One-pot alkanolamines-assisted synthesis of magnetic mesoporous silica for synthetic dye adsorption.

Magnetic mesoporous silica (MMS) was synthesized in a one-pot system using various alkanolamines (triethanolamine, diethanolamine, tris (hydroxymethyl)aminomethane) as a basic catalyst. The characterization of the composites was conducted using scanning electron microscope, transmission electron microscope, X-ray diffractometer, surface area analyzer, and X-ray photoelectros spectroscopy. The MMS synthesized with tris(hydroxymethyl)aminomethane (MMSTRIS) showed the highest specific surface area, pore volume, and average pore diameter. However, when the composites were applied as adsorbents for brilliant green (BG) dye, MMS synthesized with diethanolamine (MMSDEA) showed the highest maximum adsorption capacity of 339.7 mg g-1. The fastest adsorption rate constant of 1.57 × 10-2 g mg-1 min-1 was obtained for MMSTRIS, which has the largest average pore size among all composites. The adsorption kinetic study suggested that the adsorption of BG onto the prepared MMS composites was mainly chemisorption process, which most likely involves electrostatic interaction and hydrogen bonding between BG molecule and the surface of the composites.

Bottom-up synthesis of titanophosphate nanosheets by the aqueous solution process.

The synthesis of titanophosphate nanosheets in aqueous sols was examined by the bottom-up process. The nanosheets were formed by mixing titanium iso-propoxide, phosphoric acid, and tetraalkylammonium hydroxide (NR4OH) aqueous solutions, followed by diluting with water and heating at 80 °C, forming translucent aqueous sols of titanophosphate nanosheets with the same crystal structure as layered titanium phosphate Ti2O3(H2PO4)2·2H2O. Whether the nanosheets were crystallized depended on the reactions during the mixing of reagents before the water dilution. By controlling the acid-base reactions between the Ti species, phosphoric acid, and the hydroxides of bulky cations in the aqueous sols, the one-pot process yielded highly water-dispersible, flake-like titanophosphate nanosheets. Under some synthetic conditions, nanosheets formed even in weakly basic aqueous sols. These nanosheets can be coated on a substrate with low alkali-resistance, or used for the removal of metal ions from neutral aqueous solutions.

Highly magnetic nanoporous carbon/iron-oxide hybrid materials.

The preparation of size-controllable Fe2O3 nanoparticles grown in nanoporous carbon with tuneable pore diameters is reported. These hybrid materials exhibit strong non-linear magnetic properties and a magnetic moment of approximately 229 emu g(-1), which is the highest value ever reported for nanoporous hybrids, and can be attributed to the nanosieve effect and the strong interaction between the nanoparticles and the carbon walls.

Phase transition between layered tungstates and polyoxotungstates in aqueous solutions.

Aqueous sols of colloidal layered tetramethylammonium (TMA) tungstate nanocrystals were obtained by diluting an aqueous suspension of TMA polyoxotungstate precipitates. The slow evaporation of the colloidal-layered tungstate sols led to the deposition of TMA polyoxotungstate and significantly decreased the amount of layered tungstate nanocrystals. Moreover, the increase in the amount of TMA(+) in the sols also facilitated precipitation of the polyoxotungstates because of a common ion effect. Thus, the dissolution and formation of polyoxotungstate were reversible phenomena. The reaction between the dissolved species, which were formed by the dissolution of TMA polyoxotungstate, likely provided the highly water-dispersible layered tungstate nanocrystals. Furthermore, transmission electron microscopy observation suggested that the layered tungstate nanocrystals had a layer structure similar to those of H2WO4 and H2WO4·H2O, which is a layered tungstic acid.

Diversity in the matrix structure of eggshells in the Testudines (Reptilia).

The eggshells of 56 chelonians were examined by electron microscopy and X-ray diffractometry. They were classified into six types in terms of the matrix structure of their calcareous layer; type I was composed of a thin calcareous layer with minerals in an amorphous structure; type II with shell units composed of mammillary cores calcified with aragonite crystals; type III with shell units composed of mammillary cores, plus a single palisade layer also calcified with aragonite crystals, and with each shell unit separated; type IV with shell units the same as type III, but tightly packed together; type V with shell units composed of mammillary cores plus two palisade layers; and type VI with a cuticle layer calcified with calcite crystals over the same structure as that of type V. X-ray diffraction analyses at the outer surface of eggshells showed a gradual change in crystal disposition from the random disposition of type II to the single direction-oriented disposition of type V. The shell height was approximately parallel to the development of the palisade-layer matrix. The limiting membrane of all eggshell types was perforated with canals and that of type I was partially missing. Type I had a parchment shell, types II and III had a pliable shell (some were rigid) and types IV to VI had rigid shells. The present study showed that the hardness of eggshells can be determined by the composition of the shell matrices, as shell matrices are the framework for mineralization.

Synthesis of transparent aqueous sols of colloidal layered niobate nanocrystals at room temperature.

Transparent aqueous sols of colloidal tetramethylammonium niobate nanocrystals were synthesized by mixing tetramethylammonium hydroxide (TMAOH), niobium ethoxide, and water at TMAOH/Nb≥0.7 at room temperature. The X-ray diffraction patterns of the thin films prepared by evaporating the colloidal solutions on a glass substrate indicated that the colloidal niobate had a layered crystalline structure. Two types of layered structures are known as a layered niobate, i.e. M(4)Nb(6)O(17)·nH(2)O and MNb(3)O(8) (M=H, H(3)O, or alkaline metal). Raman spectra and electron diffraction suggested that the niobate nanocrystals were similar in crystal structure to M(4)Nb(6)O(17)·nH(2)O compounds. Moreover, when niobium oxide thin films were fabricated from the niobate colloidal solutions by the sol-gel method, oriented T-Nb(2)O(5) thin films, whose c-axis was parallel to the substrate surface, were obtained. The orientation of the thin films was probably attributed to the layered structure of the colloidal niobate nanocrystals.