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Öğe Charge transfer through amino groups-small molecules interface improving the performance of electroluminescent devices(ELSEVIER SCIENCE BV, 2016) Havare, Ali Kemal; Can, Mustafa; Tozlu, Cem; Kus, Mahmut; Okur, Salih; Demic, Serafettin; Demirak, KadirA carboxylic group functioned charge transporting was synthesized and self-assembled on an indium tin oxide (ITO) anode. A typical electroluminescent device [modified ITO/TPD (50 nm)/Alq(3) (60 nm)/LiF (2 nm)/(120 nm)] was fabricated to investigate the effect of the amino groups-small molecules interface on the characteristics of the device. The increase in the surface work function of ITO is expected to facilitate the hole injection from the ITO anode to the Hole Transport Layer (HTL) in electroluminescence. The modified electroluminescent device could endure a higher current and showed a much higher luminance than the nonmodified one. For the produced electroluminescent devices, the I-V characteristics, optical characterization and quantum yields were performed. The external quantum efficiency of the modified electroluminescent device is improved as the result of the presence of the amino groups-small molecules interface. (C) 2016 Elsevier B.V. All rights reserved.Öğe Effect of Fe doping on the CO gas sensing of functional calixarene molecules measured with quartz crystal microbalance technique(ELSEVIER SCIENCE SA, 2015) Özbek, Cebrail; Okur, Salih; Mermer, Ömer; Kurt, Mustafa; Sayın, Serkan; Yılmaz, MustafaThis article presents comprehensive studies of carbon monoxide (CO) responses of bare and iron doped six calix[4]arene derivatives substituted with various functional groups based on quartz crystal microbalance (QCM) technique. The functional groups in calixarene molecules were chosen to increase the affinity towards CO. The sensitive films were prepared by using drop casting method on a QCM gold electrode with resonance frequency of 7.995 MHz. The responses of bare and Fe doped calixarene molecules were investigated in details. Our QCM results showed that although both bare and Fe doped calixarene molecules are very sensitive to CO gas and Fe doped calixarene molecules have higher affinity to CO about 27.88 times greater than bare are. Therefore, these results open an approach to create new materials for the gas sensing applications. (C) 2015 Elsevier B.V. All rights reserved.Öğe Electrical characterization of PEDOT:PSS beyond humidity saturation(ELSEVIER SCIENCE SA, 2009) Kus, Mahmut; Okur, SalihPEDOT:PSS humidity sensor was fabricated using a drop-casting method between thermally evaporated gold electrodes with 30 mu m separation and 300 mu m channel width on a glass substrate. AC, DC resistivity, and AFM techniques were used to characterize the PEDOT: PSS humidity sensor in the same environmental conditions. The change of resistivity was monitored with increasing relative humidity (RH) up to 90%. The resistivity increases linearly up to a maximum value, and then it starts to decrease abruptly above 80% relative humidity (RH) after saturation of water uptake. The decrease in resistivity above 80% RH seems to be due to the water meniscus layer formed on the saturated PEDOT: PSS film. Below 80% RH, the device works like a humidity sensor. (C) 2009 Elsevier B.V. All rights reserved.Öğe Humidity Adsorption Kinetics of Calix[4]arene Derivatives Measured Using QCM Technique(Elsevier, 2010) Okur, Salih; Kuş, Mahmut; Özel, Faruk; Aybek, Vildan; Yılmaz, MustafaThis study focuses on the characterization of sulphonated calix[4]arene derivative films coated on a quartz substrate with a thickness of 40 nm by spin coating method for humidity detection. The humidity adsorption kinetics of the sulphonated calix[4]arene films was investigated by quartz crystal microbalance (QCM) technique. The Langmuir model was used to determine the adsorption rates and Gibbs free energy for various relative humidities between 11% and 97%. Our reproducible experimental results show that suphonated calix[4]arene films have a great potential for humidity sensing applications at room temperature operations.Öğe Humidity Adsorption Kinetics of Water Soluble Calix[4]arene Derivatives Measured Using QCM Technique(Elsevier Science Sa, 2010) Okur, Salih; Kuş, Mahmut; Özel, Faruk; Yılmaz, MustafaWe report on the optimization and characterization of water soluble calix[4]arene derivative as a humidity sensor based on quartz crystal microbalance technique. The moisture adsorption and desorption kinetics of calix[4]arene were investigated. The Langmuir model was used to determine the kinetic parameters such as adsorption. desorption rates and Gibbs free energy between relative humidity between 29% and 78%. Reproducible experimental results were obtained showing that water soluble calix[4]arene films have a great potential for humidity sensing applications at room temperature operations.Öğe Modification of ITO surface using aromatic small molecules with carboxylic acid groups for OLED applications(ELSEVIER SCIENCE SA, 2011) Havare, Ali Kemal; Can, Mustafa; Demic, Serafettin; Okur, Salih; Kus, Mahmut; Aydin, Hasan; Yagmurcukardes, Nesli4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) was synthesized in order to facilitate the hole-injection in Organic Light Emitting Diodes (OLED). MPPBA was applied to form self-assembled monolayer (SAM) on indium tin oxide (ITO) anode to align energy-level at the interface between organic semiconductor material (TPD) and inorganic anode (ITO) in OLED devices. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). KPFM was used to measure the surface potential and work function between the tip and the ITO surface modified by SAM technique using MPPBA. The OLED devices (ITO/MPPBA/TPD/Alq(3)/Al) fabricated with SAM-modified ITO substrates showed lower turn-on voltages and enhanced diode current compare to the OLED devices fabricated with bare ITO substrates. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.Öğe Preparation of the ferrocene-substituted 1,3-distal p-tert-butylcalix[4]arene based QCM sensors array and utilization of its gas-sensing affinities(ELSEVIER SCIENCE SA, 2014) Sayın, Serkan; Özbek, Cebrail; Okur, Salih; Yılmaz, MustafaThe article describes the synthesis of the new ferrocene-substituted calix[4]arene derivative 4 as sensitive layer, and suggests that the immobilization of it is on a quartz crystal microbalance gold electrode via the drop-casting method in order to produce the calix[4]arene-based QCM sensor. In addition, sensor response of the calix[4]arene-based QCM sensor was investigated towards carbon dioxide (CO2) and carbon monoxide (CO). The sensing and selectivity studies show that the ferrocene-substituted calix[4] arene-based QCM sensor is an effective gas sensor toward both carbon dioxide and carbon monoxide. (C) 2014 Elsevier B.V. All rights reserved.
