“…[6][7][8] As an important inorganic component of biological hard tissues, such as bones and teeth, 9,10 hydroxyapatite [Ca 10 (PO 4 Þ 6 (OH) 2 , HAp] has attracted much attention as an excellent candidate for biomedical applications, owing to its outstanding biocompatibility. 11,12 Many e®orts have been made toward fabricating HAp-based nanostructures because of their promising applications in arti¯cial bones, 13,14 drug deliveries, 15 catalysts, 16 sensors, 17 photoelectric materials, 18 chemical and environmental engineering. [19][20][21] The performance of HAp in above applications depends greatly on its crystallite size, chemical compositions, three-dimensional (3D) architectures and morphologies.…”