Inorganic Layered Materials Research Articles

Layered α‐Zirconium Phosphates and Phosphonates

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient Transdermal Penetration and Improved Stability of L-Ascorbic Acid Encapsulated in an Inorganic Nanocapsule

Encapsulation of L-ascorbic acid (vitamin C) within a bio-compatible layered inorganic material was achieved by coprecipitation reaction, in which the layered inorganic lattice and its intercalate of vitamin C are simultaneously formed. The nano-meter sized powders of vitamin C intercalate thus prepared was again encapsulated with silica nano-sol to form a nanoporous shell structure. This ternary nanohybrid of vitamin Clayered inorganic core-<TEX>$SiO_2$</TEX> shell exhibited an enhanced storage stability and a sustained releasing of vitamin C. Furthermore, the nano-encapsulation of vitamin C with inorganic mineral was very helpful in delivering vitamin C molecules into skin through stratum corneum, facilitating transdermal penetration of vitamin C in topical application.

Intercalation of Enzymes in Layered Inorganic Materials

Intercalation reaction of two enzymes, catalase and glucose oxidase (GOD) into α-zirconium phosphate, α-ZrP, was examined. The intercalation in aqueous solution was carried out in two different procedures. In the first procedure, colloidal mixture of α-ZrP and propylamine was prepared in advance and the enzyme was added to the colloidal mixture. The exfoliated lamellae were produced in the mixture and the intercalation was expected to occur on the occasion of re-cohesion of the exfoliated lamellae. α-ZrP was added in the enzyme-propylamine mixed solution in the second procedure. Simultaneous accommodation of enzyme with propylamine was expected to occur. Most of the products were amorphous irrespective of the preparation procedures. Under suitable condition, catalase and GOD intercalation compounds showed significant enzyme activity with relatively long life.

Nanotubes of the disulfides of groups 4 and 5 metals

Abstract Nanotubes of HfS2, ZrS2, NbS2, and TaS2 have been obtained by the reduction of the corresponding metal trisulfides in a stream of H2 (mixed with an inert gas in some cases) at elevated temperatures. The nanotubes have been characterized by transmission electron microscopy (TEM) and other techniques. These disulfide nanotubes make an important addition to the growing family of nanotubes of inorganic layered materials.

Intercalation compounds of layered materials for drug delivery use. II. Diclofenac sodium.

Intercalation compounds of ternary layered inorganic materials, synthetic mica (Na-TSM), with diclofenac sodium (DFS) and its drug release characteristics were investigated. Hygroscopic DFS was selected as a model drug to verify the anti-humidity and anti-oxidation of the intercalation compounds. Na-TSM powder was first mixed with the reduced-type phosphatidylcholine (H-PC) solution of chloroform or ethanol. DFS was then mixed with these solutions and heated at 37 degrees C to prepare the ternary Na-TSM/H-PC/DFS compound. A remarkable phenomenon was observed in the drug release study. The net amount of DFS from the DFS powder decreased apparently after 20 min arising from the decomposition of DFS in acidic medium. On the other hand, the net amount of the released DFS from the intercalation compound was invariant. Thermal analyses study indicated that DFS powder was hygroscopic and a significant endothermic peak was observed accompanied by a large weight loss due to the dehydration of adsorbed water from 40 to 90 degrees C. On the other hand, no significant dehydration reaction was observed in the intercalation compounds even in the sample stored under humid conditions. The present results indicated that the ternary intercalation compound was resistant to acid in addition to anti-humidity.

The Ion-Exchange Property of Some Layered Inorganic Materials with Potassium Ion, Rubidium Ion and Cesium Ion, and Selective Cesium Ion-Exchange of Synthetic Mica

Abstract The ion-exchange property of sodium difluorotetrasilicate, Na-TSM, with potassium, rubidium and cesium ions was investigated in addition to two other typical layered inorganic materials. The selectivity sequence of Na-TSM was Cs+ &amp;gt; Rb+ &amp;gt; K+ and the selectivity difference of Na-TSM was highest among the examined layered materials. It was found from a chemical analysis that cesium ion-exchange participated in magnesium ions, which is a lattice component of Na-TSM, in addition to an ordinary ion-exchange reaction with the interlayer sodium ions. The exchange of cesium ions with magnesium ions was found to be stoichiometric, and was expected to be an ideal ion-exchange reaction. It was a peculiar phenomenon only on Na-TSM. Once cesium ions were exchanged in a Na-TSM lattice, they were hardly released, due to a reverse ion-exchange with sodium ions. The highest selectivity difference and tight binding of cesium ions were interpreted by an ion-exchange with lattice magnesium ion as well as decreased dehydration, which resulted in the interlayer gallery height.

Thermal transformation of a kaolinite–poly(acrylamide) intercalation compound

The thermal transformation of a kaolinite–poly(acrylamide) (PAAm) intercalation compound has been investigated. Acrylamide molecules were intercalated between the layers of kaolinite and were subsequently polymerized by heat treatment at 300 °C for 1 h. The kaolinite–PAAm intercalation compound was heated in the range 460–620 °C under a nitrogen atmosphere. XRD analysis revealed that carbonaceous materials remained between the layers in this temperature range. The 29Si and 27Al NMR spectra of the kaolinite–PAAm compounds heated above 500 °C showed that the structural change of aluminosilicate layers was relatively suppressed compared with that of kaolinite itself, indicating that the carbonaceous materials hindered the transformation of aluminosilicate layers. This new finding provides a method for controlling the skeletal transformation of inorganic layered materials upon thermal treatment.

セラミックスのケミカルプロセッシング 無機層状物質の創製に関する研究

Material interaction is very important to find out new materials and interesting properties. Inorganic layered materials are very useful in this respect. Intercalation is one of the important properties of layered compounds. Preparation and properties are reviewed on various kinds of intercalation compounds. Further developments can be expected by controlling its microstructure in various applications such as lithium rechargeable battery. Mechanical interaction also apparently appeared on layered compounds such as high Tc cuprate oxide superconductors and misfit layered sulfides. The interaction induces oxygen or sulfur defects in their layered sublattices to reduce their mechanical stress. New compounds were also prepared applying high pressure synthesis on these layered compounds. Sputter deposited multilayered thin film is also expected to be very interesting as a functional inorganic layered material. A possibility was found out for a giant magnetization at the interface of Fe/AIN multilayer.

Assembly of thin Film Dielectrics by Sequential Adsorption Reactions of Unilamellar Inorganic Colloids

AbstractSeveral layered inorganic materials (e.g. KCa2Nb3O10, KTiNbO5, and CsPb2Nb3O10) were prepared and their alkali cations exchanged by in aqueous acid. A fraction of the interlayer protons of HCa2Nb3O10 and HTiNbO5 can be replaced by tetra-n-butylammonium (TBA+), by reaction with TBA+OH. Intercalation of a sufficient amount of TBA+ causes complete exfoliation, and single, nanometer-thick sheets of these materials are thus obtained. By sequential adsorption of these two-dimensional colloidal polyanions and polymeric cations, monolayer sheets of layered perovskites can be stacked on silicon surfaces to give thin films of any desired thickness. The layered materials, the exfoliated colloids, and the thin film multilayers on silicon were studied by X-ray diffraction, transmission electronic microscopy (TEM), ellipsometry, and atomic force microscopy (AFM). The dielectric properties of the related bulk materials were measured, and are also discussed.

Influence of humidity on transport in porous silicon

We measured systematically the influence of relative humidity on the d.c. electrical conductance of porous silicon (PS) prepared by electrochemical etching. The measurements were taken at room temperature and atmospheric pressure in the range of relative humidity 0%–100%. Between 25% and 75% relative humidity a steep increase in the conductance (of three orders of magnitude) was observed. At higher humidity the dependence saturated. Similarly, below 25% the conductance was only a weak function of relative humidity. It is worth noting that on changing the humidity, typical time constants of the process are of the order of several days. The S-shaped curve obtained is analogous with those for other porous or layered inorganic materials, for example porcelain or mica, respectively, where the enhanced conductance is due to transport via water films condensed in capillaries. Hence a transport mechanism specific to porous silicon can be expected only in samples kept at a relative humidity lower than 20% or previously evacuated. A sudden increase in the conductance at 25% relative humidity is interpreted as the beginning of wetting of the inner surfaces of porous silicon by a continuous water film.