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Hareendran C, Ravindranathan S, Ajithkumar TG. Correction to "Insights into the Structure of Sucralfate by Advanced Solid- and Liquid-State NMR". Mol Pharm 2024; 21:2059. [PMID: 38468537 DOI: 10.1021/acs.molpharmaceut.4c00201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
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Hareendran C, Ravindranathan S, Ajithkumar TG. Insights into the Structure of Sucralfate by Advanced Solid- and Liquid-State NMR. Mol Pharm 2024; 21:1390-1401. [PMID: 38329458 DOI: 10.1021/acs.molpharmaceut.3c01042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Sucralfate, which is a sucrose octasulfate aluminum complex, is an active pharmaceutical ingredient (API) falling in the category of cytoprotective agents which are very effective for gastric and duodenal ulcers. On interaction with stomach acid, it ionizes into aluminum and sucrose octasulfate ions to form a protective layer over the ulcerated region inhibiting further attack from acid. The mechanism of action of sucralfate in the context of its structure is not well understood. Considering that at least two forms of this API are available in the market, there are no reports on the various forms of sucralfate and differences in their pharmacological action. We characterized the two forms of sucralfate using multinuclear, multidimensional solid-state NMR, and the results show significant structural differences between them arising from variation in the aluminum environment and the level of hydration. The impact of structural differences on pharmacological action was examined by studying acid-induced Al release by 27Al liquid-state NMR. The sucralfate, European pharmaceutical standard, Form I, undergoes faster disruption in acid compared to Form II. The difference is explained on the basis of structural differences in the two forms which gives significant insights into the action of sucralfate in relation to its structure.
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Affiliation(s)
- Chaithanya Hareendran
- Central NMR Facility and Physical and Materials Chemistry Division, CSIR National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Sapna Ravindranathan
- Central NMR Facility and Physical and Materials Chemistry Division, CSIR National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - T G Ajithkumar
- Central NMR Facility and Physical and Materials Chemistry Division, CSIR National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Hareendran C, Alsirawan B, Paradkar A, Ajithkumar TG. In Situ Monitoring of Competitive Coformer Exchange Reaction by 1H MAS Solid-State NMR. Mol Pharm 2024; 21:1479-1489. [PMID: 38373877 DOI: 10.1021/acs.molpharmaceut.3c01118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
In a competitive coformer exchange reaction, a recent topic of interest in pharmaceutical research, the coformer in a pharmaceutical cocrystal is exchanged with another coformer that is expected to form a cocrystal that is more stable. There will be a competition between coformers to form the most stable product through the formation of hydrogen bonds. This will cause destabilization of the pharmaceutical products during processing or storage. Therefore, it is important to develop a mechanistic understanding of this transformation by monitoring each and every step of the reaction, employing a technique such as 1H nuclear magnetic resonance (NMR). In this study, an in situ monitoring of a coformer exchange reaction is carried out by 1H magic angle spinning (MAS) solid-state NMR (SSNMR) at a spinning frequency of 60 kHz. The changes in caffeine maleic acid cocrystals on addition of glutaric acid and caffeine glutaric cocrystals on addition of maleic acid were monitored. In all of the reactions, it has been observed that caffeine glutaric acid Form I is formed. When glutaric acid was added to 2:1 caffeine maleic acid, the formation of metastable 1:1 caffeine glutaric acid Form I was observed at the start of the experiment, indicating that the centrifugal pressure is enough for the formation. The difference in the end product of the reactions with a similar reaction pathway of 1:1 and 2:1 reactant stoichiometry indicates that a complete replacement of maleic acid has occurred only in the 1:1 stoichiometry of the reactants. The polymorphic transition of caffeine glutaric acid Form II to Form I at higher temperatures was a crucial reason that triggered the exchange of glutaric acid with maleic acid in the reaction of caffeine glutaric acid and maleic acid. Our results are novel since the new reaction pathways in competitive coformer exchange reactions enabled understanding the remarkable role of stoichiometry, polymorphism, temperature, and centrifugal pressure.
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Affiliation(s)
- Chaithanya Hareendran
- Central NMR Facility, and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Bashir Alsirawan
- Centre for Pharmaceutical Engineering Science, School of Pharmacy and Medical Sciences, University of Bradford, Bradford BD7 1DP, United Kingdom
| | - Anant Paradkar
- Centre for Pharmaceutical Engineering Science, School of Pharmacy and Medical Sciences, University of Bradford, Bradford BD7 1DP, United Kingdom
| | - T G Ajithkumar
- Central NMR Facility, and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Hareendran C, Shaligram PS, Gonnade R, Ajithkumar TG. A solid-state NMR method for characterization of pharmaceutical eutectics. Phys Chem Chem Phys 2024; 26:3800-3803. [PMID: 38240042 DOI: 10.1039/d3cp05615e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Pharmaceutical eutectics are extremely useful for designing formulations, and currently, there are no techniques other than differential scanning calorimetry (DSC) that can confirm their formation. In this study, we demonstrate that 1H fast magic angle spinning (MAS) solid-state NMR (SSNMR) experiments can confirm the formation of eutectics by detecting their intermolecular hydrogen bonding interactions.
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Affiliation(s)
- Chaithanya Hareendran
- Central NMR facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Parth S Shaligram
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - Rajesh Gonnade
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - T G Ajithkumar
- Central NMR facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Illath K, Ojha PK, Rath SK, Ajithkumar TG. An investigation of Al 2O 3 induced variations in the structural parameters in strontium borosilicate glasses using solid state NMR. Phys Chem Chem Phys 2023; 25:13550-13559. [PMID: 37133361 DOI: 10.1039/d3cp00751k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The physical properties of oxide glasses are crucially dependent on the atomistic structural speciation. In this study, we investigate the variation in the local ordering in the glass network of strontium borosilicate glasses (34.82 SrO, 51.84 B2O3, 13.34 SiO2 in mol%) with a progressive substitution of B2O3 by Al2O3 and estimate the structural parameters: the oxygen packing fraction, and the average network coordination number. The coordination of the network forming cations at various glass compositions is determined using 11B, 27Al, and 29Si solid-state nuclear magnetic resonance (SSNMR). The SSNMR reveals that at the higher substitution of B2O3 by Al2O3 in the glass composition, the coordination network of Al3+ exists predominantly in the 4 coordinated state, the network forming B3+ cations transform from a tetrahedral BO4 to a trigonal BO3 structure, and the Q4 form of silicates is dominant. The average coordination number and the oxygen packing fraction were calculated using the parameters obtained from the SSNMR results, and it is observed that the average coordination number decreases, and the oxygen packing fraction increases on incorporating Al. It is interesting to note that some of the thermophysical properties of these compositions closely follow the pattern shown by the average coordination number and the oxygen packing fraction.
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Affiliation(s)
- Kavya Illath
- Central NMR Facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, Maharashtra, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Prasanta K Ojha
- Naval Materials Research Laboratory, Ambernath, Thane 421506, Maharashtra, India
| | - Sangram K Rath
- Naval Materials Research Laboratory, Ambernath, Thane 421506, Maharashtra, India
| | - T G Ajithkumar
- Central NMR Facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, Maharashtra, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Neenu KV, Midhun Dominic CD, Begum PMS, Parameswaranpillai J, Kanoth BP, David DA, Sajadi SM, Dhanyasree P, Ajithkumar TG, Badawi M. Effect of oxalic acid and sulphuric acid hydrolysis on the preparation and properties of pineapple pomace derived cellulose nanofibers and nanopapers. Int J Biol Macromol 2022; 209:1745-1759. [PMID: 35469954 DOI: 10.1016/j.ijbiomac.2022.04.138] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/18/2022] [Accepted: 04/18/2022] [Indexed: 01/09/2023]
Abstract
Nanocellulose is the "green magnet" which attracts a wide spectrum of industries towards it due to its availability, biodegradability, and possible smart applications. For the first time, pineapple pomace was being explored as an economic precursor for cellulose nanofibers. Nanofiber isolation was accomplished using a chemo-mechanical method and solution casting was adopted for the development of nanopapers. Moreover, the study examines the structural, optical, crystalline, dimensional, and thermal features of nanofibers isolated using different acid hydrolysis (oxalic acid and sulphuric acid) methods. Fourier-transform infra-red spectroscopy, 13C solid-state nuclear magnetic resonance spectroscopy, and X-ray diffraction analysis indicated the presence of type I cellulose. The transmittance, crystallinity index, and thermal stability of PPNFS (sulphuric acid treated fiber) were greater than PPNFO (oxalic acid treated fiber). The transmission electron microscopy and dynamic light scattering analysis confirmed the nanodimension of PPNFO and PPNFS. While comparing the optical and mechanical properties of nanopapers, PPNFS outperforms PPNFO. The tensile strength of the prepared nanopapers (64 MPa (PPNFO) and 68 MPa (PPNFS)) was found to be high compared to similar works reported in the literature. The prepared nanopaper is proposed to be used for food packaging applications.
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Affiliation(s)
- K V Neenu
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin 682022, India
| | - C D Midhun Dominic
- Department of Chemistry, Sacred Heart College (Autonomous), Kochi, Kerala Pin-682013, India.
| | - P M Sabura Begum
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin 682022, India,.
| | - Jyotishkumar Parameswaranpillai
- Department of Science, Faculty of Science & Technology, Alliance University, Chandapura-Anekal Main Road, Bengaluru 562106, Karnataka, India
| | - Bipinbal Parambath Kanoth
- Department of Polymer Science and Rubber Technology, Cochin University of Science and Technology (CUSAT), Kerala Pin-682022, India
| | - Deepthi Anna David
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin 682022, India
| | - S Mohammad Sajadi
- Department of Nutrition, Cihan University-Erbil, Kurdistan Region, Iraq; Department of Phytochemistry, SRC, Soran University, KRG, Iraq
| | - P Dhanyasree
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin 682022, India
| | - T G Ajithkumar
- Central NMR Facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune Pin-411008, India
| | - Michael Badawi
- Laboratoire de Physique et Chimie Théoriques UMR CNRS 7019, Université de Lorraine, Nancy, France
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Midhun Dominic CD, Raj V, Neenu KV, Begum PMS, Formela K, Prabhu DD, Poornima Vijayan P, Ajithkumar TG, Parameswaranpillai J, Saeb MR. Chlorine-free extraction and structural characterization of cellulose nanofibers from waste husk of millet (Pennisetum glaucum). Int J Biol Macromol 2022; 206:92-104. [PMID: 35217088 DOI: 10.1016/j.ijbiomac.2022.02.078] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 12/29/2021] [Accepted: 02/13/2022] [Indexed: 11/05/2022]
Abstract
This study aims to extract cellulose nanofibers (CNFs) from a sustainable source, millet husk, which is considered as an agro-waste worthy of consideration. Pre-treatments such as mercerisation, steam explosion, and peroxide bleaching (chlorine-free) were applied for the removal of non-cellulosic components. The bleached millet husk pulp was subjected to acid hydrolysis (5% oxalic acid) followed by homogenization to extract CNFs. The extracted CNFs were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), Energy Dispersive X-ray Spectroscopy (EDX), Thermogravimetry (TG and DTG), Differential scanning calorimetry (DSC), and Solid state 13C nuclear magnetic resonance spectroscopy (solid state 13C NMR). The isolated CNFs show a typical cellulose type-I structure with a diameter of 10-12 nm and a crystallinity index of 58.5%. The appearance of the specific peak at 89.31 ppm in the solid state 13C NMR spectra validates the existence of the type-I cellulose phase in the prepared CNFs. The prepared CNFs had a maximum degradation temperature (Tmax) of 341 °C, that was 31 °C greater than raw millet husk (RMH). The outcome of the study implies that the nanofibers are prominent alternatives for synthetic fibers for assorted potential applications, especially in manufacturing green composites.
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Affiliation(s)
- C D Midhun Dominic
- Department of Chemistry, Sacred Heart College (Autonomous), Kochi, Pin-682013, Kerala, India.
| | - Vandita Raj
- Department of Chemistry, Sacred Heart College (Autonomous), Kochi, Pin-682013, Kerala, India; Department of Chemistry, PSGR Krishnammal College for Women, Peelamedu, Coimbatore Pin-641004, Tamil Nadu, India
| | - K V Neenu
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin-682022, India
| | - P M Sabura Begum
- Department of Applied Chemistry, Cochin University of Science and Technology (CUSAT), Kerala Pin-682022, India
| | - Krzysztof Formela
- Department of Polymer Technology, Faculty of Chemistry, Gdańsk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gdańsk, Poland
| | - Deepak D Prabhu
- Department of Chemistry, Sacred Heart College (Autonomous), Kochi, Pin-682013, Kerala, India
| | - P Poornima Vijayan
- Department of Chemistry, Sree Narayana College for Women, Kollam Pin-691001, Kerala, India
| | - T G Ajithkumar
- Central NMR Facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune Pin-411008, India
| | - Jyotishkumar Parameswaranpillai
- School of Biosciences, Mar Athanasios College for Advanced Studies Tiruvalla (MACFAST), Pathanamthitta, Kerala Pin-689101, India
| | - Mohammad Reza Saeb
- Department of Polymer Technology, Faculty of Chemistry, Gdańsk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gdańsk, Poland
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Tomar D, Lodagekar A, Gunnam A, Allu S, Chavan RB, Tharkar M, Ajithkumar TG, Nangia AK, Shastri NR. The effects of cis and trans butenedioic acid on the physicochemical behavior of lumefantrine. CrystEngComm 2022. [DOI: 10.1039/d0ce01709d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A study of the differences in the effects of cis (maleic acid) and trans (fumaric acid) isomers of butenedioic acid on the crystallinity, amorphous nature, and pharmaceutical behaviour of the antimalarial drug lumefantrine is provided.
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Affiliation(s)
- Devendrasingh Tomar
- Solid-State Pharmaceutical Research Group (SSPRG), Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad, 500 037, India
| | - Anurag Lodagekar
- Solid-State Pharmaceutical Research Group (SSPRG), Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad, 500 037, India
| | - Anilkumar Gunnam
- School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli Central University P.O., Hyderabad 500 046, India
| | - Suryanarayana Allu
- School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli Central University P.O., Hyderabad 500 046, India
| | - Rahul B. Chavan
- Solid-State Pharmaceutical Research Group (SSPRG), Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad, 500 037, India
| | - Minakshi Tharkar
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
| | - T. G. Ajithkumar
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
| | - Ashwini K. Nangia
- School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli Central University P.O., Hyderabad 500 046, India
- CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India
| | - Nalini R. Shastri
- Solid-State Pharmaceutical Research Group (SSPRG), Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad, 500 037, India
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Ajithkumar TG, Mathew L, Sunilkumar KN, Rajagopal R, Alfarhan A, Ock Kim Y, Kim H, Kim HJ. In vitro assessment of anti-inflammatory and anti-arthritic effects of Helicanthes elasticus (Desv.) Danser accessions collected from six different hosts. Saudi J Biol Sci 2020; 27:3301-3306. [PMID: 33304135 PMCID: PMC7715451 DOI: 10.1016/j.sjbs.2020.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 09/30/2020] [Accepted: 10/05/2020] [Indexed: 11/30/2022] Open
Affiliation(s)
- T G Ajithkumar
- Department of Botany, KKTM Government College, Kodungallur, Thrissur, Kerala, India
| | - Lizzy Mathew
- Department of Botany, St.Teresa's College (Autonomous), Ernakulam, Kerala, India
| | - K N Sunilkumar
- Siddha Central Research Institute (CCRS), Arignar Anna Govt. Hospital Campus, Arumbakkam, Chennai, India
| | - Rajakrishnan Rajagopal
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Ahmed Alfarhan
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Young Ock Kim
- Department of Clinical Pharmacology, College of Medicine, Soonchunhyang University, Cheonan, Republic of Korea
| | - Hyungsuk Kim
- Department of Rehabilitation Medicine of Korean Medicine, College of Korean Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Hak-Jae Kim
- Department of Clinical Pharmacology, College of Medicine, Soonchunhyang University, Cheonan, Republic of Korea
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Soni Y, Kavya I, Ajithkumar TG, Vinod CP. Correction: One pot ligand exchange method for a highly stable Au-SBA-15 catalyst and its room temperature CO oxidation. Chem Commun (Camb) 2018; 54:12892. [PMID: 30394461 DOI: 10.1039/c8cc90494d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Correction for 'One pot ligand exchange method for a highly stable Au-SBA-15 catalyst and its room temperature CO oxidation' by Yogita Soni et al., Chem. Commun., 2018, DOI: 10.1039/c8cc06887a.
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Affiliation(s)
- Yogita Soni
- Catalysis and Inorganic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India.
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Soni Y, Kavya I, Ajithkumar TG, Vinod CP. One pot ligand exchange method for a highly stable Au-SBA-15 catalyst and its room temperature CO oxidation. Chem Commun (Camb) 2018; 54:12412-12415. [PMID: 30307460 DOI: 10.1039/c8cc06887a] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A modified deposition precipitation (DP) method has been developed to address a fundamental issue of supporting well dispersed Au nanoparticles on silica. Ammonium chloride (NH4Cl) plays an important role in in situ modifying the gold precursor (HAuCl4·3H2O) solution allowing facile deposition of gold NPs in the channels of SBA-15. The Au-SBA-15 catalyst (2.8 wt%) synthesized by this procedure showed 100% conversion for CO oxidation at room temperature with excellent stability at room temperature and high temperature.
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Affiliation(s)
- Yogita Soni
- Catalysis and Inorganic Chemistry Division, Anusandhan Bhavan, 2 Rafi Marg, New Delhi 110001, India.
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Durgalakshmi D, Ajay Rakkesh R, Kesavan M, Ganapathy S, Ajithkumar TG, Karthikeyan S, Balakumar S. Highly reactive crystalline-phase-embedded strontium-bioactive nanorods for multimodal bioactive applications. Biomater Sci 2018; 6:1764-1776. [PMID: 29808842 DOI: 10.1039/c8bm00362a] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the present work, a crystallization-induced strontium-bioactive material, with a composition similar to Bioglass 45S5 system, was obtained using a sol-gel-assisted microwave method with nanorod morphologies of 30-80 nm in size. The effect of crystallization induced in the glass network, and its influence on the bioactivity and mechanical properties of bone and dentin regeneration, were the main novel findings of this work. Rietveld analysis of X-ray diffraction spectra showed the best fit with sodium (combeite, Na2Ca2Si3O9) and calcium (clinophosinaite, Ca2Na6O14P2Si2; calcium strontium silicate, Ca1.5O4SiSr0.5; and calcium carbonate, CaCO3) enriched crystal systems. Multinuclear solid-state NMR studies provided detailed atomistic insight into the presence of crystalline mineral phases in the bioactive material. The dentin matrix and antibacterial studies showed good results for 5% strontium-substituted calcium compared with basic 45S5 composition due to its smaller particle size (30 nm), which suggested applications to dentin regeneration. Simulation studies have been demonstrated with clinophosinaite crystal data from the XRD spectra, with the glycoprotein salivary metabolites also showing that 5% strontium-substituted calcium has a higher binding affinity for the salivary compound, which is suitable for dentin regeneration applications. In vitro apatite formation studies showed that this material is suitable for bone regeneration applications.
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Affiliation(s)
- D Durgalakshmi
- National Centre for Nanoscience and Nanotechnology, University of Madras, Chennai, India.
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Mandal AK, Mandal B, Illath K, Ajithkumar TG, Halder A, Sinha PK, Sen R. Preparation of colourless phosphate glass by stabilising higher Fe[II] in microwave heating. Sci Rep 2018; 8:6195. [PMID: 29670133 PMCID: PMC5906578 DOI: 10.1038/s41598-018-24287-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 03/29/2018] [Indexed: 11/09/2022] Open
Abstract
Iron impurity in raw material remains a major challenge in producing colourless glass. In this investigation, we report microwave (MW) heating capable of altering Fe-redox ratio (Fe2+/∑Fe) enabling preparation of colourless phosphate glass. The effect of Sn concentration in retention of Fe[II] in glass melted in MW was compared with conventional glasses. Colourimetric study developing Fe2+-ferrozine colour complex reveals Fe-redox ratio ≥0.49 required to obtain colourless phosphate glass. In microwave heating, addition of 1 wt.% Sn metal powder can impart the desired effect whereas addition of 1.9 wt.% Sn metal powder is required in conventional heating. The correlation equation of Fe-redox ratio with concentration of Sn metal is found to be different in microwave and conventional heating. Thus, exploiting this different redox changes in MW heating optical properties can be tailored. Preservation of higher Fe[II] in MW melted glass is also confirmed by XPS and TGA. 31P MAS NMR spectra suggest that transition from cross linked ultra phosphate to linear polymer metaphosphate network in incorporation of Sn is found different in glass prepared adopting microwave irradiation. 27A1 MAS NMR spectra suggest higher relative content of Al6+ in glass obtained from MW heating. Energy consumption analysis revels 3.4 kWh in MW heating while 14 kWh in conventional glass melting using resistance heating. Further, glass melting in MW can be completed within 2 h unlike ~5 h needed in conventional. MW heating plays a significant role in improving properties to make colourless phosphate glass in addition to significant energy and time saving.
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Affiliation(s)
- Ashis K Mandal
- CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata, - 700032, India.
| | - B Mandal
- CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata, - 700032, India
| | - Kavya Illath
- Central NMR Facility and Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr.Homi Bhabha Road, Pune, - 411008, India
| | - T G Ajithkumar
- Central NMR Facility and Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr.Homi Bhabha Road, Pune, - 411008, India
| | - A Halder
- CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata, - 700032, India
| | - P K Sinha
- CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata, - 700032, India
| | - Ranjan Sen
- CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata, - 700032, India
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Veena VS, Illath K, Lazar A, Vinod CP, Ajithkumar TG, Jayanthi S. Distribution of water in the pores of periodic mesoporous organosilicates – a proton solid state MAS NMR study. Phys Chem Chem Phys 2018; 20:29351-29361. [DOI: 10.1039/c8cp04902e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Proposed model of water layers and pore filling in ethane substituted periodic mesoporous organosilicates (PMOE) based on analysis of solid state magic angle spinning (MAS) proton NMR spectra.
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Affiliation(s)
- V. S. Veena
- Department of Physics
- Indian Institute of Space Science and Technology
- Thiruvananthapuram 695 547
- India
| | - Kavya Illath
- Central NMR Facility and Physical and Materials Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - Anish Lazar
- Catalysis and Inorganic Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - C. P. Vinod
- Catalysis and Inorganic Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - T. G. Ajithkumar
- Central NMR Facility and Physical and Materials Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - S. Jayanthi
- Department of Physics
- Indian Institute of Space Science and Technology
- Thiruvananthapuram 695 547
- India
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15
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Allu AR, Balaji S, Illath K, Hareendran C, Ajithkumar TG, Biswas K, Annapurna K. Structural elucidation of NASICON (Na3Al2P3O12) based glass electrolyte materials: effective influence of boron and gallium. RSC Adv 2018; 8:14422-14433. [PMID: 35540738 PMCID: PMC9079908 DOI: 10.1039/c8ra01676c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/04/2018] [Indexed: 11/21/2022] Open
Abstract
Understanding the conductivity variations induced by compositional changes in sodium super ionic conducting (NASICON) glass materials is highly relevant for applications such as solid electrolytes for sodium (Na) ion batteries.
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Affiliation(s)
- Amarnath R. Allu
- Glass Division
- CSIR-Central Glass and Ceramic Research Institute
- Kolkata
- India
| | - Sathravada Balaji
- Glass Division
- CSIR-Central Glass and Ceramic Research Institute
- Kolkata
- India
| | - Kavya Illath
- Central NMR Facility and Physical and Materials Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - Chaithanya Hareendran
- Central NMR Facility and Physical and Materials Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - T. G. Ajithkumar
- Central NMR Facility and Physical and Materials Chemistry Division
- CSIR-National Chemical Laboratory
- Pune
- India
| | - Kaushik Biswas
- Glass Division
- CSIR-Central Glass and Ceramic Research Institute
- Kolkata
- India
| | - K. Annapurna
- Glass Division
- CSIR-Central Glass and Ceramic Research Institute
- Kolkata
- India
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16
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Dinesh Shrivastava S, Mathai Eldho K, Rajamohanan PR, Ajithkumar TG, Vanka K, Kumaraswamy G. Molecular motifs for additives that retard PEO crystallization. POLYM ENG SCI 2016. [DOI: 10.1002/pen.24462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Sudhakar Dinesh Shrivastava
- Polymer Science and Engineering, Complex Fluids and Polymer Engineering, CSIR-National Chemical Laboratory; Pune 411008 Maharashtra, India
| | | | - P. R. Rajamohanan
- CSIR-National Chemical Laboratory; NMR Facility; Pune 411008 Maharashtra, India
| | - T. G. Ajithkumar
- CSIR-National Chemical Laboratory; NMR Facility; Pune 411008 Maharashtra, India
| | - Kumar Vanka
- Physical Chemistry Division; CSIR-National Chemical Laboratory; Pune 411008 Maharashtra, India
| | - Guruswamy Kumaraswamy
- Polymer Science and Engineering, Complex Fluids and Polymer Engineering, CSIR-National Chemical Laboratory; Pune 411008 Maharashtra, India
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17
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Eldho KM, Rajamohanan PR, Anto R, Bulakh N, Lele AK, Ajithkumar TG. Insights into the Molecular Dynamics in Polysulfone Polymers from 13C Solid-State NMR Experiments. J Phys Chem B 2015; 119:11287-94. [DOI: 10.1021/acs.jpcb.5b03103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kavalakal Mathai Eldho
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
| | - P. R. Rajamohanan
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
| | - Ralf Anto
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
| | - Neelima Bulakh
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
| | - Ashish K. Lele
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
| | - T. G. Ajithkumar
- Central NMR Facility and ‡Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411 008, India
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18
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Gnanakumar ES, Rao Chokkapu E, Kunjir S, Ajithkumar TG, Rajamohanan PR, Chakraborty D, Gopinath CS. 9-fluorenemethanol: an internal electron donor to fine tune olefin polymerization activity. Dalton Trans 2014; 43:9143-51. [PMID: 24810354 DOI: 10.1039/c4dt00793j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A new MgCl2 based molecular adduct has been synthesized with 9-fluorenemethanol (9FM) as a novel internal electron donor (IED), along with ethanol (EtOH) (MgCl2·n9FM·xEtOH). The above molecular adduct has been subjected to a variety of structural, spectroscopic and morphological characterization techniques. The results of the solid state (13)C CPMAS NMR technique suggests the coordination of 9FM to MgCl2. Observation of a low angle diffraction peak at 2θ = 5.7° (d = 15.5 Å) underscores the coordination of 9FM along the z-axis, and ethanol in the molecular adduct. Active Ziegler-Natta catalysts were prepared by two different synthesis methods; the conventional method to obtain a high surface area active catalyst, and other one with 9FM as an integral part of the active catalyst in order to study the influence of 9FM as an IED over the active sites. The active catalysts were also characterized thoroughly with different analytical tools. The XRD results show (003) facets of δ-MgCl2 (α-MgCl2) for the conventional (non-conventional) titanated catalyst. Results of the ethylene polymerization activity study reveals that the conventionally prepared highly porous active catalyst shows 1.7-2.5 times higher activity than the non-conventional prepared catalyst; however, the latter shows a low molecular weight distribution and confirms the role of the Lewis base as an IED.
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Affiliation(s)
- Edwin S Gnanakumar
- Catalysis Division, CSIR-National Chemical Laboratory, Dr Homi Bhabha Road, Pune, 411-008, India.
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19
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Thushara KS, Ajithkumar TG, Rajamohanan PR, Gopinath CS. Solid-State NMR investigations of a MgCl2·4(CH3)2CHCH2OH molecular adduct: a peculiar case of reversible equilibrium between two phases. J Phys Chem A 2014; 118:1213-9. [PMID: 24476423 DOI: 10.1021/jp412331s] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
MgCl2·xROH molecular adducts are extensively employed as a support material for Ziegler-Natta polyolefin catalysis. However, their structural properties are not well understood. Recently, we reported on the preparation of an isobutanol adduct, MgCl2·4(CH3)2CHCH2OH (MgiBuOH) ( Dalton Trans. 2012 , 41 , 11311 ), which is very sensitive to the preparation conditions, such as the temperature and refluxing time. For the present study, the structural properties of MgiBuOH adducts prepared under different conditions have been investigated thoroughly by solid-state NMR and nonambient XRD. Formation of two phases has been confirmed, and in situ variable temperature solid-state NMR measurements confirm the coexistence of two phases as well as the oscillation from one to another phase. It is expected that such molecular adducts could have a significant role in organic transformation reactions due to an oscillating structural component. An understanding of phase oscillation with the Mg(2+) ion as the central metal ion might shed some light toward understanding various biological and structural functions.
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Affiliation(s)
- K S Thushara
- Catalysis Division, §Central NMR Facility, and ⊥Centre of Excellence on Surface Science, National Chemical Laboratory , Dr. Homi Bhabha Road, Pune 411 008, India
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20
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Narendranath SB, Yadav AK, Ajithkumar TG, Bhattacharyya D, Jha SN, Dey KK, Raja T, Devi RN. Investigations into variations in local cationic environment in layered oxide series InGaO3(ZnO)m (m = 1-4). Dalton Trans 2014; 43:2120-6. [PMID: 24280831 DOI: 10.1039/c3dt52011k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Layered oxides of the series InGaO3(ZnO)m (m = 1-4) are interesting due to their structural anisotropy. Here, we report a comprehensive study of their structural details, focusing on the local cationic environment in bulk powder samples by MASNMR and EXAFS, which is hitherto not attempted. It is found that the Ga geometry varies gradually from pure pentacoordinated to a mixture of penta and tetracoordinated with increasing amounts of tetracoordination as we move across the series, contrary to previous reports suggesting exclusively trigonal bipyramidal coordination in all the compounds. A similar observation is also made in the case of Zn and structural evolution involving the dissolution of Ga in a ZnO4 tetrahedral network in a sandwich layer can be discerned, as the insulating ZnO layer size increases.
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Affiliation(s)
- Soumya B Narendranath
- Catalysis and Inorganic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
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21
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Gnanakumar ES, Gowda RR, Kunjir S, Ajithkumar TG, Rajamohanan PR, Chakraborty D, Gopinath CS. MgCl2·6CH3OH: A Simple Molecular Adduct and Its Influence As a Porous Support for Olefin Polymerization. ACS Catal 2013. [DOI: 10.1021/cs300730j] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
| | - Ravikumar R. Gowda
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai 600
036, India
| | | | | | | | - Debashis Chakraborty
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai 600
036, India
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22
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Kumaraswamy G, Surve NS, Mathew R, Rana A, Jha SK, Bulakh NN, Nisal AA, Ajithkumar TG, Rajamohanan PR, Ratnagiri R. Lamellar Melting, Not Crystal Motion, Results in Softening of Polyoxymethylene on Heating. Macromolecules 2012. [DOI: 10.1021/ma3004423] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guruswamy Kumaraswamy
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Nikita S. Surve
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Renny Mathew
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Abhimanyu Rana
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Saroj K. Jha
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Neelima N. Bulakh
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Anuya A. Nisal
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - T. G. Ajithkumar
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - P. R. Rajamohanan
- Polymer
Science and Engineering Division, ‡Central NMR Facility, and §Physical Chemistry Division, National Chemical Laboratory, Pune 411008,
India
| | - Ram Ratnagiri
- Engineering
Polymers, E.I. DuPont de Nemours and Company, Wilmington, Delaware 19880, United States
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23
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Thushara KS, Gnanakumar ES, Mathew R, Ajithkumar TG, Rajamohanan PR, Bhaduri S, Gopinath CS. MgCl2·4((CH3)2CHCH2OH): A new molecular adduct for the preparation of TiClx/MgCl2 catalyst for olefin polymerization. Dalton Trans 2012; 41:11311-8. [DOI: 10.1039/c2dt31211e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Gnanakumar ES, Thushara KS, Bhange DS, Mathew R, Ajithkumar TG, Rajamohanan PR, Bhaduri S, Gopinath CS. MgCl2.6PhCH2OH – A new molecular adduct as support material for Ziegler–Natta catalyst: synthesis, characterization and catalytic activity. Dalton Trans 2011; 40:10936-44. [DOI: 10.1039/c1dt10786k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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25
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Jijo VJ, Sharma KP, Mathew R, Kamble S, Rajamohanan PR, Ajithkumar TG, Badiger MV, Kumaraswamy G. Volume Transition of PNIPAM in a Nonionic Surfactant Hexagonal Mesophase. Macromolecules 2010. [DOI: 10.1021/ma100357h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- V. J. Jijo
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - Kamendra P. Sharma
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - R. Mathew
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - Samruddhi Kamble
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - P. R. Rajamohanan
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - T. G. Ajithkumar
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - M. V. Badiger
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
| | - Guruswamy Kumaraswamy
- Complex Fluids and Polymer Engineering, National Chemical Laboratory (NCL), Pune 411008, India
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26
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Malvi B, Sarkar BR, Pati D, Mathew R, Ajithkumar TG, Sen Gupta S. “Clickable” SBA-15 mesoporous materials: synthesis, characterization and their reaction with alkynes. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b815350g] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Patil SP, Mathew R, Ajithkumar TG, Rajamohanan PR, Mahesh TS, Kumaraswamy G. Gelation of Covalently Edge-Modified Laponites in Aqueous Media. 1. Rheology and Nuclear Magnetic Resonance. J Phys Chem B 2008; 112:4536-44. [DOI: 10.1021/jp710489n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Suhas P. Patil
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
| | - Renny Mathew
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
| | - T. G. Ajithkumar
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
| | - P. R. Rajamohanan
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
| | - T. S. Mahesh
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
| | - Guruswamy Kumaraswamy
- Department of Polymer Science and Engineering, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, Central NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India, and Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, India
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28
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Das BB, Ajithkumar TG, Ramanathan KV. Improved pulse schemes for separated local field spectroscopy for static and spinning samples. Solid State Nucl Magn Reson 2008; 33:57-63. [PMID: 18406111 DOI: 10.1016/j.ssnmr.2008.03.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 02/06/2008] [Accepted: 02/27/2008] [Indexed: 05/26/2023]
Abstract
An improved pulse sequence for SLF experiments based on the magic sandwich (MS) scheme for homo-nuclear dipolar decoupling is proposed. The sequence incorporates a double MS, both on I and S spins and has been named as EXE-MS2. The proposed scheme which has a scaling factor of 1 is observed to be free from low intensity artifacts and provides better line-widths particularly for S spins labeled at multiple sites. The pulse sequence which has been applied on static oriented samples incorporates the EXE scheme where direct polarization of the S spin in the B(0) field is utilized in the place of polarization inversion and is observed to perform well without any loss of sensitivity while ensuring considerable reduction in rf power input into the sample. The EXE scheme has also been tested for solid samples under MAS.
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Affiliation(s)
- Bibhuti B Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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29
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Das BB, Ajithkumar TG, Sinha N, Opella SJ, Ramanathan KV. Cross- and axial-peak intensities in 2D-SLF experiments based on cross-polarization--the role of the initial density matrix. J Magn Reson 2007; 185:308-17. [PMID: 17280846 DOI: 10.1016/j.jmr.2007.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 01/08/2007] [Accepted: 01/10/2007] [Indexed: 05/13/2023]
Abstract
Simulations and experiments on simple oriented systems have been used to estimate the relative ratio of cross-peak to axial-peak intensities in 2D-SLF experiments based on dipolar oscillations during cross-polarization (CP). The density matrix prior to dipolar evolution is considered and for an isolated spin pair, it is shown that direct calculations of the ratios match well with simulations and experimental results. Along with the standard CP pulse sequence, two other pulse sequences namely CP with polarization inversion (PI-CP) and another novel variation of the standard CP experiment (EXE-CP) reported recently have been considered. Inclusion of homonuclear dipolar coupling has been observed to increase the axial-peak intensities. In combination with Lee-Goldburg (LG) decoupling, experiments on an oriented liquid crystalline sample have been carried out and the performance of the pulse schemes have been compared. The applicability of the new pulse sequence for different samples and different nuclei is discussed. Such studies are expected to lead to a better understanding of the experiments and to the design of useful pulse sequences.
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Affiliation(s)
- Bibhuti B Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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30
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Kentgens APM, van Eck ERH, Ajithkumar TG, Anupõld T, Past J, Reinhold A, Samoson A. New opportunities for double rotation NMR of half-integer quadrupolar nuclei. J Magn Reson 2006; 178:212-9. [PMID: 16249109 DOI: 10.1016/j.jmr.2005.09.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2005] [Revised: 09/30/2005] [Accepted: 09/30/2005] [Indexed: 05/05/2023]
Abstract
A combined approach is presented which expands the applicability of double rotation (DOR) by overcoming its most prominent disadvantages: spinning stability and sensitivity. A new design using air-bearings for the inner rotor and a computer-assisted start-up procedure allows DOR operation over in principle unlimited time at outer rotor speeds of up to 2000Hz. Sensitivity enhancement of the DOR experiment is achieved by applying amplitude-modulated adiabatic pulses such as the double frequency sweep (DFS) before pulse excitation. Repeating the DFS enhancement and signal readout several times without allowing for spin-lattice relaxation leads to sensitivity enhancements of a factor 3 for (27)Al in various minerals. As a result, it becomes possible to study low sensitivity quadrupolar nuclei and various long duration 2D measurements can be performed routinely. Spinning is adequate to suppress residual homonuclear dipolar couplings in the spectral dimension of typical quadrupolar spin systems. In 2D-exchange spectroscopy, however, homonuclear correlation can still be established through dipolar-quadrupolar cross-terms.
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Affiliation(s)
- Arno P M Kentgens
- Department of Physical Chemistry/Solid-State NMR, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, The Netherlands.
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31
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Ajithkumar TG, van Eck ERH, Kentgens APM. Homonuclear correlation experiments for quadrupolar nuclei, spinning away from the magic angle. Solid State Nucl Magn Reson 2004; 26:180-186. [PMID: 15388182 DOI: 10.1016/j.ssnmr.2004.03.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 03/25/2004] [Indexed: 05/24/2023]
Abstract
We present a set of homonuclear correlation experiments for half-integer quadrupolar spins in solids. In all these exchange-type experiments, the dipolar interaction is retained during the mixing time by spinning the sample at angles other than the "regular magic angle" (54.7 degrees celsius). The second-order quadrupolar interaction is averaged by different strategies for the different experiments. The multiple-quantum off magic angle spinning (MQOMAS) exchange experiment is essentially a regular MQMAS experiment where the quadrupolar interaction is averaged by combining magic angle spinning with a multiple- to single-quantum correlation scheme. The sample is spun at the magic angle at all times except during the mixing time which is added to establish homonuclear correlation. In the multiple-quantum P4 magic angle spinning (MQP4MAS) exchange experiment, the sample is spun at one of the angles at which the fourth-order Legendre polynomial vanishes (P4 magic angle), the remaining second-order quadrupolar interaction now governed by a second-rank tensor is refocussed by the multiple to single-quantum correlation scheme. In the dynamic angle spinning (DAS) exchange experiment, the second-order quadrupolar interaction is averaged by correlating the evolution from two complementary angles. These experiments are demonstrated and compared, in view of their specific advantages and disadvantages, for 23Na in the model compound Na2SO3.
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Affiliation(s)
- T G Ajithkumar
- Department of Physical Chemistry/Solid-State NMR, NSRIM Center, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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32
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Ajithkumar TG, Kentgens APM. Homonuclear correlation experiments of half-integer quadrupolar nuclei using multiple-quantum techniques spinning at a P(4) magic angle. J Am Chem Soc 2003; 125:2398-9. [PMID: 12603120 DOI: 10.1021/ja0292647] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new approach for obtaining structural information in half-integer quadrupolar nuclei is proposed and demonstrated. In this method, the two-dimensional multiple-quantum experiment is performed, spinning at one of the angles at which the fourth order Legendre polynomial vanishes (P4 magic angle). In such an experiment, the dipolar interaction is retained, whereas the second-order quadrupolar broadening is refocused by the MQ-1Q correlation scheme. By adding an exchange period to this pulse scheme, we performed efficient homonuclear correlation experiments in a regular magic angle spinning probe with minor modifications. The experiment is demonstrated on a model compound, and the results are briefly discussed.
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Affiliation(s)
- T G Ajithkumar
- Department of Physical Chemistry, NSRIM Center, University of Nijmegen, Toernooiveld 1, The Netherlands
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Ajithkumar TG, Ramanathan KV, Mathias PC, Kumar A. Off-resonance effects in two-dimensional NQR spectroscopy using a single crystal. J Magn Reson 1998; 135:165-168. [PMID: 9799690 DOI: 10.1006/jmre.1998.1554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Two-dimensional nutation pure NQR experiments on 35Cl have been carried out on a single crystal of NaClO3. The 2D nutation experiment separates out different orientations of each chemically equivalent site in a unit cell as a separate frequency in the omega1 domain. The squares of the observed frequencies lie on a straight line with respect to the squares of the offsets, confirming the expected offset dependence quantitatively. The intercepts at zero offset yield the relative orientations of the efg tensors with respect to the axis of the radiofrequency coil.
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Affiliation(s)
- T G Ajithkumar
- Department of Physics, Indian Institute of Science, Bangalore, 560 012, India
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