• Giridhar Madras

      Articles written in Bulletin of Materials Science

    • Synthesis, structure and photocatalytic properties of 𝛽-ZrMo2O8

      Prangya Parimita Sahoo S Sumithra Giridhar Madras T N Guru Row

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      Monoclinic ZrMo2O8 was synthesized via solid state method and single crystals of the title compound have been grown by the hydrothermal method. The crystals belong to monoclinic crystal system with space group 𝐶2/c (No. 15) with 𝑎 = 11.4243(19) Å, 𝑏 = 7.9297(6) Å, 𝑐 = 7.4610(14) Å and 𝛽 = 122.15(2)°, 𝑍 = 4. The bandgap of the compound was 2.57 eV. Unlike the other polymorphs of ZrMo2O8, the monoclinic form has unique crystallographic features with ZrO8 and Mo2O8 polyhedra. The photocatalytic activity of this compound has been investigated for the first time for the degradation of various dyes under UV irradiation and has been compared with the photoactivity of the trigonal form of ZrMo2O8. It has been observed that this compound exhibits specificity towards the degradation of cationic dyes.

    • Synthesis of new (Bi, La)3MSb2O11 phases (M = Cr, Mn, Fe) with KSbO3-type structure and their magnetic and photocatalytic properties

      K Ramesha A S Prakash M Sathiya Giridhar Madras A K Shukla

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      Synthesis and structure of new (Bi, La)3MSb2O11 phases (M = Cr, Mn, Fe) are reported in conjunction with their magnetic and photocatalytic properties. XRD refinements reflect that Bi3CrSb2O11, Bi2LaCrSb2O11, Bi2LaMnSb2O11 and Bi2LaFeSb2O11 adopt KSbO3-type structure (space group, 𝑃𝑛$\bar{3}$). The structure can be described through three interpenetrating networks where the first is the (M/Sb)O6 octahedral network and other two are the identical networks having Bi6O4 composition. The magnetic measurements on Bi2LaCrSb2O11 and Bi2LaMnSb2O11 show paramagnetic behaviour with magnetic moments close to the expected spin only magnetic moments of Cr+3 and Mn+3. The UV-Visible diffuse reflectance spectra are broad and indicate that these materials possess a bandgap of ∼ 2 eV. The photocatalytic activity of these materials has been investigated by degrading Malachite Green (MG) under exposure to UV light.

    • Effect of crosslinker on the swelling and adsorption properties of cationic superabsorbent

      TARUN SHARMA GIRIDHAR MADRAS

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      In the present study, superabsorbents (SAPs) of cationicmonomer [2-(methacryloyloxy) ethyl] trimethylammonium chloride have been prepared by free radical solution polymerization with different crosslinkers. They were subjected to repeated cycles of swelling and de-swelling in deionized water and NaCl solution. The conductivity of the swelling medium was measured and related to the swelling/de-swelling characteristics of the SAPs. The swelling capacity was also determined in saline solution. The swelling and de-swelling processes were described by first-order kinetics. The SAPs exhibited varied swelling capacity for crosslinkers of the same functionality as well as different functionality. The SAPs were used to adsorb the dye Orange G at different initial concentrations of the dye. The equilibrium adsorption data followed the Langmuir adsorption isotherms. The SAPs were also used to adsorb three other dyes, namely, Congo red, Amido black and Alizarin cyanine green. They exhibited different adsorption capacities for different dyes. The adsorption phenomenon was found to follow first-order kinetics.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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