@article { ISI:000259342400009, title = {Size dependent coordination behavior and cation distribution in MgAl2O4 nanoparticles from Al-27 solid state NMR studies}, journal = {Journal of Physical Chemistry C}, volume = {112}, number = {38}, year = {2008}, month = {SEP}, pages = {14737-14744}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nanoparticles of spinel-type oxides such as ferrites offer great advantages and applications in many important areas. Decreasing the size of the particles to nanometer size will increase the surface-to-volume ratio and this will strongly influence the physical and chemical properties of these materials. For magnetic nanoparticles, the exchange interactions at the surface of a particle will be different from those inside due to changes in the coordination behavior at the surface. Therefore, studying and understanding the coordination and distribution behavior of the different metal ions in the nanoparticles of spinel-type oxides is very important. Solid state NMR is a useful and important technique to obtain information on local structural variations. The degree of the distribution of the Al3+ ions in the tetrahedral and octahedral sites in the nanoparticles of the nonmagnetic spinet MgAl2O4 having different particle sizes has been determined by Al-27 magic-angle spinning (MAS) NMR spectroscopy. It has been observed that the inversion parameter decreases with increasing particle size. Apart from the usual tetrahedral and octahedral coordinations present in the bulk material, the presence of five- and three-coordinated At has been observed in nanoparticles with sizes less than 18 nm and a second octahedral coordination is observed for nanoparticles of larger sizes.

}, issn = {1932-7447}, doi = {10.1021/jp800412k}, author = {Sreeja, V. and Smitha, T. S. and Nand, Deepak and Ajithkumar, Thalasseril G. and Joy, Pattayil Alias} } @article { ISI:000346214100014, title = {SBA-15 intercalated Mg-Al hydrotalcite: an environmental friendly catalyst for hydroisomerization of olefin}, journal = {Applied Catalysis A-General}, volume = {488}, year = {2014}, month = {NOV}, pages = {119-127}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

SBA-15 Molecular sieve-intercalated Mg-Al hydrotalcite (MASBA-HT) was synthesized for the first time by a simple straightforward method. The intercalation of SBA-15 molecular sieve between the interlayer of HT was evident from powder XRD, TEM and FT-IR studies. The presence of SBA-15 facilitates retention of the layered structure for first time, even after calcination at high temperature of 550 degrees C. The resultant material possesses moderate acidity which comes from incorporation of aluminum into the framework of SBA-15 and also contained soluble basicity similar to HT materials. The material shows promising activity for hydroisomerization of 1-octene resulting in good substrate conversion (80\%) and branched isomers selectivity (45\%). The catalytic activity remains constant over longer duration and repeated runs. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Branched alkenes, Hydroisomerization, Intercalated-hydrotalcite, layered materials, Mesoporous SBA-15}, issn = {0926-860X}, doi = {10.1016/j.apcata.2014.09.024}, author = {Baskaran, Thangaraj and Christopher, Jayaraj and Ajithkumar, Thalasseril G. and Sakthivel, Ayyamperumal} } @article { ISI:000331861300008, title = {Solid-state NMR investigations of a MgCl2 center dot 4(CH3)(2)CHCH2OH molecular adduct: a peculiar case of reversible equilibrium between two phases}, journal = {Journal of Physical Chemistry A}, volume = {118}, number = {7}, year = {2014}, month = {FEB}, pages = {1213-1219}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

MgCl2 center dot 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 center dot 4(CH3)(2)CHCH2OH (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 Mg2+ ion as the central metal ion might shed some light toward understanding various biological and structural functions.

}, issn = {1089-5639}, doi = {10.1021/jp412331s}, author = {Thushara, K. S. and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Gopinath, Chinnakonda S.} } @article { ISI:000329266500032, title = {Structural investigations of porous MgCl2-2-butanol molecular adduct as support for olefin polymerization}, journal = {Applied Catalysis A-General}, volume = {469}, year = {2014}, month = {JAN}, pages = {267-274}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A new heterogeneous Ziegler-Natta (Z-N) catalyst support material, MgCl2 center dot 4(CH3CH(OH)CH2CH3) (Mg2BuOH) has been synthesized. 2-Butanol, a linear, secondary alcohol was chosen for the generation of an active MgCl2 support which results in a Z-N catalyst with TiCl4. Significant feature of this work is the formation of rod shaped molecular adduct with highly porous character. Adduct material is characterized by XRD, TG-DTA, Raman spectroscopy, solid-state NMR and SEM. Activity of the Z-N catalyst supported on Mg2BuOH for ethylene polymerization is comparable with that of commercially available heterogeneous Z-N catalyst. However, there is scope to improve the activity by optimizing textural properties. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {heterogeneous catalysis, MgCl2, Molecular adduct, NMR, Polyolefin, Ziegler-Natta catalyst}, issn = {0926-860X}, doi = {10.1016/j.apcata.2013.10.002}, author = {Thushara, K. S. and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Gopinath, Chinnakonda S.} } @article { ISI:000365602800014, title = {Study on fused/cast AZS refractories for deployment in vitrification of radioactive waste effluents}, journal = {Journal of Nuclear Materials}, volume = {467}, number = {1}, year = {2015}, month = {DEC}, pages = {144-154}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Fused/cast Al2O3-ZrO2-SiO2 (FC-AZS){\textquoteright} is being considered as {\textquoteleft}glass contact refractory{\textquoteright} within ceramic melters, to be used for nuclear waste immobilization. Microstructural analyses reveal random distributions of baddeleyite (ZrO2) within aluminosilicate (Al2SiO5) matrix. Al-27 and Si-29 NMR data suggest that within aluminosilicate matrix Al occurs in both 4- and 6-fold co-ordinations whereas Si prefers a 4-fold environment. Polydispersity of pores has been studied with small-angle neutron scattering (SANS) technique. Corrosion rates of FC-AZS within 6 M HNO3, simulated wastes (500 h exposure), and borosilicate melt (975 degrees C, 800 h exposure) are found to be 0.38 x 10(3) mu my(-1), 0.13 x 10(3) mu my(-1) and 4.75 x 10(3) mu my(-1) respectively. A comparison of chemical interaction data clearly suggests that FC-AZS exhibits better chemical durability than AZC refractory (Al2O3-ZrO2-Cr2O3, also used for similar purpose). Thermal cycling studies indicate that FC-AZS retains structural integrity (including compressive strength and density) even up to 20 cycles. (C) 2015 Elsevier B.V. All rights reserved.

}, keywords = {Interaction between refractory material and hazardous liquid, Nuclear waste immobilization, Vitrification melter}, issn = {0022-3115}, doi = {10.1016/j.jnucmat.2015.09.019}, author = {Sengupta, Pranesh and Mishra, Raman K. and Soudamini, N. and Sen, D. and Mazumder, S. and Kaushik, Chetan P. and Ajithkumar, Thalasseril G. and Banerjee, K.} } @article {45886, title = {Supported imidazole as heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2}, journal = {Catalysis Communications}, volume = {59}, year = {2015}, month = {JAN }, pages = {201-205}, type = {Article}, abstract = {

Imidazole anchored onto a silica matrix, by means of a propyl linkage, is found to be an effective heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2 in near quantitative yield. The versatility of this catalyst is demonstrated by using different substrates (epichlorohydrin, propylene oxide, butylene oxide and styrene oxide) for this cycloaddition reaction. These CO2 insertion reactions were typically carried out in the temperature range of 343 to 403 K at 0.6 MPa CO2 pressure under solvent-free conditions. Several spectroscopic methods were used to characterize the catalyst and study the integrity of the fresh and spent catalysts. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Anchored imidazole, CO2 utilization, cyclic carbonates, epoxides}, issn = {1566-7367}, doi = {10.1016/j.catcom.2014.10.026}, author = {Sankar, Meenakshisundaram and Ajithkumar, Thalasseril G. and Sankar, Gopinathan and Manikandan, Palanichamy} } @article {50035, title = {Sustainable nanocellulose extraction from salacca zalacca peel using chlorine-free and low-acid treatments}, journal = {ACS Omega}, volume = {11}, year = {2026}, month = {MAR}, pages = {13253-13267}, type = {Article}, abstract = {

Conversion of agro-waste to value-added products is one of the important principles of a green circular economy. A novel sustainable technique has been reported by using chlorine-free extraction of cellulose nanofibers (CNFs) from the peels of Salacca zalacca, a common fruit found in Asia. The fruit peels were exposed to alkali treatment using 2\% NaOH (60 degrees C, 2 h), chlorine-free bleaching using 15\% hydrogen peroxide (60 degrees C, 2 h), and sulfuric acid hydrolysis (15\% v/v) for the extraction of CNFs. Various analytical methods were employed to characterize the prepared CNFs. The Fourier transform infrared spectroscopy (FTIR) and 13C solid state nuclear magnetic resonance (NMR) spectra showed the complete elimination of lignin and hemicellulose in the prepared CNFs. The elemental composition and high purity of CNFs were further verified by energy-dispersive X-ray analysis (EDX). The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images proved the fibrous morphology of the prepared CNFs, and the diameters of the cellulose nanofibers were found to be 15-30 nm. The X-ray diffraction (XRD) studies disclosed the type-I cellulosic structure in the prepared CNFs with a high crystallinity index (73\%). The thermogravimetric analysis (TGA) demonstrated the superior thermal stability of the prepared CNFs (T max is 350 degrees C) compared to the raw fiber (T max is 320 degrees C). Based on the obtained results, it has been explored that the extracted highly pure CNFs can be used for fabricating bionanocomposites for high performance applications, including food packaging, sensors, water treatment, green tires, etc.

}, issn = {2470-1343}, doi = {10.1021/acsomega.5c09694}, author = {Krishnan, Akhil and Paul, Sharon and Phiri, Resego and Srisuk, Rapeeporn and Kumar Singh, Manoj and Palaniappan, Sathish Kumar and Rangappa, Sanjay Mavinkere and Dominic, C. D. Midhun and Ajithkumar, Thalasseril G. and Siengchin, Suchart} }