Novel sodium acetate promoted, induced and stabilized mesoporous nanorods: Hydroxyapatite nanocaterpillars

• HA-NCPs were synthesized using a novel NaAc template. • Synthetic route is surfactant-free. • Synthetic route is green, efficient, low-cost and facile. • NaAc is very easy to remove by simple washing and drying. • NaAc has great advantages over surfactant template. Surfactant templated synthesis of hydroxyapatite (HA) causes many problems. Here, HA nanocaterpillars (HA-NCPs), mesoporous nanorods, were successfully synthesized using a novel sodium acetate (NaAc) template via a reflux-hydrothermal method. Ca(NO 3 ) 2 , H 3 PO 4 and NaOH were used as calcium source, phosphorus source and pH adjusting agent, respectively. The pores of 3.4, 4.3 and 6.5 nm calculated by the BJH method were well accordant with the results of TEM. The BET surface area and pore volume of HA-NCPs were 81.5 m 2 /g and 0.53 cm 3 /g, respectively. NaAc had the similar function of surfactant template and was more efficient. It played the roles of promoting HA crystallization, inducing nucleation and growth of HA-NCPs, inducing and stabilizing the mesopores in HA-NCPs. More importantly, NaAc template was very easily removed by simple washing and drying. The synthetic mechanism was discussed thermodynamically combined with theoretical calculation. This novel surfactant-free route is green, efficient, low-cost and facile, presents significant novelty in the field of mesoporous HA synthesis, has great advantages over surfactant template route and may be useful in the synthesis of other hierarchical materials.