Prabitha B Nair - Academia.edu (original) (raw)

Papers by Prabitha B Nair

Journal of Molecular Structure, Nov 1, 2017

The elimination of toxic heavy metals by the formation of stable coordination compounds with biol... more The elimination of toxic heavy metals by the formation of stable coordination compounds with biologically active ligands is applicable in drug designing. A new crystalline complex of cadmium with nicotinic acid is grown at ambient temperature using the single gel diffusion method in which the crystal structure is different from those already reported. Single crystal x-ray diffraction reveals the identity of crystal structure belonging to monoclinic system, P2 1 /c space group with cell dimensions a = 17.220 (2) Å, b = 10.2480 (2) Å, c = 7.229(9) Å, β = 91.829(4) •. Powder x-ray diffraction analysis confirmed the crystallinity of the sample. The unidentate mode of coordination between the metal atom and the carboxylate group is supported by the Fourier Transform Infra Red spectral data. Thermal analysis ensures the thermal stability of the complex. Kinetic and thermodynamic parameters are also calculated. The stoichiometry of the complex is confirmed by the elemental analysis. The UV-visible spectral analysis shows the wide transparency window of the complex in the visible region. The band gap of the complex is found to be 3.92 eV. The complex shows excellent antibacterial and antifungal activity.

Journal of Molecular Structure, 2017

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Journal of Materials Science: Materials in Electronics, Jul 14, 2012

Homogeneous and transparent BaTiO 3 thin films were prepared by sol-gel dip coating method. The p... more Homogeneous and transparent BaTiO 3 thin films were prepared by sol-gel dip coating method. The prepared BaTiO 3 thin films were annealed in air and O 2 atmosphere at different temperatures. The annealed BaTiO 3 thin films were amorphous in nature. Scanning electron microscopy (SEM) revealed the nucleation and particle growth on the films. Energy-dispersive X-ray (EDX) analysis data revealed the adsorption of oxygen atoms in the BaTiO 3 film. The direct energy band gap was found to vary (3.84-3.58 eV) as functions of annealing atmosphere and temperature. Photoluminescence (PL) revealed intense emission peaks at 393 and 675 nm. Quenching of PL intensity was observed in films annealed at high temperature and in O 2 atmosphere. This is due to reduction in the oxygen vacancy by the adsorption of oxygen in the film. Luminescence spectra also have been related to the results obtained by SEM and EDX analysis. The change in luminescence intensity of BaTiO 3 thin films makes it suitable for optoelectronic temperature sensor applications.

Bulletin of Materials Science, Apr 20, 2022

Titanium dioxide (TiO2) nanoparticles were synthesised by the modified sol–gel method at differen... more Titanium dioxide (TiO2) nanoparticles were synthesised by the modified sol–gel method at different calcination temperatures. Samples were characterized using X-ray diffraction (XRD), high-resolution transmission microscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy, Brunauer, Emmett and Teller surface area analyzer (BET) and diffuse reflectance spectroscopy (DRS). Phase transformation of TiO2 nanoparticles from anatase to rutile phase with an increase in calcination temperature from 573 to 1173 K was observed from XRD analysis. Detailed structural analysis using size–strain plot and Halder–Wagner method was done for all samples. The formation of TiO2 nanoparticles was confirmed from FTIR and EDAX spectra. The TEM image of the sample calcined at 673 K showed non-spherical shaped particles having particle sizes 13.16 ± 3.35 nm. The bandgap energy calculated from DRS decreases with an increase in calcination temperature, which supports phase transformation observed in XRD analysis. The photocatalytic degradation efficiency was evaluated by monitoring the degradation of Congo red (CR) azo dye under UV light and natural sunlight. The degradation of CR dye was confirmed by analysing the FTIR spectrum of the degraded sample. The sample calcined at 673 K, in the pure anatase phase, exhibited the highest photocatalytic activity.

International journal of engineering research and technology, Apr 24, 2018

Undoped and Tb doped TiO2 thin films (0.2, 0.3, 0.4 at%) were deposited onto quartz substrates by... more Undoped and Tb doped TiO2 thin films (0.2, 0.3, 0.4 at%) were deposited onto quartz substrates by RF magnetron sputtering. The optical and photoluminescence (PL) properties of the films, post-annealed at 873 K were examined using UV-vis optical transmission spectra and PL spectra. Tb doping caused a blue shift of the absorption edge which indicates an increase in optical band gap. An increase in refractive index was also observed with increasing Tb content. Two main PL emission peaks at 475.80 and 573.53 nm corresponding to intra 4f 5 D3 → 7 F3 and 5 D4 → 7 F4 transitions respectively of Tb 3+ ions were observed in all the Tb doped films. PL intensity was found to increase with increasing Tb content upto 0.3 at% after which it showed a decrease due to concentration quenching.

Journal of Nanoscience and Nanotechnology, Mar 1, 2012

Indium doped zinc oxide (InZnO) thin films were deposited onto corning glass substrates by RF mag... more Indium doped zinc oxide (InZnO) thin films were deposited onto corning glass substrates by RF magnetron sputtering. The dependence of crystal structure, surface morphology, optical properties and electrical conductivity on substrate temperature was investigated using XRD, AFM, UV-vis Spectrophotometer, Fluorescence Spectrophotometer and four-point probe. The films were prepared at different substrate temperatures viz, room temperature (RT), 473 K and 673 K at RF power 200 W. All the films showed preferred orientation along (002) direction. Crystallite size increased from 14 to 19 nm as the substrate temperature was increased to 473 K. With increase in substrate temperature the crystallites did not show any further growth. AFM analysis showed that the rms roughness value decreased from 60 nm to 23 nm when the substrate temperature was increased to 673 K. Optical measurements revealed maximum band gap and minimum refractive index for the film prepared at 473 K. A strong correlation between the band gap variation and the strain developed at different substrate temperatures is established.

Nucleation and Atmospheric Aerosols, 2014

ABSTRACT

Physica B-condensed Matter, Apr 1, 2010

Abstract ZnO thin films were deposited on corning glass substrates by RF magnetron sputtering at ... more Abstract ZnO thin films were deposited on corning glass substrates by RF magnetron sputtering at room temperature. The dependence of crystal structure, morphology and optical properties on post-deposition annealing was investigated using XRD, AFM and UV–vis Spectrophotometer. The as-deposited films were amorphous in nature. Post-deposition annealing for 1 h in air caused an improvement in crystallinity with preferential orientation along (0 0 2) direction. Better crystallinity was observed at 673 K. Crystallite size increased from 16 to 27 nm as annealing temperature was increased from 473 to 873 K. It is evident from AFM analysis that rms roughness of the film annealed at 673 K is minimum indicating better optical quality. Optical measurements show a decrease in direct band gap from 3.289 (as deposited) to 3.25 eV when the annealing temperature was increased to 673 K. With further increase in temperature, band gap increases.

Journal of Physics and Chemistry of Solids, Jun 1, 2011

The dependence of structural properties and optical constants on annealing temperature of a 2-((1... more The dependence of structural properties and optical constants on annealing temperature of a 2-((1,2-bis (diphenylphosphino)ethyl)amino) acetic acid-methyl red-monochloro zinc dihydride (DPEA-MR-Zn) as a novel organic semiconductor thin film was studied. The DPEA-MR-Zn thin film was deposited on silicon substrates using the spin coating technique. The as-deposited film was annealed in air for 1 h at 150, 175 and 205 C. The XRD study of DPEA-MR-Zn in its powder form showed that this complex is mere a triclinic crystal structure with a space group P-1. In addition, the XRD patterns showed that the asdeposited thin films were crystallized according to the preferential orientation [(214), (121), (026), (302), (122) and (114)]. Moreover, two additional peaks (221 and 247) were shown at 2q nearly 30 , and 69 , where, the more annealing temperature, the more the intensity of the two peaks. In addition, it was noticed that the grain size had a remarkable change with an annealing temperature of the DPEA-MR-Zn thin films. The optical measurements showed that the thin film has a relatively high absorption region where the photon energy ranges from 2 to 3.25 eV. Both of WempleeDiDomenico and single Sellmeier oscillator models were applied on the DPEA-MR-Zn to analyze the dispersion of the refractive index and the optical and dielectric constants. The outcome of the study of the structural and optical properties reported here of the DPEA-MR-Zn organic semiconductor crystalline nanostructure thin film had shown various applications in many advanced technologies such as photovoltaic solar cells.

Research on Chemical Intermediates

Bulletin of Materials Science

International journal of engineering research and technology, 2018

Progress in Natural Science: Materials International, 2014

Pure TiO 2 thin films were deposited onto quartz substrates using a ceramic TiO 2 target at an el... more Pure TiO 2 thin films were deposited onto quartz substrates using a ceramic TiO 2 target at an elevated substrate temperature of 573 K by RF magnetron sputtering, and an analysis of structural, optical and photoluminescence characteristics of the films upon phase transformation is reported in this paper. Structural investigations using X-ray diffraction revealed that the as-deposited film was amorphous in nature. Thermal annealing for 2 h at 873 K in air resulted in the formation of anatase phase, and a phase transformation to rutile was observed at 1073 K. An increase in grain size and an improvement in crystallinity were also observed on annealing. Rod-like rutile crystallites were observed in the SEM images of the film annealed at 1273 K. As-deposited films and films annealed up to 1073 K were highly transparent in the visible region with a transparency 4 80%. Optical band gap of the films decreased upon thermal annealing which is attributed to phase transformation from amorphous to anatase and then to rutile. Optical parameters such as refractive index, optical conductivity and optical dielectric constant increased with increase in annealing temperature. Since rutile is the optically active phase, the superior refractive index of the film annealed at 1073 K along with its high transparency in visible region suggests the application of this film in antireflective coatings. Photoluminescence emission of maximum intensity was observed for the film annealed at 873 K, which exhibits anatase phase. Intense blue emission observed in this film makes it suitable for use in optoelectronic display devices.

Thin Solid Films, 2014

Pure and Fe doped TiO 2 thin films were deposited onto quartz substrates maintained at room tempe... more Pure and Fe doped TiO 2 thin films were deposited onto quartz substrates maintained at room temperature by radio frequency magnetron sputtering. The films were annealed at 873 K in air for 2 h and characterized using X-ray diffraction (XRD), micro Raman spectroscopy, Scanning electron microscopy (SEM), Energy dispersive spectroscopy, ultraviolet-visible and photoluminescence (PL) spectroscopy. Pure TiO 2 thin films were XRDamorphous, but micro Raman spectra revealed the presence of anatase phase. Doping with Fe has influenced the transformation of films to anatase phase. Improved crystallinity was observed in the 0.1 at% Fe doped films, where the lattice constants approached the values for bulk anatase TiO 2 , and the films showed minimum strain. At higher Fe concentrations, micro Raman spectra revealed the presence of rutile phase also. SEM images revealed crack free surface and surface roughness was found to increase with increase in Fe concentration. Doping with Fe has resulted in a red shift of absorption edge. PL emission intensity was found to increase with Fe concentration, but at higher concentrations quenching of PL emission was observed. Fe doping resulted in enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. 0.8 at% Fe doped TiO 2 films exhibited the highest photocatalytic activity.

Applied Surface Science, 2011

TiO 2 thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples de... more TiO 2 thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873 K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58 eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75 eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544-0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions.

Journal of Materials Science: Materials in Electronics, 2013

TiO 2 thin films were deposited onto quartz substrates by RF magnetron sputtering. Inorder to inv... more TiO 2 thin films were deposited onto quartz substrates by RF magnetron sputtering. Inorder to investigate the effect of film thickness on the structural and optical properties, films were deposited for different time durations, and postannealed at 873 K. The influence of annealing atmosphere (air/ oxygen) on the film properties was also investigated. The films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. Films deposited at different time durations are amorphous-like in nature. From XRD patterns it can be inferred that deposition for longer duration is essential for achieving crystallisation in TiO 2 thin films prepared by RF magnetron sputtering. The films exhibited good adherence to the substrate and are crack free as revealed by SEM images. Film thickness was found to increase with increase in sputtering time. The optical band gap of the films was found to decrease with increase in film thickness, which is consistant with XRD observations. Film thickness did not show any significant variation when annealed in both air and oxygen. Defect related PL emission in the visible region (blue) was observed in all the investigated films, which suggests the application of these films in optoelectronic display devices.