Fehime Özkan | İZMİR INSTITUTE OF TECHNOLOGY (original) (raw)

Papers by Fehime Özkan

Green chemistry and sustainable technology, 2023

Sensor Review, Jul 15, 2019

Purpose-This paper aims to present a novel and cost-effective optical biosensor design by simple ... more Purpose-This paper aims to present a novel and cost-effective optical biosensor design by simple preparation method for detection of "parathionmethyl," which is a model pesticide pose to public health and the environment. Design/methodology/approach-The optical enzyme biosensor (TCA) for detection of pesticide "parathion-methyl" was developed on the basis of immobilization of tyrosinase enzyme on chitosan film by adsorption technique. The analytic performance of TCA was investigated by measuring its activity with Ultraviolet (UV) visible spectrophotometer. Findings-Uniform porous network structure and protonated groups of chitosan film provided a microenvironment for tyrosinase immobilization evident from Fourier transform infrared (FTIR) spectroscopy and Atomic Force Microscopy analysis. TCA has a wide linear detection range (0-1.03 mM) with high correlation coefficient and it can detect the parathion-methyl concentration as low as 159 nM by noncompetitive inhibition kinetics. Using the TCA sensor both for ten times and at least 45 days without a significant loss in its activity are the indicators of its good operational and storage stability. Moreover, TCA can be applicable to tap water, providing a promising tool for pesticides detection. Originality/value-This is the first time to use the in situ analytical technique that can improve the performance of optical enzyme sensor provided to control the pesticide residue better with respect to traditional techniques. The effect of organic solvents on the performance of optical enzyme biosensor was investigated. Inhibition kinetic of the solvents rarely encountered in literature was also studied besides the pH and temperature tolerance of the optical biosensor.

ii ACKNOWLEDGEMENTS I am deeply grateful to my advisors Assoc. Prof. Sacide Alsoy Altınkaya and P... more ii ACKNOWLEDGEMENTS I am deeply grateful to my advisors Assoc. Prof. Sacide Alsoy Altınkaya and Prof. Devrim Balköse for their great support. Thanks to Yılmaz Yürekli and Burcu Alp Akta for their help in technical works. Special thanks to Mine Bahçeci and Gökhan Erdo an for their valuable suggestions and professional approaches during the characterization studies. I also wish to thank Dr. Dan Perera for his comments on my differential scanning calorimetry analysis results. Cafer Özgür prepared my sample holders voluntarily and he have taken great care. Gözde Genç made very useful comments on scanning electron microscope analysis and she shared her industrial experiences with me, related to paint materials. Ayben Top, Selda Gökta and ebnem im ek; my dear friends helped me sincerely whenever I met with a problem.

I would like to express my intimate gratitude to my advisor, Prof. Semra Ülkü, for her guidance a... more I would like to express my intimate gratitude to my advisor, Prof. Semra Ülkü, for her guidance and support throughout this project. I am also grateful to my coadvisor Prof. Devrim Balköse for her precious suggestions. I would like to give my special thanks to Assoc. Prof. Dr. Mehmet Polat and Assist. Prof. Fehime Özkan for their valuable recommendations during the study. I would like to thank all of the research scientists in the Chemical Engineering

Key Engineering Materials, 2004

N 2 , O 2 and CO 2 pure gas permeation through sol-gel derived silica membranes were determined a... more N 2 , O 2 and CO 2 pure gas permeation through sol-gel derived silica membranes were determined and the effects of processing parameters on the microstructure of the membrane was investigated. Silica sols were prepared in an alcoholic solution by hydrolysis and condensation of TEOS as a function of acid content. The thickness of the silica membranes was determined to be about 2µm and significant infiltration into the support was observed from the SEM pictures. The supported membranes were heat treated in the 50-400 o C. The N 2 permeabilities of silica membranes varied in the 2.2*10-10-2.7*10-8 mol/m 2 .s.Pa range for single layer membranes dipped for 10s. in the sol. The CO 2 permeability of these membranes varied in the 1.2*10-9-6.95*10-8 mol/m 2 .s.Pa range. The sols became viscous and gelled at 50 o C in 16 hours. The O 2 permeability increased with aging time. The optimum dipping time during processing was determined to be 10 seconds. The increase in the acid content of the sols were observed to increase permeabilities of the membranes significantly.

Metal-organic frameworks(MOFs), highly porous crystalline materials, are composed of metal cluste... more Metal-organic frameworks(MOFs), highly porous crystalline materials, are composed of metal clusters connected by organic linkers. As they have high porosity, large surface area and large pore volume, a considerable amount of specific gases can be adsorbed onto these pores. Hydrogen, a clean energy fuel can be produced by Steam Methane Reformer (SMR) processes. Steam methane reformer off-gas, gas produced by steam methane reformer contains mainly H2 besides to CO2, (10-25%v/v), CH4 (1.3-8%v/v), CO (0.25-10%v/v) as impurities. It is critical to remove CO2 from the gas mixture not only for up-grading of SMR-off gas but also natural gas to obtain high purity H2 or CH4, respectively. MOFs are considered as a potential adsorbent material to be used in gas purification and separation. Zero Length Column (ZLC) technique was conducted to measure the intraparticle diffusion properties of porous adsorbents. The response curve, yielded from quadrupole mass spectrometer, is used to determine ads...

Key Engineering Materials, 2004

The preparation, characterization and pure gas permeation of sol-gel derived alumina membranes we... more The preparation, characterization and pure gas permeation of sol-gel derived alumina membranes were investigated in this work. The effects of acid concentration/type and water content on the particle size in the sols and pore size distributions of the unsupported membrane were investigated by N 2 adsorption/desorption isotherms and Dynamic Light Scattering. Increasing the H + /Al 3+ mole ratio from 0.1 to 0.25 caused the hydrodynamic sol particle size and BJH pore size to decrease from 65 to 30 nm and 3.6 to 2.9 nm, respectively. The pore size increased from 2.8 nm to 3 nm upon increasing the calcination temperature from 500 to 600 o C. Unsupported membranes were heat treated in the 200 to 1200 o C range for the characterization of the phase structure. Pinhole and crack free alumina membranes about 3 µm (2-layer) in thickness was observed from the SEM pictures with insignificant infiltration. The CO 2 permeability through the double layer γ-Al 2 O 3 membrane calcined at 600 o C was 2.25*10-7 mol/m 2 .s.Pa, and had a slight pressure dependence indicating Knudsen Diffusion and Laminar Flow being the effective transport mechanisms. Upon the calcination of a similar 2-layer alumina membrane at 500 o C, the CO 2 permeability decreased to 1.51*10-8 mol/m 2 .s.Pa. without pressure dependence.

Journal of Thermal Analysis and Calorimetry, 2003

Water vapour adsorption on polymers affects their processing behaviour and useful properties. Wat... more Water vapour adsorption on polymers affects their processing behaviour and useful properties. Water vapour adsorption on organic polymers, silk, Nylon 6 fibres in undrawn and permanent set forms, polyester micro fibres, plasticised PVC films with 60 phr dioctylphthalate (DOP) and inorganic polymer sepiolite particles were investigated in this study. The materials were examined using the BET equation. The surface areas

Journal of Sol-gel Science and Technology, 2002

Hollow fibers formed from water glass and metal salts of IIA(Ca), VIIB(Fe, Co, Ni) and IB(Cu) gro... more Hollow fibers formed from water glass and metal salts of IIA(Ca), VIIB(Fe, Co, Ni) and IB(Cu) groups were characterised in this study. Fragile fibres obtained herein broke down into small pieces during isolation and drying. Quantitative information about morphology, chemical composition and surface structure of the fibres were obtained. The diameter and wall thickness of the fibers were around 50

Separation Science and Technology, 1996

Flexible poly(viny1 chloride) (PVC) composites having natural zeolite clinoptillolite were prepar... more Flexible poly(viny1 chloride) (PVC) composites having natural zeolite clinoptillolite were prepared by plastisol-plastigel technology. Adsoption of methylene blue on each raw material and on composites was studied both from an equilibrium and a rate approach. It was observed that the adsorption capacity of zeolite decreased when it was embedded in composites. The equilibrium uptake of methylene blue increased with an increasing zeolite fraction in composites. Methylene blue was adsorbed from a 0.02 g.cm-' aqueous solution slowly, but was nearly adsorbed completely with a composite having a 0.3 volume fraction of zeolite. The effective diffusion coefficient of methylene blue in composites was of the order of 10-I' mZ.s-l and decreased with increasing filler fraction.

Applied Surface Science, 1998

Well-defined CoCl-containing silica gels were prepared by impregnation of the aqueous solution of... more Well-defined CoCl-containing silica gels were prepared by impregnation of the aqueous solution of the salt to silica 2 hydrogel, drying and aging methods. Silica gels having 392-437 m 2 g y1 surface area and 0.21-0.37 cm 3 g y1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl solutions decreased the surface area of silica 2 gels from 540 cm 2 g y1 to 392-430 m 2 g y1 and pore volume from 0.27 to 0.21-0.23 cm 3 g y1 for CoCl concentration 2 smaller than 0.28 mol dm y3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917-2555 J g y1 energy as determined by differential scanning calorimetry. The CoCl-containing gels were successfully used in dynamic column 2 experiments, with linear relation between velocities of inlet air and movement of blue to pink boundary. The colour change also makes the detection of the defects in column filling which causes air channelling.

Applied Catalysis A: General, 2004

In this work, isomerization reaction of ␣-pinene was studied over several heat-treated natural ze... more In this work, isomerization reaction of ␣-pinene was studied over several heat-treated natural zeolite catalysts, rich in clinoptilolite, from Balýkesir-Bigadic region in Turkey in a batch slurry reactor under nitrogen atmosphere. Zeolite samples were calcined at different temperatures such as 300, 450 and 600 • C. All catalysts were tested in the isomerization reaction of ␣-pinene and were characterised by nitrogen adsorption experiments, IR, and XRD measurements. Acidity strength and the distribution of Lewis and Bronsted acid sites of the samples were determined. Selectivities to main reaction products, camphene and limonene, and reaction kinetics were investigated. Catalytic activity, that is total conversion of ␣-pinene, of heat-treated samples decreased with increasing calcination temperatures. Selectivity to limonene is dependent on ␣-pinene conversion at high conversion levels while the selectivity to camphene is not. The formation of heavy products increased with treatment temperature. It was seen that ␣-pinene consumption could be described by a first-order kinetics.

Adsorption Science & Technology, 2003

The carbon dioxide and water vapour adsorption properties of local clinoptilolite-rich material, ... more The carbon dioxide and water vapour adsorption properties of local clinoptilolite-rich material, both as the original and as lead-, barium- and hydrogen-rich forms, were examined. The lead- and barium-rich forms were prepared by treatment of the original clinoptilolite with Pb(NO3)2 and BaCl2 respectively, while the hydrogen-rich form was prepared by NH4Cl and heat treatment. Water and CO2 adsorption experiments were conducted in a volumetric system under static conditions, with low-pressure adsorption data being used for the characterization of the natural, Pb-rich, Ba-rich and H-rich clinoptilolite samples. Although the existence of barium-exchange was not noted, an appreciable decrease in CO2 adsorption was observed with the Pb-rich and H-rich forms due to a decrease in the electrostatic interaction between the surface and the adsorbate. Application of the Dubinin–Astakhov equation to the water adsorption data established the existence of micropores of different sizes that exhibi...

Adsorption, 2005

CO 2 and N 2 adsorption on the acid treated natural and synthetic zeolites at 5 • C and 25 • C wa... more CO 2 and N 2 adsorption on the acid treated natural and synthetic zeolites at 5 • C and 25 • C was studied. The system heterogeneity was higher for CO 2 than N 2 adsorption and decreased with acid treatment.

APMIS, 1997

APMIS 105: 705-707. 1997 Printed iti Drtiniurk . All righrs riwrwd ... ALPER TUNGER,&#x27... more APMIS 105: 705-707. 1997 Printed iti Drtiniurk . All righrs riwrwd ... ALPER TUNGER,&#x27; FERIHA OZKAN,&#x27; FADIL VARDAR,~ DILEK BURHANOGLU,] MEHMET ALI OZINEL&#x27; and AYHAN TOKBAS&#x27; ... &#x27;Department of Microbiology and Clinical Microbiology and 2Department of ...

Separation and Purification Technology, 2017

Clinoptilolite supported rutile TiO 2 composites were synthesized for the enhancement of its phot... more Clinoptilolite supported rutile TiO 2 composites were synthesized for the enhancement of its photocatalytic performance in the degradation of the aqueous terephthalic acid solution under UVC illumination by the increase in its surface area and to simplify its recovery from the treated solution after use. The XRD spectra of the composites revealed the formation of pure rutile TiO 2 on the surface of the clinoptilolite. The SEM images showed the formation of the spherical TiO 2 clusters were composed of nano fibers on the surface of the clinoptilolite. For all composites synthesized, the dispersion of the TiO 2 particles on the clinoptilolite led to a surface area larger than that of the bare TiO 2 and clinoptilolite. The materials synthesized in the present study exhibited higher catalytic activity compared with the commercial Degussa P25 and anatase. Among the catalysts synthesized the TiO 2 /clinoptilolite with a weight ratio of 0.5 was found to be the most photoactive catalyst even though it contains a lesser amount of active TiO 2. The kinetic of the reactions for different catalyst was found to be consistent with the pseudofirst order kinetic model. The results of the Langmuir-Hinshelwood model showed the slight contribution of the adsorption on the degradation. The activity of the TiO 2 /clinoptilolite with a weight ratio of 0.5 decreased after repetitive use due to the accumulation of the TPA molecules on the surface of the catalyst.

CO2 and N2 adsorption on the acid treated natural and synthetic zeolites at 5◦C and 25◦C was stud... more CO2 and N2 adsorption on the acid treated natural and synthetic zeolites at 5◦C and 25◦C was studied. The system heterogeneity was higher for CO2 than N2 adsorption and decreased with acid treatment.

In this study, Clinoptilolite-rich zeolitic tuff was treated with acids such as HCl, HNO 3 , H 2 ... more In this study, Clinoptilolite-rich zeolitic tuff was treated with acids such as HCl, HNO 3 , H 2 SO 4 , and H 3 PO 4 . The effect of periods of time (3 hours and 6 hours), concentration (1 M, 2 M, 3 M, 5 M, and 10 M) and acid type were taken as parameters. In the characterization of the zeolites, XRD, ICP-AES, FTIR, and SEM techniques were used. As the acid concentration and the treatment time were increased, the aluminum and cation removal from the structure was increased. HCl and HNO 3 were more effective acids for the dealumination than H 2 SO 4 and H 3 PO 4 . It was found out that considerable change in the texture of the zeolitic tuff didn’t take place during the H 3 PO 4 treatment. On the other hands, acid treatment resulted in an increase in the micropore surface area and volume of the zeolite. Specific surface area of the zeolitic tuff (19 m 2 /g) was increased up to 213 m 2 /g, 236 m 2 /g, 202 m 2 /g, 118 m 2 /g with HCl, HNO 3 , H 2 SO 4, and H 3 P O 4 treatments, respecti...

Separation Science and Technology, 1996

Flexible poly(vinyl chloride) (PVC) composites having natural zeolite clinoptillolite were prepar... more Flexible poly(vinyl chloride) (PVC) composites having natural zeolite clinoptillolite were prepared by plastisol-plastigel technology. Adsoption of methylene blue on each raw material and on composites was studied both from an equilibrium and a rate approach. It was observed that the adsorption capacity of zeolite decreased when it was embedded in composites. The equilibrium uptake of methylene blue increased with an increasing zeolite fraction in composites. Methylene blue was adsorbed from a 0.02 g·cm−3 aqueous solution slowly, but was nearly adsorbed completely with a composite having a 0.3 volume fraction of zeolite. The effective diffusion coefficient of methylene blue in composites was of the order of 10−13 m2·s−1 and decreased with increasing filler fraction.

Journal of Thermal Analysis and Calorimetry, 2003

Green chemistry and sustainable technology, 2023

Sensor Review, Jul 15, 2019

Key Engineering Materials, 2004

Journal of Thermal Analysis and Calorimetry, 2003

Journal of Sol-gel Science and Technology, 2002

Separation Science and Technology, 1996

Applied Surface Science, 1998

Applied Catalysis A: General, 2004

Adsorption Science & Technology, 2003

Adsorption, 2005

APMIS, 1997

Separation and Purification Technology, 2017

Separation Science and Technology, 1996

Journal of Thermal Analysis and Calorimetry, 2003