Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
80 results
Search Results
Item New thiophene-based donor-acceptor conjugated polymers carrying fluorene or cyanovinylene units: Synthesis, characterization, and electroluminescent properties(John Wiley and Sons Inc, 2013) Murali, M.G.; Udayakumar, U.; Yadav, V.; Srivastava, R.Two new thiophene-based donor-acceptor (D-A) conjugated polymers, PDTOFV and PDTOCN, are synthesized and characterized. The polymers are readily soluble in common organic solvents and exhibit good thermal stability with onset decomposition temperature (Td) in the range 310-330°C. Cyclic voltammetry studies revealed that polymers possess low-lying highest occupied molecular orbital (HOMO) energy levels (-5.94 eV for PDTOFV and -5.86 eV for PDTOCN) and low-lying lowest unoccupied molecular orbital (LUMO) energy levels (-3.35 eV for PDTOFV and -3.55 eV for PDTOCN). The optical band gap is calculated from onset absorption edge of the polymer film. The polymers exhibit green fluorescence with fluorescence quantum yields (?fl) of 38% and 42%, respectively, for PDTOFV and PDTOCN. Polymer light-emitting diodes (PLEDs) are fabricated using these polymers with a device configuration of ITO/PEDOT:PSS/polymer/Al. The device based on PDTOFV emitted green light with Commission Internationale de I'Eclairage (CIE) coordinate values of (0.25, 0.39). Whereas, the device based on PDTOCN showed white light emission with CIE coordinate values of (0.32, 0.35), which is very close to the values (0.33, 0.33) of standard white light emission. The threshold voltages of the PLEDs are determined by current density-voltage characteristics and are found to be 7.3 and 3.9 V for PDTOFV and PDTOCN, respectively. © 2012 Society of Plastics Engineers.Item Nickel(II) complex of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde-4-methyl thiosemicarbazone: Synthesis, structural characterization and biological application(Elsevier Ltd, 2013) Sankaraperumal, A.; Karthikeyan, J.; Nityananda Shetty, A.N.; Lakshmisundaram, R.New complex of Ni(II) with p-[N,N-bis(2-chloroethyl)amino]benzaldehyde-4- methyl thiosemicarbazone (CEAB-4-MTSC) have been synthesized and characterized by elemental analysis, IR, electronic, 1H NMR spectroscopy. The crystal structure of the free ligand and complex has been determined by single crystal X-ray diffraction technique. In the complex, thiosemicarbazone ligand is coordinated to nickel through (1:2 complex) SNNS mode. The complex crystallizes in the triclinic with space group P1?. The complex has been tested for their antibacterial activity against various pathogenic bacteria. From this study, it was found out that the activity of complex reaches the effectiveness of the conventional bacteriocide Streptomycin compared to simple ligand. © 2012 Elsevier Ltd. All rights reserved.Item The hierarchies of hydrogen bonds in salts/cocrystals of isoniazid and its Schiff base - A case study(Royal Society of Chemistry, 2016) Oruganti, M.; Khade, P.; Das, U.K.; Trivedi, D.R.A series of two salts of isoniazid and two cocrystals of its Schiff base have been synthesised and characterized using FT-IR, 1H-NMR, DSC, XRPD and SCXRD. The crystal structures with 2,5-dihydroxybenzoic acid, 2,6-dihydroxy benzoic acid, 3-aminobenzoic acid and o-phthalic acid have been deduced. In all complexes the involvement of pyridine N (proton transfer/robust synthon) is noticed. The unit cell similarity index was calculated between two cocrystals (N-(propan-2-ylidene)isonicotinohydrazide)·(2,5-dihydroxybenzoic acid) and (3-aminobenozic acid)·(N-(propan-2-ylidene)isonicotinohydrazide). Furthermore, the index was compared with the reported complexes and it was found to be close to zero indicating isostructurality. The correlation between the NPyr-H?O (acid) hydrogen bond distance for the reported cocrystals and their corresponding pKa values has been deduced and validated. © The Royal Society of Chemistry 2016.Item ZnS semiconductor quantum dots production by an endophytic fungus Aspergillus flavus(Elsevier Ltd, 2016) Uddandarao, P.; Mohan B, R.The development of reliable and eco-friendly processes for the synthesis of metal sulphide quantum dots has been considered as a major challenge in the field of nanotechnology. In the present study, polycrystalline ZnS quantum dots were synthesized from an endophytic fungus Aspergillus flavus. It is noteworthy that apart from being rich sources of bioactive compounds, endophytic fungus also has the ability to mediate the synthesis of nanoparticles. TEM and DLS revealed the formation of spherical particles with an average diameter of about 18 nm and 58.9 nm, respectively. The ZnS quantum dots were further characterized using SEM, EDAX, XRD, UV-visible spectroscopy and FTIR. The obtained results confirmed the synthesis of polycrystalline ZnS quantum dots and these quantum dots are used for studying ROS activity. In addition this paper explains kinetics of metal sorption to study the role of biosorption in synthesis of quantum dots by applying Morris-Weber kinetic model. Since Aspergillus flavus is isolated from a medicinal plant Nothapodytes foetida, quantum dots synthesized from this fungus may have great potential in broad environmental and medical applications. © 2016 Elsevier B.V. All rights reserved.Item Bacteriological synthesis of iron hydroxysulfate using an isolated Acidithiobacillus ferrooxidans strain and its application in ametryn degradation by Fenton's oxidation process(Academic Press, 2019) Bhaskar, S.; Manu, B.; Sreenivasa, M.Y.The investigation reports the application of biogenic jarosite, an iron hydroxy sulfate mineral in Fenton's Oxidation process. Ametryn, a herbicide detrimental to aquatic life and also to human is treated by Fenton's oxidation process using synthesized iron mineral, jarosite. The jarosite synthesis was carried out by using an isolated Acidithiobacillus ferrooxidans bacterial strain with ferrous as an iron supplement. The isolated strain was characterized by molecular techniques and biooxidation activity to ferrous to ferric iron was checked. On Fenton's treatment ametryn degradation upto 84.9% and COD removal to the extent of 56.1% was observed within 2 h of treatment and the reaction follows the pseudo first order kinetics with the curve best fit. The slight increase in kinetic rate constant on jarosite loading rate increase from 0.1 g/L to 0.5 g/L with H2O2 dosage of 100 mg/L confirms that jarosite has a catalytic role in the removal of ametryn. Mass spectroscopy analysis of treated synthetic ametryn solution at various intervals reveal the degradation follows dealkylation and hydroxylation pathway with the formation of three major intermediate compounds discussed here. © 2018 Elsevier LtdItem Functionalized pyrene-based AIEgens: synthesis, photophysical characterization and density functional theory studies(John Wiley and Sons Ltd, 2019) Mohan, M.; James, J.; Satyanarayan, M.N.; Trivedi, D.Three new pyrene-based derivatives P1, P2 and P3 with a substituted pyrazole were designed, synthesized and characterized using standard spectroscopic techniques. Ultraviolet–visible (UV–vis) spectroscopic studies for P1–P3 uncovered a finite bathochromic shift of the molecules in solvents of varying polarity. Photoluminescence (PL) studies revealed the significant fluorescence emission of all molecules in higher polar solvents such as MeOH and dimethylformamide (DMF). Fluorescence quantum yield studies demonstrated the importance of P3 possessing cyanofunctionality for imparting higher emission with a quantum yield of 0.36%. Ratiometric studies performed in a tetrahydrofuran (THF)/H2O mixture indicated fluorescence enhancement with increasing overall percentage of water, confirming the aggregation-induced emission effect. Cyclic voltammetry study of molecules P1–P3 revealed an irreversible oxidation peak and the band gaps were calculated to be 2.26 eV for P1 and 2.31 eV for P2 and P3 respectively. Density functional theory (DFT) studies performed on molecules P1–P3 validate the structure correlation of the molecules. Theoretically estimated highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and bandgap correlated well with the experimental values. Furthermore, time-dependent (TD)DFT showed that the major contribution for the electronic transitions occurring in the system was governed by HOMO-1 and LUMO+1 orbitals. © 2019 John Wiley & Sons, Ltd.Item Effect of fuel and solvent on soot oxidation activity of ceria nanoparticles synthesized by solution combustion method(KeAi Communications Co., 2019) Patil, S.S.; Prasad Dasari, H.P.Effect of fuel (glycine and urea) and solvent (water, acetone and ethanol) on the soot oxidation activity of ceria nanoparticles synthesized by solution combustion method is carried out in the present study. X-ray diffraction (XRD) patterns displayed a fluorite structure and the Tauc's plot obtained from UV-Diffusive Reflectance spectroscopy (UV-DRS) showed that the band gap value was around 2.9–3.1 eV for the synthesized ceria nanoparticles irrespective of the fuel and solvent used. Ceria nanoparticles synthesized using glycine and acetone resulted in lower crystallite size, higher facet ratios ([1 0 0]/[1 1 1] and [1 1 0]/[1 1 1]) and higher lattice strain than compared to other solvents and fuels and thus resulted in better soot oxidation activity (T50 = 416 °C). The present synthesis method has played a significant role in improving the reactive facet ratios, providing lower crystallite size and high lattice strain. © 2019Item Phenanthroimidazole-based chromophores for organic light-emitting diodes: synthesis, photophysical, and theoretical study(John Wiley and Sons Ltd, 2020) Tagare, J.; Verma, N.; Tarafder, K.; Sivakumar, S.Organic light-emitting diodes (OLED) are gaining attention and making a significant contribution to the area of lighting and displays technology. The synthesis of new materials that can act as a host as well as emissive materials is crucial and efforts have been made in this direction in this research. Here, four star-shaped fluorophores, with a donor–acceptor (D–A) structure and with triphenylamine and phenanthroimidazole groups with different substitutions at the N1 position of the imidazole moiety, were designed and synthesized. Synthesized fluorophores showed sufficient thermal stability (10% Td in the range 230–280°C). Ultraviolet–visible (UV–vis) spectra of the fluorophores showed multiple absorption bands (bands in the UV region, due to ?–?* transitions of the conjugated aromatic portion) and all fluorophores showed blue emission in dichloromethane solution. Electrochemical analysis indicated that all fluorophores had excellent oxidation and reduction characteristics. Theoretical calculations were also performed to better understand the structural and electronic properties of the synthesized fluorophores. All fluorophores had higher triplet (T1) energy (ranging from 2.49–2.52 eV) than the widely used green (Ir(ppy)3 –2.4 eV) and red (Ir (piq)2 acac – 2.2 eV) dopant materials. These results indicated that these fluorophores would be useful as host materials for efficient green and red phosphorescent OLEDs. © 2020 John Wiley & Sons, Ltd.Item Imidazole-Pyrene Hybrid Luminescent Materials for Organic Light-Emitting Diodes: Synthesis, Characterization & Electroluminescent Properties(Elsevier B.V., 2021) Umasankar, G.; Ulla, H.; Madhu, C.; Gontu, G.R.; Shanigaram, B.; Nanubolu, J.B.; Bhanuprakash, B.; Karunakar, G.V.; Satyanarayan, M.N.; Rao, V.J.A series of multichromophoric, pyrene-imidazole-phenyl based hybrid luminescent small molecules (PA, PI, PnB, PtB, PoM and PnDM) with different donating groups at the para position of the phenyl attached to N1 position of imidazole moiety were designed, synthesized, and characterized, for use in blue organic light-emitting diodes (OLEDs). The photophysical, thermal and electrochemical properties of the molecules were systematically investigated. All the molecules displayed delayed fluorescence at room temperature with a lifetime ranging from 7.1 to 8.5 µs. The synthesized fragment molecules (tetraphenyl-imidazoles: IA, IoM and InDM) revealed high triplet energies of ~ 2.90eV. Glass transition temperatures determined to range from 77°C to 123°C and decomposition temperatures are found to be above 280°C. The molecules possess appropriate HOMO and LUMO energy levels for effective charge injection. The crystal structure for PI is reported. OLED devices were fabricated based on the pyrene-imidazole-phenyl hybrids as emitters and as dopants with CBP as host. OLED devices with PI doped (5% wt.) with CBP exhibits excellent device performance with a current efficiency of 9.82 cd/A, the power efficiency of 8.32 lm/W and external quantum efficiency of 4.64%. © 2021Item Kinetics and regression analysis of phenanthrene adsorption on the nanocomposite of CaO and activated carbon: Characterization, regeneration, and mechanistic approach(Elsevier B.V., 2021) Aravind Kumar, J.; Krithiga, T.; Vijai Anand, K.; Sundararaman, S.; Karthick Raja Namasivamyam, S.; Annam Renita, A.A.; Hosseini-Bandegharaei, A.; Praveenkumar, T.R.; Manivasagan, M.; Bhat, N.S.; Dutta, S.In the present study, calcium oxide supported on activated carbon (CaO@AC) nanocomposite was synthesized using Basil leaf extract as a promoter and used to remove phenanthrene, an environmental pollutant, from aqueous solution. The activated carbon (AC) was prepared by the carbonization of Palm shells under pyrolytic conditions. The CaO@AC nanocomposite was characterized by FTIR, SEM-EDX, BET, and PXRD. The characterized CaO@AC nanocomposite was employed as an adsorbent for selective removal of phenanthrene from wastewater, maintaining the optimized conditions at initial phenanthrene concentration (5 mg/L), catalyst dosage (1 g), temperature (30 °C), and pH (7.6) for all batches. The adsorption isotherm and the kinetic studies for regression analysis were well fitted for the Freundlich model (R2 = 0.9956) and non-linear Pseudo (II order) mechanism (R2 = 0.9942). The results showed that the type IV linear form of pseudo-II order kinetic expression was inadequate for the kinetic rate parameters compared to the type I - III models. The CaO@AC was demonstrated as an inexpensive, scalable, recyclable, and eco-friendly adsorbent material for removing phenanthrene from wastewater. © 2021 Elsevier B.V.