Ali Sınağ

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1).

Production and characterization of pyrolytic oils by pyrolysis of waste machinery oil.

The main objective of this work is to propose an alternative method for evaluation of the waste machinery oil which is an environmental problem in Turkey. For this purpose, pyrolysis of waste machinery oil was conducted in a tubular reactor. Effect of the experimental conditions (various temperatures, catalyst type) on the formation of pyrolytic oil, gas, and char was investigated. Nickel supported on silica and zeolite (HZSM-5) were used as catalysts. Properties of the pyrolytic oils were characterized by gas chromatograph equipped with a mass selective detector (GC-MS), gas chromatography with flame ionization detector (GC-FID for boiling point range distribution), nuclear magnetic resonance ((1)H NMR) spectroscopy, higher heating value measurement, and elemental analysis. The behavior of the metals in the waste machinery oil and the pyrolytic oil samples was also quantitatively detected by inductively coupled plasma (ICP) analysis. As, Cd and Cr contents of the all pyrolytic oils were found as <0.05 ppm, while Cu content of the pyrolytic oils varied between 0.3 ppm and 0.61 ppm. Only Vanadium contents of the pyrolytic oils obtained at 800 degrees C (0.342 ppm) and in the presence of HZSM5 (0.57 ppm) increased compared to that obtained by waste machinery oil (0.1 ppm). Lower metal contents of the pyrolytic oils reveal that pyrolysis of the waste machinery oils leads to the formation of environmental friendly pyrolytic oils with higher heating values.

Tin oxide nanoparticles-polymer modified single-use sensors for electrochemical monitoring of label-free DNA hybridization.

In this study, SnO(2) nanoparticles (SNPs)-poly(vinylferrocenium) (PVF(+)) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences.

Investigation of Photocatalytic Effect of SnO2 Nanoparticles Synthesized by Hydrothermal Method on the Decolorization of Two Organic Dyes

Tin oxide nanoparticles about 4 nm in size were successfully synthesized using hydrothermal method. The photocatalytic activity of the particles was determined by the decolorization of malachite green (MG) and titanium yellow (TY) under UV light. 12 ppm of MG and TY were used for the solution with an initial volume of 100 mL. The amounts of catalysts were 10, 30 and 50 mg. The effect of the catalyst loading on the reaction kinetic parameters and the decolorization rate constants (k) were determined. In order to reveal the photocatalytic efficiency of the nano particles, further experiments were conducted with bulk SnO2. The oxygen species registered no observable effect on the reaction mechanism as nitrogen bubbling leads to no change in decolorization rates. Results showed that the synthesized nano tin oxide particles represent excellent photocatalytic activity for the decolorization of 12 ppm MG under UV light with 150 min of irradiation time. The energies of the highest occupied molecular orbital (HOMO) EHOMO of the dyes were also calculated by using the quantum chemical software in order to discuss the differences for the decolorization of two dyes. Electrical energy efficiency values for the decolorization of two dyes were also calculated.

Electrochemical behaviour of carbon paste electrodes enriched with tin oxide nanoparticles using voltammetry and electrochemical impedance spectroscopy.

The effect of the SnO(2) nanoparticles (SNPs) on the behaviour of voltammetric carbon paste electrodes were studied for possible use of this material in biosensor development. The electrochemical behaviour of SNP modified carbon paste electrodes (CPE) was first investigated by using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The performance of the SNP modified electrodes were compared to those of unmodified ones and the parameters affecting the response of the modified electrode were optimized. The SNP modified electrodes were then tested for the electrochemical sensing of DNA purine base adenine to explore their further development in biosensor applications.

A novel carboxymethylcellulose–gelatin–titanium dioxide–superoxide dismutase biosensor; electrochemical properties of carboxymethylcellulose–gelatin–titanium dioxide–superoxide dismutase

A novel highly sensitive electrochemical carboxymethylcellulose-gelatin-TiO(2)-superoxide dismutase biosensor for the determination of O(2)(•-) was developed. The biosensor exhibits high analytical performance with a wide linear range (1.5 nM to 2 mM), low detection limit (1.5 nM), high sensitivity and low response time (1.8s). The electron transfer of superoxide dismutase was first accomplished at the carboxymethylcellulose-gelatin-Pt and carboxymethylcellulose-gelatin-TiO(2)-Pt surface. The electron transfer between superoxide dismutase and the carboxymethylcellulose-gelatin-Pt wihout Fe(CN)(6)(4-/3-) and carboxymethylcellulose-gelatin-Pt, carboxymethylcellulose-gelatin-TiO(2)-Pt with Fe(CN)(6)(4-/3-) is quasireversible with a formal potential of 200 mV, 207 mV, and 200 mV vs Ag|AgCl respectively. The anodic (ks(a)) and cathodic (ks(c)) electron transfer rate constants and the anodic (α(a)) and cathodic (α(c)) transfer coefficients were evaluated: ks(a)=6.15 s(-1), α(a)=0.79, and ks(c)=1.48 s(-1) α(c)=0.19 for carboxymethylcellulose-superoxide dismutase without Fe(CN)(6)(4-/3-), ks(a)=6.77 s(-1), α(a)=0.87, and ks(c)=1 s(-1) α(c)=0.13 for carboxymethylcellulose-superoxide dismutase with Fe(CN)(6)(4-/3-), ks(a)=6.85 s(-1), α(a)=0.88, and ks(c)=0.76 s(-1) α(c)=0.1 carboxymethylcellulose-gelatin-TiO(2)-superoxide dismutase. The electron transfer rate between superoxide dismutase and the Pt electrode is remarkably enhanced due to immobilizing superoxide dismutase in carboxymethylcellulose-gelatin and TiO(2) nanoparticles tend to act like nanoscale electrodes.

Comparison of Retorting and Supercritical Extraction Techniques on Gaining Liquid Products from Goynuk Oil Shale (Turkey)

In this study, conversion of Goynuk oil shale to liquid products was investigated. In the first part of the study, pyrolysis of organic compounds called kerogen, which is the majority of organic material in oil shale, was performed and amounts of residue char, tar, water and gas were determined. After that, oil shale samples were extracted by toluene in an Autoclave and an amount of liquid products obtained by extraction and by pyrolysis was compared with each other. In addition asphaltene, oil, residue char and gas yields in the tar and the optimum conditions at which the maximum yields are obtained were determined. In the pyrolysis experiments, the effects of temperature on residue char, tar, gas and water were investigated. In conclusion, supercritical extraction is a more available method than pyrolysis in conversion of Goynuk oil shale to liquid products.

In vitro cytotoxicity of hydrothermally synthesized ZnO nanoparticles on human periodontal ligament fibroblast and mouse dermal fibroblast cells.

The use of metal oxide nanoparticles (NPs) in industrial applications has been expanding, as a consequence, risk of human exposure increases. In this study, the potential toxic effects of zinc oxide (ZnO) NPs on human periodontal ligament fibroblast cells (hPDLFs) and on mouse dermal fibroblast cells (mDFs) were evaluated in vitro. We synthesized ZnO NPs (particle size; 7-8 nm) by the hydrothermal method. Characterization assays were performed with atomic force microscopy, Braun-Emmet-Teller analysis, and dynamic light scattering. The hPDLFs and mDFs were incubated with the NPs with concentrations of 0.1, 1, 10, 50 and 100 μg/mL for 6, 24 and 48h. Under the control and NP-exposed conditions, we have made different types of measurements for cell viability and morphology, membrane leakage and intracellular reactive oxygen species generation. Also, we monitored cell responses to ZnO NPs using an impedance measurement system in real-time. While the morphological changes were visualized using scanning electron microscopy, the subcellular localization of NPs was investigated by transmission electron microscopy. Results indicated that ZnO NPs have significant toxic effects on both of the primary fibroblastic cells at concentrations of ∼50-100 μg/mL. The cytotoxicity of ZnO NPs on fibroblasts depended on concentration and duration of exposure.

The Pyrolysis of Scrap Tire with Lignite

Abstract Mustafa Kemal Pasa lignite obtained from the Mustafa Kemal Pasa region of Bursa, Turkey was subjected to pyrolysis with scrap tires. Effects of the pyrolysis conditions, such as temperature, weight percent of the scrap tires in the blends, and synergism on the results, was investigated. Tars obtained at the end of pyrolysis were characterized by Fourier transform infrared spectroscopy and gas chromatography mass spectrometry analysis. It is found that synergism between the coal and tire leads to improved tar yields at all temperatures.

Heterostructured poly(3,6-dithien-2-yl-9H-carbazol-9-yl acetic acid)/TiO2 nanoparticles composite redox-active materials as both anode and cathode for high-performance symmetric supercapacitor applications

Herein, a facile and simple method is reported for preparation of composite electrode materials based on conducting polymer/nano metal oxide combination for supercapacitor applications. The heterostructured composite redox-active electrode materials, having both p- and n-doping ability, were fabricated using poly(3,6-dithien-2-yl-9H-carbazol-9-yl acetic acid) and nano sized TiO2 particles without any binder and conducting additives. The heterostructured composite electrodes exhibited remarkable a specific capacitance (Cspec = 462.88 F g−1), specific power (SP = 266.96 kW kg−1), specific energy (SE = 89.98 W h kg−1), good cycling performance and excellent reversible capability (81.7% capacitance retention after 8000 charge/discharge cycles) at 2.5 mA cm−2 current density within a 1.2 V potential window with two-electrode symmetric cell configuration. Besides, heterostructured composite electrode materials were fabricated using different particle sized TiO2 (3–5 nm, average 21 nm and bulk), and the effect of the particle size on supercapacitor performances was investigated and compared in detail. Our symmetric pseudo-capacitor device lighted a LED for 4.7 min with 42 s charge time at 2.5 mA cm−2 even after 8000 charge/discharge cycles.