Investigation of surfactant role in synthesis of hydroxyapatite nanorods under microwave and hydrothermal conditions

Abstract Stoichiometric hydroxyapatite (HAP) nanopowder (NP) has been acclaimed as a potential bioceramic to repair/replace the human hard tissues. The search for innovative and economic protocols to synthesize HAP NP has been drawing considerable attention in the recent times. In this investigation, HAP NPs have been synthesized with and without surfactants (EDTA and CTAB) under hydrothermal (HT) and microwave (MW) assisted synthesis techniques. Structural and physico-chemical attributes of NPs were comprehensively investigated. XRD evaluation suggested formation of monolithic HAP NPs in surfactant-free HT and MW environments, whereas, multiphasic structures evolved in the presence of both surfactants in both synthesis environments. Furthermore, FESEM examination indicated formation of nanorods-like particles in surfactant-free environments, whereas, usage of EDTA and CTAB resulted into formation of irregular shape particles of vivid morphologies and sizes. Furthermore, HRTEM examination confirmed formation of nanorods-like particles in surfactant-free synthesis environments with particle sizes varied between 10 and 16 nm. EDX corroborated the presence of elements required for apatitic formation in NPs. Isotherms suggested better mesoporous structure with specific surface area of 57.521 and 50.354 m2 g−1 for MW-AS and HT-AS powders as compared to other surfactant assistant powders. This confirmed the capability of HT and MW techniques to formulate desired morphology by simple routes without necessity to add surfactant or further sintering at higher temperature.