Advanced Materials Research Vol. 678

Abstract: Poly methyl methacrylate (PMMA) thin films were prepared by fast dip coating technique (FDCT). Benzene was used as a solvent to prepare PMMA films for various time periods ranging from 60 sec. to 1 hour. The thickness of the coated films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD-20), gravimetric method and cross checked by optical spectrophotometer. FTIR spectrum was used to identify the above said coated films. XRD spectra of as grown and films annealed at various temperatures indicated the amorphous nature. Surface morphology of the coated films was studied by scanning electron microscope (SEM). No pits and pin holes were found in the surface. Both as grown and annealed films showed smooth and amorphous structure. C-V behavior of the MISM structures with Aluminum/PMMA/p-Si/Aluminum has been studied. C-V behavior for various bias voltage range of - 20 V to +20 V was provided. As grown films showed a flat band voltage (VFB) shift towards the positive voltage where as annealed films showed a decrease in VFB shift and it moved towards the zero flat band voltage (VFB  0) value. The observed surface morphology, C-V behavior and thermal stability indicated that these films could be used as effective dielectric layer in FET applications.

Abstract: Chitin and chitosan, the most abundant biopolymers possess several excellent advantages such as biodegradability, ecological friendly, biocompatibility, low toxicity, bioactive, antimicrobial activity and low immunogenicity. They occur as ordered crystalline micro fibrils and are useful in applications that require reinforcement and strength. Nanochitosan was prepared from chitosan by oxidation degradation method using H2O2. Nanocomposites polymer electrolyte system composed of polyethylene oxide (PEO) as the host polymer, magnesium perchlorate Mg(ClO4)2 as salt and different concentration of nano-sized chitosan as filler have been studied. The effects of addition of nanochitosan on the ionic conductivity of composite polymer electrolytes are investigated and it is found to rise upon one order (10-3 Scm-1). The complexation behavior of PEO and Mg(ClO4)2 are verified through FT-IR studies. The nanocomposite films possess uniform surface morphology which has been identified by SEM analysis.

Abstract: Two reactive azo dyes Reactive yellow 84 (RY84) and Reactive Red 120 (RR120) were investigated voltammetrically using plain glassy carbon electrode (GCE) and multiwalled carbon nanotube modified GCE (MWCNT/GCE). Influence of pH, scan rate and concentration on voltammograms were studied. The irreversible oxidation process observed for both dyes was adsorption controlled. The surface characterization of the modified electrode in the absence and presence of dyes was done using scanning electron microscopy (SEM). A systematic study of the experimental parameters that affects differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived. Under optimized conditions, stripping voltammetry procedure was developed for the determination of reactive dyes. MWCNT/GCE seems to present better responses than plain GCE and the limit of detection (LOD) was 0.6 μg mL-1 for RY84 and 0.3μg mL-1 for RR120 on this modified system. Suitability of the differential pulse stripping voltammetric method using the developed Multiwalled carbon nanotube based sensor, for the trace determination of these textile dyes in real samples was also realized.

Abstract: Nanocrystalline and flower like structured TiO2 thin films are prepared by sol-gel spin coating method. The prepared films are annealed at 450°C. Natural dyes are prepared from delonix regia flower and eugenia Jambolana fruit. The prepared natural dyes were sensitized into both nanocrystalline and flower like structured TiO2 thin films. The prepared solar cell was characterized by SEM, Uv-Vis spectroscopy and J-V characteristics. Conversion of solar light into electricity was successfully accomplished with both natural dye based solar cells. The best solar energy conversion efficiency (ƞ= 0.2%) was obtained for eugenia Jambolana dye sensitized flower like structured TiO2 thin film solar cell.

Abstract: The Fe2O3 and V2O5 nanoparticles were prepared by thermal decomposition method. The XRD and FTIR spectrum of the samples confirms the formation of Fe2O3 and V2O5. The FE- SEM images showed the morphology and size of the samples. The synthesized Fe2O3 and V2O5 nanoparticles were used to modify the glassy carbon electrode (GCE) and the modified electrode was found to exhibit electrocatalytic activity for the oxidation of uric acid (UA). It shows that the nanoparticles will exhibit promising applications in the development of sensors.

Abstract: Pure PVA and composite thin films of poly vinyl alcohol (PVA)/Titanium dioxide (TiO2) were prepared on pre-cleaned glass substrates by Dip Coating Technique (DCT) and Metal Organic Deposition Technique (MODT). EDS and FTIR spectrum were used to identify the composition of the prepared films. The vibrational peaks observed at 1260 cm-1 and 851 cm-1 are assigned to C–C stretching and CH rocking of PVA. The characteristic band appearing at 1432 cm-1 is assigned to C–H bend of CH2 of PVA. The bands observed around 847 cm-1 and 601cm-1 belong to the asymmetric stretching of Ti–O–Ti groups. The last band at 460 cm-1 is due to the bending mode of Ti–O–Ti. The bands covered by Ti-O were located at 540, 700 and 950 cm-1. From the FTIR spectra, it is observed that some of the peaks of composite films were shifted and some of them were disappeared with respect to the pure compounds. This results manifested the conclusion about the specific interactions in composite polymer matrices and hence the complexation. Thus, complex formation in the composite polymer matrices has been confirmed from this analysis. The thickness of the coated films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD-20), gravimetric method and cross checked by optical spectrophotometer. XRD spectra indicated the amorphous nature of the films. Surface morphology of the coated films was studied by scanning electron microscope (SEM). The surface revealed no pits and pin holes on the surface. Both as grown and annealed films showed predominantly amorphous nature. The observed surface morphology and thermal stability indicated that these films could be used as dielectric layer in organic thin film transistors.

Abstract: Copper Indium Selenide (CIS) thin films were pulse electrodeposited at room temperature and at different duty cycles in the range of 6 – 50 %. Deposition current density was kept constant at 5 ma cm-2 in the present work. The total deposition time was 60 min. The precursors used were AR grade 0.3 M of each CuCl2 and InCl3, along with 0.2 M of SeO2. Thickness of the films estimated by Mitutoyo surface profilometer varied in the range of 0.8 to 1.2 μm with increase of duty cycle. XRD patterns of CIS films deposited at different duty cycles exhibit the chalcopyrite structure. Composition of the films indicated Cu/In ratio is greater than 1. Optical absorption studies indicated a direct energy band gap of 0.95 eV. Surface morphology of the films indicated that the grain size increased from 15 nm to 40 nm as the duty cycle increased. It is observed that as the duty cycle increases, the resistvity increases from 1.0 ohm cm to 10 ohm cm. The films were used as photoelectrodes in 0.5 M polysulphide redox electrolyte (0.5 M each Na2S, NaOH, S). At 60 mW cm-2, an open circuit voltage of 0.465 V and short circuit current density of 3.87 mA cm-2 were observed for the films deposited at 50 % duty cycle.

Abstract: We have synthesized silver nanoparticles using the leaf extract of Henna (Lawsonia inermis). The synthesized silver nanoparticles were characterized using UV – visible spectroscopy, Atomic Force Microscopy and FTIR. Effect of leaf extract concentration, pH and reaction temperature on the formation of silver nanoparticles has been analysed by studying the variations in absorbance and wavelength of SPR of silver nanoparticles. The silver nanoparticle increases photoabsorption due to Localized Surface Plasmon Resonance. In this current study, we have fabricated Photo Enhanced Dye Sensitized Solar Cell (PE – DSSC) using the Henna dye reduced silver nanoparticles as sensitizer to improve photocurrent. We have obtained photocurrent output of Henna reduced silver nanoparticle dye sensitized solar cell.

Abstract: In recent years, lot of efforts was made to develop many types of nitrogen oxide gas sensors. Among them, most interesting are WO3, V2O5, TiO2, SnO2 and NiO thin films as gas sensing layers. Relatively small effort has been done to examine nickel oxide. But reasonably good electrical properties and stability in air make it feasible for the fabrication of nickel oxide thin film based gas sensors. Hence, in the present study NiO thin films were deposited by dc reactive magnetron sputtering technique from a nickel metal target in argon and oxygen mixed atmosphere and studied its gas sensing properties towards NO2 gas. The effect of process parameters on the morphological and electrical properties of NiO was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Hall effect studies respectively. The films prepared at optimum conditions showed superior electrical properties and exhibited fine and uniform grains with RMS roughness 9.4 nm. These films were tested for gas sensing characteristics of NO2 gas. The sensitivity of NiO thin film was investigated in the temperature range 373 to 573 K. The dynamic response for the NiO films was observed at an operating temperature of 473 K and gas concentration of 50 ppm for NO2 gas.

Abstract: Nanostructure ITO thin films have been deposited on well cleaned glass and silicon substrates using dc magnetron sputtering technique. The ITO films are post annealed in air using a normal heater setup in the temperature range 100 - 400 °C. The ITO film annealed at 300°C exhibited optimum transparency and resistivity values for device applications. The thickness of the ITO thin films is determined using DEKTAK stylus profilometer. The sheet resistance and resistivity of the ITO films were determined using four probe technique. Finally, the optimized nanostructure ITO layers are incorporated on silicon solar cells and the efficiency of the solar cell are found to be in the range 12-14%. Other solar cell parameters such as fill factor(FF), open circuit voltage(Voc),Short circuit current(Isc), series resistance(Rs) and shunt resistance(Rsh) have been determined. The effect of ITO film thickness on silicon solar cells is also observed.