Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Sensitive Hybrid Plasmonic Refractive Index Sensor Based on Ag Cross-Grating Nanoantenna and Au Quantum Dot upon SiO2 Nanowire(IOP Publishing Ltd, 2026-04-03) Sanli, Atif Kerem; Kilic, Veli Tayfun; Tabaru, Timucin EmreThis study presents a distinctive hybrid plasmonic sensor architecture combining a silver (Ag) cross-shaped nanoantenna with a gold (Au) quantum dot (QD) for enhanced refractive index sensing applications. The structure consists of a silicon dioxide (SiO2) substrate and a cylindrically shaped SiO2 wire on it, topped with a silicon nitride (Si3N4) dielectric layer and an Ag cross grating, with an Au QD positioned at the center. Using free and open source 3D Finite-Difference Time-Domain (FDTD) simulations, exceptional electric field enhancement at the resonant wavelength of approximately 639-667 nm is demonstrated. The optimized structure achieves remarkable quality factors (Q-factors) exceeding 267 for biological media, representing among the highest reported values for plasmonic sensing structures. Unlike conventional red-shift sensors, our design exhibits a distinctive blue-shift sensing behavior arising from hybrid plasmonic mode coupling, achieving sensitivities ranging from 190 to 344 nm RIU-1 for various analytes, including water, blood, PDMS, body fat, ethanol, and glass. The ultrasharp resonances (FWHM similar to 2.3 nm) combined with intense field enhancement make this design highly suitable for biosensing applications.Article Performance Boost in QLEDs Using Octanethiol-Capped Core/Shell Quantum Dots(IOP Publishing Ltd, 2026-01-07) Yazici, Ahmet F.; Yuruc, Adnan M.; Kelestemur, Yusuf; Serin, Ramis Berkay; Kacar, Rifat; Ulku, Alper; Mutlugun, EvrenQuantum dots attract significant attention as one of the most promising colloidal nanocrystals with unique optical properties and potential applications for the next generation of display technology. In this paper, we evaluate the performance of CdZnSeS-based alloyed-shell quantum dots (QDs) for electroluminescence devices upon additional shell growth and ligand exchange. This includes core/shell (C/S) and core/shell/shell (C/S/S) QDs, whose latter includes an additional ZnS shell and octanethiol (OT) ligands. We present detailed characterizations of QDs using transmission electron microscopy, XRD, and various spectroscopic techniques and demonstrate their QD light emitting (QLEDs). We find the photoluminescence quantum yield of C/S/S QDs increased from 68.8% to 88.7% compared to C/S QDs whereas the emission linewidth narrows from 22.2 nm to 20.8 nm. QLEDs fabricated with C/S/S QDs exhibit a higher peak external quantum efficiency (EQE) of 4.1% and maximum luminance of 85 000 cd m-2, compared to 2.3% EQE and 67 000 cd m-2 for C/S QLEDs. In this respect, the OT-assisted shell growth significantly improves the optical property of QDs and performance of QLEDs, likely attributed to the enhanced charge balance and increased radiative recombination rate.Article A Potential Hemostatic Chitosan/Gelatin Cryogel Impregnated with Verbascum Thapsus Leaf Extract for Noncompressible Hemorrhage Management(IOP Publishing Ltd, 2025-11-01) Uzuner, Hacernur; Yuruk, Adile; Isoglu, Ismail AlperIn this study, we prepared a series of chitosan/gelatin (CS/GEL) cryogels containing Verbascum thapsus (V. thapsus) leaf extract and identified a lead formulation for noncompressible hemorrhage (NCH). Cryogels with average pore diameters ranging from 225 to 478 mu m were fabricated through cryogelation at various CS/GEL ratios. C15 was chosen as the base scaffold due to its homogeneous pore distribution, with a pore size coefficient of variation (CV) of approximately 0.22. Extract loading was 1%, 5%, 10%, and 20% w/v. Functional porosity was reported by the relative accessible void index (RAVI). In PBS, the values relative to neat C15 were 1.00, 0.27, 0.20, 0.13, and 0.09 for concentrations of 0%, 1%, 5%, 10%, and 20% w/v, respectively. In citrated blood, the series was 1.00, 0.29, 0.12, 0.14, and 0.09. After loading, equilibrium swelling decreased and the compressive modulus increased, consistent with partial pore filling in a fixed network. The cryogels maintained an interconnected macroporous network and showed swelling from 300% to 3600% in blood and PBS. Antibacterial activity reached 89% inhibition, and cell viability remained above 80%. Hemolysis was low and within acceptance limits. Clotting improved in whole blood as the blood clotting index decreased from 11.9 to 6.5, and the clotting time was approximately 6 min. The 5% w/v group provided the optimal balance of clotting, antibacterial effects, and biocompatibility. This study presents a novel hemostatic CS/GEL cryogel containing V. thapsus leaf extract that holds strong potential for future applications in NCH management.Article Tuning Mechanical Performance of PCL Scaffolds: Influence of 3D Bioprinting Parameters, Polymer Concentration, and Solvent Selection(IOP Publishing Ltd, 2025-09-01) Ceylan, Saniye Aylin; Baltacioglu, Mehmet Furkan; Bal, Burak; Bayram, Ferdi Caner; Isoglu, Ismail AlperThe mechanical performance of three-dimensional (3D) bioprinted scaffolds is susceptible to printing parameters and material formulation. In this study, poly (epsilon-caprolactone) (PCL) scaffolds were fabricated using four different polymer concentrations (10%, 25%, 50%, and 75% w/v) to investigate how these variations, along with process parameters, influence mechanical behavior. Maintaining the structural integrity of bioprinted constructs requires careful optimization of polymer concentration and precise control over parameters such as printing speed, pressure, and infill density. Tensile tests were conducted to evaluate the effects of these variables. Among the tested conditions, a 50% (w/v) concentration allowed for a broader operational window, enabling fabrication across a range of printing speeds and pressures. At a printing speed of 5 mm s-1, PCL-DCM exhibited a Young's modulus of 39.0 MPa, while PCL-CF samples printed at 10 mm s-1 achieved the highest modulus of 32.0 MPa. Notably, when the printing speed was kept constant, applying higher pressures led to an increase in Young's modulus, suggesting that pressure plays a key role in enhancing scaffold stiffness. When comparing the 50% and 75% (w/v) polymer concentrations, the 50% (w/v) formulation stood out by offering both higher elongation and greater stiffness, which makes it particularly suitable for load-bearing applications. These findings provide a quantitative framework for optimizing extrusion-based bioprinting of PCL scaffolds, with implications for customized biomedical implants and regenerative medicine.Article Citation - WoS: 1Citation - Scopus: 1Prediction of the Diffusible Hydrogen Concentration After Electrochemical Charging Utilizing Artificial Intelligence(IOP Publishing Ltd, 2025-09-01) Sivesoglu, Abdurrahman; Li, Yang; Bal, BurakThe concentration of diffusible hydrogen in a material is of high importance as it helps to predict the hydrogen embrittlement effect in the material, and the amount of mechanical properties' degradation after reaching a critical concentration. Despite that, a simple experimental setup is not available to measure hydrogen concentration at service. In this paper, a multi-layer perceptron (MLP) model is developed using weight initialization, which can estimate the diffusible hydrogen concentration of Face-Centred-Cubic (FCC) metals after electrochemical charging. The input properties of the model include the electrochemical charging parameters of current density, temperature, and charging time as well as the grain size of the specimen. The MLP model with and without the weight initialization was validated and tested with unseen test dataset. The model in both cases showed an excellent predictive performance with a higher accuracy and faster convergence when using weight initialization. A linear correlation of 89% between the experimental and predicted hydrogen concentration was observed. This demonstrates that for the family of FCC metals under electrochemical charging, the estimation of diffusible hydrogen concentration is a feasible path for material safety design analysis.Article Tapered Curved-Beam Hinges for Electret-Based Vibration Energy Harvesting Devices(IOP Publishing Ltd, 2024-12-01) Hah, DooyoungInterest in vibration energy harvesting have been growing recently for various applications. One of the major development goals for vibration energy harvesters has been improvement in energy conversion efficiency. To pursue that goal, one of the main approaches has been to broaden the spectra of harvesters. Employment of nonlinear springs, such as curved-beam hinges, has proven to be effective for that purpose. The main contribution of the current study is to introduce a lateral taper to the curved beam so as to further optimize the harvester performances. Via numerical analysis by using stochastic differential equations, the study shows that at 0.05g of vibration strength, tapered curved-beam hinges can result in higher electric power output than the non-tapered ones. Deformation-induced stress was taken into consideration as well, in reference to the fracture strength of the material (single-crystal silicon). At lower vibration strength (0.02g), spring nonlinearity becomes weaker, and as a result, the narrowest curved-beam hinge produces the highest output power. Overall, the current study demonstrates that tapering of the curved beam can be a useful addition in the vibration energy harvester design.Article Citation - WoS: 12Citation - Scopus: 13Highly Luminescent ZnCdTeS Nanocrystals With Wide Spectral Tunability for Efficient Color-Conversion White-Light(IOP Publishing Ltd, 2021-09-28) Soheyli, Ehsan; Zargoush, Sirous; Yazici, Ahmet Faruk; Sahraei, Reza; Mutlugun, EvrenCdTe-based semiconductor nanocrystals (NCs) with size and composition-dependent efficient bandgap properties are historically mature nanomaterials for colloidal optoelectronic applications. In this work, we present the highly luminescent quaternary ZnCdTeS NCs with tunable emission across a wide visible spectrum from green to red spectral range. Prepared via a direct aqueous-based approach, a second capping agent of trisodium citrate (TSC) was used to enhance the photoluminescence (PL) emission efficiency, the chemical stability, and to spectrally widen the coverage of the emission spectra of ZnCdTeS NCs. Adding TCS created a remarkable blue shift from 572 nm in the absence of TSC, to 548 nm. On the other hand, upon optimization of experimental parameters, superior ZnCdTeS NCs with a narrow PL profile typically less than 50 nm, the high quantum efficiency of 76%, and tunable emission from 515-to-645 nm were synthesized in an aqueous solvent. The keynotes were the superior and reproducible luminescent properties for the core only NCs, without shell and using relatively low reaction temperatures. It was shown that in the suggested synthesis method, the high efficiency emitted color of ZnCdTeS NCs can be easily controlled from 515-to-650 nm with excellent stability against harsh conditions. The biexponential decay profiles of samples prepared at different reaction temperatures demonstrated that the average recombination lifetime is below 40 ns and increases with the growth of the ZnCdTeS NCs. Results reveal that the excitonic energy levels have the main role in the recombination process. Finally, to demonstrate the functional advantages of the prepared NCs in optoelectronics, the NCs were used to fabricate color-conversion white light-emitting diodes. The color coordinate of the device is recorded as (0.4951, 0.3647) with CRI of 91, CCT of 1954 K, and LER of 251 lm W-1 by employing only two distinct emitters for color conversion.Article Citation - WoS: 17Citation - Scopus: 16Excitation-Independent Deep-Blue Emitting Carbon Dots With 62% Emission Quantum Efficiency and Monoexponential Decay Profile for High-Resolution Fingerprint Identification(IOP Publishing Ltd, 2022-08-15) Savaedi, Soheyla; Soheyli, Ehsan; Zheng, Guangsong; Lou, Qing; Sahraei, Reza; Shan, ChongxinReaching emissive nanomaterials at short wavelengths with a high quantum efficiency (QE) is an attractive task for researchers. This is more demanding in carbon dots (CDs) with diverse applications that usually emit photons at wavelengths around 450-620 nm. In this study, deep blue-emissive doped-CDs (d-CDs) with high photoluminescence (PL) QE up to 62% and excitation-independent properties were prepared via a short-time microwave irradiation method. The prepared CDs showed simultaneous amorphous and crystalline features, with average sizes of 4.75 nm and bright emission color located at 422 nm. It was found that the presence of sulfur-related dopant levels plays a key role in emission properties in such a way that the PL signal drops significantly in the absence of N-acetyl-l-cysteine (NAC) as a dopant source. On the other hand, the trisodium citrate dihydrate (TSC) was selected as a carbon source to form the main carbon skeleton without it no emission was recorded. Monoexponential-fitted recombination trend with an average lifetime of about 10 ns also confirmed excellent PL emission properties with uniform energy levels and minimized defect-contributing recombinations. The practical use of the as-prepared N, S-doped CDs was assessed in fingerprint detection indicating a bright and clear scheme for both core and termination regions of the fingerprint. Simplicity, cost-effectiveness, high-product yield, low toxicity, along with high/stable PL quantum efficiency in deep-blue wavelengths, and demonstrated ability for fingerprint purposes, support the prospective application of these dual doped-CDs for sensing and bioimaging applications.Conference Object Citation - WoS: 1Estimation of Cohesion for Intact Rock Materials Using Regression and Soft Computing Analyses(IOP Publishing Ltd, 2024-01-01) Koken, E.; Strzalkowski, P.; Kazmierczak, U.; Strzałkowski, P.Shear strength parameters such as cohesion (c) and internal friction angle (phi) are among the most critical rock properties used in the geotechnical design of most engineering projects. However, the determination of these properties is laboring and requires special equipment. Therefore, this study introduces several predictive models based on regression and artificial intelligence methods to estimate the c of different rock types. For this purpose, a comprehensive literature survey is carried out to collect quantitative data on the shear strength properties of different rock types. Then, regression and soft computing analyses are performed to establish several predictive models based on the collected data. As a result of these analyses, five different predictive models (M1-M5) were established. Based on the performance of the established predictive models, the artificial neural network-based predictive model (model 5, M5) was the most suitable choice for evaluating the c for different rock types. In addition, mathematical expressions behind the M5 model are also presented in this study to allow users to implement it more efficiently. In this regard, the present study can be declared a case study showing the applicability of regression and soft computing analyses to evaluate the c of different rock types. However, the number of datasets used in this study should be increased to get more comprehensive predictive models in future studies.Article Citation - WoS: 2Citation - Scopus: 2Cation Exchange Mediated Synthesis of Bright Au@ZnTe Core-Shell Nanocrystals(IOP Publishing Ltd, 2020-10-16) Sadeghi, Sadra; Melikov, Rustamzhon; Sahin, Mehmet; Nizamoglu, SedatThe synthesis of heterostructured core-shell nanocrystals has attracted significant attention due to their wide range of applications in energy, medicine and environment. To further extend the possible nanostructures, non-epitaxial growth is introduced to form heterostructures with large lattice mismatches, which cannot be achieved by classical epitaxial growth techniques. Here, we report the synthetic procedure of Au@ZnTe core-shell nanostructures by cation exchange reaction for the first time. For that, bimetallic Au@Ag heterostructures were synthesized by using PDDA as stabilizer and shape-controller. Then, by addition of Te and Zn precursors in a step-wise reaction, the zinc and silver cation exchange was performed and Au@ZnTe nanocrystals were obtained. Structural and optical characterization confirmed the formation of the Au@ZnTe nanocrystals. The optimization of the synthesis led to the bright nanocrystals with a photoluminescence quantum yield up to 27%. The non-toxic, versatile synthetic route, and bright emission of the synthesized Au@ZnTe nanocrystals offer significant potential for future bio-imaging and optoelectronic applications.