title: Single-crystalline MFe(2)O(4) nanotubes/nanorings synthesized by thermal transformation process for biological applications.
abstract: We report a general thermal transformation approach to synthesize single-crystalline magnetic transition metal oxides nanotubes/nanorings including magnetite Fe(3)O(4), maghematite gamma-Fe(2)O(3), and ferrites MFe(2)O(4) (M = Co, Mn, Ni, Cu) using hematite alpha-Fe(2)O(3) nanotubes/nanorings template. While the straightforward reduction or reduction-oxides process was employed to produce Fe(3)O(4) and gamma-Fe(2)O(3), the alpha-Fe(2)O(3)/M(OH)(2) core/shell nanostructure was used as precursor to prepare MFe(2)O(4) nanotubes via MFe(2)O(4-x) (0 < x < 1) intermediate. The transformed ferrites nanocrystals retain the hollow structure and single-crystalline nature of the original templates. However, the crystallographic orientation-relationships of cubic spinel ferrites and trigonal hematite show strong correlation with their morpologies. The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties. Moreover, they have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells, suggesting that these biocompatible magnetic nanotubes/nanorings have great potential in biomedicine and biomagnetic applications.
authors.affiliation: Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore. msefhm@nus.edu.sg
authors.forename: Hai-Ming
authors.initials: HM
authors.lastname: Fan
authors.forename: Jia-Bao
authors.initials: JB
authors.lastname: Yi
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Kiang-Wei
authors.initials: KW
authors.lastname: Kho
authors.forename: Hui-Ru
authors.initials: HR
authors.lastname: Tan
authors.forename: Ze-Xiang
authors.initials: ZX
authors.lastname: Shen
authors.forename: Jun
authors.initials: J
authors.lastname: Ding
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Sun
authors.forename: Malini Carolene
authors.initials: MC
authors.lastname: Olivo
authors.forename: Yuan-Ping
authors.initials: YP
authors.lastname: Feng
mesh_terms: D032701:Biomimetics; D045744:Cell Line, Tumor; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism; D005740:Gases / Q000737:chemistry; D006801:Humans; D008163:Luminescent Measurements; D008175:Lung Neoplasms / Q000473:pathology; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry; D043942:Nanotubes / Q000737:chemistry*; D055620:Optical Phenomena; D010544:Peroxidases / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D013696:Temperature; D028561:Transition Elements / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D005740:Gases; D028561:Transition Elements; D010544:Peroxidases