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

Vapour phase aniline alkylation is carried out over montmorillonite K10, vanadia modified montmorillonite K10, silica and vanadia modified silica. Montmorillonite K10 proved to be a better catalyst for aniline alkylation than silica. However, vanadia impregnation enhanced the alkylation ability of the latter making it as good a catalyst as vanadia impregnated montmorillonite K10. The catalyst systems are compared from the point of view of vanadia dispersion and vanadia-support interaction. The catalysts are characterised by BET surface area, XRD, ESR and by acidity measurements. Acidity measurement by step wise temperature programmed desorption of ammonia using a Micromeritics pulse chemisorb 2700 unit is described. Aniline alkylation ability of the catalysts is discussed with respect to catalytic acidity.

A comparative aniline alkylation activity of montmorillonite and vanadia-montmorillonite with silica and vanadia-silica

Oxides such as SiO2, γ-Al2O3, TiO2(anatase and rutile), ZrO2 and MgO with different properties have been used as supports for loading nickel by the pore volume impregnation method. Catalysts were calcined in air at 723 K for 6 h before reduction at the same temperature. Surface area and acidity measurements, X-ray diffraction and hydrogen and oxygen adsorption measurements along with hydrogenation of benzene were used as tools for characterising the catalyst. A measure of the availability of nickel in the bulk and on the surface of the catalyst is given by the O2/H2 ratio. In a metal–support system there is always a possibility of an interaction. The reducibility of catalysts depends on the availability of nickel ions determined by the support properties and the extent and type of interaction, and follows the order Ni/SiO2 > Ni/TiO2. (R)≈ Ni/ZrO2≈ Ni/TiO2(A) > Ni/γ-Al2O3 Z.Gtc Ni/MgO. The benzene hydrogenation activity was maximum around 433 K and for Ni/TiO2(A) it occurred beyond 473 K. Easily reducible Ni/SiO2 showed the highest activity and difficult-to-reduce Ni/MgO showed no appreciable activity. The turnover number (TON) for benzene hydrogenation is dependent on the available metal area and on the crystallite size. A smooth correlation between TON and the dispersion (Smetal//S,B.E.T.) is observed.

Influence of support on the availability of nickel in supported catalysts for hydrogen chemisorption and hydrogenation of benzene

In this contribution, we report the synthesis of CdS nanoparticles directly conjugated to an enzyme, R-chymotrypsin (CHT) by chemical reduction in aqueous solution. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry confirms the strong conjugation of CdS nanoparticles to CHT through covalent bonding in the CdS-CHT conjugates. High-resolution transmission electron microscopy (HRTEM) reveals that the CdS nanoparticles are well dispersed with an average diameter of 3 nm, and energy dispersive X-ray elemental analysis (EDAX) verifies the composition of the CdS-protein conjugates. The structural integrity of CHT before and after the conjugation of CdS nanoparticles is confirmed through circular dichroism (CD) studies. The functional integrity of CHT conjugated to CdS nanoparticles is investigated by monitoring the enzymatic activities of CHT and CHT-conjugated CdS nanoparticles by using absorption spectroscopy. The attachment of CdS nanoparticles to an enzyme with its structural and functional integrity may have impact in the future research on nanobio interface.

http://www.bose.res.in/~skpal/papers/CHT_CDS.pdf

Structural and Functional Characterization of Enzyme-Quantum Dot Conjugates: Covalent Attachment of CdS Nanocrystal to α-Chymotrypsin

The present research article reports the heat transfer characteristics of nano-phase change material (NPCM) composites: nanographite (NG)–PCM composites and multi-walled carbon nanotube (CNT)–PCM composites. For the preparation of NPCM composites, inorganic PCM, magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) was used as the pristine PCM and nanocellulose was used as a stabilizing agent. NG–PCM composites were prepared by varying the concentration of NG from 0.1–0.6 wt%, whereas CNT–PCM composites were prepared using 0.1 and 0.2 wt% of CNT. The prepared NPCM composites exhibited enhanced thermal conductivity and a faster heating rate than pristine PCMs. Two different experimental setups were used for investigating the heat transfer characteristics of the prepared NPCM composites during the melting and solidification processes: (i) conventional heating and (ii) solar illumination. The experimental observations indicated a higher heat transfer rate in the NPCM composites as compared to pristine PCM for both experimental setups. It was observed that the heating melting and solidification rate using a conventional heating setup increased by 48% and 77%, respectively, for NG–PCM composites (at 0.6 wt%) & 24% and 15%, respectively for CNT–PCM composites (at 0.2 wt%). Upon solar illumination, both NG–PCM and CNT–PCM composites demonstrated an ultrafast heating rate (of the order of few seconds) and a higher heating temperature than the conventional heating based approach. The ultrafast heating of NPCM composites upon solar illumination was attributed to the plasmonic heating effect of carbon nanomaterials, which instantly convert optical energy into heat at nanometer scale in addition to conventional thermal diffusion based slow heating, the sole mechanism responsible for slow heating of PCM composites in a conventional heating setup. Out of the two carbon nanofillers used, CNTs were shown to have a better heat transfer performance than NGs to collect, convert and store the broad spectrum solar energy as thermal energy.

Ultrafast thermal charging of inorganic nano-phase change material composites for solar thermal energy storage

Vapour phase alkylation of aniline with ethanol is studied over a series of H-ZSM-5 zeolites containing SiO2/Al2O3 ratios of 30, 50, 70, 150 and 280. The influence of feed rate, temperature and pressure on activity and selectivity of the products, namelyN-ethylaniline andN,N'-diethylaniline are investigated. The effect of acidity and SiO2/Al2O3 ratio of H-ZSM-5 on alkylation activity is discussed. H-ZSM-5 with a SiO2/Al2O3 ratio of 70 seems to have the acid sites required for optimum aniline alkylation activity and selectivity of the products.

Shankar Narayanan

Papers

A comparative aniline alkylation activity of montmorillonite and vanadia-montmorillonite with silica and vanadia-silica

Influence of support on the availability of nickel in supported catalysts for hydrogen chemisorption and hydrogenation of benzene

Structural and Functional Characterization of Enzyme-Quantum Dot Conjugates: Covalent Attachment of CdS Nanocrystal to α-Chymotrypsin

Ultrafast thermal charging of inorganic nano-phase change material composites for solar thermal energy storage

Vapour phase aniline alkylation activity and selectivity over H-ZSM-5