Researcher:
Kılınç, Necmettin

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Necmettin

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Kılınç

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Kılınç, Necmettin

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2012 - 201513

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Now showing 1 - 10 of 13
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    Fabrication and gas sensing properties of C-doped and un-doped TiO2 nanotubes
    (Elsevier, 2014) Sennik, Erdem; Işık, Müge; Ahsen, Ali Şems; Öztürk, Osman; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    In this work, un-doped and carbon (C) doped TiO2 nanotubes were fabricated and their hydrogen sensing properties were investigated. A Ti foil was anodized in an aqueous hydrofluoric acid (H:F) electrolyte (0.5 wt%) at room temperature to form TiO2 nanotube arrays. C-doped TiO2 nanotubes were obtained through two methods; a chemical process and thermal acetylene (C2H2) treatment. In the chemical method, a Ti foil was anodized 'in-situ' in aqueous solution of 0.5 wt% polyvinyl alcohol (PVA)+0.5 wt% HF. In the heat treatment method, a Ti foil was anodized in an aqueous (HF) electrolyte (0.5 wt%) to obtain TiO2 nanotubes, and then C-doped TiO2 nanotubes were obtained by heating as-prepared nanotubes at 500 degrees C in a quartz tube under a continuous N-2 and C2H2 flux (1:1). The obtained un-doped and C-doped TiO2 nanotubes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). The H-2 sensing properties of the nanotubes exposed to 5000 ppm H-2 were investigated at 100 degrees C. C-doped TiO2 nanotubes showed a lower response to H-2 than the undoped TiO2 nanotubes.
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    MEMS based blood plasma viscosity sensor without electrical connections
    (IEEE Computer Society, 2013) Yaralıoğlu, Göksenin G.; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; Kılınç, Necmettin; PhD Student; Other; Faculty Member; Researcher; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 8579; 59959
    A MEMS based viscometer is reported. The device has a disposable cartridge and a reader. The cartridge contains microfluidic channels and a MEMS cantilever sensor. The reader contains the actuator and the readout optics and electronics. A unique feature of the system is that both the actuation and the sensing are remote; therefore, no electrical connections are required between the reader and the cartridge. The reported sensor is capable of measuring viscosity with better than 0.01 cP resolution in a range of 0.8-14.1 cP, with less than 50 μl sample requirement. This range and sensitivity are sufficient for blood plasma viscosity measurements, which are in between 1.1-1.3 cP for healthy individuals and can be elevated to 3cP in certain diseases[1].
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    Electrical conduction and NO 2 gas sensing properties of ZnO nanorods
    (Elsevier, 2014) Sahin, Yasin; Öztürk, Sadullah; Kosemen, Arif; Erkovan, Mustafa; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    Thermally stimulated current (TSC), photoresponse and gas sensing properties of zinc oxide (ZnO) nanorods were investigated depending on heating rates, illumination and dark aging times with using sandwich type electrode system. Vertically aligned ZnO nanorods were grown on indium tin oxide (ITO) coated glass substrate by hydrothermal process. TSC measurements were performed at different heating rates under constant potential. Photoresponse and gas sensing properties were investigated in dry air ambient at 200 degrees C. For gas sensing measurements, ZnO nanorods were exposed to NO2 (100 ppb to 1 ppm) in dark and illuminated conditions and the resulting resistance transient was recorded. It was found from dark electrical measurements that the dependence of the dc conductivity on temperature followed Mott's variable range hopping (VRH) model. In addition, response time and recovery times of ZnO nanorods to NO2 gas decreased by exposing to white light.
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    Two cantilever based sytem for viscosity and density monitoring
    (IEEE, 2015) Yaralıoğlu, Göksenin G.; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Kılınç, Necmettin; Ürey, Hakan; PhD Student; Other; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; College of Engineering; N/A; N/A; 59959; 8579
    Viscosity and density measurements in liquids in real-time is challenging. Previous MEMS based approaches use frequency sweeps for the purpose and those methods are slow and not real-time. We show that high precision viscosity and density measurements are possible using two cantilevers with different widths and by tracking their frequencies with a Phase-Locked-Loop in real-time.
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    Hydrogen sensing properties of ZnO nanorods: effects of annealing, temperature and electrode structure
    (Pergamon-Elsevier Science Ltd, 2014) Öztürk, Sadullah; Torun, Imren; Kosemen, Arif; Sahin, Yasin; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    In this study, the hydrogen (H-2) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H2 sensor performance, the nanorods were heated at 500 C in dry air. H2 sensing measurements were done in the temperature range of 25-200 degrees C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the uncoated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure.
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    LoC sensor array platform for real-time coagulation measurements
    (Institute of Electrical and Electronics Engineers (IEEE), 2014) Yaralıoğlu, Göksenin G.; N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Kılınç, Necmettin; Ermek, Erhan; Mostafazadeh, Aref; Elbüken, Çağlar; Ürey, Hakan; PhD Student; Researcher; Other; Researcher; Researcher; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Engineering; College of Engineering; College of Engineering; N/A; 59959; N/A; N/A; N/A; 8579
    This paper reports a MEMS-based sensor array enabling multiple clot-time tests in one disposable microfluidic cartridge using plasma. The versatile LoC (Lab-on-Chip) platform technology is demonstrated here for real-time coagulation tests (activated Partial Thrompoblastin Time (aPTT) and Prothrombin Time (PT)). The system has a reader unit and a disposable cartridge. The reader has no electrical connections to the cartridge, which consists of multiple microfluidic channels and MEMS microcantilevers placed in each channel. Microcantilevers are made of electro-plated nickel and actuated remotely using an external electro-coil. The read-out is also conducted remotely by a laser and the phase of the MEMS oscillator is monitored real-time. The system is capable of monitoring coagulation time with a precision estimated at 0.1sec.
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    Fabrication of 1D ZNO nanostructures on mems cantilever for VOC sensor application
    (Elsevier, 2014) Kosemen, Arif; Öztürk, Sadullah; Yerli, Yusuf; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; Researcher; PhD Student; Other; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; 59959; N/A; N/A; 8579
    This study reports the fabrication method and sensing performance for novel 1D zinc oxide (ZnO) nanorods and nanotubes grown on nickel MEMS cantilevers. The fabrication of the nanostructures and the cantilevers are simple and low-cost using standard lithography, electrodeposition, and hydrothermal etching processes. 1D ZnO nanostructures increase the total sensitive area for biological and chemical sensor applications. We performed experiments with various VOCs with a real-time sensor system developed in our laboratory. While Ni microcantilevers produced no signal, ZnO nanostructure coated microcantilevers showed good sensitivity and repeatable changes. Furthermore, the nanotube coated microcantilevers showed more than 10 fold increase in sensitivity compared to the nanorod coated microcantilevers which can be explained to the fact that ZnO nanotubes have higher surface area and subsurface oxygen vacancies and these provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods. The tests are performed using dynamic mode of operation near resonant frequency using magnetic actuation and optical sensing. The phase stability and the limit of detection of ZnO nanotube coated microcantilevers exposed to diethylamine (DEA) were 0.02 degrees and lower than 10 ppm, respectively. ZnO nanostructure coated microcantilevers have good potential for VOC sensor applications especially for amine groups.
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    Fabrication of ZnO nanorods for NO2 sensor applications: Effect of dimensions and electrode position
    (2013) Özturk, Sadullah; Özturk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    In this study, zinc oxide (ZnO) nanorods were fabricated by using hydrothermal method and resistive type nitrogen dioxide (NO2) sensing properties of the nanorods were investigated depending on temperature, NO2 concentration, electrode position and the dimension of the nanorods. To produce ZnO seed layer, zinc acetate solution was coated on a glass substrate by using spin-coater. ZnO nanorods were grown by changing concentration of solution at 90 C for 3 h onto seed layer coated substrate. ZnO nanorods were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was observed that the diameters of ZnO nanorods were approximately 30 nm, 60 nm and 120 nm depending on solution concentration. For gas sensing measurements, interdigitated Au electrodes were coated on top or bottom of ZnO nanorods by using thermal evaporator. All samples were tested against to NO2 in dry air ambient depending on concentration (100 ppb–1 ppm) in the temperature range of 25–200 C. The highest sensor response was observed for ZnO nanorods that were 60 nm in diameter. The response and recovery times for all sensors decreased with increasing temperature and the sensors were fully recovered above temperature of 100 C.
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    Resistive hydrogen sensors based on nanostructured metals and metal alloys
    (Amer Scientific Publishers, 2013) N/A; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    Hydrogen (H-2), as a renewable energy source, has numerous applications such as chemical production, fuel cell technology, rocket engines, fuel for cars etc. The detection of H-2 is so important in safety issue due to the flammable and explosive properties of H-2 gas, in a H-2 source for leak detection and in H-2 production process because of real-time quantitative analysis of production. This paper reviews resistive type H-2 sensor based on palladium (Pd), platinum (Pt) and their alloy nano-structures in the forms of thin films, nanoporous films, nanowires, nanoparticles, nanotubes, etc. The sensing mechanism of the nanostructured Pd and Pt resistive sensor is discussed in separated section. Nanostructured Pd sensors show a decrease or an increase in their resistance towards H-2 gas depending on continuity of the nanostructure and will be examined in two parts: discontinuous (nano-gap based) and continuous Pd and Pd alloy nanostructure sensors. on the contrary to Pd nanostructure sensor, nanostructured Pt sensors require oxygen (O-2) to operate. There are limited numbers of publications about nanostructured Pt and Pt alloy sensors, so further investigation are needed to well understand sensing mechanism of the Pt sensors.
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    A VOC sensor based on micromechanical cantilever functionalized with ZNO nanorods
    (Chemical and Biological Microsystems Society, 2013) Kosemen, A.; Öztürk, S.; Yerli, Y.; Öztürk, Z.Z.; Department of Electrical and Electronics Engineering; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; Researcher; PhD Student; Other; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; 59959; N/A; N/A; 8579
    This study reports a novel method for volatile organic compound (VOC) detection with a functionalized microcantilever-based sensor. The devices are fabricated with lithography and electrodeposition processes. ZnO nanorods are deposited on Ni microcantilevers in order to expand the total sensitive area. The VOC sensor measurements are carried out with magnetic actuation and optical read out. The phase stability and limit of detection for diethylamine (DEA) were 0.02° and below 100 ppm, respectively. ZnO nanorod coated microcantilevers have potential for VOC sensor especially for amine groups due to the high surface area-to-volume ratio.