“…1,2 The large fraction of empty spaces endows them fascinating properties such as large surface area, low density, and high loading capacity, and demonstrates a large variety of applications, including micro-/ nanoreactors, catalysis, energy storage, biomedicine, sensors, environmental remediation, and so forth. 4 So far, various routes such as template method, 5-8 spray drying, 9,10 wet-chemical synthesis, 11 and flame spray pyrolysis have been developed to prepare Al 2 O 3 hollow micro-/nanospheres. 4 So far, various routes such as template method, 5-8 spray drying, 9,10 wet-chemical synthesis, 11 and flame spray pyrolysis have been developed to prepare Al 2 O 3 hollow micro-/nanospheres.…”