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: 10Citation - Scopus: 10An Efficient Method of Improving Essential Oil Retention and Sustained Release of Chitosan Films: Ultrasound-Assisted Preparation of Chitosan Composites With Surface Active Chickpea Proteins(Elsevier, 2024) Barış Kavur, Pelin; Yemenicioğlu, AhmetThis work aimed at preparing chitosan (CHI) composites with surface active chickpea protein (CP) showing better eugenol (EUG) retention and sustained release capacity than pristine CHI films. For this purpose, ionic complexation of CHI with CP (CHI:CP ratio = 2:1, w/w) in the presence of EUG at pH 5.0 was achieved using mechanical homogenization alone (HM) or in combination with ultrasonic homogenization (HM-HUS). The HM-HUS treatment provided better solubility of CP (4.4-fold), increased emulsified EUG in film-forming solutions, and denser films than HM treatment. The composite films obtained using HM-HUS (FLMCHI-CP-EUG/HM-HUS) retained 1.2–1.4-fold higher EUG after drying, and showed almost 2-fold slower EUG release in air at room temperature than composite films prepared by HM, and control CHI films prepared by HM (FLMCHI-EUG/HM) or HM-HUS (FLMCHI-EUG/HM-HUS). The FLMCHI-CP-EUG/HM-HUS films also showed better moisture barrier and mechanical properties than other films. The developed films were proved in a challenging coating application with onions. Escherichia coli and Listeria innocua counts of inoculated and FLMCHI-CP-EUG/HM-HUS (average coating thickness = 4.5 ± 1.3 μm) coated onions were significantly lower than those of uncoated (2.8 and 3.8 log) and FLMCHI/HM-HUS (1.4 and 1.3 log) coated onions after 5-days at room temperature. FLMCHI-CP-EUG/HM-HUS coating also reduced percentage of sprouted onions from 30 to 10% during storage. EUG odor of coated onions could not have been detected by 80% of panelists after 4 weeks. Compositing with CP boosts the performance of essential oil loaded CHI films by enabling use of film matrix as an encapsulant. © 2024 Elsevier LtdArticle Citation - WoS: 21Citation - Scopus: 22Characterization and Encapsulation Efficiency of Zein Nanoparticles Loaded With Chestnut Fruit Shell, Cedar and Sweetgum Bark Extracts(Elsevier, 2023) Konuk Takma, Dilara; Bozkurt, Semra; Koç, Mehmet; Korel, Figen; Şahin Nadeem, HilalZein nanoparticles (ZNPs) loaded with bioactive extracts of chestnut (Castanea sativa Mill.) shell, cedar (Cedrus libani) and sweetgum (Liquidambar orientalis) bark wastes were produced using different methods. Nanoprecipitation, high-speed homogenization and ultrasonic homogenization allowed the fabrication of ZNPs with particle sizes smaller than 202.40 nm, 430.25 nm and 325.50 nm, respectively. The smallest nanoparticle size was achieved at 132.81 nm for sweetgum bark extract-loaded ZNPs obtained by the nanoprecipitation method. Encapsulation efficiency (EE) was between 34.03 and 96.83% for all zein nanoparticles fabricated under different mixtures and process conditions. Zein concentration and extract ratio played an essential role in the EE of nanoparticles. The best conditions were determined to obtain the desired properties of ZNPs based on particle size, polydispersity index and EE by using a central composite rotatable design. The nanoprecipitation method was more appropriate for producing chestnut and cedar shell/bark extract-loaded nanoparticles. In contrast, the high-speed homogenization method was suitable for producing sweetgum bark extract-loaded nanoparticles. As a result of the encapsulation of various shell/bark extracts within zein nanoparticles, value-added products were generated from wastes having bioactive compounds. The developed zein nanoparticles for each extract type would offer eco-friendly, simple and safe food processing and packaging systems. © 2023Article Citation - WoS: 22Citation - Scopus: 27Mechanisms Behind Slow Photoresponse Character of Pulsed Electron Deposited Zno Thin Films(Elsevier, 2020) Özdoğan, Mehmet; Çelebi, Cem; Utlu, GökhanSemiconducting Zinc Oxide (ZnO) is ideal candidate for ultraviolet (UV) photodetector due to its promising optoelectronic properties. Photoconductive type ZnO photodetectors, which is fabricated in metal-semiconductor-metal configuration, show mostly very high photoconductivity under UV light, but they are plagued by slow photoresponse time as slow as several tens of hours, even more. Most of the studies claimed that atmospheric adsorbates such as water and oxygen create charge traps states on the surface and remarkably increase both the photoconductivity and response time. There are also limited studies, which claim that the defect states acting as hole trap centers prolong response time significantly. However, the underlying physical mechanism is still unclear. Here we study the effects of both adsorbates and defect-related states on the photoresponse character of Pulsed Electron Deposited ZnO thin films. In order to distinguish between these two mechanisms, we have compared the time-dependent photoresponse measurements of bare-ZnO and SiO2 encapsulated-ZnO thin film samples taken under UV light and high vacuum. We show that the dominant mechanism of photoresponse in ZnO is the adsorption/desorption of oxygen and water molecules even when the measurement is performed in high vacuum. After the encapsulation of sample surface by a thin SiO2 layer, the adsorption/desorption rates can significantly improve, and the effects of these molecules partially removed.Article Citation - WoS: 6Citation - Scopus: 7Epitaxial Graphene Thermistor for Cryogenic Temperatures(Elsevier, 2018) Kalkan, Sırrı Batuhan; Yiğen, Seren; Çelebi, CemThe thermal responsivity of monolayer epitaxial graphene grown on the Si-face surface of semi-insulating SiC substrate is investigated as a function of temperature below 300 K. The measurements showed that adsorption/desorption of atmospheric adsorbates can randomly modify the electrical characteristics of graphene which is indeed undesirable for consistent temperature sensing operations. Therefore, in order to avoid the interaction between graphene layer and adsorbates, the grown graphene layer is encapsulated with a thin SiO2 film deposited by Pulsed Electron Deposition technique. Temperature dependent resistance measurement of encapsulated graphene exhibited a clear thermistor type behavior with negative temperature coefficient resistance character. Both the sensitivity and transient thermal responsivity of the SiO2/graphene/SiC sample were found to be enhanced greatly especially for the temperatures lower than 225 K. The experimentally obtained results suggest that SiO2 encapsulated epitaxial graphene on SiC can be used readily as an energy efficient and stable temperature sensing element in cryogenic applications.