Methyl orange

Abstract: As we look toward the next millennium, we envision new technologies based on nanoscale machines and devices. Key to the realization of this nanotech world are simple, efficient methods of organizing materials (molecules, molecular clusters, polymers, or, generally speaking, building blocks) into precise, predetermined nanostructures that can be preserved in a robust engineering form. Marine organisms like diatoms and radiolaria provide us with many examples of intricately organized architectures preserved in silica or calcium carbonate. Such natural microstructures are formed by biomineralization, a templated self-assembly process in which preorganized organic surfaces regulate the nucleation, growth, morphology and orientation of inorganic crystals. To date, a variety of synthetic pathways that mimic aspects of biomineralization have been explored to prepare patterned ceramic materials. In an early attempt to achieve antigen/ antibodyselectivity inaporousadsorbent,Dickey prepared silicagels inthepresenceofthetargetmoleculetobeadsorbed (in this case methyl orange). After methyl orange extraction, the resulting templated silicas showed preferential selectivity for methyl orange over its alkyl orange homologues. In the 1960s researchers at the Mobil Oil Corporation used alkylammonium ions as templates to control the pore size, shape and periodicity of zeolites, crystalline solids that define 1-, 2-, or 3-dimensional (1-, 2-, or 3-D, respectively) networks of microporous channels. More recently Kresge and colleagues at Mobil used longer-chain alkylammonium ions in an attempt to increase the maximum pore size of zeolites beyond ~1.2 nm. They observed honeycomb-like arrays of ~4 nm pores and, based on analogies with hexagonal liquidcrystalline systems, proposed a supramolecular liquid-crystalline templating mechanism. Although excellent progress has been made in the preparationofawidevarietyofpatternedceramicmaterials, current synthetic methods have several inherent drawbacks fromthestandpointofnanotechnology:First,mosttemplating procedures are conducted in time-consuming batch operations often employing hydrothermal processing conditions. Second, the resultant products are typically ill-defined powders, precluding their general use in thin film technologies. Third, procedures developed to date are often limited to forming patterns of pores. For many envisioned nanotechnologies, it would be desirable to create patterned nanocomposites consisting of periodic arrangements of two or more dissimilar materials. This article summarizes a simple evaporation-induced self-assembly (EISA) process, that enables the rapid production of patterned porous or nanocomposite materials in the form of films, fibers, or powders.

Abstract: Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV−vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C3N4. The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C3N4 photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C3N4 can promote photodegradation of Rh B because the boron doping improves the dye adsorption and...

Abstract: A general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent. The as-prepared BiOX powders were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, and nitrogen sorption. The resulting BiOX samples were phase-pure and of hierarchical microspheres consisting of nanoplates. The band gaps of the as-prepared powders were estimated to about 3.22, 2.64, and 1.77 eV for BiOCl, BiOBr, and BiOI, respectively. On the basis of characterization results, we proposed a possible process for the growth of hierarchical BiOX nanoplate microspheres. Moreover, we evaluated their photocatalytic activities on the degradation of methyl orange and compared them with TiO2 (Degussa, P25) under UV−vis light irradiation and C-doped TiO2 under visible light (λ > 420 nm) irradiation, respectively. It was found that al...