Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Makale Koleksiyonu
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Öğe Enhanced photocatalytic hydrogen evolution via sic loaded ceo2 nanofiber composite(Elsevier B.V., 2025) Genç, Münevver Tuna; Sarılmaz, Adem; Aslan, Emre; Özel, Faruk; Patir, İmren HatayCeO2 is a significant material in the photocatalytic hydrogen evolution reactions due to the high creating ability of oxygen vacancies, high chemical stability and excellent redox properties. However, the wide band gap of CeO2 limits the visible light absorption. In this study, SiC loaded to CeO2 nanofiber catalyst by electrospinning methods to improve the light absorption efficiency and increase the active surface area result in enhanced photocatalytic performance. In the photocatalytic hydrogen evolution reactions medium, which contain eosin Y dye and triethanolamine as a photosensitizer and an electron donor, respectively. The addition of SiC to CeO2 improve the visible light absorption rate, electron transfer efficiency. The hydrogen production rate of CeO2/SiC nanofiber catalyst reaches to 5208 μmol g−1 under visible light irradiation, it is approximately 13- and 2-times higher than SiC and CeO2 nanofiber, respectively. Furthermore, CeO2/SiC nanofiber catalyst maintain more than half of it is photocatalytic activity after 3 cycles of reactions. Therefore, the CeO2/SiC nanofiber catalyst will provide innovative approaches to achieve efficient photocatalytic water splitting in the future, enabling the development of catalytic studies. © 2025Öğe A New Promising Silicate-Based Phosphor for Red Light and White Light Emitting Devices(New York : Plenum Press, c1991-, 2025) Başaran, Büşra Yazıcı; Kafadar, Vural Emir; Emen, Fatih Mehmet; Öztürk, Esra; Karaçolak, Ali İhsanThe aim of this study is to investigate the structure, particle morphology, photoluminescence, and chemical composition of materials for application in light-emitting devices. The present work primarily focuses on the synthesis and characterization of Ba₃CdSi₂O₈:RE (RE: Ce³⁺, Eu³⁺, and Dy³⁺) phosphors via the solid-state reaction method. XRD and FT-IR techniques were used to characterize the phosphors. The XRD patterns of the phosphors reveal that the peaks match those of the Ba₃Cd(SiO₄)₂ host material (PDF Card number: 00-028-0128), with no impurity peaks observed. The photoluminescence (PL) emission spectra of Ba₃CdSi₂O₈:RE (RE: Ce³⁺, Eu³⁺, and Dy³⁺) phosphors were investigated in detail. Ba₃CdSi₂O₈:Dy³⁺ phosphors show four emission bands in the blue (450-510 nm), yellow (550-600 nm), red (640-700 nm), and deep red (740-770 nm) regions. Ce³⁺-doped Ba₃CdSi₂O₈ phosphors show a broad emission band from 575 nm to 700 nm, with a maximum around 594 nm, which is assigned to the 5d-4f transition of Ce³⁺ ions. Moreover, Ba₃CdSi₂O₈:Eu³⁺ phosphors capture excitation energy through charge transfer transitions of Eu³⁺ ions and emit at 586 nm, 613 nm, 653 nm, and 700 nm, corresponding to the 5D₀ → 7 F₀, 5D₀ → 7 F₂, 5D₀ → 7 F₃, and 5D₀ → 7 F₄ transitions of Eu³⁺ ions, respectively. The CIE color coordinates confirm that Eu³⁺ doping shifts the color toward red, while Dy³⁺ and Ce³⁺ doping result in shifts within other parts of the chromaticity space.Öğe Highly efficient photocatalyst based on Zn2-xBaxSnO4 alloying nanoparticles with enhanced photocatalytic activity(Elsevier, 2025) Kamo, Alaa; Sönmezoğlu, Özlem Ateş; Sönmezoğlu, SavaşIn this study, an effective Zn2-xBaxSnO4 alloying nanoparticles were hydrothermally designed with a series of barium cation as alloying dopant and utilized as a photocatalyst to decompose the rhodamine B which causes harmful effects on humans such as allergic dermatitis, skin irritation, mutation, and cancer. It is noteworthy that the Zn1.988Ba0.012SnO4 alloying-based catalyst exhibited more than 99 % degradation in only 140 min in wastewater than barium-free ternary oxide. Moreover, the reaction rate of Zn1.988Ba0.012SnO4 alloying-based catalyst was enhanced to 0.032 min-1 compared with barium-free ternary oxide (0.0179 min-1). Based on scavenger trapping experiments, hydroxyl radicals are the main reactive oxygen species responsible for photocatalytic activity of Zn1.988Ba0.012SnO4 alloying-based catalyst. Besides, the photocatalytic rate was maintained 94.89 % after 5th cycle. This research not only provides a novel strategy for developing alloying-based catalysts but also unveils their potential in photoelectrochemistry and photocatalysis.Öğe Machine learning-driven analysis of activation energy for metal halide perovskites(Royal Soc Chemistry, 2025) Patel, Vimi; Sorathia, Kunjrani; Unjiya, Kushal; Patel, Raj Dashrath; Pandey, Siddhi Vinayak; Akın, SeçkinMetal halide perovskite single crystals (MHPSCs) are highly promising materials for optoelectronic applications, but their stability is hindered by ion migration, thereby impacting their performance. A key factor to understand this issue is calculating the activation energy. Electrochemical Impedance Spectroscopy (EIS) is a powerful technique for separating ionic and electronic processes, yet traditional analysis is labour-intensive, involving extensive measurements, circuit fitting, and manual data interpretation. In this study, we introduce a machine learning (ML)-driven approach to fully automate EIS analysis. EIS data, collected for MAPbI3 and MAPbBr3 across temperatures from 263 K to 343 K, enabled the creation of a large database. The developed ML model predicts EIS spectra at unknown temperatures, fits the appropriate electrical circuit, and automatically extracts passive component values to calculate the activation energy via an Arrhenius plot. This automated workflow streamlines the calculation process, offering fast and reliable activation energy predictions even when temperature data are incomplete or missing. Our approach enhances the efficiency of EIS analysis, providing valuable insights into the stability and performance of MHP SCs.Öğe Novel smart materials with high curie temperatures: Eu1.90Dy0.10Ge2O7, Eu1.90La0.10Ge2O7 and Eu1.90Ho0.10Ge2O7(Elsevier Ltd, 2025) Öztürk, Esra; Kalaycıoglu Ozpozan, Nilgün; Kalem, VolkanThe Eu1.90Dy0.10Ge2O7, Eu1.90La0.10Ge2O7 and Eu1.90Ho0.10Ge2O7 powder were obtained through a solid-state reaction method via multistep firing of stoichiometric ratios of Eu2O3, GeO2, Dy2O3, La2O3 and Ho2O3 in open atmosphere at temperatures from 800 to 1150 °C. The thermal behaviour, phase formation, SEM/EDX analysis, photoluminescence properties, Curie tempereture, dielectric and piezoelectric properties of the samples were investigated by TG/DTA, XRD, SEM, PL, TG/DTA, LCR-meter and d33-meter, respectively. The germenates having triclinic crystal system have 5D0→7F4, 5D0→7F3, 5D0→7F2, 5D0→7F1 transitions of Eu3+ ions. Also, the photoluminescent germenates show electrical properties and the piezoelectric charge constant of germenates showed Eu1.90Dy0.10Ge2O7> Eu1.90Ho0.10Ge2O7 > Eu1.90La0.10Ge2O7 trend. The Curie temperature of Eu1.90Dy0.10Ge2O7, Eu1.90La0.10Ge2O7 and Eu1.90Ho0.10Ge2O7 are 825, 844 and 838 °C, respectively. Compared to commonly used piezoelectric materials, Eu1.90Dy0.10Ge2O7, Eu1.90La0.10Ge2O7 and Eu1.90Ho0.10Ge2O7 materials with very high Curie temperatures were obtained with photoluminescent properties. © 2024 Elsevier LtdÖğe Synthesis and photoluminescent properties of Eu3+,yDy3+ doped molybdate based novel Ba0.5Ca0.5La2(MoO4)4 phosphors(Natl Inst Science Communication & Policy Research-Niscpr, 2024) Öztürk, Esra; Ebiç, MuratBa0.5Ca0.5La2-x-y(MoO4)(4):xEu(3+),yDy(3+) with doping concentrations of xEu(3+) and yDy(3+) (x =0.01, 0.03, 0.05, 0.1 and y= 0.01) phosphors were synthesized by solid state reaction method, one of the high temperature solid state methods. The reactions were carried out in an tube furnace at determined temperatures. Thermogravimetry-differential thermal analysis (TG/DTA) system was used to determine the synthesis temperature of the material and to examine its thermal behavior . The crystal structure of the material was checked with x-ray powder diffractometry (XRD), surface morphology and elemental analysis were done with scanning electron microscope (SEM). The photoluminescent properties of luminescence and excitation wavelength and luminescence duration were determined by photoluminescence spectrophotometer (PL). As a result of the analyzes made with photoluminescence spectrophotometer, three emission bands were observed at 619 nm, 652 nm and 706 nm, resulting from the characteristic D-5(0)->(7)Fj (J=2, 3 and 4) transitions of Eu-3+ ions.Öğe Transition Metal Dichalcogenides as Effective Dopants in Nanofiber-Based Triboelectric Nanogenerators(Wiley, 2024) Karabiber, Abdulkerim; Dirik, Ömer; Okbaz, Abdulkerim; Yar, Adem; Özen, Abdurrahman; Özel, FarukTriboelectric nanogenerators (TENGs) are advanced energy harvesters that convert mechanical energy in diverse environments into electrical energy via static electrification and electrostatic induction. However, their performance needs to be improved to expand their area of use and become more practical. In this study, we introduced molybdenum disulfide (MoS2) and tungsten disulfide (WS2) as separate additives into polyacrylonitrile (PAN) to produce composite nanofibers via electrospinning, aiming to increase the electrical output of the TENGs. This method increased contact area by narrowing the nanofiber diameters, which is a key factor in enhancing the triboelectric effect. The incorporation of MoS2 or WS2, characterized by high specific surface area, interface polarization, quantum confinement effects, and strong electron acceptance and trapping capabilities, led to a significant increase in the dielectric constant and overall electrical performance of the TENGs. Experimental evaluations, connecting the TENGs to circuits with various resistive loads, determined optimal performance at a load resistance of 4.7 M Omega. In particular, the 5 wt% WS2@PAN & polyvinylbutral (PVB) and 5 wt% MoS2@PAN & PVB TENGs exhibited a remarkable peak power output of 40.5 mW, corresponding to a power density of 25.3 W/m2 and provided open circuit voltage of 1,026 V. The integration of 5 wt% MoS2 or 5 wt% WS2 led to more than a twofold increase in electrical power density compared to pristine PAN. These outcomes demonstrate the significant impact of transition metal dichalcogenides in enhancing the energy conversion efficiency of contact-separation mode TENGs, thereby contributing to the advancement of energy harvesting technology.Öğe Determining the hydrogen production potential of ConMo6Se8 chevrel phases(Iop Publishing Ltd, 2025) Gencer, Ayşenur; Surucu, Özge; Şahin, Murat; Özel, Faruk; Surucu, GökhanIn this study, the ConMo6Se8 (n = 1, 2, 3, and 4) Chevrel phases are investigated by using Density Functional Theory (DFT) to reveal their potential for photocatalytic hydrogen production. The stability conditions of these phases reveal that CoMo6Se8, Co2Mo6Se8, and Co3Mo6Se8 satisfy the thermodynamic and mechanic stability properties, while Co4Mo6Se8 does not satisfy any of these properties. Furthermore, the formation enthalpy of these phases shows that CoMo6Se8, Co2Mo6Se8, and Co3Mo6Se8 can be synthesized experimentally due to having negative formation enthalpy values. Furthermore, the thermal stabilities of the machine-learning (ML) force fields are investigated by ab-initio molecular dynamics (AIMD) calculations. The electronic properties of these phases are also investigated in detail, and it is found that Co3Mo6Se8 has a suitable band gap for photocatalytic water splitting. Concerning the investigation of the valence band and conduction band levels, it is shown that Co3Mo6Se8 has a conduction band minimum level suitable for producing hydrogen. This study is the first attempt to reveal the hydrogen production performance of the ConMo6Se8 (n = 1, 2, 3, and 4) Chevrel phases as far as the literature is concerned, paving the ground for future investigations in this field.Öğe Synthesis, characterization, and investigation of photoluminescence optima of In3+ and Gd3+ doped Eu1.90In0.10Ru2O7 and Eu1.90Gd0.10Ru2O7 materials(Taylor & Francis Inc, 2024) Öztürk, Esra; Özpozan, Nilgün KalaycıoğluIn this study, we investigated the photoluminescence properties and structure of the In3+ and Gd3+ doped Eu2Ru2O7-based pyrochlore materials. The samples were synthesized by solid state reaction technique, investigated structurally by X-ray powder diffraction (XRD), thermally by thermogravimetry, and differential thermal analysis, morphologically by scanning electron microscopy (SEM). The photoluminescence properties of Eu1.90In0.10Ru2O7 and Eu1.90Gd0.10Ru2O7 were investigated with photoluminescence spectrometer. X-ray diffraction patterns of all the samples showed that all samples had a cubic type pyrochlore crystal structure with a = b = c = 10.252 & Aring; and alpha = beta = gamma = 90 degrees. The XRD patterns demonstrate that neither the type nor the amount of doping ion alters the unit cell parameter. The SEM images of Eu1.90In0.10Ru2O7 and Eu1.90Gd0.10Ru2O7 reveal a regular morphology, with an average sample size ranging from 0.2 to 0.5 mu m. The elementel (EDX) analysis confirm the absence of impurity elements and showing that the theoretical and experimental element ratios are consistent with EDX analysis expectations. The pyrochlore phosphors showed broad red emission band at similar to 605 nm. This red emission can be attributed to the D-5(0)-> F-7(2) transitions of Eu3+. The phosphor co-doped with In3+ ions has a considerably longer lifetime and photoluminescence intensity than the other phosphor. Eu1.90In0.10Ru2O7 and Eu1.90Gd0.10Ru2O7 phosphors, which show transitions in the red region (at 605/606 nm,D-5(0) -> F-7(2)), are suitable for optoelectronic and white LED applications.Öğe Crystal reorientation and amorphization induced by stressing efficient and stable p-ı-n vacuum-processed mapbı3 perovskite solar cells(Wiley, 2021) Kaya, İsmail Cihan; Zanoni, Kassio P. S.; Sessolo, Michele; Akyıldız, Hasan; Sönmezoğlu, Savaş; Bolink, Henk J.Herein, the long-term stability of vacuum-deposited methylammonium lead iodide (MAPbI(3)) perovskite solar cells (PSCs) with power conversion efficiencies (PCEs) of around 19% is evaluated. A low-temperature atomic layer deposition (ALD) Al2O3 coating is developed and used to protect the MAPbI(3) layers and the solar cells from environmental agents. The ALD encapsulation enables the MAPbI(3) to be exposed to temperatures as high as 150 degrees C for several hours without change in color. It also improves the thermal stability of the solar cells, which maintain 80% of the initial PCEs after aging for approximate to 40 and 37days at 65 and 85 degrees C, respectively. However, room-temperature operation of the solar cells under 1sun illumination leads to a loss of 20% of their initial PCE in 230h. Due to the very thin ALD Al2O3 encapsulation, X-ray diffraction can be performed on the MAPbI(3) films and completed solar cells before and after the different stress conditions. Surprisingly, it is found that the main effect of light soaking and thermal stress is a crystal reorientation with respect to the substrate from (002) to (202) of the perovskite layer, and that this reorientation is accelerated under illumination.Öğe Establishing the NiMo6Se8 Chevrel Phase as a Promising Material Using DFT(Wiley-V C H Verlag Gmbh, 2024) Sürücü, Gökhan; Sürücü, Özge; Usanmaz, Demet; Özel, Faruk; Gencer, AyşenurIn this study, the NiMo6Se8 Chevrel phase is analyzed using Density Functional Theory (DFT) and the Vienna Ab-initio Simulation Package (VASP). The analysis focuses on the phase's structural, electrical, and mechanical characteristics to fill gaps in the current literature. The presence of a rhombohedral crystal structure confirms its thermodynamic stability, as indicated by a negative formation enthalpy, which suggests that it can be synthesized under favorable conditions. The electronic properties of the phase are analyzed, indicating that it exhibits semiconductor characteristics with a bandgap of 1.07 eV. This makes it appropriate for various technological applications. The estimated elastic constants provide an indication of mechanical strength and flexibility, with a noticeable presence of anisotropic elasticity. The confirmation of dynamical stability is achieved by analyzing the phonon dispersion curve, which reveals the absence of any negative frequencies. Furthermore, the material has a low thermal conductivity, increasing its suitability for thermoelectric applications. The analysis emphasizes the versatile capabilities of the NiMo6Se8 Chevrel phase, especially in thermoelectric and energy storage applications, showcasing its promising potential for future technological implementation.Öğe Germanyum piramit dizisinin etkin yüzey silanizasyonu ve floresan etiketlenmesi: Optimizasyon ve karakterizasyon(2024) Açıkgöz, Sabriye; Yüngeviş, Hasan; Şahin, Ayşegül; Özünal, EminGünümüzde homojen germanyum (Ge) piramit dizileri güneş hücreleri, fotodedektörler ve yeni nesil yarı iletken lazerler gibi pek çok uygulama alanında karşımıza çıkmaktadır. Germanyum piramit yüzeylerin kullanım alanlarının daha çok geliştirilebilmesi kimyasal ve biyolojik sensör gibi uygulamalarda da aktif olarak kullanılabilmesi için bu yüzeylerin biyolojik moleküllere hızlı cevap verecek şekilde modifiye edilmesi gerekmektedir. Bu çalışmada germanyum piramit yüzeylerinin 3-aminopropiltrietoksisilan (APTES) ile modifiye edilerek biyolojik molekülere açık olacak şekilde işlevselleştirilmesi için basit ve düşük maliyetli bir yöntem araştırılmıştır. APTES'in germanyum yüzeylerinde varlığını belirlemek için APTES ile modifiye edilmiş germanyum yüzeyler floresan BODIPY molekülleri ile etiketlenmiştir. Silanizasyon süreci boyunca, reaksiyon süresi ve reaksiyon sıcaklığının yığınsal germanyum ve piramit dizisine yerleşen APTES molekülleri üzerindeki etkileri araştırılmıştır. Farklı reaksiyonlarla üretilen numuneler, fotolüminesans spektroskopisi (PL) ve floresan yaşam ömrü görüntüleme mikroskobu (FLIM) ile karakterize edilmiştir. APTES moleküllerinin oldukça iyi bir yüzey tutunması sağlayabilmesi için optimum reaksiyon süresi ve işlem sıcaklığı sırasıyla 24 saat ve 60 0C olarak belirlenmiştir. FLIM mikroskobu ile görüntülenen piramitler üzerinde BODIPY moleküllerinin yaşam ömrü 2,4 ns olarak ölçülmüştür. APTES uygulaması elektronik açıdan önemli yarı iletken yüzeylerde çeşitli molekülleri hareketsiz hale getirmek ve yüksek performanslı yeni optoelektronik cihazlar üretmek için sağlam ve güvenilir bir yol sunabilir.Öğe Doctor blade casting of thin films containing different concentrated endemic plant extracts: determination of structure and optical properties(Karamanoğlu Mehmetbey Üniversitesi, 2024) Fırat, Yunus Emre; Emsen, Buğrahan; Sarsılmaz, Adem; Sürmen, Burak; Özel, FarukThis study provides a thorough properties of the optical analysis of the thin films which produced from Astragalus tokatensis Fisch., Helichrysum noeanum Boiss. and Stachys huber-morathii R. Bhattacharjee extracts. Methanol extracts of plants were obtained via Soxhlet extractor. The highest extract yield (10.10%) was determined in H. noeanum. Doctor blade coating method is used to make thin film layer on glass substrate. The optical behavior of the deposited films is tested by means of he UV-vis-near IR absorbance and transmittance characterization. It is found that the maximum transmittance spectra reaches nearly to a value of 90 % for A. tokatensis sample. Significantly, all the samples display same optical absorbace spectra behavior. Energy band gaps of the films are presented based on Tauc relation and were found to be in the range between 3.68-3.81 eV. Besides, the analysis of functional groups available in the materials is broadly studied by Fourier transform infrared (FT-IR) spectroscopy. FT-IR measurement also confirms that all produced films have carbohydrate pattern. These findings demonstrate a cost-efficient approach for the production of thin films with plant extraction, and open a new perspective on the potential applications of optoelectronic devices.Öğe Electrical properties of Al/CZTSe nanocrystal Schottky diode(Springer, 2024) Kişnişci, Zeynep; Özel, Faruk; Karadeniz, S.; Tuğluoǧlu, Nihat; Özel, Sultan Süleyman; Yüksel, Ömer FarukIn this study, electrical changes in diode parameters of Schottky diodes that made of a kesterite semiconductor were examined under different temperatures. For this aim, Cu2ZnSnSe4 (CZTSe) nanocrystals were fabricated using the hot injection technique, and it was covered by spin coating on an ITO glass substrate. We was introduced the physical and structural analyses using scanning electron microscopy and X-ray spectroscopy. Current–voltage measurements were fulfilled at different temperature (from 100 to 325 K) under dark environment. It was observed that its electrical parameters were strongly affected by temperature.Öğe A new Bluetooth-assisted sensor based on lab-made screen-printed electrode modified with Ni-Ag2S for electrochemical detection of triclosan(Elsevier Ltd., 2024) Çetiner, Rumeysa; Sarılmaz, Adem; Özel, Faruk; Baş, Salih Zeki; Özmen, MustafaIn this study, we prepared a facile and selective Bluetooth-assisted electrochemical sensor for the analysis of triclosan (TCS), which is a broad-spectrum antibacterial and antifungal compound. Initially, a laboratory-fabricated screen-printed electrode (LabSPE) was constructed by depositing various conductive inks (carbon and silver) onto a polycarbonate substrate surface using the screen-printing technique. Subsequently, the surface of the working electrode on the LabSPE was modified with a composite comprising Ni-doped Ag2S (Ni-Ag2S) and chitosan (Chit), rendering it suitable for the detection of TCS. The effect of Ni-Ag2S amount, Chit amount, composite film thickness, and pH of buffer solution on the electrochemical signal of the prepared sensor (Ni-Ag2S-Chit/LabSPE) was also optimized. The sensor displayed remarkable analytical performance in the range of 0.05 nM-90 μM TCS with a low detection limit of 0.02 nM. The sensitivities of Ag2S/LabSPE and Ni-Ag2S-Chit/LabSPE were found to be 0.0838 µAµM−1 and 0.1097 µAµM−1, respectively, proving the contribution of doped Ni to the performance of the present sensor. The selectivity, reproducibility, reproducibility, reproducibility and stability of the sensor as well as its practical applicability have been successfully in two commercial products.Öğe Biotemplated silicon carbide-loaded ytterbium oxide: Effective catalyst for photocatalytic hydrogen evolution reactions(Elsevier B.V., 2024) Genç, Münevver Tuna; Sarılmaz, Adem; Aslan, Emre; Özel, Faruk; Patir, Imren HataySiC-doped Yb2O3 structure (Yb2O3/SiC) was prepared to enhance the photocatalytic hydrogen evolution performance of Yb2O3 nanofiber, which have been performed by using catalyst in the presence of eosin-Y dye and triethanolamine, called photosensitizer and electron donor, respectively under solar light with/out cellulose and chitosan. In this study, cellulose and chitosan were used as biotemplates to increase the hydrogen production of Yb2O3/SiC nanofibrous catalyst in the photocatalytic hydrogen evolution reaction. Bioorganic-inorganic structures, cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC, were obtained by simply adding cellulose and chitosan to the reaction cell without any additional treatment. Cellulose and chitosan also used as a mediator for dispersion, hydrophilicity, morphological transformation and adhesion to semiconductor with the help of functional groups. The hydrogen production rate of bare SiC, bare Yb2O3, Yb2O3/SiC composite have been measured as 391 μmol g−1, 818 μmol g−1 and 1685 μmol g−1, respectively. Moreover, the hydrogen production rate of cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC composites were came up to 3346 μmol g−1, 4084 μmol g−1, respectively. These results have been showed that the Yb2O3/SiC nanofibrous catalyst showed higher activity in the presence of cellulose and chitosan. The existence of biopolymers will create a new field in photocatalytic hydrogen production studies with the advantages mentioned above, thanks to the functional groups.Öğe Boron minerals with different crystal structures as performance manipulators in triboelectric nanogenerators(John Wiley and Sons Inc, 2024) Topçu, Mehmet Ali; Karabiber, Abdulkerim; Koç, Feyyaz; Sarılmaz, Adem; Özel, FarukTriboelectric nanogenerators (TENGs) are energy generation devices that naturally convert mechanical movements into electrical energy through both triboelectric and electrostatic effects. The electricity generation capacity of silicone/boron minerals-based composite and glass fiber-based vertical contact separation mode TENGs enhances by adjusting the triboelectrification characteristics by embedding natural boron minerals (NBO) such as borax, colemanite, and ulexite additives. Considering the generated voltages, the NBO-doped silicone and glass fiber-based TENGs offer the maximum performance with 2.5 wt% borax, 7.5 wt% colemanite, and 5 wt% ulexite. The highest power density of corresponding NBO-doped silicone glass fiber TENGs finds as 25.4, 26.03, and 32.03 W m−2, respectively. This work demonstrates that using boron significantly improves the TENG's power and charging capacities fabricated with silicone and glass fiber. Thus, the clean and safe generation of energy will contribute to the reduction of fossil fuel consumption and help protect the environment.Öğe Europium-doped strontium gadolinium oxide phosphor: Investigating structural and photoluminescence characteristics via sol-gel combustion synthesis(Elsevier Ltd., 2024) Sarikci, S.; Topaksu, M.; Öztürk, Esra; Souadi, G.; Madkhali, O.; Madkhli, A.Y.; Can, N.SrGd2O4 phosphors doped with Eu3+ were successfully synthesized through a sol-gel combustion method, covering a range of dopant concentrations from 0.25 mol% to 3 mol%. The structural analysis of these phosphor materials was comprehensively conducted utilizing various techniques, including X-ray powder diffraction analysis (XRD), Energy Dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). In addition to unveiling the structural characteristics, these analyses provide valuable insights into the compositional aspects, enhancing our understanding of the synthesized SrGd2O4:Eu3+ phosphors across different doping levels. XRD analysis findings validate the successful generation of the intended SrGd2O4 host, demonstrating orthorhombic system structures consistent with JPCD card number 98-019-3592. FTIR analyses conducted on the phosphor samples not only identify bending modes but also reveal intricate details about small vibration bonds within the material. When excited by the 349 nm laser, SrGd2O4:xEu3+ phosphors exhibit distinct photoluminescence (PL) properties like red emission at 614 nm from Eu3+. From the emission spectra, one can clearly observe that Eu3+ with an ionic radius close to the Gd3+ ion preferentially occupies the symmetry sites of the host lattice. The optimal doping concentration was determined to be 0.5 mol%, as revealed by the data in our study. Additionally, a deeper understanding of the luminescence quenching mechanism was attained, pinpointing the involvement of dipole-dipole (d-d) energy transfer in this intriguing phenomenon. This optimal concentration not only enhances the material's properties but also underscores the pivotal role of d-d interactions in governing the luminescence behavior within the doped system. © 2023 Elsevier LtdÖğe Applications of carbon-based materials for ımproving the performance and stability of perovskite solar cells(John Wiley and Sons Inc., 2023) Patel, Krina; Prochowicz, Daniel; Akın, Seçkin; Kalam, Abul; Tavakoli, Mohammad Mahdi; Yadav, PankajOrganic–inorganic hybrid perovskite solar cells (PSCs) attract many researchers in the field of photovoltaic because of their high-power conversion efficiency and low-cost manufacturing. However, improper interfacial charge transfer, perovskite degradation, and poor stability are major concerns for their commercialization and scale-up. Significant efforts have been made in recent years mainly by employing different strategies such as optimizing fabrication, developing novel materials, use of additives, and an interfacial layer in PSCs. Nowadays, carbon materials are widely recognized as promising candidates for alternative usage in PSCs because of their cost effectiveness, high conductivity, appropriate work function (5.0 eV), and low-temperature sintering process. In addition, the highly hydrophobic nature of the carbon-based materials prevents moisture penetration into the perovskite layer, resulting in enhanced stability. This review shows how effectively carbon-based materials can improve the performance of PSCs. First, the different carbon materials such as graphene and its derivatives, fullerenes and its derivatives, carbon quantum dots, and carbon nanotubes are described. Subsequently, the role of these carbon-based materials employed in electron-transport layers, hole-transport layers, and perovskite layers in PSCs is discussed. Thus, this review highlights the recent advancements made in carbon-based PSCs and their role in improving the performance of PSCs.Öğe Effect of Gd-codoping on photoluminescence properties of Eu-doped natural fluorapatite(Elsevier GmbH, 2023) Demir, Burak; Karacaoğlu, Erkul; Agil, Asli Asiye; Koroglu, Levent; Ayas, ErhanThis study investigated the photoluminescence properties of Eu, Gd, and Eu-Gd co-doped natural fluorapatite (FAP) particles. Ca10(PO4)6F2:EuxGd0.2−x powders were synthesized by the solid-state powder synthesis method at 1150 ⁰C. X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-Ray Spectroscopy, and Photoluminescence Spectroscopy (PL) were used to characterize the structural, morphological, chemical, and optical properties, respectively. XRD and FTIR analysis demonstrated the presence of mainly FAP while CaO and larnite as minor phases. Approximately 1–2 µm equiaxed FAP particles were seen in SEM microstructure images. Regardless of Gd3+, in the presence of Eu3+, under 253 nm excitation, the FAP samples showed characteristic emission bands of Eu3+ at 600 nm and 625 nm originating from 5D0→7F1 and 5D0→7F2 transitions, respectively. In addition, a noticeable increase was observed in the emission intensity of Eu3+ with the addition of Gd3+. On the other hand, the Gd-doped FAP sample showed an emission band at 320 nm originating from the Gd3+ 6P7/2→8S7/2 transition under excitation at 205 nm. As a result, the emissions of Eu-FAPs were improved with the Gd-codoping, and materials with high color purity and excellent chromaticity coordinate characteristics were obtained.
