• G RANGA RAO

      Articles written in Journal of Chemical Sciences

    • In situ grown nano-architectures of Co₃O₄ on Ni-foam for charge storage application

      G RAJESHKHANNA EDIGA UMESHBABU G RANGA RAO

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      Nanostructured Co₃O₄ on Ni-foam has been synthesized with diverse morphologies, high surface area and porosity by employing different surfactants under hydrothermal conditions and subsequent calcination. The surfactants strongly influence the physicochemical properties of cobalt oxide samples. The cobalt oxide grown on Ni-foam without surfactant had flower-like morphology. However, cobalt oxides synthesized by using cationic (CTAB) and non-ionic (Triton X-100) surfactants showed flake-like morphology, but the spatial arrangement of flakes was found to be different in both the samples. The surfactant-assisted cobalt oxide showed average crystallite size of ∼6.6–9.8 nm, surface area of 60–80 m2g−1 and porosity (pore diameter ∼3.8 nm). These samples were found to perform better as charge storage electrode materials. The specific capacitance values of cationic and non-ionic surfactant-assisted cobalt oxide materials, at a current density of1.0 A g−1, were 1820 and 806 F g−1, respectively, compared to 288 F g−1 of cobalt oxide prepared without surfactant. They also showed excellent capacity retention for over 3000 charge-discharge cycles at higher current densities. The difference in the capacitance values of cationic and non-ionic surfactant-assisted cobalt oxide is due to the difference in the flake arrangement.

    • Sol-gel-cum-hydrothermal synthesis of mesoporous Co-Fe@Al₂O₃−MCM-41 for methylene blue remediation

      AMARESH C PRADHAN ANIMESH PAUL G RANGA RAO

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      A combined sol-gel-cum-hydrothermalmethod has been employed to synthesize novelmonometallic (Mn, Fe, Co) and bimetallic (Co-Fe, Mn-Co, Fe-Mn) nanoparticles loaded onto Al₂O₃−MCM-41. Powder XRD, N2 sorption, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) measurements show that the materials possess mesoporosity, high surface area and nanosize. Monometallic Fe, Co and Mn @Al₂O₃−MCM-41 and bimetallic Co-Fe, Fe-Mn and Mn-Co @Al₂O₃−MCM-41 materials were tested for methylene blue remediation from aqueous media. In the present study, Co-Fe@Al₂O₃−MCM-41 was found to be an excellent adsorbent. The adsorption efficiency of Co- Fe@Al₂O₃−MCM-41 has been studied as a function of adsorbent dose and pH of the solution. Maximum adsorption of methylene blue was obtained at high pH values of the solution. Framework mesoporosity, high surface area, and narrow pore distribution are the key factors for an efficient adsorption of methylene blue onCo-Fe@Al₂O₃−MCM-41.

    • Polyoxometalate entrapped caprolactam gels and their cytotoxicity study

      K SHAKEELA G SILPA SURESH KUMAR RAYALA G RANGA RAO

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      Polyoxometalate (POM) based gels are synthesized by reacting POMs with an excess of caprolactam. These POM-entrapped caprolactam gels are thermoreversible and possess good mechanical strength. The gelation of POMs in caprolactam matrix brought the gel acidity similar to the physiological pH. The cytotoxicity studies on SCC 131 cell lines using these gels show 50% of cell death in the range of 2 to 6 mM concentration in 48 h. The supramolecular caprolactam matrix with active protons and the redox property of POMs are responsiblefor the cytotoxicity effect.

    • Cationic dye adsorption by phosphomolybdate nanoclusters immobilised on polyelectrolyte matrix

      K SHAKEELA SRUTHI GURU G RANGA RAO

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      A polyelectrolyte complex (PEC) made up of poly(di-allyl di-methylammonium chloride) and poly(styrene sulphonate) polyelectrolytes has been synthesised and used for the immobilisation of phosphomolybdate (PMo), [PMo12O40]3- nanoclusters. The material is characterised by FTIR, powder XRD, SEM, TEM and UV-Visible DRS spectroscopy. It was found that the PMo clusters are intact in the hybrid and are present as nanoaggregates within the layers of PEC. The amount of PMo present in the hybrid is estimated from thermal measurements and the optical band gap energy of the material is found to be in the semiconductor region. The presence of negatively charged PMo clusters helped in almost complete adsorption of cationic dyes, methylene blue and rhodamine B. The PMo/PEC hybrid has shown to follow Langmuir adsorption isotherm in case of both the dye molecules.

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