Browsing by Author "Koçak, ÇC"
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Item Electrochemical Determination of Hydrazine at Gold and Platinum Nanoparticles Modified Poly(L-Serine) Glassy Carbon ElectrodesKoçak, S; Altin, A; Koçak, ÇCL-serine monomer was polymerized electrochemically on a glassy carbon electrode by cyclic voltammetry. After L-serine polymerization, gold and platinum metal nanoparticles were doped by electrochemical reduction on the surface. The modified electrodes were characterized by using scanning electron microscopy and electrochemical impedance spectroscopy. The electrochemical behavior of hydrazine oxidation at the electrodes was investigated in 0.1M pH 7.0 phosphate buffer. Hydrazine oxidation peaks were observed at 650, 399, 280, and -395mV at the bare glassy carbon, poly(L-serine) modified glassy carbon, gold nanoparticle modified poly(L-serine) film glassy carbon electrode, and platinum nanoparticles modified poly(L-serine) film glassy carbon electrode, respectively. The most active surface towards hydrazine oxidation was the platinum nanoparticle modified poly(L-serine) film glassy carbon electrode with a 1045mV negative potential shift and approximately three-fold higher peak current. The hydrazine oxidation peak was shifted to a 370mV negative potential with a 2.5 times higher current at the gold nanoparticle modified poly(L-serine) film glassy carbon electrode compared to the bare electrode. The linear concentration ranges were from 1.0 to 1000 mu M and 0.5 to 1000 mu M for the gold nanoparticle modified poly(L-serine) film glassy carbon and the platinum nanoparticles modified poly(L-serine) film glassy carbon electrodes with limits of detections of 0.5 and 0.2 mu M, respectively.Item Electrochemical Determination of Sesamol in Foods by Square Wave Voltammetry at a Boron-Doped Diamond ElectrodeAslisen, B; Koçak, ÇC; Koçak, SSesamol is a phenolic compound naturally found in sesame seeds. It has beneficial health effects in humans, as it features significant antioxidant activity and has anticancer and anti-aging properties. Therefore, finding a suitable electrode surface for sesamol determination is important. The prominent advantage of boron-doped diamond electrodes is their use in many sensing platforms without the need for the surface modification. This study represents the first time that sesamol has been determined using boron-doped diamond electrodes in acidic media by square wave voltammetry. Linear responses of sesamol were obtained in the concentration range from 0.2 mu M to 1000 mu M, and the detection limit was determined to be 85 nM based on a signal-to-noise ratio of 3. The relative standard deviations were 2.1% for a 1 mu M standard with three measurements.Item Electrochemical Preparation and Characterization of Gold and Platinum Nanoparticles Modified Poly(taurine) Film Electrode and Its Application to Hydrazine DeterminationKoçak, ÇC; Altin, A; Aslisen, B; Koçak, SA highly sensitive hydrazine sensor has been developed by using gold and platinum nanoparticles (NPs) decorated poly(taurine) on modified glassy carbon electrode (GCE). First, poly(taurine) modified glassy carbon electrode was prepared by electropolymerization method using cyclic voltammetry. Then, a thin layer of poly(taurine) is coated electrochemically on a GCE and the effective parameters have been optimized. After taurine polymerization, metal nanoparticles (Au and Pt) were doped by electrochemical reduction from metal ions solution on poly(taurine)/GCE surface. Modified electrodes were characterized by using different surface techniques. The obtaining results were compared with bare GCE, poly(taurine) modified glassy carbon electrode, AuNPs/poly(taurine)/GCE, and PtNPs/poly(taurine)/GCE. The peak potential of hydrazine oxidation on bare GCE, poly(taurine)/GCE, AuNPs/poly(taurine)/GCE, and PtNPs/poly(taurine)/GCE were observed at 690 mV, 401 mV, 341 mV, and -370 mV, respectively. Finally, these modified electrodes were successfully used for the oxidation of hydrazine and exhibited excellent electrocatalytic activity with respect to hydrazine oxidation. The better sensitivity and selectivity exhibited the amperometric techniques to compare other techniques. The linear concentration ranges were found between 0.1 to 1000 mu M (R-2 = 0.9981) for AuNPs/poly(taurine)/GCE. The limit of detection (LOD) and limit of quantitation (LOQ) values were calculated to be 0.05 mu M and 0.15 mu M, respectively. The practical application of the sensor was evaluated in river water samples with good recoveries.Item Enhanced Electrochemical Determination of Catechol and Hydroquinone Based on Pd Nanoparticles/Poly(Taurine) Modified Glassy Carbon ElectrodeKoçak, ÇC; Koçak, SHere, Pd nanoparticles and poly(taurine) film was prepared on the glassy carbon electrode surface (Pd/Poly(TAU)/GCE) by the rapid electrochemical technique. The proposed composite surface was characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS). Enhanced electron transfer ability and higher electroactive surface area were achieved at Pd/Poly (TAU)/GCE as compared to the bare GCE and polymer film electrode. The new and highly stable Pd/Poly(TAU)/GCE was employed for the individual and simultaneous determination of hydroquinone and catechol which were environmentally toxic. Under the optimized conditions, HQ and CC were individually determined by using the differantial pulse voltammetry in the linear ranges of 0.008-100 mu M and 0.001-100 mu M with the detection limits of (LOD) 2.1 nM and 0.68 nM, respectively. In case of simultaneous determination, LODs were found as 10 nM and 0.88 nM for HQ and CC, respectively. The content of both analytes in the real sample analysis was evaluated in the river water and tap water successfully.Item Determination of Hydrazine at a Platinum Nanoparticle and Poly(Bromocresol Purple) Modified Carbon Nanotube ElectrodeKoçak, S; Aslisen, B; Koçak, ÇCBromocresol purple was polymerized electrochemically at a carbon nanotube modified glassy carbon electrode and platinum nanoparticles were doped on the polymer film by electrochemical reduction. The modified electrodes were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The oxidation of hydrazine was investigated at the platinum nanoparticle modified electrode in phosphate buffer. The results were compared with those obtained using other modified and bare electrodes. The best catalytic activity was obtained at the platinum nanoparticle modified electrode due to shift of the oxidation peak to more negative values and highest current. The peak potential and current for hydrazine were -445mV and 175.5 mu A, respectively. Linear calibration curves for hydrazine were obtained from 10 to 1000mM. The limits of detection and quantitation for hydrazine were 1.0 and 3.0mM, respectively.Item Electrochemical Determination of Levofloxacin Using Poly(Pyrogallol Red) Modified Glassy Carbon ElectrodeKoçak, ÇC; Aslisen, B; Karabiberoglu, S; Özdokur, KV; Aslan, A; Koçak, SIn this paper, an electrochemical sensor for levofloxacin detection was developed by electrochemical polymerization of pyrogallol red (PGR) on the glassy carbon electrode (GCE) surfaces. Surface morphology and electrical properties of the Poly(PGR)/GCE obtained was characterized by SEM and EIS techniques. Voltammetric behaviour of the levofloxacin was found pH dependent, and the best response was obtained at pH 6.0 PBS. By monitoring the peak current at around 0.9 V, a wide linear range of calibration graph: from 0.2 mu M- 15 mu M LEV and 15 mu M- 355 mu M for levofloxacin, and very low detection limit of 97 nM were achieved with amperometry. Selectivity of the method developed was proven in the presence of possible interfering substances and the method was successfully employed for levofloxacin detection in pharmaceutical tablet and synthetic urine sample.