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Dive into the research topics where Katabathini Narasimharao is active.

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Featured researches published by Katabathini Narasimharao.


Nanoscale Research Letters | 2015

Influence of crystal structure of nanosized ZrO2 on photocatalytic degradation of methyl orange.

Sulaiman N. Basahel; Tarek T. Ali; Mohamed Mokhtar; Katabathini Narasimharao

Nanosized ZrO2 powders with near pure monoclinic, tetragonal, and cubic structures synthesized by various methods were used as catalysts for photocatalytic degradation of methyl orange. The structural and textural properties of the samples were analyzed by X-ray diffraction, Raman spectroscopy, TEM, UV-vis, X-ray photoelectron spectroscopy (XPS), and N2 adsorption measurements. The performance of synthesized ZrO2 nanoparticles in the photocatalytic degradation of methyl orange under UV light irradiation was evaluated. The photocatalytic activity of the pure monoclinic ZrO2 sample is higher than that of the tetragonal and cubic ZrO2 samples under optimum identical conditions. The characterization results revealed that monoclinic ZrO2 nanoparticles possessed high crystallinity and mesopores with diameter of 100 Å. The higher activity of the monoclinic ZrO2 sample for the photocatalytic degradation of methyl orange can be attributed to the combining effects of factors including the presence of small amount of oxygen-deficient zirconium oxide phase, high crystallinity, large pores, and high density of surface hydroxyl groups.


Advanced Materials | 2015

Oriented MFI membranes by gel-less secondary growth of sub-100 nm MFI-nanosheet seed layers

Kumar Varoon Agrawal; Berna Topuz; Tung Cao Thanh Pham; Thanh Huu Nguyen; Nicole Sauer; Neel Rangnekar; Han Zhang; Katabathini Narasimharao; Sulaiman Nasir Basahel; Lorraine F. Francis; Christopher W. Macosko; Shaeel A. Al-Thabaiti; Michael Tsapatsis; Kyung Byung Yoon

A zeolite membrane fabrication process combining 2D-zeolite nanosheet seeding and gel-free secondary growth is described. This process produces selective molecular sieve films that are as thin as 100 nm and exhibit record high permeances for xylene- and butane-isomers.


Nature | 2017

Ultra-selective high-flux membranes from directly synthesized zeolite nanosheets

Mi Young Jeon; Donghun Kim; Prashant Kumar; Pyung Soo Lee; Neel Rangnekar; Peng Bai; Meera Shete; Bahman Elyassi; Han Seung Lee; Katabathini Narasimharao; Sulaiman Nasir Basahel; Shaeel A. Al-Thabaiti; Wenqian Xu; Hong Je Cho; Evgenii O. Fetisov; Raghuram Thyagarajan; Robert F. DeJaco; Wei Fan; K. Andre Mkhoyan; J. Ilja Siepmann; Michael Tsapatsis

A zeolite with structure type MFI is an aluminosilicate or silicate material that has a three-dimensionally connected pore network, which enables molecular recognition in the size range 0.5–0.6 nm. These micropore dimensions are relevant for many valuable chemical intermediates, and therefore MFI-type zeolites are widely used in the chemical industry as selective catalysts or adsorbents. As with all zeolites, strategies to tailor them for specific applications include controlling their crystal size and shape. Nanometre-thick MFI crystals (nanosheets) have been introduced in pillared and self-pillared (intergrown) architectures, offering improved mass-transfer characteristics for certain adsorption and catalysis applications. Moreover, single (non-intergrown and non-layered) nanosheets have been used to prepare thin membranes that could be used to improve the energy efficiency of separation processes. However, until now, single MFI nanosheets have been prepared using a multi-step approach based on the exfoliation of layered MFI, followed by centrifugation to remove non-exfoliated particles. This top-down method is time-consuming, costly and low-yield and it produces fragmented nanosheets with submicrometre lateral dimensions. Alternatively, direct (bottom-up) synthesis could produce high-aspect-ratio zeolite nanosheets, with improved yield and at lower cost. Here we use a nanocrystal-seeded growth method triggered by a single rotational intergrowth to synthesize high-aspect-ratio MFI nanosheets with a thickness of 5 nanometres (2.5 unit cells). These high-aspect-ratio nanosheets allow the fabrication of thin and defect-free coatings that effectively cover porous substrates. These coatings can be intergrown to produce high-flux and ultra-selective MFI membranes that compare favourably with other MFI membranes prepared from existing MFI materials (such as exfoliated nanosheets or nanocrystals).


Angewandte Chemie | 2016

Open‐Pore Two‐Dimensional MFI Zeolite Nanosheets for the Fabrication of Hydrocarbon‐Isomer‐Selective Membranes on Porous Polymer Supports

Han Zhang; Qiang Xiao; Xianghai Guo; Najun Li; Prashant Kumar; Neel Rangnekar; Mi Young Jeon; Shaeel A. Al-Thabaiti; Katabathini Narasimharao; Sulaiman Nasir Basahel; Berna Topuz; Frank J. Onorato; Christopher W. Macosko; K. Andre Mkhoyan; Michael Tsapatsis

Two-dimensional zeolite nanosheets that do not contain any organic structure-directing agents were prepared from a multilamellar MFI (ML-MFI) zeolite. ML-MFI was first exfoliated by melt compounding and then detemplated by treatment with a mixture of H2 SO4 and H2 O2 (piranha solution). The obtained OSDA-free MFI nanosheets disperse well in water and can be used for coating applications. Deposits made on porous polybenzimidazole (PBI) supports by simple filtration of these suspensions exhibit an n-butane/isobutane selectivity of 5.4, with an n-butane permeance of 3.5×10(-7)  mol m(-2)  s(-1)  Pa(-1) (ca. 1000 GPU).


Angewandte Chemie | 2015

2D zeolite coatings: Langmuir-Schaefer deposition of 3 nm thick MFI zeolite nanosheets

Neel Rangnekar; Meera Shete; Kumar Varoon Agrawal; Berna Topuz; Prashant Kumar; Qiang Guo; Issam Ismail; Abdulrahman O. Al-Youbi; Sulaiman N. Basahel; Katabathini Narasimharao; Christopher W. Macosko; K. Andre Mkhoyan; Shaeel A. Al-Thabaiti; Benjamin L. Stottrup; Michael Tsapatsis

Stable suspensions of zeolite nanosheets (3 nm thick MFI layers) were prepared in ethanol following acid treatment, which partially removed the associated organic structure-directing agent. Nanosheets from these suspensions could then be dispersed at the air-water interface and transferred to silicon wafers using Langmuir-Schaefer deposition. Using layer-by-layer deposition, control on coating thickness was demonstrated. In-plane X-ray diffraction (XRD) revealed that the deposited nanosheets contract upon calcination similar to bulk MFI crystals. Different methods for secondary growth resulted in preferentially oriented thin films of MFI, which had sub-12-nm thickness in certain cases. Upon calcination, there was no contraction detectable by in-plane XRD, indicating well-intergrown MFI films that are strongly attached to the substrate.


Angewandte Chemie | 2017

Nanoscale Control of Homoepitaxial Growth on a Two-Dimensional Zeolite

Meera Shete; Manjesh Kumar; Donghun Kim; Neel Rangnekar; Dandan Xu; Berna Topuz; Kumar Varoon Agrawal; E. Karapetrova; Benjamin L. Stottrup; Shaeel A. Al-Thabaiti; Sulaiman N. Basahel; Katabathini Narasimharao; Jeffrey D. Rimer; Michael Tsapatsis

Nanoscale crystal growth control is crucial for tailoring two-dimensional (2D) zeolites (crystallites with thickness less than two unit cells) and thicker zeolite nanosheets for applications in separation membranes and as hierarchical catalysts. However, methods to control zeolite crystal growth with nanometer precision are still in their infancy. Herein, we report solution-based growth conditions leading to anisotropic epitaxial growth of 2D zeolites with rates as low as few nanometers per day. Contributions from misoriented surface nucleation and rotational intergrowths are eliminated. Growth monitoring at the single-unit-cell level reveals novel nanoscale crystal-growth phenomena associated with the lateral size and surface curvature of 2D zeolites.


New Journal of Chemistry | 2015

Effect of pretreatment temperature on the photocatalytic activity of microwave irradiated porous nanocrystalline ZnO

Tarek T. Ali; Katabathini Narasimharao; Ivan P. Parkin; Claire J. Carmalt; Sanjayan Sathasivam; Sulaiman N. Basahel; Salem M. Bawaked; Shaeel A. Al-Thabaiti

Porous nanocrystalline ZnO photocatalysts were successfully synthesized by microwave irradiation and then thermally treated at different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The physico-chemical properties of synthesized samples were determined by using different characterization techniques. The characterization results indicated that the as-synthesized sample was comprised of both ZnO and Zn(OH)2 phases with a particle size of approximately 50 nm. Thermal treatment of the as-synthesized sample at 150 °C resulted in a pure ZnO phase with a particle size of 40 nm. The results also demonstrated that the surface area, pore diameter and bandgap energy reach a maximum value for the ZnO sample treated at 200 °C. The ZnO nanoparticles pretreated at 200 °C showed the highest photocatalytic activity (99% of degradation) in a short reaction time (90 min), which can be attributed to the combined effects of several factors including low crystallite size, relatively high surface area, pore diameter, pore volume and bandgap energy. Reusability results show that the catalysts can be readily separated from the reaction mixture by filtration after the photocatalytic reaction and reused at least five times without any loss of activity.


RSC Advances | 2016

Effect of TiO2 morphology on the benzyl alcohol oxidation activity of Fe2O3–TiO2 nanomaterials

Ghada K. Alqurashi; Abdulmohsen Ali Alshehri; Katabathini Narasimharao

Three series of Fe loaded TiO2 anatase (1, 3, 5 and 7 mol% Fe) nanomaterials with different morphologies: nanoparticles (NP), nanotubes (NT) and nanofibers (NF) were synthesized and calcined at 400 °C. The physico-chemical properties of the catalysts were studied by using elemental analysis, XRD, UV-vis, N2-physisorption, SEM, TEM, XPS, pyridine adsorption using FTIR and H2-TPR techniques. It was observed that iron oxide was highly dispersed on the TiO2-NP support due to its strong interaction. The catalytic activity of the catalysts was tested in the oxidation of benzyl alcohol with hydrogen peroxide at mild reaction temperatures (70–100 °C) and atmospheric pressure. The highest activity was observed with 3 mol% Fe supported on TiO2-NP at 100 °C. It seems that TiO2-NP is unique in stabilizing small Fe2O3 nanoparticles. A greater number of surface hydroxyl groups in TiO2-NT and NF tend to increase the density of adsorption sites and/or the affinity of the surfaces with the Fe2O3 precursor. This appears to favor agglomeration, which results in a higher density of larger iron oxide particles. Fe-TiO2-NP catalysts display high activities due to a detrimental morphology effect, high surface area of the TiO2 support, dispersion of Fe2O3, more Lewis acid sites and easy reducibility of total catalysts. It was also observed that the Fe-TiO2 nanomaterials possessed two types of Fe3+ ions on the support surface; one dispersed in which Fe3+ ions interact with the TiO2 surface and another in which Fe2O3 crystals are located on the surface of the catalyst. The catalyst which possessed the former species exhibited the best performance in the oxidation of benzyl alcohol. Metal oxide leaching studies prove the true heterogeneous nature of the reaction. The catalysts are found to be reusable and resistant to rapid deactivation.


RSC Advances | 2016

Simple and efficient protocol for synthesis of pyrido[1,2-a]pyrimidin-4-one derivatives over solid heteropolyacid catalysts

Sulaiman N. Basahel; Nesreen S. Ahmed; Katabathini Narasimharao; Mohamed Mokhtar

Aluminium exchanged tungstophosphoric acid salts with Keggin structure (AlxH3−xPW12O40) were prepared by simple ion exchange method. The prepared heteropolyacid salts were characterized by various techniques such as elemental analysis, XRD, FTIR, UV-vis, N2-physisorption, NH3-TPD and FTIR-pyridine adsorption. All the prepared catalysts possess both Bronsted and Lewis acid sites, however increase of surface area and Lewis acid sites was observed with increase of Al content. The catalysts have been applied as heterogeneous catalysts to synthesize pyrido[1,2-a]pyrimidines under mild reaction conditions. A variety of biologically active pyrido[1,2-a]pyrimidines were obtained in best yields ever (above 90%) by using a simple, eco-friendly and efficient protocol catalyzed by AlxH3−xPW12O40 catalysts. Al3PW12O40 catalyst showed highest activity due to introduction of more number of Lewis acid sites to parent H3PW12O40 by complete exchange of H+ ions by Al3+ ions.


RSC Advances | 2015

Heteropolyacid generated on the surface of iron phosphate nanotubes: structure and catalytic activity studies

Ebtesam Al-Mutairi; Katabathini Narasimharao; Mohamed Mokhtar

Structural and catalytic properties of a Mo based heteropolyacid generated after impregnation of MoOx on the surface of porous iron phosphate nanotubes (FeP) were studied. Nano sized MoOx–FeP composites with different Mo molar loadings (1–5%) have been prepared under acidic conditions. Synthesized composites were characterised by elemental analysis, X-ray diffraction, transmission electron microscopy, Raman spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, acidity measurements using FTIR, N2-physisorption and H2-temperature programmed reduction methods. Spectroscopic characterization results suggest that Keggin-type FeMoP species were formed on the surface of the iron phosphate nanotubes in the case of catalysts with higher (4 and 5 mol%) Mo loadings. Pure iron phosphate nanotubes, Fe2O3, MoO3 and bulk FeMoP HPA samples are less active than MoOx–FeP composite samples for the benzylation of benzene with benzyl chloride, particularly the 5 mol% Mo loaded catalyst showed high activity. The enhanced catalytic activity of this catalyst is attributed to the presence of easily reducible, acidic and porous FeMoP heteropolyacid species. These materials can be readily separated from the reaction system for reuse. They are resistant to leaching of the active heteropolyacid species.

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Mohamed Mokhtar

King Abdulaziz University

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Tarek T. Ali

King Abdulaziz University

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Meera Shete

University of Minnesota

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