Morphology evolution of GaPO4 mesocrystals in a nonionic triblock copolymer system by pH-dependent control

Abstract

In the synthesis of gallium phosphate, GaPO₄, crystals via a hydrothermal route, using amphiphilic triblock copolymer F127, [(EO)₁₀₆(PO)₇₀(EO)₁₀₆]–OH, as a surfactant-template, a pH-dependent morphology evolution is observed in the progress of crystal growth. By altering the initial pH level from 7.34 to 11.54, the morphology of crystals is varied from the mesoscale assembly of nanoparticles with porosity, so-called porous mesocrystals, to colloidal crystalline nanoparticles. Thus far, the porous GaPO₄ mesocrystals created by self-assembled nanoparticles, is reported for the first time. The typical pore size distribution of porous GaPO₄ mesocrystals derived from the adsorption branch by the Barrett–Joyner–Halenda (BJH) model ranges from 1.0 to 3.5 nm with a major distribution peak centered at 2.5 nm.