Synthesis of Morphology Processable α-AlPO4Nanoparticles, Nanowires, and Multi-strand Nano-ropes

Abstract

In this paper we present aluminum phosphate nanocrystals, prepared by a hydrothermal reaction, using amphiphilic triblock copolymer F127 [(EO) 1 0 6 (PO) 7 0 (EO) 1 0 6 ] as a morphology-directing template. By verifying the pH from 10 to 12, the morphology progression of AlPO 4 nanocrystals from nanoparticles to nanoparticle-aggregated nanowires, and finally to multi-strand nano-ropes, was successfully demonstrated. The most influential factors in the morphology process were the initial pH level, the participation of surfactant-template F127, and the change in pH during the reaction. We proposed a pH-dependent model to illustrate both the growth of AlPO 4 nanocrystals inside F127 amphiphilic domains and the chemical driving force that aggregated the nanoparticles into chain-shaped nanowires. The incorporation of water molecules as H-bonding linkers, to combine single nanowires into multi-strand nano-ropes, is also discussed in this model. Powder X-ray diffraction (XRD) patterns of the nanoparticle-aggregated nanowires and multi-strand nano-ropes were consistent with a mixed phase of berlinite and cristobalite structures, corresponding to the low-temperature form (a-form), while the AlPO 4 nanoparticles showed a pure berlinite phase only.