“…57 The top-down approach, despite its convenience, is not well suited to producing nanoparticles with small sizes and unified shapes. Physical techniques, including ball milling, 58,59 thermal evaporation, 60,61 laser ablation, 62 and sputtering, 63,64 are some examples of methods adopting the top-down approach. However, these techniques are usually costly because they require considerable amounts of energy to maintain hightemperature and high-pressure conditions during the production process.…”