solution of FSN was increased above the reaction temperature. Using these strategies and a synthesis temperature of 30 °C, kilogram-scale synthesis of FSN (506 g in one batch) was achieved, paving the way for the practical application of FSN.