Electrical characterization of PEDOT: PSS beyond humidity saturation

PEDOT: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.TÜBİTAK project number of TBAG-108T718 and DPT2003K12039

Improvement in electrical performance of half-metallic Fe3O4/GaAs structures using pyrolyzed polymer film as buffer layer

WOS:000340051400006In this work, the Fe3O4 magnetic nanoparticles (MNPs) were synthesized by a colloidal method. TEM images reveal that Fe3O4 MNPs are spherical in shape with a narrow size distribution in the range of 6-7 nm. These MNPs were used in the fabrication of two types of n-GaAs-based structures: (i) Fe3O4/n-GaAs (reference); and (ii) Fe3O4/PPF/n-GaAs. We present that carbon-based pyrolyzed polymer films (PPFs), as a buffer layer, can control the electrical characteristics of a conventional Fe3O4/n-GaAs device. The behaviour of the apparent barrier height and ideality factor with the interfacial layer due to the presence of the interface state density is discussed. PPF raises the barrier height in a Fe3O4/PPF/n-GaAs half-metallic/insulator/semiconductor (h-MIS) device as high as 0.62 +/- 0.002 eV. Furthermore, Fe3O4/PPF interfaces exhibit unique electronic properties including high-quality interface, low series resistance (from 17.73 k Omega to 85.66 Omega) and extremely low interface state density (1.76 x 10(12) eV(-1) cm(-2)). Compared to the electrical performance for the Fe3O4/n-GaAs junction, that for the Fe3O4/PPF/n-GaAs junction was enhanced

Humidity adsorption kinetics of water soluble calix[4]arene derivatives measured using QCM technique

We 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.DPT project number DPT2003K120390 and Selcuk University Scientific Research Counci

Solution processed white light photodetector based N, N '-di(2-ethylhexyl)-3,4,9,10-perylene diimide thin film phototransistor

WOS:000344749400005In this study, a solution-processed n-type photo-sensing organic thin film transistor was investigated using polymeric dielectric under different white light illuminations. N, N'-di (2-ethylhexyl)-3,4,9,10-perylene diimide and divinyl tetramethyl disiloxane-bis (benzo-cyclobutene) were used as a soluble active organic semiconductor and as a dielectric material, respectively. Stable amplification was observed in the visible region without gate bias by the device. The electrical characterization results showed that an n-type phototransistor with a saturated electron mobility of 0.6 x 10(-3) cm(2)/V.s and a threshold voltage of 1.8 V was obtained. The charge carrier density of the channel of the device exhibited photo-induced behaviors that strongly affected the electrical properties of the transistor. The photosensitivity and photoresponsivity values of the device were 63.82 and 24 mA/W, respectively. These findings indicate that perylene diimide is a promising material for use on organic based phototransistors. (C) 2014 Elsevier B.V. All rights reserved.FP7-LAMAND project [PN: 245565]We are grateful to the FP7-LAMAND (PN: 245565) project for providing support funds. In addition, we thank Ass. Prof. A. Tahir Bayrac for proofreading the text

Humidity adsorption kinetics of calix[4]arene derivatives measured using QCM technique

This 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.DPT2003K120390; TÜBİTAK TBAG 109T240 and Selcuk University Scientific Research Counci

Preparation of MIP-based QCM nanosensor for detection of caffeic acid

WOS:000331670700076PubMed:24401452In the present work, a new caffeic acid imprinted quartz crystal microbalance (QCM) nanosensor has been designed for selective assignation of caffeic acid in plant materials. Methacrylamidoantipyrine-iron (III) [MAAP-Fe(III)] as metal-chelating monomer has been used to prepare selective molecular imprinted polymer (MIP). MIP film for detection of caffeic acid has been developed on QCM electrode and selectivity experiments and analytical performance of caffeic acid imprinted QCM nanosensor has been studied. The caffeic acid imprinted QCM nanosensor has been characterized by AFM. After the characterization studies, imprinted and non-imprinted nanosensors was connected to QCM system for studies of connection of the target molecule, selectivity and the detection of amount of target molecule in real samples. The detection limit was found to be 7.8 nM. The value of Langmuir constant (b) (4.06 x 10(6)) that was acquired using Langmuir graph demonstrated that the affinity of binding sites was strong. Also, selectivity of prepared caffeic acid imprinted nanosensor was found as being high compared to chlorogenic acid. Finally, the caffeic acid levels in plant materials was determined by the prepared QCM nanosensor. (C) 2013 Elsevier B.V. All rights reserved.Commission of Scientific Research Projects of Selcuk UniversitySelcuk University [13201004]The financial support from Commission of Scientific Research Projects of Selcuk University (Project No: 13201004) is gratefully acknowledged

Effect of doping on thin film solar cell efficiency based on ZnMn2O4 nanocrystals

International Congress on Semiconductor Materials and Devices (ICSMD) -- AUG 17-19, 2017 -- Selcuk Univ, Konya, TURKEYWOS:000495858400010The present study reports, for the first time, a facile synthesis for ternary ZnMn2O4 nanocrystals synthesized by a simple and low cost two-phase method. Those nanocrystals were used on thin film solar cell as active absorber layer. The resulting nanocrystals were characterized by XRD, TEM, AFM-MFM, FTIR and JV characterization techniques to investigate the crystalline behavior, chemical composition, morphology and optical properties. Two phase method allows the successful synthesis of oleic acid (OA) capped ZnMn2O4 nanocrystals with 5-10 nm particle size. After doping of the ZnMn2O4 nanocrystals at different ratios with P3HT:PCBM, an enhancement was observed in the solar cell performances based on thin films. The power conversion efficiency of P3HT:PCBM-ZnMn2O4 thin film solar cell was investigated by J-V characteristic curve and as a result of this study, the highest efficiency was achieved as 3.27% with a doping ratio of 1%. Thus we believe that this work will open a new perspective to the synthesis of ZnMn2O4 materials for applications in the field of energy conversion systems. (C) 2019 Elsevier Ltd. All rights reserved.TUBITAK (The Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [109T881]; Selcuk UniversitySelcuk University [12101017]; Karamanoglu Mehmetbey UniversityKaramanoglu Mehmetbey University [02-YL-15]The authors would like to thank to TUBITAK (The Scientific and Technological Research Council of Turkey) (109T881) for supporting this work as well as Selcuk and Karamanoglu Mehmetbey University for Scientific Research Foundation (12101017 and 02-YL-15, respectively)

Controlling spontaneous emission of CdSe nanoparticles dispersed in electrospun fibers of polycarbonate urethane

Luminescent 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