Yazar "Aydin, Duygu Yilmaz" seçeneğine göre listele

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    Chiral-Dependent Redox Capacitive Biosensor Using Cu-Cys-GSH Nanoparticles for Ultrasensitive H2O2 Detection
    (Mdpi, 2025) Aydin, Duygu Yilmaz; Wu, Jie Jayne; Chen, Jiangang
    Copper-thiolate nanostructures, formed through the self-assembly of cysteine (Cys) and glutathione (GSH) with copper ions, offer a versatile platform for redox-active applications due to their structural stability and chemical functionality. In this study, Cu-Cys-GSH nanoparticles were synthesized and employed to develop a capacitive biosensor for the ultralow concentration detection of hydrogen peroxide (H2O2). The detection mechanism leverages a Fenton-like reaction, where H2O2 interacts with Cu-Cys-GSH nanoparticles to generate hydroxyl radicals (OH) through redox cycling between Cu2+ and Cu+ ions. These redox processes induce changes in the sensor's surface charge and dielectric properties, enabling highly sensitive capacitive sensing at gold interdigitated electrodes (IDEs). The influence of chirality on sensing performance was investigated by synthesizing nanoparticles with both L- and D-cysteine enantiomers. Comparative analysis revealed that the stereochemistry of cysteine impacts the catalytic activity and sensor response, with Cu-L-Cys-GSH nanoparticles exhibiting superior performance. Specifically, the biosensor achieved a linear detection range from 1.0 fM to 1.0 pM and demonstrated an ultra-sensitive detection limit of 21.8 aM, outperforming many existing methods for H2O2 detection. The sensor's practical performance was further validated using milk and saliva samples, yielding high recovery rates and confirming its robustness and accuracy for real-world applications. This study offers a disposable, low-cost sensing platform compatible with sustainable healthcare practices and facilitates easy integration into point-of-care diagnostic systems.
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    EXPERIMENTAL INVESTIGATION OF THE EFFECT OF BORON-CONTAINING NANOFLUID ON HEAT PIPE THERMAL PERFORMANCE
    (Begell House Inc, 2025) Guru, Metin; Karakaya, Ugur; Alici, Doga Sahin; Olgun, Seyma; Aydin, Duygu Yilmaz
    This study examined the effects of boron nanofluid on the performance of a two-phase closed thermosyphon heat pipe. The boron nanofluid was prepared via a two-step method, using deionized water as the base fluid and boron nanoparticles at mass concentrations of 0.5%, 1%, and 2%. Alkyl polyglycoside was added as a surfactant at a constant 0.5% by mass. Thermophysical property analysis of the nanofluid showed that the boron-containing nanofluid displayed superior thermal properties compared to deionized water. Heat pipe tests were conducted at heating powers of 200 300 W, and 400 W, with cooling water flow rates of 5 g/s, 7.5 g/s, and 10 g/s in the evaporator section. Temperature distributions in the evaporator and condenser sections were tracked using 8 K-type thermocouples. To evaluate the effect of nanoparticles on thermal efficiency, tests were conducted with both deionized water and nanofluid suspensions. Results showed a 20% efficiency increase with 2% boron nanofluid at 400 W heating power and a cooling water mass flow rate of 10 g/s. The highest observed improvement in thermal resistance due to boron nanofluid was 28%.
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    Pendant drop motion and stability in vertical airflow
    (Aip Publishing, 2024) Dockery, Jacob D.; Aydin, Duygu Yilmaz; Dickerson, Andrew K.
    When exposed to an ascending flow, pendant drops oscillate at magnitudes determined by windspeed, drop diameter, and needle diameter. In this study, we investigate the retention stability and oscillations of pendant drops in a vertical wind tunnel. Oscillation is captured by a high-speed camera for a drop Reynolds number Re=200-3000. Drops at Re less than or similar to 1000 oscillate up to 12 times the frequency of drops with high Re. Increasing windspeed enables larger volume drops to remain attached to the needles above Re=500. We categorize drop dynamics into seven behavioral modes according to the plane of rotation and deformation of shape. Video frame aggregation permits the determination of a static, characteristic shape of our highly dynamic drops. Such a shape provides a hydraulic diameter and the evaluation of the volume swept by the oscillating drops with time. The maximum swept volume per unit drop volume occurs at Re=600, corresponding to the peak in angular velocity.
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    Synthesis of Zinc Fluoroborate by Wet Method and Its Application as a Flame Retardant for Cotton Fabrics
    (Academic Publication Council, 2023) Aydin, Duygu Yilmaz; Guru, Metin
    In this study, zinc fluoroborate was synthesized by wet method using fluoroboric acid and zinc oxide as reactants, and its usability as a flame retardant for cotton fabrics was investigated. The wet method is economical, green, efficient, and applicable on a large scale. The maximum yield was related to the variation of reactant ratio, temperature, reaction time, and stirring rate. The product was characterized using Fourier-transform infrared spectroscopy, BF4-ion-selective electrode, and X-ray diffraction. The maximum yield of 97% was achieved at the reactant mole ratio (nZnO/nHBF4) of 1:3, temperature of 90 degrees C, and reaction time of 90 min. The purity of the synthesized product was 98%. Flame retardancy and high-temperature resistance effects of zinc fluoroborate on cotton fabrics were investigated using the limiting oxygen index (LOI) and high-temperature durability tests, respectively. Although the LOI value of the untreated original fabric was 16, this value increased to >55 upon impregnating the fabric with 50% zinc fluoroborate solution.
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    The effects of particle mass fraction and static magnetic field on the thermal performance of NiFe2O4 nanofluid in a heat pipe
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2023) Aydin, Duygu Yilmaz; Aydin, Emrullah; Guru, Metin
    In this study, experimental investigations are performed in order to determine the thermal performance of NiFe(2)O(4 )nanoparticles dispersed in deionized water in a thermosyphon-type heat pipe. The effects of the magnetic flux density and nanoparticle mass fraction were analyzed at different heat inputs and cooling water flow rates. The magnetic field was generated by the current-carrying solenoid. Our results indicated that the use of NiFe2O4 nanofluid significantly improves the thermal performance of the heat pipe which also showed that the enhancement of heat transfer coefficient can be obtained with increasing mass fraction and in presence of a low parallel magnetic field. A decrease of 26.6% was achieved in the temperature difference between the evaporator and the condenser regions compared to distilled water at a 3% mass fraction and under a magnetic field. The maximum improvement in heat pipe's thermal resistance was found as 30.4%, through NiFe(2)O(4 )nanofluid usage under magnetic field. Compared to base fluid, the application of magnetic nanofluid and parallel magnetic field reduces the thermal resistance, increases heat pipe efficiency and the heat transfer coefficient.
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    Thermal and Exergetic Performance Analyses of a Heat Pipe Heat Exchanger Using CMC/Co3O4-Based Non-Newtonian Nanofluids
    (Mdpi, 2025) Aydin, Duygu Yilmaz
    This study presents an experimental evaluation of the thermal and exergetic performance of an air-to-air heat pipe heat exchanger using a cobalt oxide (Co3O4)-based non-Newtonian nanofluid, with the additional incorporation of carbon black (CB). Nanofluids were synthesized via a two-step method and tested under turbulent flow conditions across varying Reynolds numbers. The results demonstrated that increasing the Co3O4 nanoparticle concentration and adding CB substantially improved both the thermal and exergetic performance compared to deionized water. Specifically, maximum thermal efficiency improvements of 62.7% and 75.4% were recorded for nanofluids containing 1% and 2% Co3O4, respectively. The addition of CB further enhanced the thermal efficiency, achieving a maximum improvement of 79.2%. Furthermore, the maximum reduction in thermal resistance reached 61.4% with CB incorporation, while the 2% Co3O4 nanofluid achieved a maximum decrease of 50.2%. The use of nanofluids led to a significant reduction in exergy loss, with exergy-saving efficiencies reaching up to 33.6%. These findings highlight the considerable potential of Co3O4- and CB-based hybrid nanofluids in advancing waste heat recovery technologies and enhancing the thermodynamic performance of air-to-air heat pipe heat exchanger systems.