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Öğe Electrochemical amperometric biosensor applications of nanostructured metal oxides: a review(Iop Publishing Ltd, 2019) Sahin, Bunyamin; Kaya, TolgaBiological sensors have been extensively investigated during the last few decades. Among the diverse facets of biosensing research, nanostructured metal oxides (NMOs) offer a plethora of potential benefits. In this article, we provide a thorough review on the sensor applications of NMOs such as glucose, cholesterol, urea, and uric acid. A detailed analysis of the literature is presented with organized tables elaborating the fundamental characteristics of sensors including the sensitivity, limit of detection, detection range, and stability parameters such as duration, relative standard deviation, and retention. Further analysis was provided through an innovative way of displaying the sensitivity and linear range of sensors in figures. As the unique properties of NMOs offer potential applications to various research fields, we believe this review is both timely and provides a comprehensive analysis of the current state of NMO applications.Öğe Facile preparation and characterization of nanostructured ZnO/CuO composite thin film for sweat concentration sensing applications(Elsevier Sci Ltd, 2021) Sahin, Bunyamin; Kaya, TolgaThis research presents the morphological, structural, optical characterization and sweat sensing response of ZnO/CuO nanocomposite thin films synthesized by the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The particle and crystallite size were increased with increasing SILAR cycles. AFM studies showed that the increase in the number of SILAR cycles resulted a decrease in surface roughness from 60 nm to 23 nm. The optical band energy and transmittance of the nanocomposite thin films were determined from the UV-Vis. spectrum as well as Tauc's plot, which showed a decrease in the optical band energy (from 2.06 to 1.89) with the increase of film thickness. Human hydration level sensing of the nanocomposite ZnO/CuO thin films was investigated by artificial sweat application. It was observed that there was a monotonous increase with the sensing response with respect to the artificial sweat concentration.Öğe A first-principle study of nanostructured CuO thin film-based caffeine sensing scheme(Elsevier Science Sa, 2021) Sahin, Bunyamin; Kaya, TolgaIn this study, we demonstrated the feasibility of nanostructured CuO thin film usage for caffeine sensing. Our morphological studies revealed that ellipse- or spiral-shaped nanostructured were formed with good crystal qualities. It was shown that the film thickness was decreased from 803 nm to 717 nm with an-nealing. Better crystalline quality of annealed films resulted in higher sensing response. Moreover, caffeine sensing response time was decreased to 19 s from 28 s for annealed films compared to as-grown CuO films. Both films exhibited excellent linearity with higher than 0.93 R-2 values for the caffeine values from 0.5 mM to 10 mM, which is the range for most caffeinated hot and cold beverages. Caffeine is considered the only legal stimulant and its excessive use is not healthy. Knowing the caffeine content of beverages using portable, cheap sensor devices will be beneficial for the health-conscious society. We believe our sensing scheme in using nanostructured semiconductor thin films will pave the way to ultimately create advanced materials-based portable sensor devices. (C) 2021 Elsevier B.V. All rights reserved.Öğe Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping(Elsevier Science Bv, 2016) Sahin, Bunyamin; Kaya, TolgaIn this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity. (C) 2015 Elsevier B.V. All rights reserved.Öğe Improved sensing response of nanostructured CuO thin films towards sweat rate monitoring: Effect of Cr doping(Elsevier Sci Ltd, 2020) Dinc, Serdar; Sahin, Bunnyamin; Kaya, TolgaIn this research, we have studied the effect of chromium doping of CuO on the main physical properties and hydration level sensing ability of thin-film samples synthesized by SILAR method on soda-lime glass substrates. The structural, morphological and optical properties as well as hydration level sensing behavior of pristine and CrxCu1-xO (x = 0.01 and 0.02) films were investigated under different Cr concentrations. Optical and structural analysis verified the Cr-doping into CuO films without degrading the uniformity of the metal oxide semiconductor structure. It was shown that the resistivity increases with Cr-doping, which was attributed to the additional holes introduced to the semiconductor crystal. Sweat sensing response of the metal oxide films improved significantly with doping (sensing response from 0.45 to 8.50 for heavy doping). Transient analysis of the sweat response also showed that response time is less than 60 s. We conclude that Cr-doping improves the sensing performance of CuO thin films and offers to be implemented in sweat sensing devices as the sensing material.Öğe A novel amperometric sweat sensor approach through characterization of Hausmannite (Mn3O4) thin films(Elsevier Sci Ltd, 2019) Sahin, Bunyamin; Aslan, Busra; Kaya, TolgaNanostructured metal oxides offer unique advantages for their sensing capabilities hence have been studied immensely. In the context of Mn3O4 films, this study focuses on the sweat sensing prospects of these advanced materials using SILAR method, for the first time. Mn3O4 films were successfully produced with varying thicknesses using SILAR method effectively. This repeatable process allowed these films to be tested in varying artificial sweat concentrations and it was found that Mn3O4 films are very responsive to varying sweat concentrations. Morphological, structural, and optical measurements showed the successful growth of Mn3O4 films with good uniformity, crystallinity, and smooth surface characteristics. Amperometric measurements with and without sweat concentrations showed that Mn3O4 films can indeed be used for sweat sensing applications.Öğe Real-time sweat analysis via alternating current conductivity of artificial and human sweat(Amer Inst Physics, 2015) Liu, Gengchen; Alomari, Mahmoud; Sahin, Bunyamin; Snelgrove, Samuel E.; Edwards, Jeffrey; Mellinger, Axel; Kaya, TolgaDehydration is one of the most profound physiological challenges that significantly affects athletes and soldiers if not detected early. Recently, a few groups have focused on dehydration detection using sweat as the main biomarker. Although there are some proposed devices, the electrical and chemical characteristics of sweat have yet to be incorporated into the validations. In this work, we have developed a simple test setup to analyze artificial sweat that is comprised the main components of human sweat. We provide theoretical and experimental details on the electrical and chemical behavior of the artificial sweat for various concentration values within a temperature range of 5 degrees C to 50 degrees C. We have also developed an efficient sweat collecting and detection system based on 3D printing. Human studies were conducted and this particular protocol has shown that dehydration starts to take effect as early as 40 min into the physical activity if there is no fluid intake during the exercise. We believe that our device will lead to developing viable real-time sweat analysis systems. (C) 2015 AIP Publishing LLC.Öğe Simple and low-cost synthesis of Al-doped ZnO/CuO composite nanowires for highly efficient hydration level sensing(Elsevier Sci Ltd, 2021) Sahin, Bunyamin; Acar, Aysegul; Kaya, TolgaIn this paper, we report on our investigation of the impact of Al doping on the primary physical properties of SILAR fabricated CuO/ZnO composite nanowires. Our characterization on surface and structural analysis showed that we were able to lightly dope the nanocomposites effectively using the SILAR method, which is cost-effective and repeatable. Conductivity of the Al-doped films changed significantly which resulted in greater sensing response for hydration. We utilized artificial sweat solutions to characterize the sensing response of the films and we demonstrated that sensing response almost doubled with Al doping. Transient response of sweat application also showed that response times were less than 10 s for 2% Al-doping. We conclude that Al doping on CuO/ZnO nanocomposites is an excellent candidate to be utilized for hydration sensing through sweat.
