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164 results on '"Sugunan, Sankaran"'

26. Z-scheme mechanism for methylene blue degradation over Fe2O3/g-C3N4 nanocomposite prepared via one-pot exfoliation and magnetization of g-C3N4.

Author

Mullakkattuthodi, Shemeena, Haridas, Vijayasree, Sugunan, Sankaran, and Narayanan, Binitha N.

Abstract

The low surface area, high recombination rate of photogenerated charge carriers, narrow visible range activity, and difficulty in the separation from cleaned solutions limit the wide application of g-C3N4 as a photocatalyst. Herein, we have succeeded in developing a one-pot strategy to overcome the above-mentioned difficulties of g-C3N4. The broadening of the visible-light response range and inducing magnetic nature to g-C3N4 was succeeded by preparing a nanocomposite with Fe2O3 via a facile solvothermal method. The preparation method additionally imparted layer exfoliation of g-C3N4 as evident from the XRD patterns and TEM images. The strong interaction between the components is revealed from the XPS analysis. The broadened visible-light absorbance of Fe2O3/g-C3N4 with a Z-scheme photocatalytic degradation mechanism is well evident from the UV—Vis DRS analysis and PL measurement of the composite with terephthalic acid. The active species of photocatalysis were further investigated using scavenging studies in methylene blue degradation that revealed hydroxyl radicals and holes as the major contributors to the activity of Fe2O3/g-C3N4. [ABSTRACT FROM AUTHOR]

Published
2022
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29. Novel rice husk ash - reduced graphene oxide nanocomposite catalysts for solvent free Biginelli reaction with a statistical approach for the optimization of reaction parameters

Author

Sugunan Sankaran, Binitha N. Narayanan, and Divya P. Narayanan

Subjects
Nanocomposite, Materials science, Graphene, Biginelli reaction, Oxide, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Husk, 0104 chemical sciences, law.invention, Catalysis, chemistry.chemical_compound, chemistry, Chemical engineering, law, General Materials Science, Fourier transform infrared spectroscopy, 0210 nano-technology, Dispersion (chemistry)
Abstract

Here we report the preparation of novel rice husk ash – reduced graphene oxide nanocomposites and their catalytic application in Biginelli reaction. Hydrothermal treatment is given to a mixture of rice husk ash and graphene oxide for the formation of a uniform composite. XRD and FTIR spectral analyses confirmed the partial reduction of graphene oxide in the nanocomposites during hydrothermal treatment. The binding between rice husk silica particles and graphene sheets through Si O C bonding is revealed from XPS analysis. Graphene is found to be less defective in nature in the composite as evident from the reduced ID/IG value in the Raman spectrum. SEM and TEM images showed the effective dispersion of rice husk SiO2 particles on the wrinkled graphene layers. Present study also exploited the use of a statistical model, response surface methodology, for the optimization of reaction parameters on the catalytic synthesis of dihydropyrimidinones via multicomponent solvent free Biginelli reaction. The cost effective highly efficient rice husk ash - reduced graphene oxide catalyst is found to be reusable till 7 repeated cycles with only about 4% reduction of its initial activity.

Published
2019
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32. Functionalized carbon dot adorned coconut shell char derived green catalysts for the rapid synthesis of amidoalkyl naphthols

Author

Binitha N. Narayanan, Sudha Kochiyil Cherikallinmel, Divya P. Narayanan, and Sugunan Sankaran

Subjects
010405 organic chemistry, Chemistry, One-pot synthesis, chemistry.chemical_element, 010402 general chemistry, Heterogeneous catalysis, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Catalysis, Biomaterials, Colloid and Surface Chemistry, Yield (chemistry), Char, Fourier transform infrared spectroscopy, High-resolution transmission electron microscopy, Carbon, Nuclear chemistry
Abstract

A one pot synthesis of carbon dot incorporated porous coconut shell char derived sulphonated catalyst is reported here for the first time and is effectively used in the multicomponent synthesis of amidoalkyl naphthol. Macroporous nature of the char is revealed from scanning electron microscopic (SEM) analysis, whereas the dispersion of carbon dots (CDs) on the porous coconut shell char is confirmed from the high resolution transmission electron microscopic (HRTEM) analysis. Fluorescence emission spectrum further confirmed the presence of CDs in the catalyst. Fourier-transform infrared (FTIR) spectral analysis of the materials indicated that sulphonation occurred both to the CD and to the porous char. X-ray photo electron spectroscopic (XPS) analysis of the most active catalyst confirmed the presence of both sulphonic acid and carboxylic acid groups in the catalyst. The coconut shell char derived materials prepared by varying the amount of H2SO4 are successfully utilized as efficient alternative green catalysts for the multicomponent reaction, where excellent activity in amidoalkyl naphthol synthesis is obtained within short periods under solvent free reaction conditions. A maximum yield of 98% is obtained in the synthesis of N-[Phenyl-(2-hydroxy-naphthalen-1-yl)-methyl]-benzamide, the representative amidoalkyl naphthol, with the best catalyst within 3 min of reaction. The catalyst is highly active for the reactions carried out with varieties of aldehydes and amides with a product yield in the range of 88–98%. The best catalyst system retained more than 90% of its initial activity even upto 6th repeated run.

Published
2018
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49. Novel cost-effective synthesis of non-doped turbostratic graphene from a graphite intercalation compound: development of a durable and stable electrocatalyst for the oxygen reduction reaction.

Author

Haridas, Vijayasree, Yaakob, Zahira, Sugunan, Sankaran, and Narayanan, Binitha N.

Subjects
GRAPHITE intercalation compounds, OXYGEN reduction, CHEMICAL vapor deposition, GRAPHENE, EPITAXY, DIFFRACTION patterns, GRAPHITE, GRAPHITE oxide
Abstract

Expensive and high-temperature methods like chemical vapour deposition and epitaxial growth are mainly investigated for turbostratic graphene preparation, whereas cost-effective production by a top-down approach from graphite is presented here. Interlayer catalytic exfoliation of randomly oriented Fe2O3 intercalated graphite sheets with H2O2 resulted in turbostratic graphene. The retained Fe species on the sheets are further removed by acid treatment. The formation of turbostratic graphene is evident from the Moiré fringes in the transmission electron microscopic images and the multiplicity of spots in the selected area electron diffraction patterns. The development of cost-effective, durable electrocatalysts for the oxygen reduction reaction (ORR) is vital due to the high cost and poor methanol tolerance of commercial Pt/C. Here, non-doped turbostratic graphene layers have been effectively used for the ORR. Due to the excellent electronic properties of suspended graphene together with the robustness of few-layer graphene, the prepared turbostratic graphene shows promising ORR activity, satisfactory cyclic stability, a positive onset potential, and a reasonably good half-wave potential. The absence of metal in the catalyst results in superior methanol tolerance in comparison with Pt/C. The current density is higher than the commercial 20 wt% Pt/C catalyst and most of the reported graphene-based systems. [ABSTRACT FROM AUTHOR]

Published
2021
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