@article { ISI:000332188100018, title = {Large increase in the energy product of Fe3Se4 by Fe-site doping}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {8}, year = {2014}, month = {FEB}, pages = {4016-4022}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Fe3Se4 possesses a large coercivity at room temperature. At lower temperature, a coercivity value up to 40 kOe has been achieved. However, due to a relatively lower saturation magnetization value, the energy product of this material is not suitable for its use as rare-earth-free hard magnetic material. Although the anisotropy and magnetic structure of Fe3Se4 have been topics of research, there is no attempt to increase the energy product. Here, we report the synthesis of Fe3-xMnxSe4 (x = 0.01-0.2) nanorods. As required for practical applications, after doping, the Curie temperature remains unchanged; however, at optimum (x = 0.03) doping of manganese ions, the magnetization of the host matrix increases significantly from 4.84 to 7.54 emu/g. The corresponding energy product value was found to be increased by more than 130\%. At low temperature (10 K) the energy product shows almost a 2 order of magnitude increase (similar to 0.12 MG Oe), which makes it valuable for many low temperature applications. This improvement is a vital step for its use in some of the household applications where a large volume and relatively lower energy product are needed.

}, issn = {1932-7447}, doi = {10.1021/jp411956q}, author = {Sen Bishwas, Mousumi and Das, Raja and Poddar, Pankaj} } @article { ISI:000361085800009, title = {Construction of polynuclear lanthanide (Ln = Dy-III, Tb-III, and Nd-III) cage complexes using pyridine-pyrazole-based ligands: versatile molecular topologies and smm behavior}, journal = {Inorganic Chemistry}, volume = {54}, number = {17}, year = {2015}, month = {SEP}, pages = {8197-8206}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Employment of two different pyridyl pyrazolyl-based ligands afforded three octanudear lanthanide(III) (Ln = Dy, Tb) cage compounds and one hexanudear neodymium(III) coordination cage, exhibiting versatile molecular architectures including a butterfly core. Relatively less common semirigid pyridyl pyrazolyl-based asymmetric ligand systems show an interesting trend of forming polynuclear lanthanide cage complexes with different coordination environments around the metal centers. It is noteworthy here that construction of lanthanide complex itself is a challenging task in a ligand system as soft N-donor rich as pyridyl pyrazol. We report herein some lanthanide complexes using ligand containing only one or two O-donors compare to five N-coordinating sites. The resultant multinuclear lanthanide complexes show interesting magnetic and spectroscopic features originating from different spatial arrangements of the metal ions. Alternating current (ac) susceptibility measurements of the two dysprosium complexes display frequency- and temperature-dependent out-of-phase signals in zero and 0.5 T direct current field, a typical characteristic feature of single-molecule magnet (SMM) behavior, indicating different energy reversal barriers due to different molecular topologies. Another aspect of this work is the occurrence of the not-so-common SMM behavior of the terbium complex, further confirmed by ac susceptibility measurement.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.5b00334}, author = {Bala, Sukhen and Sen Bishwas, Mousumi and Pramanik, Bhaskar and Khanra, Sumit and Fromrn, Katharina M. and Poddar, Pankaj and Mondal, Raju} } @article { ISI:000371479000046, title = {Observation of magnetic anomalies in one-step solvothermally synthesized nickel-cobalt ferrite nanoparticles}, journal = {Nanoscale}, volume = {8}, number = {9}, year = {2016}, month = {JAN}, pages = {5200-5213}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Magnetic anomalies corresponding to the Verwey transition and reorientation of anisotropic vacancies are observed at 151 K and 306 K, respectively, in NiCoFe2O4 nanoparticles (NPs) synthesized by a modified-solvothermal method followed by annealing. Cationic disorder and spherical shape induced non-stoichiometry suppress the Verwey transition in the as-synthesized NPs. On the other hand, reorientation of anisotropic vacancies is quite robust. XRD and electron microscopy investigations confirm a single phase spinel structure and the surface morphology of the as-synthesized NPs changes from spherical to octahedral upon annealing. Rietveld analysis reveals that the Ni2+ ions migrate from tetrahedral (A) to octahedral (B) sites upon annealing. The Mossbauer results show canted spins in both the NPs and the strength of superexchange is stronger in Co-O-Fe than Ni-O-Fe. Magnetic force images show that the as-synthesised NPs are single-domain whereas the annealed NPs are multi-domain octahedral particles. The FMR study reveals that both the NPs have a broad FMR line-width; and resonance properties are consistent with the random anisotropy model. The broad inhomogeneous FMR line-width, observation of the Verwey transition, tuning of the magnetic domain structure as well as the magnetic properties suggest that the NiCoFe2O4 ferrite NPs may be promising for future generation spintronics, magneto-electronics, and ultra-high-density recording media as well as for radar absorbing applications.

}, issn = {2040-3364}, doi = {10.1039/c5nr06791j}, author = {Datt, Gopal and Sen Bishwas, Mousumi and Raja, M. Manivel and Abhyankar, A. C.} } @article { ISI:000375255500006, title = {Study of magnetic entropy and heat capacity in ferrimagnetic Fe3Se4 nanorods}, journal = {Journal Of Physics D-Applied Physics}, volume = {49}, number = {19}, year = {2016}, month = {MAY}, pages = {195003}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {

Change in the magnetic entropy and specific heat capacity in Fe3Se4 nanorods synthesized by a wet-chemical method in a broad temperature (215-340 K) and magnetic field range (0-60 k Oe) was studied. The isothermal magnetic entropy change (Delta S-M) is estimated by an indirect method from the isothermal magnetization curves measured in this temperature range. S-M(max) of -46 x 10(-2) J kg(-1).K-1 was obtained at similar to 317 K when the field was changed from 0 to 60 kOe. The maximum in the isothermal magnetic entropy change (Delta S-M) is observed in close proximity to TC (similar to 323 K), which is linked to the order-disorder transition. The nature of this transition was analyzed by universal curve behavior. The temperature and magnetic field dependence of specific heat capacity was studied and analyzed to estimate the adiabatic temperature change (Delta T-ad). The magnetic entropy change of Fe3Se4 nanoparticles is found to be comparable with similar ferrite and manganite nanoparticle systems and a broad operating temperature window of similar to 30 K was observed around room temperature.

}, keywords = {heat capacity, iron selenide, Magnetic anisotropy, magnetic entropy, order-disorder phase transition}, issn = {0022-3727}, doi = {10.1088/0022-3727/49/19/195003}, author = {Sen Bishwas, Mousumi and Poddar, Pankaj} } @article {44120, title = {Ln(8) (Ln = Gd, Ho, Er, Yb) Butterfly core-exhibiting magnetocaloric effect and field-induced SMM behavior for Er analouge}, journal = {ChemistrySelect}, volume = {2}, year = {2017}, month = {DEC}, pages = {11341-11345}, type = {Article}, abstract = {

In this article, we report four pyridyl-pyrazolyl based poly-nuclear cluster complexes with Ln(8) {Ln = [Gd-8(III)(mu(3)-OH)(4)(L-1)(4)(DEA)(4)Cl-4](DMF)(2)(MeOH)(1), [Ho-8(III)(mu(3)-OH)(4)(L-1)(4)(DEA)(4)Cl-4](2), [Er-8(III)(mu(3)-OH)(4)(L-1)(4)(DEA)(4)Cl-4](DMF)(MeOH)(H2O)(3), [Yb-8(III)(mu(3)-OH)(4)(L-1)(4)(DEA)(4)Cl-4](DMF)(MeOH)(4) [DEA = Diethanolamine] cores. The impetus for this study was to explore the magnetic behaviour of lanthanide ions which are often ignored or overlooked. X-ray crystal analysis show that these complexes are isostructural and exhibit an interesting butterfly like topology. The semi-rigidity and asymmetric nature of the ligand led to different coordination environment around the metal centres. The lanthanide ions adopt two types of geometry, a bicapped trigonal prism and a distorted square antiprismatic geometry around the metal center. Such dissimilar coordination environments around the lanthanide centre can have profound effects on their magnetic behaviour. Indeed, the magnetic measurements revealed significant magnetocaloric effect for octanuclear gadolinium complex 1 with magnetic entropy change (-Delta S-m ) of 31.4 J kg(-1) K-1 for Delta H = 9 T at T = 3 K whereas Er analogue complex 3 displayed SMM behavior.

}, doi = {10.1002/slct.201701905}, author = {Bala, Sukhen and Adhikary, Amit and Bhattacharya, Sudeshna and Sen Bishwas, Mousumi and Poddar, Pankaj and Mondal, Raju} } @article {44165, title = {Tetranuclear cubane Cu4O4 complexes as prospective anticancer agents: Design, synthesis, structural elucidation, magnetism, computational and cytotoxicity studies}, journal = {Inorganic Chimica Acta}, volume = {473}, year = {2018}, month = {MAR}, pages = {121-132}, abstract = {Two new homometallic Cu4O4 cubane clusters 1 and 2 have been synthesized by self-assembly of copper (II) acetate and ligand, 2-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-2-hydroxymethyl-propane-1, 3-diol (H4L) and characterized thoroughly by various spectroscopic techniques and single crystal X-ray diffraction analysis. Temperature- dependent magnetic susceptibility measurements have been performed to elucidate the antiferromagnetic and ferromagnetic nature in Cu4O4 clusters 1 and 2, respectively. In vitro DNA binding studies of cubane clusters were carried out by employing optical spectroscopic techniques. Gel electrophoretic mobility assay performed to examine the nuclease activity of the complexes 1 and 2 with pBR322 DNA, and results revealed oxidative DNA cleavage via reactive oxygen species (ROS) species viz., O-2(.-), O-1(2), etc. In vitro cell proliferation via MTT assay was studied to calculate the cytotoxicity of complexes 1 and 2. The IC50 evaluated were similar to 20 mu M in MCF-7 (Breast) and similar to 30-35 mu M in HepG2 (Liver) cancer cell lines. Additionally, in the presence of 1 and 2, ROS and TBARS (Thiobarbituric acid reactive substance) levels amplified significantly, coupled with GSH (glutathione) levels in cancer lines. Hence, the results exhibited the major role of ROS in apoptosis induced by 1 and 2 clusters and validate their prospective to be efficient anticancer drug entities. (C) 2018 Elsevier B.V. All rights reserved.}, keywords = {Cu4O4 cubane complexes, Cytotoxicity, DFT, DNA binding, Magnetism, Nuclease activity}, issn = {0020-1693}, doi = {10.1016/j.ica.2017.12.039}, author = {Usman, Mohammad and Arjmand, Farukh and Khan, Rais Ahmad and Alsalme, Ali and Ahmad, Musheer and Sen Bishwas, Mousumi and Tabassum, Sartaj} } @article {47426, title = {Raman spectroscopy-based sensitive, fast and reversible vapour phase detection of explosives adsorbed on metal-organic frameworks UiO-67}, journal = {New Journal of Chemistry}, volume = {45}, year = {2021}, month = {APR}, pages = {7145-7153}, type = {Article}, abstract = {

In this work, we report highly sensitive, selective, rapid, and reversible detection of explosive molecules in the vapour phase, adsorbed on metal-organic frameworks (MOFs) under ambient laboratory conditions. The sensing is based on the quenching of the Raman intensity of a zirconium-based MOF, Zr6O4(OH)(4)(dcppy)(6) (MOF 1, UiO-67-dcppy; dcppy is 2-phenylpyridine-5,4{\textquoteright}-dicarboxylate), where 50\% of the signal quenches swiftly within similar to 5 s of its exposure to trinitrophenol (TNP) vapours, while 90\% of the Raman signal was quenched in 30 s. The high surface area of porous MOFs provides increased adsorption of various nitro analytes. The quenching of Raman peaks resulted from the pi-pi interactions of the analytes with the benzene ring of the MOF. The sensors have also been proven to be reversible and stable by mild heat treatment (80 degrees C for 5 min). These notable results using Raman spectroscopy point to a new and important approach towards explosive sensing using metal-organic frameworks considering their vast versatility. This work emphasizes the importance of a non-invasive and non-destructive technique that can be used to develop handheld vapour phase explosive detectors.

}, issn = {1144-0546}, doi = {10.1039/d0nj04915h, Early Access Date = MAR 2021}, author = {Sen Bishwas, Mousumi and Malik, Monika and Poddar, Pankaj} }