Herein is reported the soft-templating synthesis of visible-light photoactive bismuth ferrite （BiFeO3） nanoarchitectures in the form of thin fihns using a poly（ethylene-co-butylene）-block-poly（ethylene oxide） di...Herein is reported the soft-templating synthesis of visible-light photoactive bismuth ferrite （BiFeO3） nanoarchitectures in the form of thin fihns using a poly（ethylene-co-butylene）-block-poly（ethylene oxide） diblock copolymer as the structure-directing agent. We establish that （1） the self-assembled materials employed in this work are highly crystalline after annealing at 550 ℃ in air and that （2） neither the bismuth-poor Bi2Fe4O9 phase nor other impurity phases are formed. We further show that there is a distinct restructuring of the high quality cubic pore network of amorphous BiFeO3 during crystallization. This restructuring leads to films with a unique architecture that is composed of anisotropic crystallites intermingled with a continuous mesoporosity. While this article focuses on the characterization of these novel materials by electron microscopy, krypton physisorption, grazing incidence small-angle X-ray scattering, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, UV-vis and Raman spectroscopy, we also examine the photocatalytic properties and show the benefits of the combination of mesoporosity and nanocrystallinity. Templated BiFeO3 thin films （25% porosity） with a direct optical band gap at 2.9 eV exhibit a catalytic activity for the degradation of rhodamine B much better than that of nontemplated samples. We attribute this improvement to the nanoscale porosity, which provides for more available active sites on the photocatalyst.展开更多
文摘Herein is reported the soft-templating synthesis of visible-light photoactive bismuth ferrite （BiFeO3） nanoarchitectures in the form of thin fihns using a poly（ethylene-co-butylene）-block-poly（ethylene oxide） diblock copolymer as the structure-directing agent. We establish that （1） the self-assembled materials employed in this work are highly crystalline after annealing at 550 ℃ in air and that （2） neither the bismuth-poor Bi2Fe4O9 phase nor other impurity phases are formed. We further show that there is a distinct restructuring of the high quality cubic pore network of amorphous BiFeO3 during crystallization. This restructuring leads to films with a unique architecture that is composed of anisotropic crystallites intermingled with a continuous mesoporosity. While this article focuses on the characterization of these novel materials by electron microscopy, krypton physisorption, grazing incidence small-angle X-ray scattering, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, UV-vis and Raman spectroscopy, we also examine the photocatalytic properties and show the benefits of the combination of mesoporosity and nanocrystallinity. Templated BiFeO3 thin films （25% porosity） with a direct optical band gap at 2.9 eV exhibit a catalytic activity for the degradation of rhodamine B much better than that of nontemplated samples. We attribute this improvement to the nanoscale porosity, which provides for more available active sites on the photocatalyst.
