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Shankar Narayanan

Bio: Shankar Narayanan is an academic researcher from Rensselaer Polytechnic Institute. The author has contributed to research in topics: Catalysis & Alkylation. The author has an hindex of 36, co-authored 152 publications receiving 4060 citations. Previous affiliations of Shankar Narayanan include S.N. Bose National Centre for Basic Sciences & Centre national de la recherche scientifique.


Papers
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Journal ArticleDOI
28 Apr 2017-Science
TL;DR: The design and demonstration of a device based on a porous metal-organic framework 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).
Abstract: 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.

1,041 citations

Journal ArticleDOI
30 Mar 2018-Science
TL;DR: This work reports a regime for dendrite evolution in which repeated doses of high-current-density healing treatment enables the safe cycling of Li-sulfur batteries with high coulombic efficiency.
Abstract: Lithium (Li) metal electrodes are not deployable in rechargeable batteries because electrochemical plating and stripping invariably leads to growth of dendrites that reduce coulombic efficiency and eventually short the battery. It is generally accepted that the dendrite problem is exacerbated at high current densities. Here, we report a regime for dendrite evolution in which the reverse is true. In our experiments, we found that when the plating and stripping current density is raised above ~9 milliamperes per square centimeter, there is substantial self-heating of the dendrites, which triggers extensive surface migration of Li. This surface diffusion heals the dendrites and smoothens the Li metal surface. We show that repeated doses of high-current-density healing treatment enables the safe cycling of Li-sulfur batteries with high coulombic efficiency.

335 citations

Journal ArticleDOI
TL;DR: In this paper, the esterification of benzyl alcohol with acetic acid has been studied over zeolites Hβ, HY, and HZSM5, and it has been shown that the reaction follows the Eley-Rideal mechanism.
Abstract: The esterification of benzyl alcohol with acetic acid has been studied over zeolites Hβ, HY, and HZSM5. In the case of zeolites Hβ and HY, apart from the expected product benzyl acetate, dibenzyl ether was also formed. In the absence of a catalyst and also over zeolite HZSM5 only the ester was formed. Acidic sites responsible for the reaction are predominantly inside the pores of the zeolites. The pore architecture seems to influence the product selectivity. Kinetic studies have shown that the esterification reaction follows the Eley–Rideal mechanism. The energy of activation for the reaction follows the order: Hβ

123 citations

Journal ArticleDOI
TL;DR: Palladium hydrotalcite catalysts are obtained by impregnation of PdCl 2 aqueous solution on HTs and are well characterized by XRD, surface area, IR, SEM, DTA as discussed by the authors.
Abstract: Hydrotalcites (HTs) are prepared by low supersaturation and high supersaturation methods, containing CO 2− 3 , Cl − , SO 2− 4 interlayer anions and with different Al(III)/Al(III)+Mg(II) ( x =0.33 and 0.25) ratios. Palladium hydrotalcite catalysts are obtained by impregnation of PdCl 2 aqueous solution on HTs. Different precursors of palladium are used for loading the metal onto HT prepared at high supersaturation. HT and palladium HTs are well characterized by XRD, surface area, IR, SEM, DTA. CO chemisorption is used to estimate palladium dispersion and metal area. The activity is evaluated for phenol hydrogenation reaction. The selectivity to cyclohexanone is always ≥90% even though phenol conversion varies with metal area.

90 citations

Journal ArticleDOI
02 Aug 2011-Langmuir
TL;DR: A semianalytical, continuum analysis of evaporation of water confined in a cylindrical nanopore is presented, wherein the combined effect of electrostatic interaction and van der Waals forces is taken into account.
Abstract: A semianalytical, continuum analysis of evaporation of water confined in a cylindrical nanopore is presented, wherein the combined effect of electrostatic interaction and van der Waals forces is taken into account. The equations governing fluid flow and heat transfer between liquid and vapor phases are partially integrated analytically, to yield a set of ordinary differential equations, which are solved numerically to determine the flow characteristics and effect on the resulting shape and rate of evaporation from the liquid–vapor interface. The analysis identifies three important parameters that significantly affect the overall performance of the system, namely, the capillary radius, pore-wall temperature, and the degree of saturation of vapor phase. The extension of meniscus is found to be prominent for smaller nanoscale capillaries, in turn yielding a greater net rate of evaporation per unit pore area. The effects of temperature and ambient vapor pressure on net rate of evaporation are shown to be anal...

78 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: 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 …

33,785 citations

Journal ArticleDOI
TL;DR: 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.
Abstract: 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.

1,721 citations

Journal ArticleDOI
TL;DR: It is shown here that highly selective protein adsorption, added to the fact that particles can reach subcellular locations, results in significant new potential impacts for nanoparticles on protein interactions and cellular behavior.

1,556 citations

Journal ArticleDOI
28 Apr 2017-Science
TL;DR: The design and demonstration of a device based on a porous metal-organic framework 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).
Abstract: 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.

1,041 citations