Formation of Na 0.44 MnO 2 nanowires via stress-induced splitting of birnessite nanosheets

Nano Research (Impact Factor: 7.39). 01/2009; 2(1). DOI: 10.1007/s12274-009-9003-1

ABSTRACT High aspect ratio Na 0.44 MnO 2 nanowires with a complex one-dimensional (1 D) tunnel structure have been synthesized. We found that the reaction went through layered birnessite nanosheet intermediates, and that their conversion to the fi nal product involved splitting of the nanosheets into nanowires. Based on our observations, a stress-induced splitting mechanism for conversion of birnessite nanosheets to Na 0.44 MnO 2 nanowires is proposed. The fi nal and intermediate phases show topotaxy with001 f // 020 b or110 b where f represents the fi nal Na 0.44 MnO 2 phase and b the intermediate birnessite phase. As a result of their high surface areas, the nanowires are effi cient catalysts for the oxidation of pinacyanol chloride dye.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Orthorhombic LiMnO2 nanoparticles and LiMnO2 nanorods have been synthesized by hydrothermal methods. LiMnO2 nanoparticles were synthesized by simple one-step hydrothermal method. To obtain rod-like LiMnO2, γ-MnOOH nanorods were first synthesized and then the H+ ions were completely replaced by Li+ resulting in LiMnO2 nanorods. Their electrochemical performances were thoroughly investigated by galvanostatic tests. Although the LiMnO2 nanoparticles have smaller size than LiMnO2 nanorods, the latter exhibited higher discharge capacity and better cyclability. For example, the discharge capacities of LiMnO2 nanorods reached 200 mA·h/g over many cycles and remained above 180 mA·h/g after 30 cycles. However, the maximum capacity of LiMnO2 nanoparticles was only 170 mA·h/g and quickly decreased to 110 mA·h/g after 30 cycles. Nanorods with one-dimensional electronic pathways favor the transport of electrons along the length direction and accommodate volume changes resulting from charge/discharge processes. Thus the morphology of LiMnO2 may play an important role in electrochemical performance. KeywordsLiMnO2 nanoparticles-nanorods-hydrothermal synthesis-one-dimensional nanomaterial-electrochemical performance
    Nano Research 2(12):923-930. · 7.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report a simple and effective method to synthesize single-crystalline Mn3O4 nanowires using solvothermal technique. These nanowires with diameter in the range 15–40 nm grow uniformly along {2 0 0} direction and crystallize in tetragonal symmetry. A blue-shift in the absorption edge is observed when the synthesis temperature (T S) increases from 150 to 250 °C. The surface chemical analysis confirms the oxidation state of manganese as Mn3+. A relatively broad, intense, and symmetrical electron spin resonance (ESR) signal is detected at room temperature with the ‘g’ value 2. The relative intensity of ESR signal decreases and broadens with the rise of synthesis temperature due to the relaxation of surface anisotropy and induced magnetic field. The magnetization versus field measurements (M–H) at 300 and 5 K of Mn3O4 nanowires show hysteresis curves with large coercive field (H C) due to the large surface anisotropy. A step increase in the magnetization (ΔM = 1.7 emu/g) is noticed at H ~±1.1 kOe in the M–H curves. Possible origin of such field-induced transition is discussed. The magnitude of magnetic moment, remanence magnetization, and H C values drastically reduces with increasing the T S due to the disassembly of nanowire arrays.
    Journal of Nanoparticle Research 01/2012; 14(9). · 2.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Various sizes and shapes of Mn3O4 nanocrystals have been prepared in a one-pot synthesis in extremely dilute solution by soft template self-assembly. To better control size and shape, the effects of varying the growth time, reaction temperature, surfactant, and manganese source were examined. The average size of octahedral Mn3O4 crystallites was found to be related to the reaction time, while higher reaction temperature (150 °C) and the use of a cetyltrimethylammonium bromide/poly(vinylpyrrolidone) (CTAB/PVP) mixture allowed construction of a better-defined octahedral morphologies. When PVP or poly(ethylene oxide)-poly(propylene oxide) (P123) was used as template, large-scale agglomeration resulting in loss of the octahedral morphology occurred and crystallites with a quasi-spherical shape were obtained. The nano-octahedral crystallites were shown to be an efficient catalyst for the oxidation of methylene blue. KeywordsMn3O4 -octahedron-nanocrystals-self-assembly-methylene blue
    Nano Research 01/2010; 3(4):235-243. · 7.39 Impact Factor

Full-text (4 Sources)

Available from
Jun 5, 2014