Faculty Publications
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Item Effect of media characteristics on performance of upflow aerobic biofilters(2008) Srinikethan, G.; Shrihari, S.; Pradeepan, V.S.Laboratory studies were conducted to assess the influence of media related factors such as porosity, pore size, particle size and specific surface area on the performance of upflow aerobic biofilters (ABFs). Three simple models of 8 litre capacity upflow submerged ABFs packed with support media of size 40 mm, 20 mm and 10 mm respectively were installed. The hydraulic retention time (HRT) was maintained as 12 hours. The study was carried out for a period of 90 days. The reactor performance indicated that the aerobic biofilter (ABF-3), associated with media of lowest porosity, pore size, particle size and highest specific surface area, demonstrating the highest BOD and COD removal efficiency of 93.32 % and 85.01 % respectively.Item Efficacy of titanium doped-indium tin oxide (Ti/TiO2-ITO) films in rapid oxygen generation under photocatalysis and their suitability for bio-medical application(2014) Subrahmanyam, A.; Ananthakrishnan, A.; Rakibuddin, M.; Paul Ramesh, T.; Raveendra Kiran, M.R.; Shankari, D.; Chandrasekhar, K.The present work describes in detail the photocatalytic properties of controlled titanium doped indium tin oxide (Ti/TiO2-ITO) composite thin films prepared by DC magnetron sputtering and their applicability to developing a bio-medical lung assistive device. The catalytic films of various thicknesses (namely, C1, C2, C3 and C4) were characterized using surface imaging (SEM), X-ray analyses (XRD and EDX), and Raman studies. The optical band gaps of the prepared films are ?3.72-3.77 eV. Photocatalytic efficiencies of the film catalysts were investigated with the aid of a model organic molecule (Rhodamine B dye). The overall photodegradation capacity of the films was found to be slow kinetically, and the catalyst C1 was identified as having a better degradation efficiency (RhB 5 ppm, at pH 6.5) over 5 h under irradiation at 254 nm. The distinctive features of these composite films lie in their oxygen accumulation capacity and unique electron-hole pair separation ability. Investigations on oxygen species revealed the formation of superoxide radicals in aqueous systems (pH 6.5). The prepared films have TiO2 in the anatase phase in the surfaces, and possess the desired photocatalytic efficiency, compatibility to the heme system (are not involved in harmful hydroxyl radical production), and appreciable reusability. Especially, the thin films have a significant ability for mobilization of oxygen rapidly and continuously in aqueous medium under the irradiation conditions. Hence, these films may be a suitable choice for the photo-aided lung assistive design under development. © the Partner Organisations 2014.Item Preparation, characterization and the effect of PANI coated TiO2 nanocomposites on the performance of polysulfone ultrafiltration membranes(Royal Society of Chemistry, 2015) Pereira, V.R.; Isloor, A.M.; Ahmed, A.A.; A.F., A.F.Polysulfone ultrafiltration (UF) membranes with PANI-TiO2 (polyaniline-titania) nanocomposites and PEG 1000 (Polyethylene Glycol 1000) as additives were prepared by the phase inversion method. PANI-TiO2 nanocomposites were synthesized by coating TiO2 nanotubes with PANI via chemical oxidative polymerization. The synthesized PANI-TiO2 nanocomposite was characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) analysis. PANI-TiO2 nanocomposites with varying concentrations (0-1.5 wt%) were dispersed in the polysulfone membrane matrix with N-methyl-2-pyrrolidone (NMP) as solvent along with PEG 1000 as the pore former. The effect of addition of PANI-TiO2 nanocomposites with different concentrations (0-1.5 wt%) on the membrane structure, performance, hydrophilicity and the antifouling nature of the membranes was analyzed. PANI-TiO2 nanocomposite membranes showed better hydrophilicity, improved permeability, enhanced porosity, water uptake and good antifouling ability when compared with neat polysulfone membranes. The performance of the membranes improved with the increase in the addition of the PANI-TiO2 nanocomposite. However, the membrane performance decreased slightly at 1.5 wt% addition of PANI-TiO2 due to the agglomeration of PANI-TiO2 at higher concentration. The well performed membranes were also subjected to heavy metal ion rejection. The membranes showed a rejection of 83.75% and 73.41% during the polymer enhanced ultrafiltration (PEUF) process and a rejection of 68% and 53.78% during the UF process for Pb2+ and Cd2+ respectively. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015.Item Novel one-pot green synthesis of graphene in aqueous medium under microwave irradiation using a regenerative catalyst and the study of its electrochemical properties(Royal Society of Chemistry, 2015) Subramanya, B.; Bhat, D.In this work we report an economic, eco-friendly, high yielding and facile one-pot method for the large scale synthesis of few layer graphene (FLG) nanosheets directly from graphite in aqueous medium using a regenerative catalyst, sodium tungstate. This method is fast and makes use of environmental friendly chemicals and microwave radiation. The as-synthesized FLG nanosheets are characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. Raman analysis indicates that the as-synthesized graphene is bilayered with a smaller domain size of 3.9 nm which is responsible for a higher specific surface area of FLG nanosheets (1103.62 m2 g-1). Moreover, XPS analysis of FLG nanosheets shows a high C:O ratio (?9.6) which is the best among the graphene prepared from green chemicals. The electrochemical performance of as-synthesized FLG nanosheets is analysed by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) in neat 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. The superior capacitive performance with large capacitance (219 F g-1), high energy density (83.56 W h kg-1) and excellent cyclability (3000 cycles) exhibited by these graphene nanosheets make them an excellent candidate for supercapacitor material. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015.Item Nano Fe3O4@APTES@Ni(OH)2 as a catalyst for alcohol oxidation(Royal Society of Chemistry, 2015) Bhat, P.B.; Badekai Ramachandra, B.R.A nanorod shaped nickel hydroxide coated ferrite nanocatalyst was synthesized by a traditional co-precipitation method. The particle size of the nanoferrite was tuned using a variable surfactant ratio to achieve a high surface area. A very high BET surface area (334.55 m2 g-1) was achieved for particles with sizes of 40-130 nm. The superparamagnetic reusable catalyst was found to be active for the selective liquid phase oxidation of alcohols with hydrogen peroxide as a mild oxidant. Nickel hydroxide acted as a Bronsted base working in synergy with the nanoferrite catalyst for alcohol oxidation. The catalytic system was found to catalyse primary and secondary alcohols efficiently (86%) to their corresponding carbonyls in good yields. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015.Item Interparticle interactions and lacunarity of mechano-chemically activated fly ash(Elsevier, 2015) Patil, A.G.; Shanmugharaj, A.M.; Anandhan, S.A class F fly ash was subjected to high-energy ball milling-induced mechano-chemical activation aided by a surfactant. The resultant nanostructured fly ash was characterized by various techniques. X-ray fluorescence results showed that the amount of iron oxide was reduced from 4.39% to 2.75% after pre-treatment of fly ash by magnetic separation. Ethyl acetate as the milling medium, a ball to powder ratio of 12:1 and 2wt% of surfactant reduced the average particle size of fly ash to 329nm and led to a specific surface area of 8.73m2/g. The decrease in crystallite size of mechano-chemically activated fly ash was confirmed from a reduction in peak intensity with a broadened amorphous phase by X-ray diffraction studies. X-ray photoelectron spectroscopic characterization illustrated that peak area of major elements (O, Si and Al) increased after milling. Morphological and FTIR studies revealed that the smooth and inert surface of the fly ash was converted to a rough and more reactive one after mechano-chemical activation. The surface modification of fly ash with the surfactant was determined from FTIR spectroscopy. Also, a fractal approach was used to characterize the lacunarity of the agglomerates in the nanostructured fly ash. © 2014 Elsevier B.V.Item Self-assembly synthesis of Co3O4/multiwalled carbon nanotube composites: An efficient enzyme-free glucose sensor(Royal Society of Chemistry, 2015) Prasad, R.; Badekai Ramachandra, B.R.Self-assembled cobalt oxide-multiwalled carbon nanotube composites were synthesized by simple and effective wet chemical routes. Using these materials, a modified glassy carbon electrode was fabricated and investigated for enzyme-free glucose sensor applications. The fabricated sensor exhibited a high sensitivity of 5089.1 ?A mM-1 cm-2 with a detection limit of 10.42 ?M over a glucose concentration ranging from 0.05 to 12 mM. The sensor also shows promising sensor features like stability, selectivity and fast detection. Moreover, the detection of glucose in human blood serum samples with the as-developed sensor agreed well with the results obtained from commercial glucose meters. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Microstructure and corrosion behavior of laser processed NiTi alloy(Elsevier Ltd, 2015) Marattukalam, J.J.; Singh, A.K.; Datta, S.; Das, M.; Balla, V.K.; Bontha, S.; Kalpathy, S.K.Abstract Laser Engineered Net Shaping (LENS™), a commercially available additive manufacturing technology, has been used to fabricate dense equiatomic NiTi alloy components. The primary aim of this work is to study the effect of laser power and scan speed on microstructure, phase constituents, hardness and corrosion behavior of laser processed NiTi alloy. The results showed retention of large amount of high-temperature austenite phase at room temperature due to high cooling rates associated with laser processing. The high amount of austenite in these samples increased the hardness. The grain size and corrosion resistance were found to increase with laser power. The surface energy of NiTi alloy, calculated using contact angles, decreased from 61 mN/m to 56 mN/m with increase in laser energy density from 20 J/mm2 to 80 J/mm2. The decrease in surface energy shifted the corrosion potentials to nobler direction and decreased the corrosion current. Under present experimental conditions the laser power found to have strong influence on microstructure, phase constituents and corrosion resistance of NiTi alloy. © 2015 Elsevier B.V.Item Effect of current density during electrodeposition on microstructure and hardness of textured Cu coating in the application of antimicrobial Al touch surface(Elsevier Ltd, 2016) Augustin, A.; Huilgol, P.; Udupa, K.R.; Bhat, K.U.Copper is a well proven antimicrobial material which can be used in the form of a coating on the touch surfaces. Those coating can offer a good service as touch surface for very long time if only they possess good mechanical properties like scratch resistance and microhardness. In the present work the above mentioned mechanical properties were determined on the electrodeposited copper thin film; deposited on double zincated aluminium. During deposition, current density was varied from 2 A dm?2 to 10 A dm?2, to produce crystallite size in the range of 33.5 nm to 66 nm. The crystallite size was calculated from the X-ray peak broadening (Scherrer?s formula) which were later confirmed by TEM micrographs. The scratch hardness and microhardness of the coating were measured and correlated with the crystallite size in the copper coating. Both characteristic values were found to increase with the reduction in crystallite size. Reduced crystallite size (Hall–Petch effect) and preferred growth of copper films along (111) plane play a significant role on the increase in the hardness of the coating. Further, TEM analysis reveals the presence of nano-twins in the film deposited at higher current density, which contributed to a large extent to the sharp increase of coating hardness compared to the mechanism of Hall–Petch effect. The antimicrobial ability of the coated sample has been evaluated against Escherichia coli bacteria and which is compared with that of commercially available bulk copper using the colony count method. 94% of E. coli cells were died after six hours of exposure to the copper coated surface. The morphology of the copper treated cells was studied using SEM. © 2016 Elsevier LtdItem Fabrication of a novel hollow fiber membrane decorated with functionalized Fe2O3 nanoparticles: Towards sustainable water treatment and biofouling control(Royal Society of Chemistry, 2017) Hebbar, R.S.; Isloor, A.M.; Kulal, K.; Abdullah, M.S.; A.F., A.F.The development of sustainable, surface-functionalized hollow fiber membranes with advanced nanomaterials has enabled the tailoring and targeted control of their physicochemical properties. This provides the material with improved features of hydrophilicity and permeability, excellent selectivity, and superior antifouling and antimicrobial activity. We explored a new strategy using well dispersed functionalized Fe2O3 nanoparticles to fabricate a polyetherimide nanocomposite hollow fiber membrane with enhanced surface and anti-biofouling properties. To confirm the membrane modification, a series of characterizations such as contact angle, surface energy, water uptake capacity, porosity, zeta potential, and morphological analysis were performed. The permeation experiment indicated superior hydrodynamic permeability and antifouling properties with more than 95% rejection of BSA protein molecules after inclusion of a 1.5 wt% additive dosage. Moreover, the nanocomposite membrane exhibited a relatively higher normalized flux and rejection up to 94% during the filtration of hazardous natural organic matter (NOM) with differing parameters such as the feed solution pH and ionic strength. The presence of modified Fe2O3 nanoparticles in the membrane significantly inhibits the growth of bacteria and other microorganisms on the membrane surface, resulting in an enhanced anti-biofouling property. In particular, the demonstrated method illustrates a fast, facile strategy for the functionalization of Fe2O3 nanoparticles to improve the membrane properties and anti-biofouling activity, giving them great potential for effective and sustainable water treatment applications. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.