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701.
Nanoparticles of MgFe2O4 are synthesized using sol–gel autocombustion method. Structural studies are carried out using X-ray diffraction (XRD). The XRD pattern of MgFe2O4 provides information about single-phase formation of spinel structure with cubic symmetry. The grain size and lattice constant are obtained using XRD data. The cation distribution is also proposed theoretically. The change in site preference of cations in nano-MgFe2O4 is compared with its bulk counterpart. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is conformed using Fourier transform infrared spectroscopy (FTIR), which also lends support for the cation distribution proposed using XRD data. The effect of nanoregime on parameters such as bond length, vibration frequency and force constant are discussed with the help of FTIR data. The M–H loop of MgFe2O4 has been traced using the Vibrating Sample Magnetometer (VSM) and magnetic parameters such as saturation magnetization (MS), coercivity (HC) and retentivity (MR) are obtained from VSM data. 相似文献
702.
703.
Poly-methylmethacrylate/Mg–Al layered double hydroxide (PMMA/LDH) based nanocomposites have successfully been synthesised with varying LDH content by in situ polymerisation technique and systematically studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT IR), UV-Visible spectroscopy and microscopic (FE SEM and HR TEM) analysis. In particular, thermogravimetric analysis (TGA) and gas barrier properties measurement were carried out to assess the suitable application of these materials. The thermal property of PMMA/LDH composites was compared with neat PMMA and an enhancement in thermal stability was noticed with gradual increase in LDH content in the composite. Gas permeability measurement data showed significant decrease in oxygen permeability value of the PMMA/LDH nanocomposites in comparison to the pristine PMMA. Enhancement in thermal stability along with significant reduction in oxygen permeability of PMMA upon composite formation indicate the possible application of these materials in packaging industries. 相似文献
704.
Lithium substitution in polypyrrole can be accomplished by a variety of approaches and the present work introduces one of the cost-effective techniques using a relatively less expensive lithium salt, n-butyllithium in hexanes (n-BuLi), as the dopant. Chemical oxidative polymerization method is employed to synthesize polypyrrole (PPy) using anhydrous ferric chloride as the oxidant and it is dedoped using NH4OH solution in the fully reduced state. The dedoped polypyrrole is treated with n-butyllithium in hexanes (n-BuLi) in an argon-filled glove box to get the lithiated form of polypyrrole (PPyL) and the concentration of n-BuLi is varied to improve metalation. The lithiated PPy is characterized by FTIR spectroscopy, XRD, FESEM, and TEM techniques to understand the structural and the morphological details. The lithium content in the lithiated samples is estimated using ICP-AES analysis. The thermal studies using the TGA technique show that the lithiated polypyrrole has good thermal stability. Coin cells are assembled in the argon-filled glove box using Li-substituted polypyrrole as the cathode, lithium metal foil as the anode, and lithium hexafluorophosphate (LiPF6) as the electrolyte. The assembled cells are electrochemically characterized using cyclic voltammetry and charge–discharge cycling techniques and it is seen that the Li-substituted polypyrrole-based Li-ion cells are electrochemically active. 相似文献
705.
Bibhuti Bhusan Champati Bhuban Mohan Padhiari Asit Ray Tarun Halder Sudipta Jena Ambika Sahoo Basudeba Kar Pradeep Kumar Kamila Pratap Chandra Panda Biswajit Ghosh Sanghamitra Nayak 《Molecules (Basel, Switzerland)》2022,27(9)
Andrographolide, the principal secondary metabolite of Andrographis paniculata, displays a wide spectrum of medicinal activities. The content of andrographolide varies significantly in the species collected from different geographical regions. Therefore, this study aims at investigating the role of different abiotic factors and selecting suitable sites for the cultivation of A. paniculata with high andrographolide content using a multilayer perceptron artificial neural network (MLP-ANN) approach. A total of 150 accessions of A. paniculata collected from different regions of Odisha and West Bengal in eastern India showed a variation in andrographolide content in the range of 0.28–5.45% on a dry weight basis. The MLP-ANN was trained using climatic factors and soil nutrients as the input layer and the andrographolide content as the output layer. The best topological ANN architecture, consisting of 14 input neurons, 12 hidden neurons, and 1 output neuron, could predict the andrographolide content with 90% accuracy. The developed ANN model showed good predictive performance with a correlation coefficient (R2) of 0.9716 and a root-mean-square error (RMSE) of 0.18. The global sensitivity analysis revealed nitrogen followed by phosphorus and potassium as the predominant input variables influencing the andrographolide content. The andrographolide content could be increased from 3.38% to 4.90% by optimizing these sensitive factors. The result showed that the ANN approach is reliable for the prediction of suitable sites for the optimum andrographolide yield in A. paniculata. 相似文献
706.
Arpita Varadwaj Pradeep R. Varadwaj Helder M. Marques Koichi Yamashita 《Molecules (Basel, Switzerland)》2022,27(11)
In chemical systems, the arsenic-centered pnictogen bond, or simply the arsenic bond, occurs when there is evidence of a net attractive interaction between the electrophilic region associated with a covalently or coordinately bound arsenic atom in a molecular entity and a nucleophile in another or the same molecular entity. It is the third member of the family of pnictogen bonds formed by the third atom of the pnictogen family, Group 15 of the periodic table, and is an inter- or intramolecular noncovalent interaction. In this overview, we present several illustrative crystal structures deposited into the Cambridge Structure Database (CSD) and the Inorganic Chemistry Structural Database (ICSD) during the last and current centuries to demonstrate that the arsenic atom in molecular entities has a significant ability to act as an electrophilic agent to make an attractive engagement with nucleophiles when in close vicinity, thereby forming σ-hole or π-hole interactions, and hence driving (in part, at least) the overall stability of the system’s crystalline phase. This overview does not include results from theoretical simulations reported by others as none of them address the signatory details of As-centered pnictogen bonds. Rather, we aimed at highlighting the interaction modes of arsenic-centered σ- and π-holes in the rationale design of crystal lattices to demonstrate that such interactions are abundant in crystalline materials, but care has to be taken to identify them as is usually done with the much more widely known noncovalent interactions in chemical systems, halogen bonding and hydrogen bonding. We also demonstrate that As-centered pnictogen bonds are usually accompanied by other primary and secondary interactions, which reinforce their occurrence and strength in most of the crystal structures illustrated. A statistical analysis of structures deposited into the CSD was performed for each interaction type As···D (D = N, O, S, Se, Te, F, Cl, Br, I, arene’s π system), thus providing insight into the typical nature of As···D interaction distances and ∠R–As···D bond angles of these interactions in crystals, where R is the remainder of the molecular entity. 相似文献
707.
Carlos Tardío Vuppu Vinay Pradeep Raúl Martín Ana M. Rodríguez Antonio de la Hoz Ravi Jada Dr. Mari Annadhasan Prof. Pilar Prieto Prof. Rajadurai Chandrasekar 《化学:亚洲杂志》2021,16(21):3476-3480
Ambient pressure chemical vapour deposition of 5,5′-bis((2-(trifluoromethyl)phenyl)ethynyl)-2,2′-bithiophene provides ultrapure needle-shaped crystals. The crystal‘s supramolecular structure consists of an array of hydrogen bonds and π-π interactions leading to anisotropic arrangements. The cyan emitting crystals exhibit an optical waveguiding tendency with guided polarised optical emissions due to anisotropic molecular arrangements. 相似文献
708.
Alfredo Torres-Benítez Jos Erick Ortega-Valencia Marta Sanchez Pradeep Kumar Divakar Mario J. Simirgiotis María Pilar Gmez-Serranillos 《Molecules (Basel, Switzerland)》2022,27(22)
The lichen species Lecania brialmontii, Pseudephebe pubescens, and Sphaerophorus globosus are part of the prominent lichenoflora of the Antarctic territory. In this work, we report the metabolomic identification of ethanolic extracts of these species, their antioxidant and cholinesterase enzyme inhibitory activity, and conduct a molecular docking analysis with typical compounds. Eighteen compounds were identified by UHPLC-ESI-QTOF-MS in L. brialmontii, 18 compounds in P. pubescens, and 14 compounds in S. globosus. The content of phenolic compounds was variable among the species, ranging from 0.279 to 2.821 mg AG/g, and all three species showed high inhibition potential on the cholinesterase enzymes. Molecular docking showed important interactions between AChE and BChE with the selected compounds. This study evidences the chemical fingerprint of three species of the order Lecanorales that support the continuation of the study of other biological activities and their potential for medical research. 相似文献
709.
Pradeep R. Varadwaj Arpita Varadwaj Gilles H. Peslherbe 《Journal of computational chemistry》2012,33(26):2073-2082
The proton accepting and donating abilities of cyclopropenylidene (c‐C3H2) on its complexation with hydrogen halides H? X (X = F, Cl, Br) are analyzed using density‐functional theory with three functionals (PBE0, B3LYP, and B3LYP‐D) and benchmarked against second‐order Møller–Plesset (MP2) theory. Standard signatures including, inter alia, dipole moment enhancement, charge transfer from the carbenic lone pair to the antibonding σ*(H? X) orbital, and H? X bond elongation are examined to ascertain the presence of hydrogen bonding in these complexes. The latter property is found to be accompanied with a pronounced red shift in the bond stretching frequency and with a substantial increase in the infrared intensity of the band on complex formation. The MP2/aug‐cc‐pVTZ c‐C3H2···H? F complex potential energy surface turns out to be an asymmetric deep single well, while asymmetric double wells are found for the c‐C3H2···H? Cl and c‐C3H2···H? Br complexes, with an energy barrier of 4.1 kcal mol?1 for proton transfer along the hydrogen bond in the latter complex. Hydrogen‐bond energy decomposition, with the reduced variational space self‐consistent field approach, indicates that there are large polarization and charge‐transfer interactions between the interacting partners in c‐C3H2···H? Br compared to the other two complexes. The C···H bonds are found to be predominantly ionic with partial covalent character, unveiled by the quantum theory of atoms in molecules. The present results reveal that the c‐C3H2 carbene divalent carbon can act as a proton acceptor and is responsible for the formation of hydrogen bonds in the complexes investigated. © 2012 Wiley Periodicals, Inc. 相似文献
710.
Pradeep K. Vuppala Sai P. Boddu Edward B. Furr Christopher R. McCurdy Bonnie A. Avery 《Chromatographia》2011,74(9-10):703-710
A simple, sensitive and rapid ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) method was developed and validated for the quantification of mitragynine in rat plasma using amitriptyline hydrochloride as an internal standard. Sample preparation involved a one-step liquid?Cliquid extraction using methyl t-butyl ether. Mitragynine was separated on an Acquity UPLC? BEH HILIC column using isocratic elution with a mobile phase of 10 mM ammonium formate buffer containing 0.1% formic acid:acetonitrile (15:85, v/v). At a flow rate of 0.2 mL min?1, the retention time of mitragynine was found to be 1.3 min. Ionization was performed in the positive ion electrospray mode. The selected mass-to-charge (m/z) ratio transition of mitragynine ion [M + H]+ used in the selected ion recording (SIR) was 399.1. The calibration curve was found to be linear over a concentration range of 1?C5,000 ng mL?1 (r = 0.999) with a lower limit of quantification (LLOQ) of 1 ng mL?1. Intra- and inter-day assay variations were found to be less than 15%. The extraction recoveries ranged from 85?C93% at the three concentrations (2, 400 and 4,000 ng mL?1) in rat plasma. This method was successfully used to quantify mitragynine in rat plasma following intravenous administration of the compound. 相似文献