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Öğe Detection of Diazinon Organophosphates Using Magnetoelastic Sensor(Ieee-Inst Electrical Electronics Engineers Inc, 2022) Atalay, Selcuk; Ates, Burhan; Balcioglu, Sevgi; Inan, Orhan Orcun; Kolak, Seda; Simsek, Murat; Kolat, Veli SerkanIn this study, 2826MB (Fe40Ni38Mo4B18) amorphous ferromagnetic ribbons were used as a magnetoelastic sensor (MES) to detect diazinon organophosphates (OP). Since enlarging the sensor surface area makes a significant contribution to the sensitivity of the sensor, nanofibers were coated on the sensor surface, and then, the nanofibers were functionalized with glutaraldehyde (GA) in order to covalently bind acetylcholinesterase (AChE) enzyme to the surface. It was found that binding of OPs to the AChE enzyme at the functional amorphous ribbon surface, a large change in the resonance frequency was observed. The results showed that functionalized MES shows a linear change according to the amount of OP detected in the range of 0-140 nL or 0-150 ppm in the solution.Öğe Diagnosis, Bacterial Density, Food, and Agricultural Applications of Magnetoelastic Biosensors: Theory, Instrumentation, and Progress(Springer, 2024) Balcioglu, Sevgi; Inan, Orhan Orcun; Kolak, Seda; Ates, Burhan; Atalay, SelcukMagnetoelastic biosensors have emerged as a promising technology for the sensitive and label-free detection of a wide range of biological analytes. These biosensors use the magnetoelastic effect, which describes how the mechanical properties of magnetostrictive materials change in response to a magnetic field. This effect is utilized to detect biological analytes by immobilizing specific recognition elements, such as antibodies or nucleic acids, on the magnetoelastic material's surface. The binding of target analytes to the recognition elements induces a mass change, leading to a shift in the resonance frequency of the magnetoelastic material. Magnetoelastic biosensors find applications across various fields, including medical diagnostics, environmental monitoring, and food safety. In medical diagnostics, they offer rapid and sensitive capabilities for detecting pathogens, biomarkers, and toxins. For environmental monitoring, they demonstrate the ability to detect pollutants and heavy metals. Furthermore, in ensuring food safety and quality, magnetoelastic biosensors detect allergens, pathogens, and contaminants effectively. Ongoing research and technological advancements suggest that these biosensors hold great potential for revolutionizing various fields, including healthcare, environmental monitoring, and food safety, contributing to improved disease diagnosis, environmental protection, and public health. This review article provides an overview of the principles, fabrication methods, diagnosis, bacterial density, food, and agricultural applications of magnetoelastic biosensors.Öğe Influences of deposition time and pH on magnetic NiFe nanowires fabrication(Elsevier Science Sa, 2009) Atalay, Funda Ersoy; Kaya, Harun; Atalay, Selcuk; Tari, SueleymanIn this work, NiFe nanowires were grown into highly ordered porous anodic alumina oxide (AAO) templates by dc electrodeposition at various deposition times and pH values. During the deposition process some electrochemical bath parameters such as ion content, deposition voltage, and temperature of solution were kept constant. The morphological properties of the nanowire arrays were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the chemical composition was determined by examination of the energy dispersive X-ray (EDX) spectra, and the magnetic behavior of the arrays was determined by vibrating sample magnetometer (VSM). (C) 2008 Elsevier B.V. All rights reserved.Öğe Investigation of a weak magnetic field effect on the in vitro catalytic activity of adenosine deaminase and xanthine oxidase(General Physiol And Biophysics, 2011) Batcioglu, Kadir; Dogan, Metin; Uyumlu, Ayse B.; Satilmis, Basri; Bayri, Nevzat; Atalay, Selcuk; Demirtas, HakanThe effect of a weak magnetic field (MF) on adenosine deaminase (ADA) and xanthine oxidase (XOD) activities have been investigated. A 50 Hz uniform MF was generated, and the magnitude of the field was kept constant at 5.8 mT. The changes in ADA activity over time were significantly different in and out of the MF; MF caused a steeper decline in ADA activity compared to the situation when no MF is present. In addition, MF caused a significant increase in XOD activity. There were no significant time-related changes for either enzyme in the absence of the MF. We suggest that a weak MF affects enzymatic systems.Öğe Magnetoelastic Humidity Sensors with TiO2 Nanotube Sensing Layers(Mdpi, 2020) Atalay, Selcuk; Izgi, Tekin; Kolat, Veli Serkan; Erdemoglu, Sema; Inan, Orhan OrcunIn this study, TiO2 nanotubes (TiO2-NTs) are coated with a drop-casting method on Fe40Ni38Mo4B18 amorphous ferromagnetic ribbons and the humidity response of the prepared magnetoelastic sensors (MES) is investigated. The synthesis of TiO2-NTs is performed using a hydrothermal process. Sample characterization is carried out using X-ray diffraction and scanning electron microscopy. The results show that the sensors can measure moisture values in the range of 5% to 95% with very high precision and very low hysteresis. The humidity variation between 5% and 95% shows a change in the sensor resonance frequency of 3180 Hz, which is a significant change compared to many magnetoelastic humidity sensors developed so far.Öğe A Positive Effect of Magnetic Field on the Catalytic Activity of Immobilized L-Asparaginase: Evaluation of its Feasibility(Springer, 2023) Dik, Gamze; Ulu, Ahmet; Inan, Orhan Orcun; Atalay, Selcuk; Ates, BurhanEnzyme immobilization is an attractive strategy to improve enzyme stability, however, the activity significantly reduces after immobilization. To solve this issue, we designed a novel magnetic carrier that both enhanced enzyme activity and improved its stability. For this purpose, the magnetic nanoparticles were synthesized and L-asparaginase was immobilized physically. All materials were structurally and morphologically characterized. Besides, the biochemical properties of the immobilized enzyme were investigated and compared with the free one. Moreover, the activity of the immobilized enzyme was investigated under a weak magnetic field. The optimum pH and optimum temperature of the free and immobilized enzyme were found to be 8.5 and 45 degrees C, 7.5 and 40 degrees C, respectively. Moreover, even after 10 cycles of use, the immobilized enzyme retained 54% of its initial activity. K-m for free and the immobilized enzyme was found to be 10.37 +/- 0.5, and 7.06 +/- 2.99 mM, respectively, and V-max was found to be 138.88 +/- 2.64, and 121.95 +/- 1.07 molimin, respectively. Most importantly, the activity increased approximately 3.2-fold and 4.3-fold at 10 Hz and 20 mT, respectively. Overall, the results suggested that, if the activity of the immobilized enzyme is very low, applying a weak magnetic field may be necessary to enhance the enzyme reaction. [GRAPHICS] .Öğe A Rapid Response Humidity Sensor for Monitoring Human Respiration with TiO2-Based Nanotubes as a Sensing Layer(Springer, 2020) Atalay, Selcuk; Erdemoglu, Sema; Kolat, Veli Serkan; Izgi, Tekin; Akgeyik, Emrah; Yilmaz, Hatice Caglar; Kaya, HarunThe use of TiO2-based samples with nanotube (NT) shape for humidity sensing has been investigated. Sample characterization was carried out using x-ray diffraction analysis, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy. x-Ray diffraction analysis showed that the nanotubes had TiO2, NaO3, and H2Ti2O5 phases. SEM revealed that the NTs had diameters ranging from 20 nm to 200 nm and very different lengths. TiO2-based nanotubes were coated using the drop-casting method onto a quartz crystal microbalance (QCM). The synthesis of TiO2-based NTs was performed using a hydrothermal process. Humidity sensing measurements showed that the resonant frequency of TiO2-based NTs deposited onto the QCM was very sensitive to humidity changes. It was also shown that the sensor could be used for respiratory monitoring purposes.Öğe Rapid synthesis and characterization of maghemite nanoparticles(Amer Scientific Publishers, 2008) Tural, Bilsen; Oezenbas, Macit; Atalay, Selcuk; Volkan, MuervetFe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe2O3-SiO2, nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.Öğe Resonance Frequency Shift of Vibrating Amorphous Ribbon via Surface Adsorption of Magnetic Fe3O4 Nanoparticles(Springer, 2023) Atalay, Selcuk; Inan, Orhan Orcun; Kolat, Veli Serkan; Kaya, Ali OnurIn this study, Fe40Ni38Mo4B18 amorphous ferromagnetic ribbon was used as a vibrating reed sensor to detect Fe3O4 magnetic nanoparticles. The sensor surface was not subjected to any treatment: the amorphous ribbon was used directly as a sensor. Nanoparticles with a diameter of 25 nm in ddH(2)O were dripped on the sensor surface at different rates. Different amounts of magnetic nanoparticles ranging from 1 to 12 mu g were dripped, and it was observed that the sensor resonance frequency decreased linearly with the mass of magnetic nanoparticles dripped. It was shown that 1 mu g MNP could be easily detected by the vibrating reed method.Öğe Structural, Magnetic, and Magnetocaloric Properties of La1-x Bi x MnO3 (x=0.01, 0.03, 0.06, 0.1, 0.2) Compounds(Springer, 2015) Kolat, Veli Serkan; Atalay, Selcuk; Izgi, Tekin; Gencer, Huseyin; Bayri, NevzatBi-doped lanthanum manganites with chemical composition of La1-x Bi (x) MnO3 (x = 0.01, 0.03, 0.06, 0.1, and 0.2) were prepared by a standard solid-state process. Magnetic and magnetocaloric properties of the samples were investigated in detail. X-ray diffraction measurement showed that the sample crystallized in the single phase of orthorhombic structure. It was found that the magnetization, Curie temperature, and the maximum value of magnetic entropy change decrease with increasing Bi content. The decrease in magnetic entropy change was attributed to the decrease in saturation magnetization and a change of the nature of the phase transition from first order to second order with increasing Bi content.
