A.Y. Oral

A Novel Label-Free Optical Biosensor Using Synthetic Oligonucleotides from E. coli O157:H7: Elementary Sensitivity Tests

SiO2-TiO2 thin films for use as fiber optic guiding layers of optical DNA biosensors were fabricated by the sol-gel dip coating technique. The chemical structure and the surface morphology of the films were characterized before immobilization. Single probe DNA strands were immobilized on the surface and the porosity of the films before the hybridization process was measured. Refractive index values of the films were measured using a Metricon 2010 prism coupler. On the surface of each film, 12 different spots were taken for measurement and calculation of the mean refractive index values with their standard deviations. The increased refractive index values after the immobilization of single DNA strands indicated that immobilization was successfully achieved. A further refractive index increase after the hybridization with target single DNA strands showed the possibility of detection of the E. coli O157:H7 EDL933 species using strands of 20-mers (5′-TAATATCGGTTGCGGAGGTG -3′) sequence.

Effects of Mg doping on sol-gel derived nanocrystalline hydroxyapatite thin films

Abstract Both pure and Mg doped thin films were fabricated by sol–gel dip coating. The films were sintered either at 800 or 1000°C. The average grain size of the films was significantly affected by Mg substitution in the hydroxyapatite (HA) structure and change in the sintering temperature. The grains were considerably larger in the films sintered at higher temperatures. In addition, Mg doped films contained significantly larger grains compared to undoped HA films. Mg doping also caused rodlike grains at 800°C, and led to whitlockite (β-TCP) formation at 1000°C. The ratio of the existing phases was estimated as β-TCP/HA=27 : 73. All the films had rough surfaces with high porosity. It was also observed that undoped films had higher surface roughness than Mg doped ones.

DNA Biosensors for E. Coli O157:H7 Detection in Drinking Water Resources Using Sol-Gel Derived Waveguides

SiO2 -TiO2 thin films were fabricated by sol-gel dip coating technique to be used as the fiber optic guiding layers of optical DNA biosensors. The chemical structure of the films was examined by Fourier Transformed Infrared Spectroscopy (FTIR, Bio – Rad Tropical Option for FTS 175 C) and the surface morphology of the films was observed by Scanning Electron Microscopy (SEM, Philips XL 30 SFEG). The probe DNA was immobilized on the surface and the pores of the waveguide films before the hybridization process was carried out. By using Metricon 2010 prism coupler, 12 different spots were determined to be measured. Then the mean refractive index values and their standard deviations were calculated. The increased refractive index values after the DNA immobilization indicated that immobilization was successfully achieved. Further increase after the hybridization with complementary DNA showed the possibility of detection of the E. coli O157:H7 EDL933 species by using 20-mers (5’- TAATATCGGTTGCGGAGGTG-3’) sequence of GeneID: 957271.

Effects of Commercial Inert Glass (CIG) Addition on Mechanical and Microstructural Properties of Chicken Hydroxyapatite (CHA)

Hydroxyapatite (HA) can be obtained by both synthetic and natural methods. The synthetic hydroxyapatite is the most commonly used type of HA and it is highly reliable. However fabrication of synthetic hydroxyapatite is complex and expensive. The production of natural hydroxyapatite is easy and inexpensive. In spite of being a biocompatible and bioactive material, hydroxyapatite has a limited usage as an implant material because of its weak mechanical properties. For this reason, HA based composites are required to supply improvement of strength and toughness of the implant materials without losing biocompatibility. In this study, HA composites were synthesized by using natural chicken hydroxyapatite (CHA) reinforced with 5 and 10wt. % commercial inert glass (CIG) powders. Then their physical, mechanical, microstructural properties were characterized. Finally, the most suitable CIG containing CHA composite for orthopedical applications was determined.

Microstructural and Optical Study of ITO Thin Films Prepared by Sol-Gel Method

Indium tin oxide (ITO), a transparent conductive oxide, is a wide band gap compound semiconductor with a cubic bixbyte structure. Sn-doped indium oxide (IO) thin films (In:Sn=90:10) were deposited on microscope glass substrates by a sol-gel spin coating technique. The precursor solution was prepared by mixing indium (III) nitrate pentahydrate (In(NO3)3 . 5H2O) and tin (IV) chloride bis(2,4-pentanedionate) (SnCl2(C5H7O2)2 dissolved in acetic acid and acetone mixture. Crystalline ITO thin films were obtained after an annealing process at temperatures between 450 o C-550 o C for one hour. The microstructure and optical properties of ITO films were investigated as function of annealing temperature. XRD analysis revealed single phase In2O3 (JCPDS 06-0416). The optical transmittance of the films in the visible range was more than %80. The direct optical band gap of ITO films was measured between 3.7-3.9 eV.

Phase and Microstructural Development of Sol-gel-derived Strontium Barium Niobate Thin Films

Microstructural changes in sol-gel-derived Sr xBa1−xNb2O6 (SBN) thin films were monitored as a function of Ba-to-Sr ratio (from x 4 0 to x 4 1), choice of substrate (Si or MgO), and processing variations. Sols were created using Ba, Sr, and Nb alkoxides dissolved in acetic acid. The relatively high decomposition temperature for the organics led to a tendency to form defects, but careful control of thermal process parameters could be used to produce a uniform film microstructure. An unexpected phase, interpreted as a hexagonal (pseudo-orthorhombic) variant of hexagonal BaNb2O6, was encountered in Ba-rich sol-gel-derived SBN powders and thin films annealed at 750 °C. Increased (001) orientation was observed for SBN thin films deposited on (100) MgO when fast thermal processing was used.

Sintering behavior of ZnO: Mn ceramics fabricated from sol-gel derived nanocrystalline powders

Abstract Undoped and Mn doped ZnO ceramics, sintered at 1200 °C, were produced from sol-gel derived nanocrystalline powders calcined at 750 °C. Mn doped powders showed trace amounts of spinel (ZnMn2O4) phase in addition to a dominant zincite phase, while Mn doped ceramics were comprised solely of zincite structure. X-ray mapping of the powders did not reveal any Mn concentrated areas, indicating that the ZnMn2O4 phase was homogeneously distributed with a very small grain size. The grain size of the undoped powders was around 50 nm, and there was a minor increase in the grain size when powders were doped with Mn. Undoped ceramics exhibited grain sizes distributed in the range 2 – 10 μm while Mn doped ceramics displayed slightly smaller grains. Relative densities of the undoped and Mn doped ceramics were measured as 0.695 and 0.950, respectively.

Sol-Gel Fabrication of Lithium Doped Zinc Oxide Thin Films

Li doped zinc oxide thin films were deposited on glass substrates by a sol-gel technique. Acetates of zinc and lithium were used as metal sources. A homogeneous and stable solution was prepared by dissolving acetates in the solution of 2-propanol and ethanolamine. ZnO:Li thin films were obtained after preheating the spin coated films at 250 C for 1 minute after each coating. A post annealing between 450-600 C was applied after the deposition of the last layers. XRD analysis revealed ZnO with zincite structure (Card no: 36-1451) in all films. The thickness of the films was measured as 75 nm per layer. The optical band gap of the films increased as doping concentration of Li increased and decreased as the post-annealing temperature increased.

The Sol-Gel-Like Preparation of Cu0.95Me0.05Ox Thin Films and the Study of their Microstructures and Optical Properties

Cu0.95Me0.05Ox (Me=V, Mn, Li, La) thin films were prepared by a sol-gel-like method on microscope glass substrates. Precursor solutions were prepared by dissolving copper acetate in isopropyl alcohol. Diethanolamine and ethyleneglycol were used to enhance the solubility of copper acetate and to strengthen the adhesion between the films and the glass substrates. The doping type (Me) substantially affected the microstructure and the transparency of the films. All films showed good transparency in near IR region (<75%) while only Mn doped films showed considerable transparency in UV region (<45%). The optical band gaps of the films were between 1.64 (Me=La)-1.84 (Me=Mn) eV. Introduction There are two well-known copper oxides: Cu2 1+ O (cuprite) and Cu 2+ O (tenorite) [1]. A metastable copper oxide, Cu4O3 (paramelaconite), which is an intermediate compound between the previous two, has been also reported [2]. CuO is a promising semiconductor for solar cell fabrication due to its suitable optical properties [3]. Furthermore, it is attractive as a selective solar absorber since it has a high solar absorbency and a low thermal emittance [4]. Recently, it has been discovered that CuO also shows high temperature superconductivity, in which the specific coordination between Cu and O atoms is believed to play a crucial role [5,3,6]. Pure CuO films have been reported to show native p-type conductivity due to copper vacancies in the structure [7]. CuO has a band gap reported between 1.3–1.7eV with a black color and a partial transparency in the visible range. Cu ion has three oxidation states, which are Cu + , Cu +2 and Cu +3 . Therefore, both hole and electron doping is possible [8]. An important advantage of using CuO in device applications is that it is nontoxic and its constituents are available in abundance. In the present work, the fabrication of Me (Li, La, V and Mn) doped copper oxide thin film by a sol-gel-like processing was studied. The effect of doping type on the microstructure and optical properties of the films was examined by SEM, XRD and UV-VIS scanning spectrophotometer. Experimental A flow diagram of the experimental procedure is given in Fig. 1. The undoped precursor solutions were prepared by dissolving copper acetate in isopropanol and diethanolamine (DEA, C4H11NO2). Ethylene glycol and water were added to the resulting solution to improve the adhesion between the film and glass substrate and to obtain optimum viscosity of the solution for spin coating. The volume percentages of isopropanol, diethanolamine, ethyleneglycol and water were 88, 5, 5 and 2 respectively. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 573-576 doi:10.4028/www.scientific.net/KEM.264-268.573

Preparation and Characterization of CuxO/Cu Thin Films by Reactive d.c. Magnetron Sputtering

Abstract. CuxO/Cu thin films were prepared by reactive d.c. magnetron sputtering on (100) Si substrates. Microstructures of the films were significantly affected by substrate temperature, oxygen flow rate and applied bias. It was observed that the films mainly crystallized to Cu2O with trace amount of CuO under strongly oxidizing deposition conditions. Relative amount of CuO increased with increasing substrate temperature, oxygen flow rate and decreasing bias. It was observed that the films fully crystallized to CuO with tenorite structure after heat-treated at 600°C for 60 minutes. General appearances of the films were uniform and reddish brown in color.