• U S Sajeev

      Articles written in Bulletin of Materials Science

    • Magnetic field induced assembling of nanoparticles in ferrofluidic liquid thin films based on Ni𝑥Fe1-𝑥Fe2O4

      V S Abraham S Swapna Nair S Rajesh U S Sajeev M R Anantharaman

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      Ultra fine precursors for ferrofluid synthesis, belonging to the series, Ni𝑥Fe1-𝑥Fe2O4 (where `𝑥’ varies from `0’ to `0.6’ in steps of 0.1), were synthesized. Ferrofluids based on these fine particles were prepared with oleic acid as surfactant and kerosene as carrier. Ferrofluidic thin films were made on glass substrates and magnetic field induced laser transmission was studied. The pattern exhibited by the films under the influence of a magnetic field was observed with the help of a CCD camera. The analysis of results confirms the chain formation of particles in the presence of an applied magnetic field and their saturation at higher applied fields.

    • On the optical and electrical properties of rf and a.c. plasma polymerized aniline thin films

      U S Sajeev C Joseph Mathai S Saravanan Rajeev R Ashokan S Venkatachalam M R Anantharaman

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      Polyaniline is a widely studied conducting polymer and is a useful material in its bulk and thin film form for many applications, because of its excellent optical and electrical properties. Pristine and iodine doped polyaniline thin films were prepared by a.c. and rf plasma polymerization techniques separately for the comparison of their optical and electrical properties. Doping of iodine was effected in situ. The structural properties of these films were evaluated by FTIR spectroscopy and the optical band gap was estimated from UV-vis-NIR measurements. Comparative studies on the structural, optical and electrical properties of a.c. and rf polymerization are presented here. It has been found that the optical band gap of the polyaniline thin films prepared by rf and a.c. plasma polymerization techniques differ considerably and the band gap is further reduced by in situ doping of iodine. The electrical conductivity measurements on these films show a higher value of electrical conductivity in the case of rf plasma polymerized thin films when compared to the a.c. plasma polymerized films. Also, it is found that the iodine doping enhanced conductivity of the polymer thin films considerably. The results are compared and correlated and have been explained with respect to the different structures adopted under these two preparation techniques.

    • Control of nanostructures in PVA, PVA/chitosan blends and PCL through electrospinning

      U S Sajeev K Anoop Anand Deepthy Menon Shanti Nair

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      Aqueous solutions of polyvinyl alcohol (PVA) were electrospun and its characteristics were studied as a function of applied potential, tip-target distance and solution flow rate. Solutions of PVA and chitosan were homogeneously mixed and electrospun to result in blend nanofibres and their properties were investigated. Conditions were revealed under which multiscale bi-modal fibres could be electrospun in a single step, producing structures that have potential applications in tissue engineering. Electrospun fibres having a bimodal size distribution of poly(caprolactone) (PCL) were also fabricated using a modified electrospinning setup. Nanofibrous microporous PVA scaffolds were fabricated using a cryogenic grinding method with subsequent compaction. Such multiscale porous structures would offer ideal matrices for tissue engineering applications.

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