Browsing by Author "Rajarao, R."
Now showing 1 - 15 of 15
- Results Per Page
- Sort Options
Item Activated carbon derived from non-metallic printed circuit board waste for supercapacitor application(Elsevier Ltd, 2016) Rajagopal, R.R.; Aravinda, L.S.; Rajarao, R.; Badekai Ramachandra, B.R.; Sahajwalla, V.Activated carbons (ACs) have been synthesized by using waste PCBs via physical activation subsequent to pyrolysis processes. The physical and chemical properties of the produced activated carbons were studied using nitrogen adsorption, FT-IR spectroscopy, RAMAN spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy techniques. Among the synthesized ACs, AC with the highest surface area of 700 m2 g-1 produced at 850 °C for a time interval of 5 h was subjected to electrochemical studies. Capacitance behaviour of the obtained AC sample has been evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GC-D) measurements and electrochemical impedance spectroscopy (EIS) technique. Specific capacitance (Cspec) values vary from 220, 185 and 156 F g-1 for corresponding scan rate of 30, 50 and 100 mV s-1 respectively. The well-developed surface area properties and good capacitance values associated with nitrogen functionalities indicates the AC developed is a good and suitable candidate for the supercapacitor fabrication. © 2016 Elsevier Ltd.Item All-optical switching and limiting properties of a Ru (II) Schiff-base complex for nonlinear optical applications(Institute of Physics Publishing michael.roberts@iop.org, 2017) Manjunatha, K.B.; Rajarao, R.; Umesh, G.; Badekai Ramachandra, B.R.; Poornesh, P.A salen-based ruthenium (Ru) (II) complex was synthesized for possible use in nonlinear optical device applications. The Ru complex was doped in a polymer matrix to fabricate films using a low-cost spin-coating technique. The third-order nonlinear optical parameters of the complex were investigated by Z-scan and degenerate four-wave mixing techniques. The study reveals two-order enhancement of third-order optical susceptibility ? (3) and exhibits superior limiting capability due to a reverse saturable absorption process. All-optical switching action for the films indicates that the sample can function as an optical inverter or a NOT gate. Hence, the Ru (II) Schiff-base complex materializes as a possible candidate for use in nonlinear optical devices. © 2017 Astro Ltd.Item Bulk scale production of carbon nanofibers in an economical way(2012) Rajarao, R.; Badekai Ramachandra, B.R.An economical route for the scalable production of carbon nanofibers (CNFs) on a sodium chloride support has been developed. CNFs have been synthesized by chemical vapor deposition (CVD) method by using metal formate as catalyst precursors at 680°C. Products were characterized by SEM, TEM, Raman spectroscopy and XRD method. By thermal analysis, the purity of the as grown products and purified products were determined. This method avoids calcination and reduction process which was employed in commercial catalysts such as metal oxide or nitrate. The problems such as detrimental effect, environmental and even cost have been overcome by using sodium chloride as support. The yield of CNFs up to 7800 wt.% relative to the nickel catalyst has been achieved in the growth time of 15 min. The advantage of this synthesis technique is the simplicity and use of easily available low cost precursors. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg.Item Enhanced photostability and optical nonlinearity of nickel and cobalt organometallic complexes(Elsevier B.V., 2019) Manjunatha, K.B.; Rajarao, R.; Poornesh, P.; Rudresha, B.J.; Umesh, G.; Badekai Ramachandra, B.R.Nonlinear optical and limiting properties of nickel, cobalt metal-organic complexes and ligand (L) {L = N,N?-o-phenylenebis (4-hyrdoxy-salicylideneimine)} were studied using Z-scan technique using Q-switched Nd: YAG laser with nanosecond pulses at 532 nm. The results reveal that metal complexes exhibit large negative nonlinear refractive index (n2) of the order of 10?11 esu. The metal complexes displays large nonlinearity than the ligand due to effective charge delocalization between metal ion and ligand. The magnitude of ground state absorption cross section is small compared to the effective excited-state absorption cross section implying the observed nonlinearity is due to reverse saturable absorption. Further, metal-organic complexes exhibit enhanced optical limiting behaviour at nanosecond laser pulses. © 2019 Elsevier B.V.Item Green approach to synthesize multi-walled carbon nanotubes by using metal formate as catalyst precursors(2013) Rajarao, R.; Badekai Ramachandra, B.The multi-walled nanotubes (MWNTs) have been synthesized in large scale by using metal formate as catalyst precursors. The calcium carbonate is used as catalyst support, it is chosen because of its non toxic and easily soluble nature. The synthesis was carried out by chemical vapor deposition method for 15 min under optimized conditions. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD) method. The purity of the as grown products and purified products were determined by thermal analysis. The obtained yield of MWNTs was about 8300 wt% relative to the nickel catalyst. This synthesis route avoids the lengthy process of calcination and reduction for the preparation of catalysts hence this method is more economical. This economical and environmental friendly synthesis route can be used for synthesizing MWNTs in large scale. Copyright © 2013 American Scientific Publishers All rights reserved.Item Immobilized magnetic nano catalyst for oxidation of alcohol(Elsevier, 2015) Bhat, P.B.; Rajarao, R.; Sahajwalla, V.; Badekai Ramachandra, B.R.Covalent attachment of Schiff base on magnetic nanoparticles yielded good selectivity for oxidation of alcohols. The ferromagnetic interaction in the complex added comprehensive advantage in enhancing the catalytic activity of the nanocatalyst. A greener approach for alcohol oxidation was achieved in solventless method with good yield (>78%). Leaching experiments confirmed a strong interaction between magnetic support and complex. The catalyst showed significant conversion even after 5 catalytic runs. © 2015 Elsevier B.V. All rights reserved.Item Investigation of nonlinear optical and all-optical switching properties of novel ruthenium complex(2012) Manjunatha, K.B.; Shettigar, S.; Rajarao, R.; Umesh, G.; Ramachandra, Bhat, B.The nonlinear optical, optical limiting and all-optical switching properties of novel ruthenium complex doped PMMA film were investigated at 532 nm. The investigations show that the complex is a potential molecule for photonic applications. � 2012 OSA.Item Investigation of nonlinear optical and all-optical switching properties of novel ruthenium complex(IEEE Computer Society help@computer.org, 2012) Manjunatha, K.B.; Shettigar, S.; Rajarao, R.; Umesh, G.; Badekai Ramachandra, B.The nonlinear optical, optical limiting and all-optical switching properties of novel ruthenium complex doped PMMA film were investigated at 532 nm. The investigations show that the complex is a potential molecule for photonic applications. © 2012 OSA.Item Investigation of Nonlinear Optical and All-Optical Switching Properties of Novel Ruthenium Complex(Optica Publishing Group (formerly OSA), 2012) Manjunatha, K.B.; Shettigara, S.; Rajarao, R.; Umesh, G.; Badekai Ramachandra, B.The nonlinear optical, optical limiting and all-optical switching properties of novel ruthenium complex doped PMMA film were investigated at 532 nm. The investigations show that the complex is a potential molecule for photonic applications. © 2012 OSA - The Optical Society. All rights reserved.Item Large scale synthesis of carbon nanofibres on sodium chloride support(InTech Europe info@sagepub.co.uk, 2012) Rajarao, R.; Badekai Ramachandra, B.R.Large scale synthesis of carbon nanofibres (CNFs) on a sodium chloride support has been achieved. CNFs have been synthesized using metal oxalate (Ni, Co and Fe) as catalyst precursors at 680 °C by chemical vapour deposition method. Upon pyrolysis, this catalyst precursors yield catalyst nanoparticles directly. The sodium chloride was used as a catalyst support, it was chosen because of its non-toxic and water soluble nature. Problems, such as the detrimental effect of CNFs, the detrimental effects on the environment and even cost, have been avoided by using a water soluble support. The structure of products was characterized by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The purity of the grown products and purified products were determined by the thermal analysis and X-ray diffraction method. Here we report the 7600, 7000 and 6500 wt% yield of CNFs synthesized over nickel, cobalt and iron oxalate. The long, curved and worm shaped CNFs were obtained on Ni, Co and Fe catalysts respectively. The lengthy process of calcination and reduction for the preparation of catalysts is avoided in this method. This synthesis route is simple and economical, hence, it can be used for CNF synthesis in industries. © 2012 Rajarao and Bhat.Item Large-scale synthesis of high purity carbon nanotubes by novel catalytic route(2013) Rajarao, R.; Badekai Ramachandra, B.Large-scale production of carbon nanotubes is achieved by using metal formates as catalyst precursors by chemical vapor deposition method. The calcium carbonate is used as catalyst support, it is chosen because of its nontoxic and easily soluble nature. The synthesis was carried out at 700°C in quartz reactor for 15 min. The obtained yield of carbon nanotubes was about 96 times relative to the Ni/Co catalyst. The lengthy process of calcination and reduction for the preparation of catalysts is avoided in this method. This economical synthesis route is more efficient and environmentally friendly. Copyright © Taylor & Francis Group, LLC.Item Multi-walled carbon nanotube bound nickel Schiff-base complexes as reusable catalysts for oxidation of alcohols(2012) Rajarao, R.; Kim, T.H.; Badekai Ramachandra, B.R.Nickel salen and salophen complexes have been covalently anchored on multi-walled carbon nanotubes (MWNTs). The MWNT-supported nickel complexes have been characterized by inductive coupled plasma spectroscopy, FT-IR spectroscopy, UV-Vis spectrophotometry, transmission electron microscopy, and X-ray diffraction. The catalytic performance for the oxidation of primary and secondary alcohols was evaluated using periodic acid as oxidant. Reaction conditions have been optimized for MWNT-supported salen and salophen complexes by considering the effect of parameters such as solvent, reaction time, concentration of catalyst, amount of oxidant, etc. The catalytic activity was higher for supported catalysts than similar homogeneous ones. These supported catalysts were highly stable and reused several times without the loss of catalytic activity. © 2012 Taylor & Francis.Item Optical nonlinearity, limiting and switching characteristics of novel ruthenium metal-organic complex(Elsevier B.V., 2017) Manjunatha, K.B.; Rajarao, R.; Umesh, G.; Badekai Ramachandra, B.R.; Poornesh, P.We report the nonlinear optical properties of Ruthenium metal complex a promising organic material for use in scientific and technological applications. The thin films of newly synthesized ruthenium metal–organic complex were fabricated using spin coating technique. Z-scan and degenerate four wave mixing (DFWM) techniques used to extract the third-order nonlinear optical (NLO) parameters. The data reveals the investigated material exhibited relatively large NLO properties. The pump–probe experiments shows that the switch-on and off times of the material were in the order of ?s at different pump intensities and the energy dependent transmission studies reveal good limiting property of the material in nanosecond regime. © 2017 Elsevier B.V.Item Performance of an activated carbon supercapacitor electrode synthesised from waste Compact Discs (CDs)(Korean Society of Industrial Engineering Chemistry A-803 Twin Bldg 275-3 Yangjae-Dong Seocho-Kul Seoul 137-130, 2018) Farzana, R.; Rajarao, R.; Badekai Ramachandra, B.R.; Sahajwalla, V.Microporous activated carbon was synthesised using waste compact discs as precursor through physical activation method for supercapacitor electrode application. The activated carbon prepared at 900 °C for a time interval of 8 h showed highest surface area of 1214.25 m2 g?1. The electrochemical measurements showed that waste CDs derived activated carbon exhibited good specific capacitance, cycle stability and good rate capability compared to other waste derived activated carbon. The specific capacitance 51 F g?1 at the current density of 10 mV s?1 and energy density of 21.43 Wh kg?1 at power density 0.7 kW kg?1 was achieved in non-aqueous electrolyte. © 2018 The Korean Society of Industrial and Engineering ChemistryItem Plant root nodule like nickel-oxide-multi-walled carbon nanotube composites for non-enzymatic glucose sensors(Royal Society of Chemistry, 2015) Prasad, R.; Gorjizadeh, N.; Rajarao, R.; Sahajwalla, V.; Badekai Ramachandra, B.R.Herein, in this work we synthesized plant root nodule like NiO-MWCNT nanocomposites by a simple, rapid and solvent-free method using nickel formate as a precursor. Using a first-principle simulation study the interactions and charge transfer behaviour of the NiO and MWCNT composite is investigated. The as-prepared NiO-MWCNT composite is employed to fabricate a modified non-enzymatic carbon paste electrode (CPE) for glucose sensing. From the electrochemical investigation, the fabricated sensor shows an excellent sensitivity of 6527 ?A mM-1 cm-2 with a detection limit of 19 ?M and a linear response over a range from 0.001 mM to 14 mM of glucose concentrations, at an applied potential of 0.5 V. Importantly the sensor also exhibits greater stability, selectivity and reproducibility. A first principle simulation study shows the differences in charge density and charge transfer behaviour from nanotubes to NiO nanoparticles, which in turn enhances the electro catalytic property of the NiO-MWCNT composite. Hence, these results indicate that the NiO-MWCNT composite is a potential material for non-enzymatic electrochemical glucose sensors. This journal is © The Royal Society of Chemistry.