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Öğe Characterization of Plasma-Polymerized Thiophene Thin Films and Nanoparticles Synthesized by a Double-Discharge Technique(Wiley-V C H Verlag Gmbh, 2009) Goktas, Hilal; Ince, Fatma GulPTH nanoparticles and thin films were synthesized via a plasma polymerization technique using a double-discharge system. This system has a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow discharge and a high-current pulsed one. The samples were characterized by SEM, TEM, XPS, UV-vis and FT-IR spectroscopy. We found that superposing two discharges allows to control the morphology of the films. In the high-temperature region, smooth and uniform thin films were produced, whereas gas-phase polymerization resulted in films with grains of irregular shape. However, the films produced in the gas-phase region exhibited highly thiophenic structures and could be dispersed in DCM, giving nanoparticles of 30 to 50 nm diameter.Öğe Improved bone formation in osteoporotic rabbits with the bone morphogenetic protein-2 (rhBMP-2) coated titanium screws which were coated by using plasma polymerization technique(Institute of Immunobiology and Human Genetics, 2014) Gulsen, Salih; Cokeliler, Dilek; Goktas, Hilal; Kucukturhan, Aysu; Ozcil, Bilgehan; Caner, HakanDelaying of bone fusion in osteoporotic patients underwent spinal stabilization surgery leads to screw loosening, and this causes pseudoarticulation, mobility and fibrosis at vertebral segments. To prevent these complications, the screws coated with recombinant bone morphogenetic protein-2 (rhBMP-2) could be used. To verify this hypothesis, we coated 5 Titanium screws with rhBMP-2 using plasma polymerization method, and also used 10 uncoated screws for making comparison between coated and uncoated screws in different groups. And 15 skeletally mature white New Zealand female rabbits were assigned into three different groups: Group 1(N = 5): No osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 1; group 2 (N = 5): Osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 2; group 3 (N = 5) rhBMP-2 coated Titanium screw inserted into right sacrum of each rabbit in group 3. In summary, using of these coated screws provides new bone formation, but causes less fibrosis and less inflammation than uncoated screws at the interface between the coated screw and bone. Then the plasma polymerization technique provides controlled releasing of rhBMP-2 from the screw to the bone tissue in osteoporotic rabbits. © 2014 Gulsen et al.Öğe Infection Free Titanium Alloys by Stabile Thiol Based Nanocoating(Amer Scientific Publishers, 2010) Coekeliler, Dilek; Goktas, Hilal; Tosun, Pinar Deniz; Mutlu, SelmaAs biomedical materials, titanium and titanium alloys (Ti-6Al-4V) are superior to many materials in terms of mechanical properties and biocompatibility. However, they are still not sufficient for prolonged clinical use because the biocompatibility of these materials must be improved. In this study, the prevention of the attachment of test microorganism on the Ti alloy surfaces by thiol (-SH) and hydroxyl (-OH) functional group containing monomer in plasma based electron beam generator was reported in order to prepare anti-fouling surfaces. The precursor, 11-mercaptoundecanoic acid is used as plasma source to create nano-film with 30-60 nm approximately. The surface chemistry and topology of uncoated and coated samples are characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM). Static contact angle measurements are performed to state the change of surface hydrophilicity. All coated samples are tested in-vitro environment with Staphylococcus epidermidis that is chosen as the test bacteria strain in view of its significance for the pathogenesis of medical-device-related infections. This test is repeated after certain period of times and samples are waited in dynamic fluid media in order to investigate the stability of nano-coating. Plasma polymerized 11-mercaptounclecanoic acid film (PP MUA) with 42 +/- 4 nm is found alternative, stabile and simple method to create bacterial anti-fouling surfaces. The static contact angle of the coated surface is 34 +/- 8 degrees whereas the uncoated surface is 57 +/- 5 degrees. For the coated surface, the presence of C-OH and C=O groups in infrared spectra defining the PP MUA is achieved by the plasma polymerization. The attachment of the model microorganism on the biomaterial surface prepared by PP MUA is reduced 85.3% if compared to unmodified control surface.Öğe Langmuir-Blodgett thin film for chloroform detection(Elsevier Science Bv, 2015) Capan, Rifat; Goktas, Hilal; Ozbek, Zikriye; Sen, Sibel; Ozel, Mehmet Emin; Davis, FrankCalix[4]resorcinarene (C11TEA) molecules could be deposited as an LB film by the Langmuir-Blodgett (LB) technique onto suitable substrates. Surface plasmon resonance (SPR) and UV-vis spectroscopy were employed for the characterization of these LB films. A high quality and uniform Langmuir monolayer from the water surface can be transferred onto a glass or gold coated substrates with a transfer ratio of over 95%. Thickness and refractive index values of the resultant LB films were measured using surface plasmon resonance with a value of 1.04nm per layer and 1.4 respectively. For the sensing application towards chloroform, this LB film yields a fast and almost fully reversible response to chloroform in few seconds. (C) 2015 Elsevier B.V. All rights reserved.Öğe Optical phase distribution evaluation by using an S-transform(Optical Soc Amer, 2007) Ozder, Serhat; Kocahan, Ozlem; Coskun, Emre; Goktas, HilalAn experimental study of the use of an S-transform to evaluate the phase distribution from a two-dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y, is presented. The phase distribution is extracted from the optical fringe pattern by using an S-transform gradient and S-transform phase methods. The experimental result for the Fourier transform profilometry algorithm is compared with the results of the S-transform. analysis. (c) 2007 Optical Society of AmericaÖğe Plasma Copolymerization of Thiophene and Pyrrole(IEEE-Inst Electrical Electronics Engineers Inc, 2011) Goktas, Hilal; Gunes, Taylan; Atalay, Betul; Er, Ali Oguz; Kaya, İsmetThe copolymerization of thiophene and pyrrole thin films synthesized by using a double discharge technique which has a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow discharge and a high-current pulsed one is presented. Quartz glass substrates were coated at a pressure of 0.8 mbar and 19-kV pulsed and 2-kV dc potentials. The analysis of functional groups by FTIR spectrometry showed that the molecular structure of the copolymerized thin films with the filamentary discharge part almost preserves the conventional polymeric structure.Öğe Polyfluorene Thin Films Synthesized by a Novel Plasma Polymerization Method(Springer, 2012) Goktas, Hilal; Mansuroglu, Dogan; Atalay, Betul; Bilikmen, Sinan; Kaya, İsmetThe synthesis of polyfluorene (PF) thin films by simultaneously superposing a continuous and pulsed discharge and the characterizations of these samples are presented. The double discharge plasma system is constructed by superposing two discharges; namely, a low pressure dc glow one and a high current pulsed one. The fluorene monomer in powder form was vaporized in the system at argon plasma without any modification, at 0.5 mbar operating pressure. The structure of the thin films was investigated via XPS, UV-visible, FTIR, XRD and SEM. The FTIR and the UV-visible results revealed that the fluorene structure was retained at the produced samples. Semi-conducting behavior was established, and upon the iodine doping, the optical energy band gap (E-g) dropped down from 3.7 to 2.4 eV. The morphology of the synthesized PF thin films was amorphous, with granular structures of different sizes depending on the location of the substrate.Öğe Preparation and characterization of ethylenediamine and cysteamine plasma polymerized films on piezoelectric quartz crystal surfaces for a biosensor(Elsevier Science Sa, 2008) Mutlu, Selma; Coekeliler, Dilek; Shard, Alex; Goktas, Hilal; Ozansoy, Berna; Mutlu, MehmetThis paper describes a method for the modification of quartz crystal surfaces to be used as a transducer in biosensors that allow recognition and quantification of certain biomolecules (antibodies, enzymes, proteins, etc). Quartz crystal sensors were modified by a plasma based electron beam generator in order to detect the level of the toxin histamine within biological liquids (blood, serum) and food (wine, cheese, fish etc.). Cysteamine and ethylenediamine were used as precursors in the plasma. After each modification step, the layers on the quartz crystal were characterized by frequency measurements. Modified surfaces were also characterized by contact angle, X-ray photoelectron spectroscopy and atomic force microscopy to determine the physical and chemical characteristics of the surfaces after each modification. Finally, the performance of the sensors were tested by the response to histamine via frequency shifts. The frequency shifts of the sensors prepared by plasma polymerization of ethylenediamine and cysteamine were approximately 3230 Hz and 5630 Hz, respectively, whereas the frequency change of the unmodified crystal surface was around 575 Hz. (C) 2007 Elsevier B.V. All rights reserved.Öğe The optical properties of plasma polymerized polyaniline thin films(Elsevier Science Sa, 2013) Goktas, Hilal; Demircioglu, Zahide; Sel, Kivanc; Gunes, Taylan; Kaya, İsmetWe report herein the characterizations of polyaniline thin films synthesized using double discharge plasma system. Quartz glass substrates were coated at a pressure of 80 Pa, 19.0 kV pulsed and 1.5 kV dc potential. The substrates were located at different regions in the reactor to evaluate the influence of the position on the morphological and molecular structure of the obtained thin films. The molecular structure of the thin films was investigated by Fourier transform infrared (FTIR) and UV-visible photospectrometers (UV-vis), and the morphological studies were carried out by scanning electron microscope. The FTIR and UV-vis data revealed that the molecular structures of the synthesized thin films were in the form of leuocoemeraldine and exhibited similar structures with the films produced via chemical or electrochemical methods. The optical energy band gap values of the as-grown samples ranged from 2.5 to 3.1 eV, which indicated that these materials have potential applications in semiconductor devices. The refractive index in the transparent region (from 650 to 1000 nm) steadily decreased from 1.9 to 1.4 and the extinction coefficient was found to be on order of 10(-4). The synthesized thin films showed various degrees of granular morphologies depending on the location of the substrate in the reactor. (C) 2013 Elsevier B.V. All rights reserved.
