UK-China Forum on Nanostructure for Water 11-13 November 2010, The University of Hong Kong Assembled Hollow Metal Oxide Nanostructures for Water Treatment Junbai Li Institute of Chemistry, Beijing CAS Key Lab of Colloid and Interface Science Chinese Academy of Sciences
Metal Oxide Nanomaterials Features Large surface area Various modification Rich valence states Diversity of electronic structure
TiO 2 (B) nanofibers with a shell of anatase nanocrystals-an efficient photocatalyst structure Zhao, J. C. et al. J. Am. Chem. Soc. 2009, 131, 17885 Photocatalytic degradation of RB by TiO 2 hollow spheres Photo-inactivating E. coli by TiO 2 nanorods A C B Li, X. Y., Xie, Y., et al. Inorg. Chem. 2006, 45, 3493 Joo, J., Kwon, S. G., et al. J. Phys. Chem. B 2005, 109, 15297
MnO 2 nanorods degrading methyl blue Zhang, W. X., Yang, Z. H. et al. Catal. Commun. 2006, 7, 408 6
Controlled Preparation of MnO 2 Hierarchical Hollow Nanostructures MnSO 4 NH 4 HCO 3 KMnO 4 HCl C 2 H 6 O MnCO 3 MnCO 3 @MnO 2 MnO 2 Fei, J. B., Li, J. B. et al, Adv. Mater. 2008, 20, 452 7
MnCO 3 crystalline as precursor MnCO 3 MnO 2 SAED Hollow MnO 2 sphere with hierarchical structure 8
The relevant chemical reaction ΔG o = - 99.0 kj/mol XRD patterns: (a) MnCO 3 crystals; (b) MnO 2 hierarchical hollow nanostructures; (c) the remained core after selective removal of the shell. 9
MnO 2 hierarchical hollow nanostructures MnCO 3 MnCO 3 @MnO 2 MnO 2 10
Kirkendall effect 11
Hierarchical Nanostructures easier separation and recycle compared with common nanoparticles retaining high specific surface area and high catalytic activity effectively preventing further aggregation unblocked mass transferring 12
Different treating time by KMnO 4 a) 2; b) 6; c)10 min; and d) remove the core of MnCO 3 with HCl 13
Controlled thickness of MnO 2 shells 0.01:1 0.02:1 0.04:1 0.1:1 M KMnO4 : M MnCO3 Wall thickness increasing 14
Controllable 3D self-assembly by limited diffusion growth MnSO 4 NH 4 HCO 3 C 2 H 6 O KMnO 4 HCl (NH 4 ) 2 SO 4 MnCO 3 MnCO 3 @MnO 2 MnO 2 15
MnCO 3 microcubes MnO 2 hollow microcubes 16 Single MnO 2 microcube The surface structure of MnO 2
Adsorption of Congo red to MnO 2 shells Absorbance 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 b 3 300 400 500 600 Wavelength (nm) 4 1 2 5 0 min 5 min 10 min 20 min 30 min C/Co 1.0 0.8 0.6 0.4 0.2 0.0 a Commercial MnO2 b Commercial Fe2O3 NPs MnO2 as-prepared e f d c 0 20 40 60 80 100 120 Time (min) Uv-vis spectra curve: Congo red(100mg//l, 20mL), MnO 2 (0.03g) Adsorption curve, e-f regenerated MnO 2 particles 17
Wastewater treatment Absorption of Congo red, the capacity is about 60 mg/g. 18
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Controlled Assembly of Conductive Polymers with Hollow Hierarchical Nanostructures MnO 2 Polymers MnO 2 +4H + +2e Mn 2+ +2H 2 O (E o =1.2 V) Fei, J. B., Li, J. B., et al. ACS Nano 2009, 3, 3714
Monomer pyrrole thiophene aniline 1,2-diaminobenzene o-aminophenol Polymerization Potential 0.6~0.8V 0.7~1.8V ~0.8V ~0.9V ~0.7V
C 4 H 5 N+MnO 2 +H + PPY+Mn 2+ + H 2 O
Summary Hierarchical hollow MnO 2 nanostructure with intricate and well-controlled 3D morphologies have been assembled by combining the Kirkendall effect with removable crystalline template; MnO 2 superstructures at a micro- and nanoscale showed a good ability to remove organic pollutant in waste water; This approach will find wide acceptance and use in the field of template-directed nanostructure synthesis. 23
Co-workers: Acknowledgements Dr. Qiang He Dr. Yue Cui Dr. Jinbo Fei Dr. Xuehai Yan Dr. Yang Yang Financial Supports: Chinese Academy of Sciences (CAS) National Nature Science Foundation of China (NNSFC) Ministry of Science and Technology of China (MOST) Max Planck Society (MPG) EU FP 6 Project-Active Biometics 24