The preparation of hydroxyapatite nanowires and nanorods via aliphatic micelles as soft templates

Abstract

Hydroxyapatite (HAP) nanocrystals have been widely investigated for tunable synthesis with various morphologies via the use of a three-phase reaction system. However, the template-induced mechanism for the microscale structures has not been sufficiently clarified. Here, four types of eighteen-carbon (C₁₈) aliphatic–ethanol–water three-phase mixture systems were investigated via an emulsion–hydrothermal synergistic method. Fatty acids (stearic acid and oleic acid) formed an entangled long wormlike micelle structure as a soft template for phase transfer. One fatty alcohol (stearyl alcohol) formed micelles for the selective adsorption of ions at the interface of micelles during the nucleation and growth process, acting as an indirect soft template, and oleyl alcohol showed phase separation. The two essential conditions for the formation of HAP using micelles as direct/indirect soft templates were proposed and verified using OP-10 as a surfactant. These findings provide a theoretical basis for the development of HAP nanocrystals using micelles in three-phase mixture solvents.