Robert Morley Tindwa

Bio: Robert Morley Tindwa is an academic researcher from Texas A&M University. The author has contributed to research in topics: Intercalation (chemistry) & Zirconium phosphate. The author has an hindex of 2, co-authored 2 publications receiving 184 citations.

Intercalation of n-alkylamines by α-zirconium phosphate

Abstract: The intercalation behaviour of α-zirconium phosphate, Zr(HPO4)2·H2O, towards n-alkylamines has been examined. Amines with small carbon chains (C1–C4) initially form a phase in which the chain backbone lies parallel to the zirconium phosphate layers. As more amine is intercalated the amines form a bilayer in which the carbon chains incline at roughly 60° to the zirconium phosphate layers. Methyl and propylamine form disordered gels at intermediate levels of intercalation but recrystallize at high levels of amie uptake. The longer-chain amines form a bilayer even at low uptakes. The wet intercalates contain 10–12 mol water per formula weight, mostly as interparticle water rearrangement. On drying to the monohydrates, the interlayer spacings do not change when the solids have a high amine content. At lower amine contents the amine rearranges to yield phases with lower interlayer spacings.

Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism

Abstract: MICROPOROUS and mesoporous inorganic solids (with pore diameters of ≤20 A and ∼20–500 A respectively)1 have found great utility as catalysts and sorption media because of their large internal surface area. Typical microporous materials are the crystalline framework solids, such as zeolites2, but the largest pore dimensions found so far are ∼10–12 A for some metallophosphates3–5 and ∼14 A for the mineral cacoxenite6. Examples of mesoporous solids include silicas7 and modified layered materials8–11, but these are invariably amorphous or paracrystalline, with pores that are irregularly spaced and broadly distributed in size8,12. Pore size can be controlled by intercalation of layered silicates with a surfactant species9,13, but the final product retains, in part, the layered nature of the precursor material. Here we report the synthesis of mesoporous solids from the calcination of aluminosilicate gels in the presence of surfactants. The material14,15 possesses regular arrays of uniform channels, the dimensions of which can be tailored (in the range 16 A to 100 A or more) through the choice of surfactant, auxiliary chemicals and reaction conditions. We propose that the formation of these materials takes place by means of a liquid-crystal 'templating' mechanism, in which the silicate material forms inorganic walls between ordered surfactant micelles.

A new family of mesoporous molecular sieves prepared with liquid crystal templates

Abstract: The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.

Proteins Immobilized at the Galleries of Layered α-Zirconium Phosphate: Structure and Activity Studies

Abstract: Facile immobilization of myoglobin (Mb), lysozyme (Lys), hemoglobin (Hb), chymotrypsin (CT), and glucose oxidase (GO) at the interlayer regions of layered α-zirconium phosphate (α-ZrP) under ambient conditions (pH 7.2, room temperature) is described. The proteins retain their structure and activity after immobilization. The interlayer spacings of α-ZrP (observed in powder XRD experiments) increased from 7.6 A (for α-ZrP) to 53, 47, 66, 62, and 108 A when Mb, Lys, Hb, CT, and GO are bound to the matrix, respectively. These XRD data strongly suggest intercalation of the proteins in the galleries. The binding constants of the above proteins with α-ZrP, estimated from the centrifugation method, are in the range of 104−106 M-1. The α, β, and the soret absorption bands of Mb/Hb immobilized on α-ZrP were essentially superimposable with those of the native proteins in solution. The FTIR spectra of the enzyme−α-ZrP composites, measured with an attenuated total reflectance accessory, show that the amide I and amide...