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Öğe Chemiresistive CuO sensors for label-free C-reactive protein detection(Elsevier Science Sa, 2022) Bayansal, Fatih; Cetinkara, Haci AliIn this study, we developed fast and highly sensitive, label-free Ca-doped cupric oxide (CuO) based che-miresistive biosensors to detect C-reactive protein (CRP). The Successive Ionic Layer Adsorption and Reaction (SILAR) method was used to deposit pure and Ca-doped CuO thin films on interdigitated gold electrodes. Film surfaces were functionalized with monoclonal anti-C-reactive protein antibody (anti-CRP) by random physisorption method. Sensor fabrication steps were monitored using the linear sweep vol-tammetry method. Scanning electron microscopy was used to investigate the surface morphology. Energy-dispersive X-ray spectroscopy was used to determine the elemental composition. The structure of the films was investigated by the powder X-ray diffractometry method. Sensor parameters were determined by the change in sensor resistance over time. The sensors showed a good response to CRP with a linear detection range of 0.1-5.0 pg/ml, which was within the clinically significant range. Detection limits of 49.61 and 48.81 ng/ml were estimated using the standard deviation of the y-intercept and the standard deviation of the regression line, respectively. Dynamic response times of all fabricated sensors were found to be less than 30 s (c) 2022 Elsevier B.V. All rights reserved.Öğe Effect of Cobalt Doping on Nanostructured CuO Thin Films(Springer, 2014) Bayansal, Fatih; Taskopru, Turan; Sahin, Bunyamin; Cetinkara, Haci AliThe growth of cobalt-doped nanostructured CuO thin films using the successive ionic layer adsorption and reaction (SILAR) method is presented. It is found that Co doping considerably influences the structural (X-ray diffraction (XRD)), morphological (finite-element-scanning electron microscopy (FESEM)), and optical (ultraviolet/visible (UV/vis.) and Raman) properties of the films. XRD experiments evidence that the crystallite size of the films decreased with increasing Co doping. FESEM images reveal that the grain size of the nanostructures decreased with increasing doping concentration. By UV/vis. analysis, it is found that Co doping has a decreasing effect on band gap energy. The broadening and downshift of the Raman peaks are mainly attributed to the quantum confinement effect of CuO nanostructures.Öğe Effects of annealing on morphological, structural and electrical properties of thermally evaporated WO3 thin films(Academic Press Ltd- Elsevier Science Ltd, 2012) Usta, Metin; Kahraman, Suleyman; Bayansal, Fatih; Cetinkara, Haci A.Tungsten trioxide (WO3) thin films were prepared by thermal evaporation method onto quartz substrates at room temperature. Effect of annealing temperature (from 200 to 800 degrees C) to morphology, crystallographic structure and electrical properties were investigated. In order to investigate the temperature dependant resistivity properties of the films dark current-voltage measurements were done at the temperatures of 30, 60, 90, 120 and 150 degrees C. From the AFM pictures it is seen that the increasing annealing temperature causes an increase in grain sizes. At elevated temperatures the grains combine to each other and thus form continuous and homogenous surfaces. From the XRD patterns it was seen that the as-prepared and annealed films at 200, 300, 310 and 320 degrees C were amorphous. On the other hand at 330 degrees C and higher temperatures the films were found as in crystallized structures (monoclinic phase). From the current-voltage measurements it was seen that the contacts areohmic and the current increased with increasing temperatures. From the calculated values it was seen that the produced films shows good semiconducting nature. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Hydrostatic pressure dependence of interface state density of Cd/n-type GaAs Schottky barrier diodes(Elsevier, 2010) Sonmezoglu, Savas; Bayansal, Fatih; Cankaya, GuevenThe interface state density obtained from current-voltage (I-V) characteristics of Cd/n-type GaAs Schottky barrier diodes (SBDs) at room temperature under hydrostatic pressure was investigated. SBD parameters such as ideality factor (n), series resistance (R-s), and barrier height (phi(b)), were obtained from I-V measurements using Cheung's method. The diode parameters, such as ideality factor, series resistance, and barrier heights, were found in the range of 1.464-1.474, 0.995-4.359 k Omega and 0.739-0.777 eV, respectively, with sweeping pressure. The diode shows non-ideal I-V behaviors with an ideality factor greater than unity. Additionally, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results have shown that the presence of the interfacial native oxide layer between the metal and the semiconductor seriously affects interface state density under hydrostatic pressure. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.Öğe A novel approach to enhancement of surface properties of CdO films by using surfactant: dextrin(Taylor & Francis Ltd, 2015) Sahin, Bunyamin; Bayansal, Fatih; Yuksel, MustafaWe studied the effect of an organic surfactant, dextrin, concentration on structural, morphological and optical properties of nanostructured CdO films deposited on glass substrates by using an easy and low-cost SILAR method. Microstructures of the nanostructured CdO films were optimized by adjusting dextrin concentration. XRD, SEM and UV-Vis Spectroscopy were used to study phase structure, surface morphology and optical properties of CdO films. Furthermore, effects of dextrin concentration on the surface roughness characteristics of CdO samples were reported. The results showed that the presence of organic surfactant highly affected the physical properties of CdO nanomaterials.Öğe Preparation and Characterization of Zn x Cu(1-x)O Composite Films on Glass Substrates Through SILAR Processing(Springer, 2015) Bayansal, Fatih; Sahin, Bunyamin; Yuksel, MustafaCuO composite thin films with and without Zn-doping are deposited onto glass substrates by the SILAR method. All the films are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis spectrophotometry, temperature dependent dc conductivity, and X-ray diffraction (XRD) measurements. SEM results show that the particle size decreases from 27 to 16 nm with increasing Zn-doping. EDX analysis evidences the amount of Zn in CuO films, which increases with increasing Zn concentration in the growth solutions. Transmittance, optical band gap, and activation energy values of the films are found to be increasing from the UV-Vis and temperature dependent dc conductivity measurements with increasing Zn-doping. It also is found from the XRD patterns that mean crystallite size of the films decreases from 18.94 to 13.70 nm with increasing Zn-doping. Moreover, increase in Zn concentration results peak shifts to lower 2 theta values. (C) The Minerals, Metals & Materials Society and ASM International 2015Öğe SILAR yöntemi ile üretilen CuO filmlerin yapısal, morfolojik ve optik özelliklerine ikili katkılamanın (Zn, Li) etkisi(2016) Aydın, Raşit; Şahin, Bünyamin; Bayansal, FatihBu çalışmada katkısız CuO ve farklı konsantrasyonlarda Li-katkılı Li-ZnCuO filmler cam altlıklar üzerine SILAR yöntemi ile başarılı bir şekilde büyütüldü. Üretilen bu filmler metalurjik mikroskop (MM), X-ışını kırınımı (XRD) ve UV-Vis. spektroskopi ile karakterize edildi. MM sonuçları, CuO filmlerin morfolojisi üzerine Li-Zn ikili katkılama konsantrasyonunun önemli bir etkiye sahip olduğunu gösterdi. XRD verileri filmlerin nanoboyutta kristalize olduklarını ve kristallenme kalitesinin katkı konsantrasyonuna bağlı olarak değiştiğini açığa çıkardı. Uv-Vis. analiz sonuçları, filmlerin hem optik bant aralığı değerlerinde hem de geçirgenliklerinde katkı konsantrasyonuna bağlı olarak önemli farklılıkların oluştuğunu ortaya koydu.Öğe Sodium dodecyl sulfate-assisted SILAR synthesis of nanostructured cadmium oxide films(Elsevier Sci Ltd, 2016) Aydin, Rasit; Sahin, Bunyamin; Bayansal, FatihNanostructured CdO films were prepared on glass substrates by a surfactant sodium dodecyl sulfate (SDS) assisted SILAR technique. The influence of SDS concentrations of the growth solution on the structural, morphological and optical properties of the films was investigated and discussed. From the metallurgical microscope and scanning electron microscope images, it was seen that the surface morphology of the films are significantly enhanced by SDS addition. XRD investigations confirmed that the films have good crystallinity levels and are grown preferentially in (111) and (200) orientations. UV-vis. spectroscopy investigations showed that the bandgap and transmittance values of the films are affected dramatically by SDS concentrations. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Synthesis, characterization and humidity sensing properties of Mn0.2Ni0.8Fe2O4 nanoparticles(Elsevier Science Sa, 2013) Koseoglu, Yuksel; Aldemir, Ismail; Bayansal, Fatih; Kahraman, Suleyman; Cetinkara, Haci AliMn0.2Ni0.8Fe2O4 nanoparticles were synthesized by PEG assisted hydrothermal technique. XRD and FT-IR analysis confirmed the composition and structure as spinel ferrite. The average crystallite size was found as 27 nm from the XRD pattern. SEM measurements have revealed that the nanoparticles exhibit large grain structures having regular morphology (polygons) with soft agglomerations. Gas sensing characteristics of the film fabricated by Mn0.2Ni0.8Fe2O4 nanoparticles were investigated for different concentrations of humidity, ethanol, acetone, methanol, toluene and benzene and for oxygen gas. It was found that the sensor is highly sensitive to humidity but weakly sensitive for the other organic volatile compounds and especially for oxygen gas. (C) 2013 Elsevier B.V. All rights reserved.
