There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high-valency metal-carboxylate frameworks and low-valency metal-azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Bronsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.

Stable Metal-Organic Frameworks: Design, Synthesis, and Applications.

http://csmres.co.uk/cs.public.upd/article-downloads/lynch.pdf

Protein-nanoparticle interactions

Atmospheric water is a resource equivalent to ~10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, especially at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-organic framework {MOF-801, [Zr6O4(OH)4(fumarate)6]} that captures water from the atmosphere at ambient conditions by using low-grade heat from natural sunlight at a flux of less than 1 sun (1 kilowatt per square meter). This device is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20% and requires no additional input of energy.

https://science.sciencemag.org/content/sci/early/2017/04/12/science.aam8743.full.pdf

Water harvesting from air with metal-organic frameworks powered by natural sunlight

The influence of calcination temperature on alumina and on alumina-supported nickel has been systematically studied. Identification of the nickel species has been made using the techniques of X-ray photoelectron spectroscopy (X.p.s.) and X-ray diffraction (X.r.d.). Hydrogen and oxygen adsorption measurements were used to calculate the dispersion and crystallite size of the metal. Calcination of γ-alumina between 873 and 1073 K, before loading the metal, reduces the interaction of the metal and support, thereby increasing the area of metal available for hydrogen adsorption and for the hydrogenation of benzene. X.p.s. and X.r.d. indicate the presence of surface and bulk NiAl2O4 on catalysts calcined at temperatures > 873 K. Benzene hydrogenation is a facile reaction and depends directly on the available metal area, irrespective of the nickel content of the catalyst.

Studies of the Effect of Calcination on the Dispersion and Reduction of Nickel Supported on Alumina by X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, Chemisorption and Catalytic Activity.

The prepn. of a metallic catalyst contg. a metal of the Pt gp., Sn and a zeolite comprises the following steps:- (a) Formation of a hydrogel cont. sources of Sn, SiO2, a cpd. contg. N and water, (b) Crystallisation of the hydrogel at autogenous pressure and at 140-200 deg C., (c) Filtration-water-washing, and drying of the material, (d) Calcination of the dried material in an inert atmos., then in the presence of O2 at 400-700 deg C., (e) Cooling of the calcined material to room temp. (f) Reaction with a soln. of a Pt source (constantly stirred) at 1-99 deg C., (g) Concn. of the liq. phase, (h) Drying of the concn. prod. under O2, then under H2 at 200-600 deg C., and (i) Cooling of the catalyst obtd. Also claimed, is the use of the catalyst in the conversion of alkanes to alkenes.

Procedure for metallic catalyst prepn.

A recent discovery of super-Planckian radiation in the far-field has attracted a great deal of interest in thermal radiation control using photonic crystals (PC) architecture. The finding is based on a careful comparison of radiation intensity emitted from a PC nano-filament and a blackbody at the same temperature and same wavelength at λ∼1.7 μm. Extending that finding, we determined the absolute spectral radiance of such a PC filament at λ∼1.7 μm at elevated temperature, T = 445–723 °K, and compared its value to that predicted by Planck's blackbody radiation law. Our data confirmed that the PC spectral radiance surpassed that of a blackbody by an order-of-magnitude. We also determined the spectral emissivity of our PC filament and showed that its value far exceeded unity at resonance and fell below unity away from resonance. The observation of non-equality between absorptivity and emissivity suggests that a strong optical non-reciprocity takes place in our PC nano-filament.

https://ieeexplore.ieee.org/ielx7/4563994/4814557/09917305.pdf

Experimental Determination of Absolute Spectral Radiance and Emissivity of a Photonic Crystal Filament

Disproportion of toluene, dealkylation of ethylbenzene and cumene and isomerization of o-xylene were carried out over mordenites with and without metal. Metal mordenites were prepared by ion exchange and impregnation methods. Hydrogen mordenite is not the most active catalyst studied. Partially exchanged sodium hydrogen mordenite and nickel sodium mordenite were more active for cumene dealkylation and o-xylene isomerization than for disproportionation of toluene and o-xylene. Nickel seems to have a positive influence on the activity of hydrogen mordenite for these reactions.

Shankar Narayanan

Papers

Studies of the Effect of Calcination on the Dispersion and Reduction of Nickel Supported on Alumina by X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, Chemisorption and Catalytic Activity.

Procedure for metallic catalyst prepn.

Experimental Determination of Absolute Spectral Radiance and Emissivity of a Photonic Crystal Filament

Mordenite catalysts: influence of metal on disproportionation, dealkylation and isomerization