Güven Turgut

An investigation of the Nb doping effect on structural, morphological, electrical and optical properties of spray deposited F doped SnO2 films

F and Nb + F co-doped SnO2 thin films were deposited on glass substrates by the spray pyrolysis method. The microstructural, morphological, electrical and optical properties of the 10 wt% F doped SnO2 (FTO) thin films were investigated specifically for niobium (Nb) doping in the range of 0–4 at.% with 1 at.% steps. As shown by the x-ray diffraction patterns, the films exhibited a tetragonal cassiterite structure with (200) preferential orientation. It was observed that grain sizes of the films for (200) and (301) peaks depended on the Nb doping concentration and varied in the range of 25.11–32.19 and 100.6–183.7 nm, respectively. The scanning electron microscope (SEM) micrographs showed that the FTO films were made of small pyramidal grains, while doubly doped films were made of small pyramidal grains and big polyhedron grains. From electrical studies, although 1 at.% Nb doped FTO films have the lowest sheet resistance and resistivity values, the highest figure-of-merit and optical band gap values obtained for FTO films were 16.2 × 10−2 Ω−1 and 4.21 eV, respectively. Also, infrared reflectivity values of the films were in the range of 97.39–98.98%. These results strongly suggest that these films are an attractive candidate for various optoelectronic applications and for photothermal conversion of solar energy.

Single and multiple doping effects of silicon–boron and fluorine on ZnO thin films deposited with sol–gel spin coating technique

Undoped, Si and B single doped, Si–B co-doped and Si–B–F triple doped ZnO thin films were grown by sol–gel spin coating method. Effects of these doping elements on microstructural, morphological and optical properties were investigated. X-ray diffraction studies showed that all films had hexagonal wurtzite structure. Although Si doping increased crystallinity of ZnO, single boron doping, Si–B co-doping and Si–B–F triple doping gave rise to a decreasing in crystallinity. Scanning electron microscope micrographs indicated that the grain size and morphological characters of ZnO depended on doping element type and their concentrations. The micrographs also demonstrated that Si doping deteriorated grain size and their distribution on film surface of ZnO structure. Although single B, doubly Si–B and triple Si–B–F doping at low contents improved grain distribution and film morphology, when their content increased, film morphology started to deteriorate. Optical band gap value of undoped film increased with Si doping irrespective of Si doping content. Although single B, doubly Si–B and triple Si–B–F doping at low contents caused an increase in optical band gap of undoped ZnO, more doping content brought about a decrease in optical band gap. From the optical parameters such as absorption coefficient, the Urbach energy values of the films were calculated by using ln α vs. photon energy graphs. In generally, Urbach energies of the films changed reversely with the band gap energies of the films.

The Risk Evaluation of Tungsten Oxide Nanoparticles in Cultured Rat Liver Cells for Its Safe Applications in Nanotechnology

Tungsten (VI) oxide (WO3) nanoparticles (NPs) are used for many industrial purposes in everyday life. However, their effects on human health have not been sufficiently evaluated. Therefore, the present study was designed to investigate the toxicity potentials of various concentrations (0 to 1000 ppm) of WO3NPs (<100 nm particle size) in cultured primary rat hepatocytes. The results of cell viability assay showed that the higher concentrations of dispersed WO3 NPs (300, 500 and 1000 ppm) caused significant (p<0.05) decreases of cell viability. Also, dose dependent negative alterations were observed in oxidative status and antioxidant capacity levels after the application of WO3 in cultured rat primary hepatocytes. The results of genotoxicity tests revealed that these NPs did not cause significant increases of micronucleated hepatocytes (MNHEPs) but increased 8-oxo-2-deoxyguanosine (8-OH-dG) levels as compared to the control culture.

Growth and structural characterizations of GaSe and GaSe:Cd single crystals

GaSe and GaSe:Cd single crystals used in this research were grown by using the Bridgman/Stockbarger method. All of the samples were freshly and gently cleaved with a razor blade from the grown ingots and no further polishing and cleaning treatments were required because of the natural mirror-like cleavage faces. The Samples were cleaved along the cleavage planes (001). The structure and lattice parameters of the undoped GaSe and GaSe:Cd semiconductors have been analyzed using a X-ray diffractometer (XRD), Scanning electron microscopy (SEM) and energy dispersive X-rays (EDX) techniques. It is found that GaSe and GaSe:Cd crystals have hexagonal structure, quite close 2θ peak values. XRD measurements indicate that there is an increase in peak intensities at specific annealing temperatures (500°C). Cd doping causes a significant decrease in the XRD peak intensity.