Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Book Part Citation - Scopus: 1A Recycling Route of Plastics Via Electrospinning: From Daily Wastes To Functional Fibers(Walter de Gruyter GmbH, 2019) Isık, Tuğba; Horzum,N.; Demir, Mustafa MuammerSince large-scale plastic production has begun in the 1940s, plastics have been produced and used globally, bringing many advantages to modern life. The consumption of plastics has increased exponentially due to their low cost, chemical resistance, lightness, durability and ability to combine with other materials. However, plastic materials represent high tonnage in urban wastes, and it is known that these plastics discarded at the end of their useful life by filling the landfill sites. Electrospinning is a well-established and versatile technique for the fabrication of submicron fibers. In addition, it is a promising approach for the recycling of waste polymers without using complex methodologies. In this chapter, utilization of electrospinning approach for the recycling of daily wastes will be discussed. The literature about the daily wastes of both synthetic materials and natural/agricultural materials will be analyzed, and the applications of these materials will be given in detail. © 2019 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Conference Object X-Ray Fluorescence Spectroscopic Determination of Heavy Metal and Trace Element Concentrations of Origanum Sipyleum From Turkey(Georg Thieme Verlag, 2015) Erdoğan, T. F.; Gönenç, T. M.; Kayalar, H.; Durmuşkahya, Cenk; Hortooğlu, Zehra Sinem; Toktaş, Ümit; Boyalı, F.[No abstract available]Book Citation - Scopus: 19Advanced Sensor and Detection Materials(John Wiley and Sons Inc., 2014) Tiwari, Ashutosh; Demir, Mustafa MuammerPresents a comprehensive and interdisciplinary review of the major cutting-edge technology research areas-especially those on new materials and methods as well as advanced structures and properties-for various sensor and detection devices. The development of sensors and detectors at macroscopic or nanometric scale is the driving force stimulating research in sensing materials and technology for accurate detection in solid, liquid, or gas phases; contact or non-contact configurations; or multiple sensing. The emphasis on reduced-scale detection techniques requires the use of new materials and methods. These techniques offer appealing perspectives given by spin crossover organic, inorganic, and composite materials that could be unique for sensor fabrication. The influence of the length, composition, and conformation structure of materials on their properties, and the possibility of adjusting sensing properties by doping or adding the side-groups, are indicative of the starting point of multifarious sensing. The role of intermolecular interactions, polymer and ordered phase formation, as well as behavior under pressure and magnetic and electric fields are also important facts for processing ultra-sensing materials. The 15 chapters written by senior researchers in Advanced Sensor and Detection Materials cover all these subjects and key features under three foci: 1) principals and perspectives, 2) new materials and methods, and 3) advanced structures and properties for various sensor devices. © 2014 Scrivener Publishing LLC. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Green Fabrication of Lanthanide-Doped Hydroxide-Based Phosphors: Y(oh)(3):eu3+ Nanoparticles for White Light Generation(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2019) Güner, Tuğrul; Kuş, Anılcan; Özcan, Mehmet; Genç, Aziz; Şahin, Hasan; Demir, Mustafa MuammerPhosphors can serve as color conversion layers to generate white light with varying optical features, including color rendering index (CRI), high correlated color temperature (CCT), and luminous efficacy. However, they are typically produced under harsh synthesis conditions such as high temperature, high pressure, and/or by employing a large amount of solvent. In this work, a facile, water-based, rapid method has been proposed to fabricate lanthanide-doped hydroxide-based phosphors. In this sense, sub-micrometer-sized Y(OH)(3):Eu3+ particles (as red phosphor) were synthesized in water at ambient conditions in <= 60 min reaction time. The doping ratio was controlled from 2.5-20 mol %. Additionally, first principle calculations were performed on Y(OH)(3):Eu3+ to understand the preferable doping scenario and its optoelectronic properties. As an application, these fabricated red phosphors were integrated into a PDMS/YAG:Ce3+ composite and used to generate white light. The resulting white light showed a remarkable improvement (approximate to 24%) in terms of luminous efficiency, a slight reduction of CCT (from 3900 to 3600 K), and an unchanged CRI (approximate to 60) as the amount of Y(OH)(3):Eu3+ was increased.Article Citation - WoS: 3Citation - Scopus: 4Experimental and First-Principles Investigation of Cr-Driven Color Change in Cesium Lead Halide Perovskites(American Institute of Physics, 2019) Özen, Sercan; Güner, Tuğrul; Topçu, Gökhan; Özcan, Mehmet; Demir, Mustafa Muammer; Şahin, HasanHerein, we report room temperature Cr-doping for all-inorganic perovskites that have attracted great attention in recent years due to their extraordinary optical properties, low cost, and ease of synthesis. Incorporation of Cr 3 + ions into the perovskite crystal lattices is achieved by following a facile route involving an antisolvent recrystallization method at room temperature. It is shown that both Cr-doping and formation of crystals in the CsPbBr x Cl 3 - x phase are provided by increasing the concentration of the CrCl 3 solution. It is also observed that the doping procedure leads to the emergence of three types of distinctive peaks in the PL spectrum originating from CsPbBr x Cl 3 - x domains (476-427nm), Cr-strained host lattices (515nm), and midgap states formed by Cr dopants (675-775nm). It is also found that the Cr-doped perovskites emitting a dark violaceous color change their color to white with a high color rendering index (88) in 30-day time intervals. Easy-tunable optical properties of all-inorganic Cs perovskites indicate their great potential for future optoelectronic device applications.Article Citation - WoS: 50Citation - Scopus: 58Chemically Modified Optical Fibers in Advanced Technology: an Overview(Elsevier, 2019) Shukla, S. K.; Kushwaha, Chandra Shekhar; Güner, Tuğrul; Demir, Mustafa MuammerIn recent years, chemically modified optical fibers have widely used for development of several advanced chemical and biosensors, biomedical technology and environmental monitoring. The chemically modified optical fiber bears several valuable properties like energy loss, catalytic behaviour, refractive index, and mechanical strength to advance the optical fiber technology. In this article, we reviewed the chemically-modified optical fiber and their applications in different optical fiber-based technologies. The basics of optical fiber and their modification are discussed along with the adopted methodologies. The advancements in different optical fiber based technologies viz sensing, imaging, tomography, magnetic resonance imaging, photodynamic therapy, optogenics, surgery and environmental monitoring are discussed in the light of the contribution of chemically modified optical fibers. In conclusion, success and challenges for the use of chemically modified-optical fiber are presented on the basis of existing literature.Article Citation - WoS: 25Citation - Scopus: 27Osteogenic Differentiation of Mesenchymal Stem Cells on Random and Aligned Pan/Ppy Nanofibrous Scaffolds(SAGE Publications, 2019) Selamet, Yusuf; İnce Yardımcı, Atike; Baskan, Öznur; Yılmaz, Selahattin; Meşe, Gülistan; Özçivici, EnginThe aim of this study was to develop random and aligned polyacrilonitrile (PAN)/polypyrrole (PPy) nanofibrous scaffolds by electrospinning technique for osteogenic differentiation of mesenchymal stem cells. Nanofibers were fabricated successfully as straight, smooth, and free from bead formation. The average diameter of random and aligned nanofibers was 268(+/- 49) nm and 225(+/- 72) nm, respectively. Alignment process increased the tensile strength of nanofibers 3.9-fold, while the tensile strain of nanofibers decreased by 78%. PAN/PPy nanofibers were hydrophilic with the contact angle value of about 32 degrees and alignment did not affect the contact angle value. Random and aligned PAN/PPy nanofibers were investigated as a scaffold material for osteogenic differentiation of D1 ORL UVA mouse bone marrow mesenchymal stem cells. Cells were able to attach and grow on nanofibers confirmed by cell viability results. Stem cells that were cultured with osteogenic induction were able to mineralize on electrospun nanofibers based on alizarin red and Von Kossa dye staining. For aligned PPy nanofibers, mineralization occurred in the fiber alignment direction. Consequently, PAN/PPy nanofibrous mats in both random and aligned forms would be potential candidates for bone tissue engineering.Article Citation - WoS: 4Citation - Scopus: 4Color-Tunable All-Inorganic Cspbbr3 Perovskites Nanoplatelet Films for Photovoltaic Devices(American Chemical Society, 2019) Özcan, Mehmet; Özen, Sercan; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, HasanHerein, we demonstrate a novel coating approach to fabricate CsPbBr3 perovskite nanoplatelet film with heat-free process via electrospraying from precursor solution. A detailed study is carried out to determine the effect of various parameters such as ligand concentration, electric field, flow rate, etc. on the optical properties. By controlling the volume ratios of the oleylamine (OAm) and oleic acid (OA), the coalescing and thickness of the resulting nanoplatelets can be readily tuned that results in control over emission in the range of 100 nm without any antisolvent crystallization or heating processes. The varying electrical field and flow rate was found as inefficient on the emission characteristics of the films. In addition, the crystal films were obtained under ambient conditions on the ITO coated glass surfaces as in the desired pattern. As a result, we demonstrated a facile and reproducible way of synthesizing and coating of CsPbBr3 perovskite nanoplatelets which is suitable for large-scale production. In this method, the ability of tuning the degree of quantum confinement for perovskite nanoplatelets is promising approach for the one-step fabrication of crystal films that may enable the use in optoelectronics.Article Citation - WoS: 85Citation - Scopus: 91Ballistic Thermoelectric Properties of Monolayer Semiconducting Transition Metal Dichalcogenides and Oxides(American Physical Society, 2019) Özbal, Gözde; Senger, Ramazan Tuğrul; Sevik, Cem; Sevinçli, HaldunCombining first-principles calculations with Landauer-Mittiker formalism, ballistic thermoelectric transport properties of semiconducting two-dimensional transition metal dichalcogenides (TMDs) and oxides (TMOs) (namely MX2 with M = Cr, Mo, W, Ti, Zr, Hf; X = O, S, Se, Te) are investigated in their 2H and 1T phases. Having computed structural, as well as ballistic electronic and phononic transport properties for all structures, we report the thermoelectric properties of the semiconducting ones. We find that 2H phases of four of the studied structures have very promising thermoelectric properties, unlike their 1T phases. The maximum room temperature p-type thermoelectric figure of merit (ZT) of 1.57 is obtained for 2H-HfSe2, which can be as high as 3.30 at T = 800 K. Additionally, 2H-ZrSe2, 2H-ZrTe2, and 2H-HfS2 have considerable ZT values (both nand p-type), that are above 1 at room temperature. The 1T phases of Zr and Hf-based oxides possess relatively high power factors, however their high lattice thermal conductance values limit their ZT values to below 1 at room temperature.Article Citation - WoS: 6Citation - Scopus: 8Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator(American Chemical Society, 2019) Gökbulut, Belkıs; İnanç, Arda; Topçu, Gökhan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa Muammer; İnci, Mehmet NaciIn this paper, CdTe quantum dots (QDs)-doped single electrospun polymer nanofibers are partially coated with gold nanoparticles to form distinct hybrid photonic-plasmonic nanoresonators to investigate the critical role of the cavity-confined hybrid mode on the modification of the spontaneous emission dynamics of the fluorescent emitters in low-Q photonic cavities. A total enhancement factor of 11.2 is measured via a time-resolved experimental technique, which shows that there is an increase of about three times in the spontaneous emission rate for the QDs-doped gold nanoparticle-decorated nanofibers as they are compared with those uncoated ones. The physical mechanism affecting the spontaneous emission rate of the encapsulated QDs in such a hybrid photonic-plasmonic nanoresonator is explained to be due to regeneration of the mode field in the nanofiber cavity upon the interaction of the dipoles with the surface plasmons of distinctive gold nanoparticles that surround the outer surface of the nanofiber.