“…Hollow silica particles can be synthesized by several methods, such as by using polymer micelles, reverse microemulsions, inorganic (e.g., calcium carbonate, carbon, hydroxy apatite) particles, polymer (e.g., polystyrene; PS) particles, and bacteria as templates [ 22 , 23 , 24 , 25 , 26 , 27 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Similarly, some other unconventional methods, including etching of solid silica particles and spray drying a solution of solid silica particles, have also been explored [ 50 , 51 , 52 , 53 ].…”