Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
18 results
Search Results
Item Synthesis and in vitro biological evaluation of new pyrazole chalcones and heterocyclic diamides as potential anticancer agents(Elsevier B.V., 2015) Sankappa Rai, U.; Isloor, A.M.; Shetty, P.; Pai, K.S.R.; Fun, H.-K.Synthesis and characterization of new heterocyclic pyrazole chalcones (4a-. e) and diamide (6a-. e) derivatives are described. Pyrazole chalcones were synthesized by the reaction of pyrazole aldehydes and suitable aromatic ketones. Diamides were synthesized by the reaction of phthalic acid and amines. Newly synthesized compounds were characterized by spectral studies and their biological activity was assessed in vitro using MCF-7 (human breast adenocarcinoma) and HeLa (human cervical tumor cells) cell lines. Few of the synthesized molecules inhibited the growth of the human breast cancer cell lines and human cervical tumor cell lines at low micromolar to nanomolar concentrations. © 2014 King Saud University.Item Investigation on structural, magneto-transport, magnetic and thermal properties of La0.8Ca0.2-xBaxMnO3 (0 ? x ? 0.2) manganites(Elsevier Ltd, 2015) Manjunatha, S.O.; Rao, A.; Subhashini, u.; Okram, G.S.A systematic study on the structural, electrical, magnetic and thermo-electric properties of La0.8BaxCa0.2-xMnO3 (0 ? x ? 0.2) manganites is carried out in the present work. The samples have been prepared using solid state reaction technique. All the samples are single phased. It is seen that Ba-doping introduces a structural phase transformation viz. from rhombohedral to cubic system. Electric and magnetic studies respectively show that the metal-insulator transition temperature, TMI and Curie temperature, TC increase with Ba-content. Magneto-resistance (MR) data shows that it decreases with Ba-doping. Analyses of the electrical transport data in metallic region i.e. T < TMI shows that the electrical transport is governed predominantly by electron-electron scattering process. On the other hand, the adiabatic small polaron hopping (ASPH) model is appropriate in the high-temperature insulating range viz. T > TMI. We have used the electrical resistivity data in the entire temperature range (50-300 K) and analyzed using the phenomenological percolation model which is based on the phase segregation mechanism. We have analyzed the Seebeck coefficient data which reveals that the small polaron hopping mechanism is operative in high temperature regime and the low temperature region is examined by taking into account the impurity, electron-magnon scattering, and spin wave fluctuation terms. It is established that the electron-magnon scattering is dominating for the thermoelectric transport below TMI. © 2015 Elsevier B.V.Item Low-temperature sonochemical synthesis of high dielectric Lanthanum doped Cerium oxide nanopowder(Elsevier Ltd, 2018) Kishor Kumar, M.J.; Kalathi, J.T.Lanthanum (La) doped Cerium Oxide (CeO2) nanopowder was synthesized at a relatively lower temperature (70°C), without calcination in a simple, faster, and efficient way through sonochemical method. X-ray diffraction (XRD) results confirmed the formation of a cubic fluorite structure of nanocrystalline CeO2 and lattice deformation due to La-doping in CeO2. TEM analysis revealed that the size of La-doped CeO2 particles is in the range of 20?50 nm. In addition, selective area electron diffraction (SAED) and high-resolution TEM (HRTEM) analyses portrayed the nano-crystallinity, lattice fringe pattern, and d-spacing details of La-doped CeO2 powder. Lanthanum doping in CeO2 was further confirmed by a shift in Raman band towards the lower frequency (from 464 cm?1 to 457cm?1) along with peak intensity increase. Photoluminescence (PL) emission spectra showed that emission intensity of the La-doped CeO2 at 510 nm is increased due to oxygen vacancy mediated charge transfer. All these results confirm the successful doping of La in CeO2. The La-doped CeO2 powder possesses a high dielectric constant (?r) of 106 and a low dielectric loss (tan ?) of < 0.4 % at 1 kHz. The La-doped CeO2 finds potential applications on developing devices in the field of a thin film capacitor, transistors, and solid oxide fuel cells. © 2018 Elsevier B.V.Item PMMA-LZO Composite Dielectric Film with an Improved Energy Storage Density(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Kishor Kumar, M.J.; Kalathi, J.T.Energy storage materials in modern electronic devices and renewable energy systems are inevitable. The incorporation of inorganic fillers into the polymer matrix is a promising option for the advancement of storage materials with high energy density. The agglomeration of inorganic fillers in the polymer matrix and phase separation remain the main obstacles to efficient applications of the composites for energy storage. Here, the primary attention was given to achieve a uniform distribution of high-k LZO (Lanthanum Zirconium Oxide) filler into a PMMA (Polymethylmethacrylate) matrix to enhance the dielectric constant and energy storage density of PMMA while keeping dielectric loss at minimum. We prepared PMMA-LZO composite films with variable LZO content by ultrasound-assisted mixing followed by spin coating the solution on ITO (Indium tin oxide) coated glass. The effect of LZO content on dielectric properties of the LZO-PMMA films was studied. Dielectric constant (k) of PMMA was found to be increased from 3.1 to 15.3 at 15 vol.% LZO loading with a dielectric loss of 0.0582. However, 10 vol.% LZO loaded PMMA showed an improved dielectric constant of 13.4 while the dielectric loss remained the same as that of the neat PMMA. The LZO-PMMA films with 10 vol.% and 15 vol.% of LZO loading exhibited maximum energy density of 5.94 J cm?3 and 6.53 J cm?3, respectively. Overall, the 10 vol.% LZO loading was found to be optimum to achieve a stable film with improved dielectric properties. This work provides a viable approach for the development of flexible, high-energy density materials with a minimum dielectric loss. © 2019, The Minerals, Metals & Materials Society.Item Studies on the Solid Oxide Cell Perovskite Electrode Materials for Soot Oxidation Activity(Springer, 2019) Shenoy, C.S.; Patil, S.S.; Govardhan, P.; Shourya, A.; Prasad Dasari, H.P.; Saidutta, M.B.; Harshini, H.Solid oxide cell (SOC) perovskite electrode materials (BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-?), LSCF (La0.6Sr0.4Co0.2Fe0.8O3-?) and LSCM (La0.75Sr0.25Cr0.5Mn0.5O3-?)) were synthesised using microwave-assisted reverse-strike co-precipitation method and tested for soot oxidation activity. The calcined perovskite materials were characterized using FT-IR, XRD, SEM and BSE, BET and BJH and XPS analysis. The mean activation energy for soot oxidation was calculated from Ozawa plots at various heating rates (5, 10, 15 and 20 K/min) at different levels of soot conversions (T10 to T90) for BSCF, LSCM and LSCF perovskite materials and was around 133 ± 11.5, 138 ± 9.9 and 152 ± 7.2 kJ/mol, respectively. Irrespective of the heating rates, BSCF material showed the lowest T50 temperature than compared to other samples, and it is correlated to the presence of Fe3O4 as a secondary phase. © 2019, Springer Nature Switzerland AG.Item High-Intensity Ultrasound-Assisted Low-Temperature Formulation of Lanthanum Zirconium Oxide Nanodispersion for Thin-Film Transistors(American Chemical Society service@acs.org, 2020) Pujar, P.; Madaravalli Jagadeeshkumar, K.K.; Naqi, M.; Gandla, S.; Cho, H.W.; Jung, S.H.; Cho, H.K.; Kalathi, J.T.; Kim, S.The process complexity, limited stability, and distinct synthesis and dispersion steps restrict the usage of multicomponent metal oxide nanodispersions in solution-processed electronics. Herein, sonochemistry is employed for the in situ synthesis and formulation of a colloidal nanodispersion of high-permittivity (?) multicomponent lanthanum zirconium oxide (LZO: La2Zr2O7). The continuous propagation of intense ultrasound waves in the aqueous medium allows the generation of oxidant species which, on reaction, form nanofragments of crystalline LZO at ?80 °C. Simultaneously, the presence of acidic byproducts in the vicinity promotes the formulation of a stable as-prepared LZO dispersion. The LZO thin film exhibits a ? of 16, and thin-film transistors (TFTs) based on LZO/indium gallium zinc oxide operate at low input voltages (?4 V), with the maximum mobility (?) and on/off ratio (Ion/Ioff) of 5.45 ± 0.06 cm2 V-1 s-1 and ?105, respectively. TFTs based on the compound dielectric LZO/Al2O3 present a marginal reduction in leakage current, along with enhancement in ? (6.16 ± 0.04 cm2 V-1 s-1) and Ion/Ioff (?105). Additionally, a 3 × 3 array of the proposed TFTs exhibits appreciable performance, with a ? of 3-6 cm2 V-1 s-1, a threshold voltage of -0.5 to 0.8 V, a subthreshold swing of 0.3-0.6 V dec-1, and an Ion/Ioff of 1-2.5 (×106). © © 2020 American Chemical Society.Item TiO2 nanofluid for oxygen mass transfer intensification in pulsed plate column(Taylor and Francis Ltd., 2021) Shet, A.S.; Shetty K, K.Oxygen mass transfer coefficient (kLa) is a key parameter in biochemical, photochemical, or other reactors. Pulsed plate column (PPC) has a potential application as a gas-liquid contactor. In the present work, TiO2 nanofluid mediated oxygen mass transfer intensification in PPC is studied. The pulsing velocity (A × f) and nanoparticle loading in volume percent (?) have an interacting effect on kLa. The effect of ? on kLa, showed a dual regime of an increase in kLa with an increase in ? up to a critical loading (? CL) and decrease in kLa on further increase in ?. The effect of (A × f) on kLa showed three regimes. ? CL & kLa were found to decrease as the nanoparticle's size increased. Dimensionless correlations based on multiple regression analysis and ANN models were developed to predict the kLa values in PPC with TiO2 nanofluids. © 2020 Taylor & Francis Group, LLC.Item Dilatometer studies on LAMOX based electrolyte materials for solid oxide fuel cells(Elsevier Ltd, 2021) Das, A.; Lakhanlal, u.; Shajahan, I.; Prasad Dasari, H.P.; Saidutta, M.B.; Harshini, H.The present study deals with the citrate complexion synthesis of LAMOX-based Solid Oxide Fuel Cell (SOFC) electrolyte materials (La1.8Dy0.2Mo2-xWxO9 (x = 0, 0.1, 0.2, 0.5, and 1), La1.8Dy0.2Mo2-xGaxO9 (x = 0.1 and 0.2), and La1.8Dy0.2Mo2-xVxO9 (x = 0.025, 0.05, 0.1, and 0.2)) and their characterization to understand the sintering behaviour and phase stability. From the dilatometer studies, the linear shrinkage and shrinkage rate of the LDMW (x = 0, and 0.1) showed better shrinkage than LM and LDM. Gallium addition (LDMG) and Vanadium addition (LDMV) showed a negative impact on shrinkage behaviour. In the temperature range of 500–580 °C, the abrupt change in shrinkage rate showed the transition of phase from ? to ? for the LM. The modification of LM to LDM, LDMW, and LDMV suppressed the formation of the ? phase. During thermal expansion behaviour study in the temperature range of 100–500 °C and 550–800 °C, the LM sintered pellet showed the coefficient of thermal expansion (CTE) values of 13.3 ? 10?6/°C and 21.6 ? 10?6/°C respectively. The LDM and LDMW sintered pellets showed the CTE values in the range of 14–15 ? 10?6/°C and 16–19 ? 10?6/°C, respectively. The relative density of the sintered pellets (1100 °C/5 h in air) (LM, LDM, LDMW, and LDMG (x = 0.1)) is found to be >90%. It provides the suitability of these materials for further investigation as electrolytes of SOFCs/SOECs. © 2020 Elsevier B.V.Item Electrical conductivity studies on LAMOX based electrolyte materials for solid oxide fuel cells(Elsevier Ltd, 2022) Srijith; Lakhanlal, u.; Das, A.; Prasad Dasari, H.P.; Saidutta, M.B.In this study, the electrical conductivity of the LAMOX based electrolytes (La1.8Dy0.2Mo2-xWxO9 (x = 0, 0.1, 0.2, 0.5, and 1), and La1.8Dy0.2Mo2-xGaxO9 (x = 0.1)) synthesized by the citrate complexion method has been studied using DC four-probe method. The electrical conductivity of the electrolytes is measured in the temperature range of 800–400 °C in the air (∼100 ml min−1). The effect of W and Ga substitution at the Mo site on the electrical conductivity is evaluated. The long-term electrical conductivity stability test (time on stream) (5 h) is conducted at 650, 580, and 520 °C to study the effect of possible phase transition on electrical conductivity. A high-temperature XRD study is also conducted in the temperature range of 500–650 °C (during heating and cooling) on selected electrolyte materials (La1.8Dy0.2Mo2-xWxO9 (x = 0 and 0.1) and La1.8Dy0.2Mo2-xGaxO9 (x = 0.1)) to study the α↔β phase transition. The electrical conductivity of these electrolytes in the air at 800 °C is in the range of 5.3 × 10−2 – 14 × 10−2 S cm−1. The activation energy (EA) of these electrolytes is in the range of 1.11–1.62 eV. The VTF parameters σo, B, and To are in the range of 67.46–395.88 S cm−1 K0.5, 0.122–0.254 eV, and 247–347 °C, respectively. The La1.8Dy0.2Mo2-xWxO9 (x = 0.1) shows highest electrical conductivity (14 × 10−2 S cm−1, EA = 1.54 eV) among all electrolytes in air at 800 °C and for this material the VTF parameters σo, B, and To are 170.32 S cm−1 K0.5, 0.153 eV, and 302 °C, respectively. © 2022 Elsevier Ltd and Techna Group S.r.l.Item Magnetic complexity, magnetodielectric effect and DFT calculations on correlation driven Gd2CoMnO6 insulator(Elsevier B.V., 2022) Prashanth, C.H.; Reddy, I.; Tarafder, K.; Chandrasekhar Kakarla, D.; Yang, H.D.; Adyam, V.; Jyothinagaram, K.In the family of Re2CoMnO6 manganite double perovskites, in contrast to parent La2CoMnO6 compound, Gd2CoMnO6 exhibits multiple magnetic transitions; ferromagnetic (FM) ordering, TC ∼ 112 K followed by AFM transition, TN ∼ 47 K, Gd spins ordering for T < 10 K and large isothermal entropy changes. A study of DC field-superimposed AC magnetic susceptibility measurements revealed the field-induced magnetic glassy behavior below TC and enhancement of FM correlations above TC. From the analysis of Almeida-Thouless behavior and dynamical power-law fit to frequency dependent AC susceptibility, Gd2CoMnO6 exhibits a volume spin glass-like nature below the freezing temperature, Tf ∼ 117.5 K. The isothermal field-dependent magnetic and dielectric permittivity data and temperature dependent Raman measurements (reported in ref. R. X. Silva et al., J, Appl. Phys. 114 194,102 (2013)) confirms the spin-phonon coupling induced magnetodielectric effect. Further, the ground-state electronic structure and magnetic properties of Gd2CoMnO6 are investigated using DFT + U formalism with Vienna Ab-initio Simulation Package (VASP) code and predicted the material to be a correlation-driven insulator. The correlation value of the Hubbard U parameter at the 4f-Gd elements changes the stability of the magnetic state from Ferri to FM spin alignment for Ueff ≥ 3 eV and is correlated to the experimentally observed field-induced transformation of the short-range-order FiM/spin-glass-like phase into the long-range ordered FM phase. © 2022