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Open access

Aseel A. Kareem

Abstract

Polyimide/polyaniline nanofiber composites were prepared by in situ polymerization with various weight percentages of polyaniline (PANI) nanofibers. X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), proved the successful preparation of PANI nanofiber composite films. In addition, thermal stability of PI/PANI nanofiber composites was superior relative to PI, having 10 % gravimetric loss in the range of 623 °C to 671 °C and glass transition temperature of 289 °C to 297 °C. Furthermore, the values of the loss tangent tanδ and AC conductivity σAC of the nanocomposite films were notably higher than those of pure polyimide. The addition of 5 wt.% to 15 wt.% PANI nanofiber filler enhanced the activation energy of PI composites from 0.37 eV to 0.34 eV

Open access

Talat Zeeshan, Safia Anjum, Hina Iqbal and Rehana Zia

Abstract

A series of copper substituted cobalt chromium ferrites, CuxCo1 - xCr0,5Fe1,5O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) has been synthesized, by employing powder metallurgy method. Calcination of the samples has been carried out for 24 hours at 1100 °C. The resultant materials have been investigated by using a variety of techniques, including X-ray diffractometry (XRD), Fouriertransform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM)), scanning electron microscopy (SEM), andultraviolet visible spectroscopy (UV-Vis). The XRD patterns confirmed that all compositions had a cubic spinel structure witha single phase and the lattice parameter was found to increase with increasing copper concentration. FT-IR spectroscopy hasbeen used for studying the chemical bonds in the spinel ferrite. Shifting of the bands ᶹ1 and ᶹ2 has been observed. It hasbeen revealed from VSM analysis that saturation magnetization and coercivity decrease with rising the Cu+2 doping. Magneticproperties have been explained on the basis of cation distribution. Scanning electron microscopy (SEM) has been used to studythe surface morphology of prepared samples. UV-Vis analysis revealed the optical absorption of the samples. An increase inband gaps has been observed with increasing copper concentration in the sample

Open access

Nouman Rafiq, Waqar A.A. Syed, Aulia Rifada, M. Asad Ghufran, Ijaz-Ur-Rehman Shah, Ahsan Ali and Wiqar Hussain Shah

Abstract

We report a simple approach for synthesizing monodispersed, crystalline and size-tunable tin sulfide nanoparticles for environment friendly next generation solar cell applications. Both SnS and SnS2 nanoparticles could be a potential nanomaterial for solar cells. The structural, morphological, thermal and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The XRD spectra revealed hexagonal and orthorhombic phases of SnS and SnS2 nanoparticles, respectively, where the grains size ranged from 11 nm to 30 nm. The weight percentage as a function of temperature was determined using TGA analysis. Functional groups were observed by FT-IR. The energy bandgap was determined as 1.41 eV showing usefulness of the nanoparticles in next generation environmental friendly solar energy applications

Open access

A. M. Abd-Elnaiem, M. Mohamed, R. M. Hassan, M. A. Abdel-Rahim, A. A. Abu-Sehly and M. M. Hafiz

Abstract

Effect of annealing temperature on the structural and optical properties of As30Te60Ga10 thin film was studied using various techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSC analysis revealed that the As30Te60Ga10 glass has a single glass transition and crystallization peak while XRD results confirmed that the as-prepared and annealed films have crystalline nature. The coexistence of the crystalline phases in the investigated films could be attributed to the formation of orthorhombic As, hexagonal Ga7Te10, and monoclinic As2Te3 phases. It was found that the average crystallite size and optical parameters of the studied films depend on the annealing temperature. For example, the optical band gap decreased from 1.54 eV to 1.11 eV as the annealing temperature increased from 300 K to 433 K.

Open access

Ziaul Raza Khan, Munirah, Anver Aziz and Mohd. Shahid Khan

Abstract

High-quality CdS nanocrystalline thin films were grown by sol-gel spin coating method at different solution temperatures on glass substrates. As-deposited films exhibited nanocrystalline phase with hexagonal wurtzite structure and showed good adhesion and smooth surface morphology. It was clearly observed that the crystallinity of the thin films improved with the increase in solution temperature. Crystallites sizes of the films also increased and were found to be in the range of 10 mm to 17 nm. The influence of the growth mechanism on the band and sub-band gap absorption of the films was investigated using UV-Vis and photothermal deflection spectroscopy (PDS). The band gap values were calculated in the range of 2.52 eV to 2.75 eV. The band gap decreased up to 9 % with the increase in solution temperature from 45 °C to 75 °C. Absorption coefficients estimated by PDS signal showed the significant absorption in low photon energy region of 1.5 eV to 2.0 eV. The dark and illuminated I-V characteristics revealed that the films were highly photosensitive. The results demonstrated the potential applications of sol-gel grown CdS nanocrystalline thin films as photoconductors and optical switches.

Open access

Jiyong Deng, Qiang Tao, Dong Yan, Xianwei Huang and Yunfeng Liao

Abstract

Small molecules of ThQuTh, CzQuTh, CzQuCz and TPAQuCz were designed and synthesized, based on quinoxaline acceptor, and electron donating groups, i.e. alkyl-thioephene, carbazole and triphenylamine on both side chains and molecular backbones. Their thermal, optical and electrochemical properties were systematically compared and studied. The absorption spectra of the small molecules were strongly affected by the donor units attached to quinoxaline. Strong electron donating groups, such as carbazole on the molecular backbone would lower optical band gap, resulting in a wide absorption and the strong donor on the side chain would enhance the absorption intensity in short wavelength region. The highest occupied molecular orbital (HOMO) energy levels of the four molecules were up-shifted with increasing the electron donating properties of donor units. The bulk-heterojunction organic solar cells with a device structure of ITO/PEDOT:PSS/SMs:PC61BM/LiF/Al were fabricated, in which the small molecules functioned as donors while PC61BM as acceptor. Because the electron-donating ability of carbazole (Cz), triphenylamine (TPA) is higher than that of thiophene (Th), CzQuTh, CzQuCz and TPAQuCz show higher power conversion efficiency (PCE) than that of ThQuTh. Furthermore, being the strongest in absorption intensity and widest in absorption spectrum, TPAQuCz has the highest power conversion efficiency. Further improvement of the device efficiency by optimizing the device structure is currently under investigation

Open access

A. J. Nagajothi, R. Kannan and S. Rajashabala

Abstract

Chitosan has been successfully incorporated as a filler in a polyethylene oxide (PEO) and lithium trifluoromethanesulfonate (LiCF3SO3) matrix with a combination of plasticizers, namely 1,3-dioxolane (DIOX) and tetraethylene glycol dimethylether (TEGDME). The composite gel-polymer electrolyte (CGPE) membranes were prepared by solution casting technique in an argon atmosphere. The prepared membranes were subjected to SEM, TG/DTA and FT-IR analyses. A Li/CGPE/Li symmetric cell was assembled and the variation of interfacial resistance was measured as a function of time. The lithium transference number (Li+ 1 ) was measured and the value was calculated as 0.6 which is sufficient for battery applications. The electrochemical stability window of the sample was studied by linear sweep voltammetry and the polymer electrolyte was found to be stable up to 5.2 V.

Open access

Akhalakur Rahman Ansari, Shahir Hussain, Mohd Imran, Attieh A. Al-Ghamdi and Mohammed Rehaan Chandan

Abstract

In this article, ZnO thin-film deposition on a glass substrate was done using microwave induced oxygen plasma based CVD system. The prepared thin-films were tested in terms of crystallinity and optical properties by varying the microwave power. The effect of power variation on the morphology and size of final products was carefully investigated. The crystal structure, chemical composition and morphology of the final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and photoluminescence (PL). This technique confirmed the presence of hexagonal ZnO nanocrystals in all the thin-films. The minimum crystallite grain size as obtained from the XRD measurements was ~9.7 nm and the average diameter was ~18 nm.

Open access

Amr A. Nada, Hanaa Selim, Mikhael Bechelany, Mona El-Sayed, R.M. Hegazey, Eglal R. Souaya and M.F. Kotkata

Abstract

The dye-sensitized solar cells made of NiO@ZnO nanoparticles were synthesized by a novel Pechini route using different NiO molar concentration ratios. The thermal, structural morphological, optical and electrical properties of the prepared samples were investigated using thermal gravimetric analysis and differential scanning calorimetery (TGA/DSC), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), FT-IR and Raman spectroscopy, UV-diffuse reflectance (UV-DRS), photoluminescence (PL) and current-voltage (I-V) measurements. The success of doping process was confirmed by the XRD patterns, which revealed the existence of new peak at 43.2° corresponding to secondary phase NiO. UV spectra exhibited red shifts in NiO doped ZnO NCs and PL spectra showed strong emission band at 355 nm. The doping of ZnO with NiO was intended to enhance the surface defects of ZnO. The current-voltage measurements showed an improvement of the short circuit photocurrent (Jsc) and fill factor (FF) and a decrease in the open circuit voltage (VOC) for dye-sensitized solar cell (DSSC) based on NiO-ZnO NCs. A clear enhancement in efficiency of DSSC from 1.26 ±0.10 % for pure ZnO to 3.01±0.25 % for NiO-ZnO NCs at the optimum doping with 1.5 mol% of NiO to ZnO (ZN1.5) was observed. The obtained material can be a suitable candidate for photovoltaic applications.

Open access

S. Khodorov, M. Karpovski, I. Feldman and V. Shelukhin

Abstract

Direct writing of low resistance wires on an amorphous Ge-Sb-Te matrix is reported. A 1342 nm continuous wave laser was used for local heating of the sample to form these wires. Mechanical contact was not needed for making the conducting elements. The properties of the samples were investigated down to 1.4 K and the laser conditions required for the writing of low resistance GST wires were found. The results are discussed with a view to possible applications, such as connectors and electrical wires made only via remote light exposure of the samples to make different resistors and non-linear elements.