Yazar "Ipekci, Hasan Huseyin" seçeneğine göre listele

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    Holey MoS2-based electrochemical sensors for simultaneous dopamine and uric acid detection
    (Royal Soc Chemistry, 2023) Ipekci, Hasan Huseyin
    In this study, two-dimensional holey MoS2 (h-MoS2) nanosheets were used to develop electrochemical sensors for simultaneous detection of dopamine (DA) and uric acid (UA). The holes were created on MoS2 layers using hydrogen peroxide (H2O2) in the presence of Bovine Serum Albumin (BSA). h-MoS2 was characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS), and ultraviolet-visible spectroscopy (UV-vis). Electrochemical dopamine and uric acid sensors were prepared by drop-casting h-MoS2 on a glassy carbon electrode (GCE). The electroanalytical performance of the sensors was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods. The sensors revealed linear ranges between 50-1200 mu M and 200-7000 mu M with a limit of detection (LOD) of 4.18 mu M and 5.62 mu M for DA and UA, respectively. Furthermore, the h-MoS2-based electrochemical sensors showed high stability, sensitivity, and selectivity. The reliability of the sensors was elucidated in human serum. Recoveries ranging between 100.35% and 102.48% were calculated from real sample experiments.
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    Ink-jet printing of particle-free silver inks on fabrics with a superhydrophobic protection layer for fabrication of robust electrochemical sensors
    (Elsevier, 2021) Ipekci, Hasan Huseyin; Gozutok, Zehra; Celik, Nusret; Onses, M. Serdar; Uzunoglu, Aytekin
    The present work demonstrates the fabrication of novel flexible sensors by the deposition of conductive silver patterns on polyester-based fabrics. The conductive layer on the textile surface was formed by ink-jet printing of particle-free silver inks and a subsequent heat treatment. A novel approach is presented to define the working area and ensure high electrode stability by deposition of a superhydrophobic coating on the conductive patterns. The physical and chemical characterizations of the fabricated electrodes were conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), and contact angle measurements. The conductivity of the printed electrodes was highly stable against repeated bending cycles. Hydrogen peroxide was used as the model analyte to evaluate the electrochemical sensing performance of the textile-based flexible sensors. The chronoamperometry results indicated a high sensitivity of 295.3 ? 0.04 ?A mM-1 cm-2 (n = 5) with the linear range of 50 ?M-70 mM. The results suggested that our novel textile-based electrode design is an excellent candidate for the construction of flexible electrochemical sensors with high conductivity and catalytic activity, high bending resilience, wide sensing window, and excellent storage stability.
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    Inkjet printing of highly dispersed, shortened, and defect-rich MWCNTs to construct flexible electrochemical sensors for the detection of bisphenol A in milk samples
    (Pergamon-Elsevier Science Ltd, 2023) Sarikaya, Sumeyye; Ipekci, Hasan Huseyin; Kotan, Hasan; Uzunoglu, Aytekin
    An inkjet-printed electrochemical bisphenol A (BPA) sensor was developed by exploiting the high dispersibility of shortened and defect-rich nitrogen-doped multi-walled carbon nanotubes (MWCNTs). To enhance the dispersibility of MWCNTs in water-based dispersant, the defect concentration was increased by both creating shortened CNT and heteroatom doping, and modification of their surfaces with sulfonate (SO3H) groups. CNTbased inks were prepared by dispersing modified CNT structures in deionized water and the stability and physical properties of the inks were determined. The results suggested that the shortening of MWCNT and SO3H functionalization strategies improved the stability of CNT-based aqueous inks significantly, which enabled the preparation of highly concentrated inks up to 20 mg/ml with high stability. The CNT-based inks were printed on flexible polyethylene tetraflate (PET) and used as an electrochemical BPA sensor. The electrochemical analytical performance of the printed sensors was evaluated using chronoamperometry and differential pulse voltammetry methods. The sensors showed a wide linear range of 5-100 (CA) and 60-700 (DPV) with a LOD of 0.7 mu M. The real sample analysis was conducted in milk and high recoveries were obtained, suggesting the applicability of the sensors in real media.
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    Ni/NiO/Ni-B/graphene heterostructure-modified electrodes and their electrochemical activities towards acetaminophen
    (Royal Soc Chemistry, 2021) Ipekci, Hasan Huseyin; Ozcan, Merve; Turkyilmaz, Busra Gizem; Uzunoglu, Aytekin
    The surface of graphene was decorated with nickel/nickel oxide/nickel-boron particles to develop high-performance electrochemical sensors. The nanohybrid structures were prepared via a one-step reduction method under an oxygen-rich atmosphere to obtain an oxide phase besides metallic nickel nanoparticles. In addition, the use of NaBH4 as the reducing agent enabled simultaneous formation of Ni-B species on the graphene surface. XRD, XPS, TEM, Raman, and TGA analyses were implemented to characterize the samples. The XRD and XPS results revealed the presence of Ni/NiO/Ni-B on the surface of graphene. The electroanalytical performance of the nanocomposite was investigated against acetaminophen, which is an extensively exploited antipyretic and analgesic drug. The analytical performance results showed that the Ni/NiO/Ni-B/Gr-based sensors had a very wide working window between 10 mu M and 2500 mu M (y (mu A) = 10.706x (mM) + 0.3151 (R-2 = 0.9993)). The excellent storage stability, selectivity, and recovery results along with the high analytical performance make the novel Ni/NiO/Ni-B/Gr hybrid systems promising materials for the development of novel sensor platforms.
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    Two-Dimensional (2D) materials in the detection of SARS-CoV-2
    (Elsevier, 2023) Uzunoglu, Aytekin; Altuntas, Evrim Gunes; Ipekci, Hasan Huseyin; Ozoglu, Ozum
    The SARS-CoV-2 pandemic has resulted in a devastating effect on human health in the last three years. While tremendous effort has been devoted to the development of effective treatment and vaccines against SARS-CoV-2 and controlling the spread of it, collective health challenges have been encountered along with the concurrent serious economic impacts. Since the beginning of the pandemic, various detection methods like PCR-based methods, isothermal nucleic acid amplification-based (INAA) methods, serological methods or antibody tests, and evaluation of X-ray chest results have been exploited to diagnose SARS-CoV-2. PCR-based detection methods in these are considered gold standards in the current stage despite their drawbacks, including being high-cost and time-consuming procedures. Furthermore, the results obtained from the PCR tests are susceptible to sample collection methods and time. When the sample is not collected properly, obtaining a false result may be likely. The use of specialized lab equipment and the need for trained people for the experiments pose additional challenges in PCR-based testing methods. Also, similar problems are observed in other molecular and serological methods. Therefore, biosensor technologies are becoming advantageous with their quick response, high specificity and precision, and low-cost characteristics for SARS-CoV-2 detection. In this paper, we critically review the advances in the development of sensors for the detection of SARS-CoV-2 using two-dimensional (2D) materials. Since 2D materials including graphene and graphene-related materials, transition metal carbides, carbonitrides, and nitrides (MXenes), and transition metal dichalcogenides (TMDs) play key roles in the development of novel and high-performance electrochemical (bio)sensors, this review pushes the sensor technologies against SARSCoV-2 detection forward and highlights the current trends. First, the basics of SARS-CoV-2 detection are described. Then the structure and the physicochemical properties of the 2D materials are explained, which is followed by the development of SARS-CoV-2 sensors by exploiting the exceptional properties of the 2D materials. This critical review covers most of the published papers in detail from the beginning of the outbreak.
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    The use of CeO2-modified Pt/C catalyst inks for the construction of high-performance enzyme-free H2O2 sensors
    (Elsevier Science Sa, 2019) Uzunoglu, Aytekin; Ipekci, Hasan Huseyin
    In this work, the development of novel enzyme-free electrochemical hydrogen peroxide (H2O2) sensors with high sensitivity and wide linear range is described. The electrochemical sensors were constructed by the physical modification of commercial Pt/C catalysts with CeO2 metal oxide nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2-adsorption, and Raman spectroscopy methods were used to characterize the metal oxide nanoparticles. The CeO2 particles showed fluorite-type structure with the average crystalline size of 13.8 nm. Furthermore, the Raman spectroscopy results indicated the presence of high degree of oxygen defects indicating the high redox property of the nanoparticles. The physical surface area of the metal oxide nanoparticles was determined to be 68.8 m(2)g(-1). The catalyst inks were prepared by mixing commercial Pt/C and CeO2 nanoparticles with different weight ratios. The analytical performance of the sensors was studied using cyclic voltammetry (CV) and chronoamperometry (CA) methods. The results revealed that the introduction of CeO2 nanoparticles into the catalyst layer improved the sensor performance significantly compared to Pt/C sensors. A high sensitivity of 185.4 +/- 6.5 mu A mM(-1)cm(-2) was obtained from CeO2-modified sensors in a wide linear range of 0.01-30 mM. Depending on the obtained results it can be suggested that the novel sensor design holds a great promise for the construction of electrochemical sensors with high sensitivity, selectivity, and wide working window.