Block Copolymer-Templated BiFeO3 Nanoarchitectures Composed of Phase-Pure Crystallites Intermingled with a Continuous Mesoporosity: Effective Visible-Light Photocatalysts?
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Herein is reported the soft-templating synthesis of visible-light photoactive bismuth ferrite (BiFeO3) nanoarchitectures in the form of thin films 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.
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Block Copolymer-Templated BiFeO3 Nanoarchitectures Composed of Phase-Pure Crystallites Intermingled with a Continuous Mesoporosity: Effective Visible-Light Photocatalysts?
Abstract
Herein is reported the soft-templating synthesis of visible-light photoactive bismuth ferrite (BiFeO3) nanoarchitectures in the form of thin films 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.
References(38)
Ramesh, R.; Spaldin, N. A. Multiferroics: Progress and prospects in thin films. Nat. Mater. 2007, 6, 21-29.
Stolichnov, I.; Riester, S. W. E.; Trodahl, H. J.; Setter, N.; Rushforth, A. W.; Edmonds, K. W.; Campion, R. P.; Foxon, C. T.; Gallagher, B. L.; Jungwirth, T. Non-volatile ferroelectric control of ferromagnetism in (Ga, Mn)As. Nat. Mater. 2008, 7, 464-467.
Hill, N. A. Why are there so few magnetic ferroelectrics? J. Phys. Chem. B 2000, 104, 6694-6709.
Eerenstein, W.; Mathur, N. D.; Scott, J. F. Multiferroic and magnetoelectric materials. Nature 2006, 442, 759-765.
Cheong, S. W.; Mostovoy, M. Multiferroics: A magnetic twist for ferroelectricity. Nat. Mater. 2007, 6, 13-20.
Catalan, G.; Scott, J. F. Physics and applications of bismuth ferrite. Adv. Mater. 2009, 21, 2463-2485.
Chu, Y. H.; Martin, L. W.; Holcomb, M. B.; Gajek, M.; Han, S. J.; He, Q.; Balke, N.; Yang, C. H.; Lee, D.; Hu, W. et al. Electric-field control of local ferromagnetism using a magnetoelectric multiferroic. Nat. Mater. 2008, 7, 478-482.
Wang, J.; Neaton, J. B.; Zheng, H.; Nagarajan, V.; Ogale, S. B.; Liu, B.; Viehland, D.; Vaithyanathan, V.; Schlom, D. G.; Waghmare, U. V. et al. Epitaxial BiFeO3 multiferroic thin film heterostructures. Science 2003, 299, 1719-1722.
Fiebig, M. Revival of the magnetoelectric effect. J. Phys. D: Appl. Phys. 2005, 38, R123-R152.
Ederer, C.; Spaldin, N. A. Weak ferromagnetism and magnetoelectric coupling in bismuth ferrite. Phys. Rev. B 2005, 71, 060401.
Gao, F.; Chen, X. Y.; Yin, K. B.; Dong, S.; Ren, Z. F.; Yuan, F.; Yu, T.; Zou, Z.; Liu, J. M. Visible-light photocatalytic properties of weak magnetic BiFeO3 nanoparticles. Adv. Mater. 2007, 19, 2889-2892.
Yang, H.; Luo, H. M.; Wang, H.; Usov, I. O.; Suvorova, N. A.; Jain, M.; Feldmann, D. M.; Dowden, P. C.; DePaula, R. F.; Jia, Q. X. Rectifying current-voltage characteristics of BiFeO3/Nb-doped SrTiO3 heterojunction. Appl. Phys. Lett. 2008, 92, 102113.
Mills, A.; Davies, R. H.; Worsley, D. Water-purification by semiconductor photocatalysis. Chem. Soc. Rev. 1993, 22, 417-425.
Hoffmann, M. R.; Martin, S. T.; Choi, W. Y.; Bahnemann, D. W. Environmental applications of semiconductor photocatalysis. Chem. Rev. 1995, 95, 69-96.
Chatterjee, D.; Dasgupta, S. Visible light induced photocatalytic degradation of organic pollutants. J. Photochem. Photobiol. C 2005, 6, 186-205.
Selbach, S. M.; Einarsrud, M. A.; Grande, T. On the thermodynamic stability of BiFeO3. Chem. Mater. 2009, 21, 169-173.
Mann, S.; Ozin, G. A. Synthesis of inorganic materials with complex form. Nature 1996, 382, 313-318.
Yang, P. D.; Zhao, D. Y.; Margolese, D. I.; Chmelka, B. F.; Stucky, G. D. Block copolymer templating syntheses of mesoporous metal oxides with large ordering lengths and semicrystalline framework. Chem. Mater. 1999, 11, 2813-2826.
Goltner, C. G.; Antonietti, M. Mesoporous materials by templating of liquid crystalline phases. Adv. Mater. 1997, 9, 431-436.
Soler-Illia, G. J. D.; Sanchez, C.; Lebeau, B.; Patarin, J. Chemical strategies to design textured materials: From microporous and mesoporous oxides to nanonetworks and hierarchical structures. Chem. Rev. 2002, 102, 4093-4138.
Brinker, C. J.; Lu, Y. F.; Sellinger, A.; Fan, H. Y. Evaporation-induced self-assembly: Nanostructures made easy. Adv. Mater. 1999, 11, 579-585.
Brezesinski, T.; Wang, J.; Senter, R.; Brezesinski, K.; Dunn, B.; Tolbert, S. H. On the correlation between mechanical flexibility, nanoscale structure, and charge storage in periodic mesoporous CeO2 thin films. ACS Nano 2010, 4, 967-977.
Sel, O.; Sallard, S.; Brezesinski, T.; Rathousky, J.; Dunphy, D. R.; Collord, A.; Smarsly, B. M. Periodically ordered meso- and macroporous SiO2 thin films and their induced electrochemical activity as a function of pore hierarchy. Adv. Funct. Mater. 2007, 17, 3241-3250.
Brezesinski, K.; Ostermann, R.; Hartmann, P.; Perlich, J.; Brezesinski, T. Exceptional photocatalytic activity of ordered mesoporous β-Bi2O3 thin films and electrospun nanofiber mats. Chem. Mater. 2010, 22, 3079-3085.
Richmann, E. K.; Kang, C. B.; Brezesinski, T.; Tolbert, S. H. Ordered mesoporous silicon through magnesium reduction of polymer templated silica thin films. Nano Lett. 2008, 8, 3075-3079.
Brezesinski, K.; Wang, J.; Haetge, J.; Reitz, C.; Steinmueller, S. O.; Tolbert, S. H.; Smarsly, B. M.; Dunn, B.; Brezesinski, T. Pseudocapacitive contributions to charge storage in highly ordered mesoporous group V transition metal oxides with iso-oriented layered nanocrystalline domains. J. Am. Chem. Soc. 2010, 132, 6982-6990.
Cseri, T.; Bekassy, S.; Kenessey, G.; Liptay, G.; Figueras, F. Characterization of metal nitrates and clay supported metal nitrates by thermal analysis. Thermochim. Acta 1996, 288, 137-154.
Kodama, H. Synthesis of a new compound, Bi5O7NO3, by thermal decomposition. J. Solid State Chem. 1994, 112, 27-30.
Singh, M. K.; Jang, H. M.; Ryu, S.; Jo, M. H. Polarized Raman scattering of multiferroic BiFeO3 epitaxial films with rhombohedral R3c symmetry. Appl. Phys. Lett. 2006, 88, 042907.
Kothari, D.; Reddy, V. R.; Sathe, V. G.; Gupta, A.; Banerjee, A.; Awasthi, A. M. Raman scattering study of polycrystalline magnetoelectric BiFeO3. J. Magn. Magn. Mater. 2008, 320, 548-552.
Yang, Y.; Sun, J. Y.; Zhu, K.; Liu, Y. L.; Chen, J.; Xing, X. R. Raman study of BiFeO3 with different excitation wavelengths. Physica B 2009, 404, 171-174.
Brezesinski, T.; Groenewolt, M.; Pinna, N.; Amenitsch, H.; Antonietti, M.; Smarsly, B. M. Surfactant-mediated generation of iso-oriented dense and mesoporous crystalline metal-oxide layers. Adv. Mater. 2006, 18, 1827-1831.
Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. Handbook of Photoelectron Spectroscopy; Perkin-Elmer Corp., Physical Electronics Division, Eden Prairie: Minnesota, USA, 1992.
Jaiswal, A.; Das, R.; Vivekanand, K.; Abraham, P. M.; Adyanthaya, S.; Poddar, P. Effect of reduced particle size on the magnetic properties of chemically synthesized BiFeO3 nanocrystals. J. Phys. Chem. C 2010, 114, 2108-2115.
Gujar, T. P.; Shinde, V. R.; Lokhande, C. D. Nanocrystalline and highly resistive bismuth ferric oxide thin films by a simple chemical method. Mater. Chem. Phys. 2007, 103, 142-146.
Li, J.; Collins, R. W.; Musfeldt, J. L.; Pan, X. Q.; Schubert, J.; Ramesh, R.; Schlom, D. G. Optical band gap of BiFeO3 grown by molecular-beam epitaxy. Appl. Phys. Lett. 2008, 92, 142908.
Clark, S. J.; Robertson, J. Band gap and Schottky barrier heights of multiferroic BiFeO3. Appl. Phys. Lett. 2007, 90, 132903.
Rolison, D. R. Catalytic nanoarchitectures—the importance of nothing and the unimportance of periodicity. Science 2003, 299, 1698-1701.
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Acknowledgements
This work was supported by the Fonds der Chemischen Industrie through a Liebig fellowship (T. B.). Portions of this research were carried out at the German synchrotron radiation facility HASYLAB/DESY. The authors would also like to thank Jan Perlich, Bruno K. Meyer, Daniel Reppin, Bernd M. Smarsly, M. Rohnke, and Stephan V. Roth for their assistance in materials preparation and measurements.
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