Spontaneous Formation of Inorganic Paper‐Like Materials

Abstract

As the ethanol slowly evaporates, an iridescent film is formed on top of the glass slide. A sample can be made over 7±10 days, and the photonic crystal (PC) films are used as grown without any annealing. The three-dimensional structures of the samples and the microgrooves on the PC films were characterized using scanning electron microscopy (Hitachi, S-4200) and atomic force microscopy (AutoProbe CP Research System), respectively. Optical reflectance measurements were performed with a spectrophotometer (Ocean Optics, Inc., S2000). A pair of PC-coated ITO glass substrates were stacked and sealed to fabricate a vacant cell with a spacer. The cell gap was 7.0 lm and the y-directions of each substrate were set parallel to each other. Nematic liquid crystals (LCs) (ZLI2293, Merck) were introduced into the prepared cells using capillary action at the temperature of isotropic phase of the LCs. LC textures were observed using a polarizing microscope. The electro-optic measurements were made using He±Ne laser light (632.8 nm) with crossed polarizers at room temperature. Next, another nematic LC (PA1109) [17] was used in polarized reflectance measurements of a LC-filled Fabry±Perot cavity with PC films as a function of the amplitude of the applied rectangular voltage (f = 1 kHz). [1±7] Formation of ordered macroscopic, mesoscopic, and microscopic materials such as inorganic thin films and membranes has been an important goal, especially when specific physical properties such as porosity, permeability, and conductivity are of interest. These structures have potential applications as sensors, catalysts, and energy-storage devices, and in photoelectronics and separation processes.[8±10] Here we report the fabrication of ordered porous manganese oxide paper-like free-standing membranes (FSMs) by simply heating ªpulpº-like homogeneous suspensions at low temperatures. These free-standing membranes are robust and flexible, and can be formed on a patterned substrate in order to make micropatterns. Tangled manganese oxide nanowires in suspension aggregate and align systematically to form such membranes. The paper-like membrane is composed of single-crystal cryptomelane-type manganese oxide (OMS-2) fibers. The membrane has a metallic luster and can be folded or cut into various shapes. Manganese oxide structures can form mixed-valent octahedral molecular sieves with one-dimensional tunnel structures. Cryptomelane-type manganese oxide materials are an important group of octahedral molecular sieves. OMS-2 with a 2 2 tunnel structure has been synthesized via different methods including reflux, sol±gel, and solid-state chemical reactions, as well as by hydrothermal treatments, [11±13] to produce nanofibers, nanorods, and nanoneedles. Stoichiometric mixtures of potassium sulfate, potassium persulfate, and manganese sulfate monohydrate were hydrothermally treated at 250 C to produce cylindrical rigid solids.

Hierarchically multifunctional K-OMS-2/TiO2/Fe3O4 heterojunctions for the photocatalytic oxidation of humic acid under solar light irradiation

“…K-OMS-2 nanowires were synthesized via a hydrothermal method [22]. In a typical procedure, 12 mmol of K 2 SO 4 , 12 mmol of K 2 S 2 O 8 , and 8 mmol of MnSO 4 ·H 2 O were dissolved in 70 ml of deionized water.…”

Synthesis of Polyaniline Nanotubes with a Reactive Template of Manganese Oxide

“…No Mn element was detected in these samples, revealing that all of the manganese oxide had been entirely converted into watersoluble Mn 2+ ions and left no residue in the final products. As the composition of cryptomelane-phase manganese oxide is KMn 2.65 O 5.40 · 0.17 H 2 O, [31] the value of the reactive molar ratio was estimated to be manganese oxide/Ani = 1.31, which is close to the conventional (NH 4 )S 2 O 8 /Ani molar ratio (1.25:1). Table 1 indicates the parameter dependence of the PAni tube on the template wire.…”

Nanowire Membrane-based Nanothermite: towards Processable and Tunable Interfacial Diffusion for Solid State Reactions

“…Hydrogen bond plays a critical role in the formation of this network membrane in aqueous solution because MnO 2 nanowires obtained by hydrothermal method were highly functionalized with hydroxyl groups2425. In order to improve dispersion and intimate contact of reactants in aqueous solution, the MnO 2 nanowires were modified to get positively charged by a long-chain polyelectrolyte PDDA (Figure 2a)2627.…”