γ-MnOOH Nanorods Research Articles

A room temperature process for making Mn 2O 3 nano-particles and γ-MnOOH nano-rods

Nano-size crystals of Mn 2O 3 and MnOOH have been prepared by a simple precipitation process using dilute aqueous solutions of manganese sulphate and ammonia in the presence of sodium lauryl sulphate — a surface active agent. X-ray diffraction spectrometry has been used to identify the phases and to calculate the size of the nano-size crystals using the Scherrer method. The morphology of the crystals has been studied by TEM/HRTEM and Edax has been used to estimate their elemental constituents. The sonication of the prepared nano-size material in acetone leads to the conversion of MnOOH to nano-sized Mn 2O 3.

Synthesis and characterization of single crystalline MnOOH and MnO 2 nanorods by means of the hydrothermal process assisted with CTAB

Large-scale γ-MnOOH and β-MnO 2 nanorods have been synthesized via the hydrothermal process assisted with CTAB at 200 °C for 20 h using MnSO 4 and NaOH as source and subsequent calcination of γ-MnOOH nanorods at 300 °C for 3 h, respectively. The characterization of X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) indicate that the γ-MnOOH and β-MnO 2 nanorods prepared are monoclinic and tetragonal single crystalline, respectively. Furthermore, the mechanism for the CTAB assisted hydrothermal synthesis of γ-MnOOH nanorods has been preliminarily presented.

Nanorods of manganese oxides: Synthesis, characterization and catalytic application

Single-crystalline nanorods of β-MnO 2, α-Mn 2O 3 and Mn 3O 4 were successfully synthesized via the heat-treatment of γ-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of γ-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050 °C, the precursor γ-MnOOH was first changed to β-MnO 2, then to α-Mn 2O 3 and finally to Mn 3O 4. When calcined in N 2 atmosphere, γ-MnOOH was directly converted into Mn 3O 4 at as low as 500 °C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor γ-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H 2O 2.

One-Dimensional Nanostructures from Layered Manganese Oxide

In this paper, we report the preparation of one-dimensional (1D) nanostructures from layered compounds (2D). γ-MnOOH nanorods were successfully prepared from platelike layered Na-birnessite by simple hydro(solvo)thermal treatment at low temperature. It was observed that the reaction medium plays an important role in the phase and morphology modifications. The γ-MnOOH was thermally treated under different conditions of atmosphere (inert or oxidizing) and temperature, which led to several phases of manganese oxide nanorods, such as MnO2 (pyrollusite), Mn2O3 (bixbyite), and Mn3O4 (hausmannite). Indeed, the achievement of such phase tuning was possible because of the outstanding structural flexibility of manganese oxides. Considering the simplicity, reproducibility, and high yield of these methods, they may be employed for low-cost large-scale production of one-dimensional manganese oxide nanostructures.

Synthesis and characterization of single-crystalline nanorods of α-MnO 2 and γ-MnOOH

Single-crystalline α-MnO 2 nanorods have been prepared by reducing KMnO 4 with graphite in concentrated H 2SO 4 solution at 0 °C. Hydrothermal treatment of the α-MnO 2 nanorods at 100 °C results in the formation of single-phase γ-MnOOH nanorods. The structure and morphology of the α-MnO 2 and γ-MnOOH are characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) spectroscopy, respectively.

Preparation of β-MnO 2 nanorods through a γ-MnOOH precursor route

A new MnOOH precursor route has been developed to synthesize single-crystalline nanorods of tetragonal β-MnO 2. Uniform γ-MnOOH nanorods were first prepared by reducing KMnO 4 with KI under hydrothermal conditions at 120 °C. After calcination of the γ-MnOOH nanorods at 250 °C for 2 h in air, β-MnO 2 nanorods retaining the morphologies of γ-MnOOH nanorods were obtained. The temperature, time and heating speed of calcination were found to be important for the morphologies of the β-MnO 2 nanorods.