Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 35Citation - Scopus: 37Modification of Ito Surface Using Aromatic Small Molecules With Carboxylic Acid Groups for Oled Applications(Elsevier Ltd., 2011) Havare, Ali Kemal; Can, Mustafa; Demiç, Şerafettin; Okur, Salih; Kuş, Mahmut; Aydın, Hasan; Yağmurcukardeş, Nesli; Tarı, Süleyman4-[(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/Alq3/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.Article Citation - WoS: 34Citation - Scopus: 37Humidity Adsorption Kinetics of Water Soluble Calix[4]arene Derivatives Measured Using Qcm Technique(Elsevier Ltd., 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. © 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 36Citation - Scopus: 30Humidity Adsorption Kinetics of Calix[4]arene Derivatives Measured Using Qcm Technique(Elsevier Ltd., 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. © 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 141Citation - Scopus: 154Electrical Characterization of Pedot: Pss Beyond Humidity Saturation(Elsevier Ltd., 2009) Kuş, Mahmut; Okur, SalihPEDOT:PSS humidity sensor was fabricated using a drop-casting method between thermally evaporated gold electrodes with 30 μm separation and 300 μm 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.Article Citation - WoS: 15Citation - Scopus: 15Controlling Spontaneous Emission of Cdse Nanoparticles Dispersed in Electrospun Fibers of Polycarbonate Urethane(American Chemical Society, 2009) Demir, Mustafa Muammer; Soysal, Duygu; Ünlü, Caner; Kuş, Mahmut; Özçelik, SerdarLuminescent fibrous composite films consisting of submicrometer diameter fibers were prepared by electrospinning of segmented polycarbonate urethane (PCU) in dimethyl formamide and tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals (5 nm in diameter) in toluene. Using a pair of conductive electrodes separated with an air gap, we successfully produced randomly deposited and uniaxially aligned electrospun fibers. The surface structure of the electrospun fibers was studied using atomic force microscopy (AFM) and was compared to the corresponding film prepared by casting. In cast film, tapping mode AFM imaging suggests that hard urethane segments organize into rodlike morphology dispersed in soft polycarbonate. When PCU/ CdSe dispersions were subjected to electrospinning, copolymer domains were forced to arrange into lamella along the fiber axis due to elongational flow and high stretching. Molecular orientation in the domains of the composite fibers was confirmed by polarized infrared spectroscopy. We demonstrated that formation of the oriented domains by electrospinning develops a hierarchical structure, which consequently modifies spectral properties because new multiple sharp lines appeared in the photoluminescence (PL) spectra of the fibers. In contrast to randomly deposited fibers, the PL intensity of uniaxially aligned fibers was found to be angle dependent. We propose that the elongated internal structure within the fibers controls the spontaneous emission of CdSe nanoparticles dispersed throughout the electrospun mat. A discussion on the nature of the controlled spontaneous emission is provided.Article Citation - WoS: 32Citation - Scopus: 32Optical and Electrochemical Properties of Polyether Derivatives of Perylenediimides Adsorbed on Nanocrystalline Metal Oxide Films(Elsevier Ltd., 2013) Kuş, Mahmut; Haklı, Özgül; Zafer, Ceylan; Varlıklı, Canan; Demiç, Şerafettin; Özçelik, Serdar; İçli, SıddıkWe report optical and electrochemical properties of polyether derivatives of perylenediimides (PDIs) thin films formed in various materials (semiconductor, insulator, amorphous and self-assembly). Perylenediimides adsorbed on nanocrystalline TiO2(NT) nanocrystalline alumina (NA), amorphous silicon (PS) and neat self-assemblied (SA) films were prepared and characterized based on spectroscopic, electrochemical, spectro-electrochemical techniques. The absorption and fluorescence spectra of PDIs in chloroform exhibit vibronic features. The fluorescence quantum yields (Uf) of PDIs with end amino substituents in chloroform solutions are over 0.95, while the quantum yield of triethoxyphenyl substituted PDIUfvalue is 0.024 in solution. Optical spectroscopy proves that PDIs in metal oxide thin films form aggregated type complexes. An electrochromism, a color change from red to blue/violet, is observed on metal oxide films, that indicates existence of mono and dianion forms of PDIs. Reversibility of electrochemical reductions in NT film depends on the scanning rate. However, electrochromism in NA films is stable and reversibility is independent from scanning rate. Stable mono and diaionic species are formed on NA films. SA films show broad absorption peaks during the voltammetric scan. On the other hand, the first reduction onset potentials of PDIs are almost equal to the onset potential of capacitive current of TiO2which lead to low efficiency in dye-sensitized solar cells.