Browsing by Author "Uysal, Bengü Özuğur"

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Citation Count: 0
3D self-assemble formation of molybdenum disulfide $(MoS_2 )-doped$ polyacrylamide (PAAm) composite hydrogels
(2022) Durmaz, Sümeyye; Yıldız, Ekrem; Uysal, Bengü Özuğur; Pekcan, Önder
Polyacrylamide (PAAm), a renowned member of the hydrogel class, has many uses throughout a wide range of industrial processes, including water absorbed diapers, contact lenses, wastewater treatment, biomedical applications such as drug delivery vehicles and tissue engineering because of its physical stability, durability, flexibility easier shaping, and so on. PAAm also provides new functionalities after the incorporation of inorganic structures such as molybdenum disulfide $(MoS_2 )$. During the copolymerization process, the transmittance of all samples reduced significantly after a particular time, referred to as the gel point. Microgels form a tree above the gel point as projected by Flory-Stockmayer classical theory. Because of microgels positioned at the junction points of the Cayley tree, the addition of $MoS_2$ results in strong intramolecular crosslinking and looser composites. Moreover, fractal geometry provides a quantitative measure of randomness and thus permits characterization of random systems such as polymers. Fractal dimension of these polymer composites is calculated from power-law-dependent scattered intensity. It was also confirmed that a hydrogel rapidly formed within a few seconds, indicating a 3D network formation inside the gel. These materials may have a great potential for application in wearable and implantable electronics due to this highly desired 3D self-assemble feature.
Citation Count: 2
Characterization of MWCNT-TiO2 Qps and TiO2 QDs in self-assembled films
(Elsevier, 2017) Akkaya Arier, Ümit Özlem; Uysal, Bengü Özuğur
In this study the solution which includes TiO2 quantum dots (QDs) was mixed with the multi-wall carbon nanotubes (MWCNTs) to prepare MWCNT-TiO2 QDs composite films. The effect of microstructures on the structural and optical properties of MWCNT-TiO2 QDs composite films was evaluated. The activation energy for crystallite growth of TiO2 QDs which are produced in brookite phases was calculated as 20.3 kJ/mol. The properties of MWCNT-TiO2 QDs composite films were characterized by X-ray diffraction (XRD) scanning electron microscopy (SEM) atomic force microscopy (AFM) and ultraviolet-visible absorption spectroscopy (UV-vis). (C) 2017 Elsevier GmbH. All rights reserved.
Citation Count: 7
Controlling the growth of particle size and size distribution of silica nanoparticles by the thin film structure
(Springer, 2012) Uysal, Bengü Özuğur; Tepehan, Fatma Zehra
Nanostructured silicondioxide thin films were prepared by sol-gel spin coating technique. The SiO2 films were made using a conventional mixture of tetraethoxysilane (TEOS) deionized water and ethanol with various NH3/TEOS ratios. The nanostructured silica films were made using a mixture of the SiO2 sol and regular SiO2 sol to control the enlargement of the particles inside the films. The structural morphological and optical characterizations of the as-deposited and annealed films were carried out using X-ray diffraction (XRD) atomic force microscopy scanning electron microscopy NKD spectrophotometer and ultraviolet-visible (UV-vis) spectroscopy. The transmittance data of the infrared spectra of the films were recorded using an FT-IR Spectrometer. The XRD studies showed that as-deposited films were amorphous and the formation of the alfa-cristobalite phase of the silica film was investigated at annealing temperature close to 1100 A degrees C. Optical properties of the transmittance spectra in the s and p-polarization modes were collected. Refractive indices and extinction coefficients were determined with respect to the NH3/TEOS ratios in the compositions of the films. Optical cut-off wavelength values were investigated from the extrapolation of the absorbance spectra which was estimated from the UV-vis spectroscopy measurements. A red shift in the absorption threshold indicated that the size of silica nanoparticles was increased by an increase in the NH3/TEOS volume ratio from 1:64 to 1:8.
Citation Count: 0
Determination of growth kinetics and size dependent structural morphological optical characteristics of sol-gel derived silica nanoparticles in silica matrix
(De Gruyter Poland Sp Zoo, 2019) Uysal, Bengü Özuğur; Tepehan, Fatma Zehra
Nanocomposite silica thin films made using the sol-gel method were studied. The nano-silica films were prepared using a mixture of tetraethyl orthosilicate (TEOS) deionized water ethanol and ammonia solution. To control the growth of the particles inside the film the nanocomposite silica film was prepared using a mixture of the nano-silica sol and the silica sol. The change in the particle size with the heat treatment temperature ranging from 450 degrees C to 1100 degrees C was investigated. X-ray diffraction (XRD) atomic force microscopy (AFM) scanning electron microscopy (SEM) NKD (refractive index-N extinction coefficient-K and thickness-D) and ultraviolet-visible (UV-Vis) spectrophotometry were used for characterization purposes. The XRD studies showed that the nano-silica thin films were amorphous at all annealing temperatures except for 1100 degrees C. The alpha-cristobalite crystal structure formed at the annealing temperature of 1100 degrees C. Optical parameters such as refractive indices and extinction coefficients were obtained using the NKD analyzer with respect to the annealing temperature of the films. The activation energy and enthalpy of the nanocomposite silica film were evaluated as 22.3 kJ/mol and 14.7 kJ/mol respectively. The cut-off wavelength values were calculated by means of extrapolation of the absorbance spectra estimated using the UV-Vis spectroscopy measurements. A red shift in the absorption threshold of the nanocomposite silica films indicated that the size of the silica nanoparticles increased with an increase of the annealing temperatures from 450 degrees C to 900 degrees C and this confirms the quantum confinement effect in the nanoparticles.
Citation Count: 3
The effects of Dea:water ratio on the properties of ZnO nanofilms obtained by spin coating method
(Elsevier Science, 2014) Akkaya Arier, Ümit Özlem; Uysal, Bengü Özuğur
In this work the ZnO were fabricated with the sol-gel spin coating method and the effects of the Dea:water ratios on the properties of the as-prepared ZnO thin films were determined by using a X-ray diffractometer transmission electron microscope scanning electron microscope atomic force microscope ultraviolet-visible spectrophotometer and spectrophotometer. Experimental results indicated that the Dea:water ratio affected the structural and optical properties of the ZnO films considerably. The activation energy for the particle growth of ZnO nanofilms and the effects of the Dea:water ratios on the band gap values of the ZnO films were investigated. The film has an activation energy of 26.3 kJ/mol and optical band gap of 3.27-3.31 eV is proportional to the Dea:water ratio. (c) 2014 Elsevier Ltd. All rights reserved.
Citation Count: 4
Effects of Precursor Parameters on the Optical and Electrical Properties of AZO Nano-Composite Films
(Elsevier GMBH Urban & Fischer Verlag, 2016) Akkaya Arier, Ümit Özlem; Uysal, Bengü Özuğur
Al doped ZnO (AZO) nano-composite films were synthesized on glass substrates with the sol gel spin coating method at the room temperature. The activation energy of AZO nano-composite films was calculated to be 49 kj/mol for the particles growth. The electrical structural and optical properties of AZO films were determined by changing ZnO:water and ZnO:Al ratios. ZnO:water and ZnO:Al ratios play an important role in controlling the electrical conductivity of the AZO nano-composite films. The optimum doping ratio of Al was found to be 2% in terms of the lowest resistivity and above 2% Al-doping concentration the surface resistivity of AZO nano-composite films starts to increase. The optical highest transmittance of the films of 86% in visible region and low surface resistivity of 70 Omega/square can be obtained for the optimum doping ratio of Al. (C) 2016 Elsevier GmbH. All rights reserved.
Citation Count: 4
The Electrochromic Performances of Single Phase VO2 Nanoparticled Films
(Elsevier Science SA, 2016) Akkaya Arier, Ümit Özlem; Uysal, Bengü Özuğur
In the present work pure phase vanadium oxide VO2 nanoparticled films were synthesized using acetate based sol-gel precursors. The effect of the water: Vanadyl acetylacetonate ratio on electrochemical and structural properties of nanostructured vanadium oxide films was examined. The X-ray diffraction studies indicated that very strong crystallization of the VO2 monoclinic phase occurred for the as-deposited films at the annealing temperature of 500 degrees C. According to the atomic force microscopy and scanning electron microscopy measurements the size and morphology of the granular structured film depend on the water: Vanadyl acetylacetonate ratio. I-V curve spectra were used to compute several characteristics of the films coated on indium tin oxide substrates such as the optical density color efficiency and diffusion coefficient. Even though water: Vanadyl acetylacetonate ratio of 0.1 is expected to give the highest color efficiency value (33 cm(2)/C) higher diffusion coefficient (3.15 x 10(-12) cm(2)/s) is observed in the ratio of 0.01. As a result the correlation between the ratios and electrochromic properties of the films was established. (C) 2016 Elsevier B.V. All rights reserved.
Enhanced structural, optical and antibacterial properties of ZnO doped TiO2 composites
(Kadir Has Üniversitesi, 2021) Sümer, Mehmet Eymen; Uysal, Bengü Özuğur
Günlük yaşamda bakteriyel enfeksiyonlar insan sağlığı için yaygın bir sorundur. Bu nedenle araştırmacılar, antibakteriyel enfeksiyonları ve çevresel kirleticileri önlemek için değerli materyaller arıyorlar. İnce film, fotokatalitik ve biyolojik aktivite için iyi bilinen bir uygulamadır. Bu nedenle, ince film oluşumu, nano boyutlu kalınlığı ve geliştirilmiş tek katmanlı veya çok katmanlı yapısı nedeniyle bu sorunların üstesinden gelmek için mükemmel bir yoldur. İnce film üretimi için en yaygın malzeme titanyum oksittir (TiO2). Yapısal ve optik özellikler gibi ince filmlerin etkinliğini arttırmak için çeşitli özelliklere sahiptir. Bununla birlikte, saf TiO2'nin tek kullanımı bu problemlerde bazı sınırlamalara sahiptir. Bu nedenle, bu sınırlamaların üstesinden gelmek için yeni tekniklerin uygulanması gerekir ve buna doping denir. Doping, gelişmiş işlevsellik sağlamak için malzeme özelliklerini manipüle etmek için standart bir yöntemdir. Bu nedenle, iyi bant aralığı enerjisi ve yüksek elektron aktivitesi nedeniyle ZnO katkı maddesi olarak seçilmiştir. Böylece, bu tez temel olarak saf TiO2 ve ZnO katkılı TiO2'nin antibakteriyel, yapısal ve optik aktivite farklılıklarına odaklanmıştır. Diğer farklı ince film biriktirme yöntemleri içinde, oda sıcaklığında sürecin kolay ilerlemesi, düşük maliyeti ve homojenlik özellikleri nedeniyle bu araştırmada sol-jel yöntemi kullanılmıştır. UV-vis spektrofotometre (Labomed Spectro 22), 190–1100 nm dalga boyu spektral aralığında optik analiz için kullanılmıştır. Homojenliği ve parçacık boyutunu içeren yapısal farklılıklar, X-ışını difraktometresi (XRD, Philips PW-1800) tarafından belirlenmiştir. ISO 22196 protokolü standardına göre gram pozitif "Staphylococcus aureus" ve gram negatif "Escherichia coli"ye karşı saf ve katkılı TiO2 ince filmlerin antibakteriyel aktivitesi analiz edilmiştir. Sonuç olarak, XRD ve UV-vis spektrofotometre ölçümleri, katkı maddesi ZnO'nun saf TiO2'nin bant aralığı enerjisini verimli bir şekilde arttırdığını ve ZTA-B-R (5-10) konsantrasyonu aralığında dağılabilirlik ve homojenlik arasındaki korelasyonun sağlandığını göstermiştir
Citation Count: 2
Fractal Features and Structural Morphological Optical Characteristics of Sol-Gel Derived Silica Nanoparticled Thin Films
(Polish Acad Sciences Inst Physics, 2018) Uysal, Bengü Özuğur; Pekcan, Önder
Nanostructured silica films using a simple and effective sol-gel spin coating technique were synthesized and the influence of ammonia/sol ratios on the particle size and thickness of this film was investigated. In addition fractal dimensions of the prepared films were determined using the scattering response technique. The samples were characterized by atomic force microscopy and UV-vis spectroscopy. Comparing optical method and image analysis of atomic force microscopy micrographs the fractal dimension of silica nanoparticled thin films was determined. The fractal dimensions of the films verified by atomic force microscopy analysis were found to be around 2.03 which is very close to the values (2.0358 2.0325 and 2.0335) obtained using optical method. As a result of these findings precise determination of the nanoparticled silica thin films fractal dimension using both optical and surface analysis methods was realized.
Mos2'nin tnbc kanser ilaci yükleme ve salimina yönelik basit ve yeni peg k-carrajenan hidrojel üzerinde etkisi
(2023) Hassan, Gana Sherıf; Uysal, Bengü Özuğur
İki boyutlu inorganik bir molekül olan molibden disülfür (MoS2), ayırt edici özellikleri nedeniyle son zamanlarda tıbbi araştırmalarda farmasötiklerin taşınması açısından incelenmiştir. Oluşturulacak biyobozunur bir polimer sistemi, MoS2 ilavesiyle kanser ilacı dağıtımında uygulanabilir. Bu yazıda MoS2 miktarının yeni jel karışımımızın özellikleri ve performansı üzerindeki etkisini araştırıyoruz. Üçlü negatif meme kanseri (TNBC) ilaç taşıyıcı sisteminde uyarana duyarlı polimerik hidrojel olarak taşıyıcı olarak kullanılma potansiyeline sahip olduğu düşünülen MoS2 katkılı polietilen glikol ile yeni bir jel karışımının hazırlanması amaçlandı. PEG)/k-karagenan kombinasyonunun ilk özelliklerinin verilmesi. Bu 2D malzeme, polimerik jelin normal MoS2 içermeyen yapısına kıyasla geçirgenlik, şişme ve elastikiyet performansını artırarak hidrojeli etkiledi. Polimer karışımı özellikleri esas olarak UV-VIS spektrofotometresi ve gravimetrik analiz kullanılarak test edildi. Bu jel karışımlarının çeşitli özellikleri beş farklı kütlede araştırıldı. 5 mg MoS2, yeni ve basit malzeme kombinasyonumuza MoS2 eklenmesinin hidrojel özelliklerinin iyileştirilmesiyle sonuçlandığını gösteren verilere göre esneklik açısından araştırılan en iyi örnekti. Araştırmanın sonuçları, kanser ilaçlarının kesin olarak hedeflenmiş ve düzenlenmiş dağıtımı için ilaç yükleme ve ilaç salma kinetiğine kadar genişletilebileceğini gösterdi. Yakın gelecekteki bu hedefe yönelik ön veriler oluşturmak amacıyla doksorubisin ilacının üretilen jele yüklenme ve salınma mekanizmaları incelendi. Anahtar Kelimeler – Molibden Disülfür, geçirgenlik, şişme, K-Karragenan, Polietilen Glikol
The optical and electrical characteristics of ZnO /MoS2 transparent oxide composite films
(Kadir Has Üniversitesi, 2021) Al-Zubaidi, Shahad Tareq Radeef; Kirkil, Gökhan; Uysal, Bengü Özuğur
Optoelektronikte saydam iletken oksit kullanımı, verimliliği düşürmeden veya maliyeti artırmadan esneklik, dayanıklılık ve taşınabilirlik becerisinin elde edildiği bir devrim yaratmaktadır. ZnO / MoS2 saydam iletken kompozit filmi basit bir süreç oluşu ve düşük maliyeti nedeniyle en önemli yöntem olarak kabul edilen sol-jel yöntemi ile üretilmiştir. ZnO / MoS2'nin kristal yapı özellikleri, X-Işını kırınım modeli (XRD) ile karakterize edilmiştir. XRD spektroskopisi ile, farklı miktarlarda MoS2 katkılı ZnO filminin kristal boyutu tayin edilmiştir. UV- görünür bölge absorpsiyon spektrometresi, filmin spektroskopik analizini gerçekleştirmek için kullanılmıştır. Absorpsiyon eğrisinin altındaki alan ve yarı maksimum absorbans verilerinin tam genişliği hesaplanmıştır. Bu değerle kullanılarak en iyi katkı maddesi dağılımı için MoS2 miktarı tespit edilmiştir. Ayrıca, en iyi saydam iletken malzemeyi belirlemek üzere, dört nokta prob yöntemi kullanılarak elde edilen direnç değerleri farklı MoS2 katkı miktarları için kıyaslanmıştır. Bu çalışmada, bir ZnO / MoS2 saydam iletken oksit filmin optik ve elektrik karakterizasyonlarını incelenmiştir.
Citation Count: 29
Structural and optical properties of SnO2 nano films by spin-coating method
(Elsevier Science Bv, 2015) Uysal, Bengü Özuğur; Akkaya Arier, Ümit Özlem
In this work tin oxide (SnO2) nano films were deposited on glass substrates with different water content using the sol-gel spin-coating method. SnO2 is a wide band gap semiconductor and it belongs to the class of transparent conductive oxides (TCO). The influence of the water content and the heat treatment temperature on the structural and optical properties of the thin films is characterized by X-ray diffractometer (XRD) scanning electron microscope atomic force microscope ultraviolet visible spectrophotometer and spectrophotometer. Crystallite size of nano SnO2 films was controlled by SnCl2:water ratios. The most significant characteristic of nano materials is the increase in surface area as particle size decreases. XRD studies showed that the formation of tetragonal rutil phase was initiated at an annealing temperature close to 450 degrees C. The activation energy of nano SnO2 films for particle growth was calculated. The film has an activation energy of 42.8 kJ/mol and the optical band gap of 3.02-3.35 eV is proportional to the SnCl2:water ratio. The quantum size effect of nano particles was confirmed by the band gap energy shift using ultraviolet visible spectroscopy (UV-vis). SnO2 films have been considered as one of the most promising functional materials due to their wide direct band-gap and excellent electrical and optical properties. Those properties of SnO2 films allow them to be used in electronic and optoelectronic devices like gas sensors solar cells and lithium batteries etc. (C) 2015 Elsevier B.V. All rights reserved.
Structural, optical and antibacterial properties of WS2 doped ZnO nanoparticles
(2023) Beytür, Sercan; Uysal, Bengü Özuğur; Eşsiz, Şebnem
Yapısal ve optik özelliklerinin yanı sıra antibakteriyel özellikleri ile tanınan ZnO nanoparçacıkları, çeşitli alanlarda yaygın olarak uygulanmaktadır. Metaller veya metal oksitler gibi farklı malzemelerin ZnO'ya katkılanmasının özelliklerini iyileştirdiği bilinmektedir. Burada %5, %15 ve %25 oranlarında WS2 katkılı ZnO'dan oluşan nanofilmler sentezlenmekte ve özellikleri araştırılmaktadır. Moleküler yerleştirme analizleri ile desteklenen, farklı oranlarda WS2 ilave edildikten sonra bakterisidal özelliklerin arttırılması vurgulanmaktadır ve ilgili proteinlerin hedeflenmesi yoluyla bakteriyel hayatta kalmada çok önemli bir rol oynayan kalıntıların inhibe edici etkileşimi tarafından desteklenmektedir.
Citation Count: 9
Surfactant-free one-step fabrication of gelatin/PAAm/MWCNT composites for biomedical applications
(Springer, 2021) Duzkan, Berke; Uysal, Bengü Özuğur; Pekcan, Önder
Well-dispersed multiwalled carbon nanotube (MWCNT) and gelatin-enhanced polyacrylamide (PAAm) composites were synthesized via a free-radical copolymerization method. MWCNTs were added to the composite mixture in various amounts (0.5 mg, 1.0 mg, 1.5 mg, and 2.0 mg) during the nucleation process in order to increase the conductivity. Gelatin/PAAm/MWCNT composites containing different amounts of MWCNTs were then characterized using the ultraviolet-visible (UV-vis) spectroscopic technique to illuminate the dispersibility, and optical properties of the composites. Bandgap energies were evaluated by measuring the absorbance spectra of the composites in a quartz cuvette of the UV-vis spectrophotometer. By calculating the resonance ratio and normalized width values from the absorption response of the composites according to the wavelength, the dispersion rate of the MWCNTs in the composite matrix was determined. The proper ultra-sonication process has been realized so as to maintain the good dispersion of the MWCNTs inside the polymeric matrix lowering the normalized width and increasing the resonance ratio. Polymeric composite materials based on carbon nanotubes are of considerable interest for a variety of biomedical applications. Furthermore, in this work, it is argued that the use of gelatin, another biocompatible material, together with MWCNT makes the properties of the formed composite, suitable for the desired biomedical applications.
Citation Count: 2
Tailoring The Electrical and Optical Properties of Carbon Nanotube Reinforced Transparent Tio 2 Composites by Varying Nanotube Concentrations
(World Scientific Publ Co Pte Ltd, 2019) Uysal, Bengü Özuğur; Akkaya Arier, Ümit Özlem; Pekcan, Önder
In the present work multi-walled carbon nanotube (MWCNT)-doped TiO 2 nanocomposite films were synthesized by sol-gel method. The influence of nanotube concentration on the structural electrical and optical properties of the films was investigated. The beneficial effects of the addition of carbon nanotubes into a TiO 2 film and titania-coated MWCNTs have much in common. On the other hand this work contributes to the previous studies in terms of the optical and electrical properties of MWCNT. For this reason MWCNT/rare brookite-phased TiO 2 matrix as simple sol-gel deposited composite films were investigated in our study. The XRD studies showed that the composite film has a brookite crystal structure at the annealing temperature of 450C. According to the surface morphology investigations SEM image of nanocomposite film shows that composite film has a granular and rod-like structure. The absorbance measurements of the films were carried out by the UV-Vis spectrophotometer to investigate transparency and to calculate the bandgap energy of composite films. The surface resistivity of the MWCNT-doped TiO 2 composites decreased from 2.50×1010 to 2.20×109 ohm/sq with increase in MWCNT content. © 2019 World Scientific Publishing Company.
Citation Count: 6
The WS(2)dependence on the elasticity and optical band gap energies of swollen PAAm composites
(Sage Publications, 2020) Evingür, Gülsen Akın; Sağlam, Nafia Alara; Çimen, Büşra; Uysal, Bengü Özuğur; Pekcan, Önder
New generation nano-filler polymer composites have many applications including biomedical, electronic and maritime related applications because of their mechanical, electronic and optical properties. The properties of composites were investigated as a function of nano-filler content. Among these, tungsten disulfide (WS2) has the potential to be used as a component in electronic devices owing to its high electron mobility and easily tunable optical band gap energy. Tungsten disulfide (WS2)- Polyacrylamide (PAAm) composite was prepared using free radical co-polymerization and wet laboratory methods with WS(2)content. Composites were characterized for mechanical and optical properties using an Elasticity Instrument and UV-vis Spectrophotometer, respectively. Elastic modulus was modeled by a statistical thermodynamics model. Tauc's and Urbach's Tail model for direct transition were used to model for the optical band gap. In this study, the swelling and WS(2)effect on the optical band gap and elasticity of WS2- PAAm composites were investigated. It was observed that the elasticity presented a reversed behavior of optical band gap energies with respect to WS(2)content. For the applications of nano-filler doped polymer composites in flexible electronic devices, WS(2)content strongly influences the mechanical and optical properties.