Kadriye Ertekin - Academia.edu (original) (raw)

Papers by Kadriye Ertekin

Ceramics International, Jul 1, 2016

Abstract Bulk and thin film forms of titanium dioxide (TiO2) have been studied many times due to ... more Abstract Bulk and thin film forms of titanium dioxide (TiO2) have been studied many times due to its very promising optical properties. In this study, low-cost flame spray pyrolysis (FSP) synthesis of Nd3+/Er3+doped TiO2 nanoparticles has been reported for the first time. The produced particles were post-annealed after FSP process at 550 °C in order to obtain crystalline structure. The phase and elemental analysis of the produced materials were performed by X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS), respectively. The surface morphology, accurate size and specific surface area of the primary particles were identified using scanning electron microscopy (SEM) and particle size analyser. Luminescent properties of the produced nanoparticles were investigated by steady state and time resolved fluorescence spectra. Doping of TiO2 nanoparticles with the rare earths of Nd3+and Er3+resulted in visible and near-infrared light emission when excited at 364 nm. The utilized nanoparticles yielded bi-and tri-exponential decay curves. Additionally, they exhibited typical upconversion luminescence when radiated by 810 nm.

Sensor Letters, Sep 1, 2015

ABSTRACT Most of the ruthenium dyes suffer from leaching from host matrices. In this work, alkyl ... more ABSTRACT Most of the ruthenium dyes suffer from leaching from host matrices. In this work, alkyl branched Ru(II) derivatives were used along with silver nanoparticles (AgNPs) in two different silicon based matrices for oxygen sensing purposes. By this way, we securely entrapped the dye molecules without any leaching from the matrix. The sensing materials were fabricated in form of thin films and electrospun nanofibers. 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI+][BF–4]) and perfluoro compounds (PFCs) were exploited as additives to enhance the response to oxygen. O2 induced spectral changes at 630 nm were followed for both gas phase and dissolved oxygen as the analytical signal. The oxygen sensitivities of the probes were also tested by lifetime based and kinetic mode measurements. Utilization of the amphiphilic Ru dyes in silicon along with AgNPs in form of electrospun fibers resulted in many advantages such as enhanced long term stability, increased surface area, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered design were also tested in presence of vapors of benzene, toluene, ethylbenzene, hexane and xylene. The offered composite can be employed for both, gas phase and dissolved O2 measurements even in refinery conditions.

Chemical Papers, Aug 27, 2022

Journal of Materials Science: Materials in Electronics, Oct 30, 2021

Up to now, luminescence properties of Eu2+-activated Ca-α-Sialon (Ca-α-Sialon:Eu2+) and Ce3+-dope... more Up to now, luminescence properties of Eu2+-activated Ca-α-Sialon (Ca-α-Sialon:Eu2+) and Ce3+-doped lutetium aluminium garnet (LuAG:Ce3+) have been widely studied in free or encapsulated forms in polymeric matrices individually. On the other hand, quinine sulphate (QS), which has been accepted as a “quantum yield standard” for the fluorescence spectroscopy due to the excellent emission performance, has also been investigated many times, for different purposes. In this work, we studied excitation and emission behaviour of quinine sulphate–phosphor blends consisting of Ca-α-Sialon:Eu2+/QS and LuAG:Ce3+/QS in polymethyl methacrylate matrix for the first time. The Ca-α-Sialon exhibited approximately 44% increase in the emission intensity when encapsulated along with the Quinine sulphate in the solid state. Similarly, the LuAG:Ce3+ exhibited 98% increased brightness when used in QS containing PMMA matrix. Decay time measurements performed in nanosecond and microsecond time scales supported a potential energy transfer from the QS to the phosphors. The promising results obtained in this study may open a cost-effective way to enhance the optical performance of the both phosphors, which are basic materials for the fabrication of LED bulbs, smartphone and televisions screens, monitors, and panels of other electronic devices.

Research Square (Research Square), Sep 20, 2021

In this work, nanoscale luminescent materials dispersed in the air were collected and quanti ed b... more In this work, nanoscale luminescent materials dispersed in the air were collected and quanti ed by the uorescence spectroscopy. A well-known phosphor; LuAG:Ce 3+ was chosen as the model particle due to its strong, measurable and repeatable signal which can easily be excited by the blue light and emits at yellow wavelengths. The ionic liquid modi ed polymethylmethacrylate based lters were fabricated by electrospinning technique. Samples were collected by means of a vacuum pump from the laboratory environment during the grinding, weighing, transfer, washing, drying and packaging of the phosphorus particles, for different time intervals. The spectro uorometric method was used for the quanti cation of the airborne concentration of the nano and microscale dusts. Presented method was also tested in terms of precision, LOD, LOQ, and stability. To the best of our knowledge, this is the rst attempt to measure the airborne concentrations of the nano-scale luminescent phosphor particles and can easily be adopted for the quanti cation of other nanoscale-emitting particles in workplaces. Additionally, the offered design allows miniaturization since it is possible to excite the particles with cost-effective LED based light sources, integrate the system with ber optics and detect the received optical response by photodiodes.

Journal of Advanced Ceramics, Mar 1, 2017

Monoclinic yttrium tantalate (M′-YTaO 4 , M′-YTO), and two different kinds of yttrium niobium-tan... more Monoclinic yttrium tantalate (M′-YTaO 4 , M′-YTO), and two different kinds of yttrium niobium-tantalate (M′-YTa 0.85 Nb 0.15 O 4 (M′-YTNO) and Eu 3+ doped M′-YTa 0.85 Nb 0.15 O 4 (M′-YTNO:Eu 3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach. Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and thermogravimetry and differential thermal analysis (TG-DTA). Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu 3+ were presented. The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation. Emission intensities were strongly dependent on the host lattice composition and film morphology. 1.5% Eu 3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm. To the best of our knowledge, this is the first attempt in the production of M′-YTO, M′-YTNO, and M′-YTNO:Eu 3+ films on single crystalline Si (100) substrate via sol-gel spin coating.

Dyes and Pigments, Jul 1, 2004

In most of the common designs, pH optodes rely on weak acidic dyes whose dissociated and undissoc... more In most of the common designs, pH optodes rely on weak acidic dyes whose dissociated and undissociated forms have different absorption or emission maximums. In this work the newly synthesized Schiff bases; N,N 0-bis(4-diaminobenzyliden)-1,2-cyclohexandiamine [I], N,N 0-bis(4-diaminobenzyliden)-1,2-ethanediamine [II] and 2,6-bis[(4-dimethylaminophenylimino)ethyl]pyridine [III], have been used for pH sensing in four different plasticized PVC matrices. The Schiff bases exhibited absorption and emission based optical responses to protons in the pH range of 3.0-7.8, and, therefore, can be used as an optical pH sensor for near neutral region of pH scale. The absorption and emission spectra were recorded by preparing thin films on a Mylar polyester support. Responses of the sensor slides were fully reversible within the dynamic range and the response time was approximately 3 min under batch conditions. All of the compositions exhibited a significant absorption based response to pH in immobilized form. Throughout spectroscopic studies, relative signal change of 79% has been achieved for sensor dye (I). In contrast to the weak emission peaks of (I) and (II), the sensor dye (III) exhibited a significant emission based response and is evaluated in a different category.

Journal of Materials Science, Jun 17, 2021

In this study, sol–gel-based erbium (Er3+), terbium (Tb3+) and Er3+: Tb3 co-doped 1393 bioactive ... more In this study, sol–gel-based erbium (Er3+), terbium (Tb3+) and Er3+: Tb3 co-doped 1393 bioactive glass powders and electrospun nanofibers were prepared. Structural and morphological properties of the bioactive glasses as well as the photoluminescence characteristics were investigated in detail. The median particle size and average diameter of the prepared glass powders and fibers were in the range of ~ 1.5–3.5 μm and 280–660 nm, respectively. The steady-state photoluminescence and decay kinetics of the samples were investigated under excitation (374 nm) where only Er3+ and Tb3+ ions close to Si nanoclusters can be excited. All the samples prepared in the study exhibited bright green emission upon excitation at 374 nm. Results showed that the dopant concentration and the sample morphology have significant influence on the photoluminescence and decay properties of the glasses. Sol–gel-derived bioactive glass particles exhibited stronger emission intensity, whereas electrospun nanofibers showed extended decay times. In vitro bioactivity experiments revealed that Er3+ and Tb3+ doping did not inhibit the conversion of the glass samples to hydroxyapatite treated in simulated body fluid for 30 days. It was concluded that Er3+ and Tb3+-containing 1393 bioactive glasses have a potential to be used in tissue engineering applications as well as bioimaging studies.

Journal of Fluorescence, Jan 14, 2017

High oxygen permeable [poly(TMSP)] nanofibers incorporating porphyrin macrocycle as luminescence ... more High oxygen permeable [poly(TMSP)] nanofibers incorporating porphyrin macrocycle as luminescence indicators were prepared by electrospinning technique. The porphyrins involves were modified by i) introducing phenylacetylide substituents on the para position of the phenyl moieties and ii) varying the metal centers [Pt(II) or Pd(II)] of the mesotetrakisphenylporphyrins. A set of nanofibers; (Pt-TPP)NF, (Pd-TPP)NF, (Pt-TPA)NF and (Pd-TPA)NF were obtained to study their structure-activity relationship toward oxygen. The lifetime-based technique was privileged to take advantage of their long-lived phosphorescent properties. A twofold enhancement was observed for (Pt-TPA)NF and (Pd-TPA)NF compared to (Pt-TPP)NF and (Pd-TPP)NF demonstrating the positive effect of the phenylacetylide moieties on the lifetime. Also, Silver nanoparticles were included in nanofibers to investigate their influence on lifetime-based oxygen sensitivity, showing that the presence of AgNPs only affects (Pd-TPA)NF.

Sensors and Actuators B-chemical, Jun 1, 2006

An emission based simple and fast method has been proposed for the determination of gaseous and d... more An emission based simple and fast method has been proposed for the determination of gaseous and dissolved CO 2. Perfluorochemicals (PFCs), also known as medical gas carriers have been used for the first time together with newly synthesized fluorophore; 4-[(p-N,N-dimethylamino)benzylidene]-2-phenyloxazole-5-one (DPO), in ethyl cellulose matrix. In the first stage of the study precise determination of the acidity constant (pK a) of the DPO has been performed in the employed polymer matrix. In second stage, the response of the sensor composition to gaseous and dissolved CO 2 has been evaluated in the absence and presence of the PFC. It should be noted that the solubility of CO 2 in fluorocarbons is about 10-20 times as that observed in the parent hydrocarbons or in water, respectively, and once doped into the sensing film, considerably enhance the response of the sensing agent.

Dyes and Pigments, Apr 1, 2005

4-Arylidene-2-aryl-5-oxazolone (azlactone) structures have wide range of applications arising fro... more 4-Arylidene-2-aryl-5-oxazolone (azlactone) structures have wide range of applications arising from their promising photophysical and photochemical activities. Some of this class of dyes exhibit pH-dependent absorption and emission based response. For this reason, precise determination of the acidity constants (pKa) of the azlactone derivatives is necessary for further studies in different media. In this study, five different azlactone derivatives were chosen

Materials Chemistry and Physics, 2009

Photophysical characteristics and emission based response of tris(2,2-bipyridyl)ruthenium(II)chlo... more Photophysical characteristics and emission based response of tris(2,2-bipyridyl)ruthenium(II)chloride (Ru(bipy) 3 2+) to gaseous oxygen was investigated in ionic liquid modified sol-gel matrix. The ionic liquid; 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4) was used for the first time in acid-catalyzed tetraethyl orthosilicate (TEOS) based sol-gel matrix. Effects of the ionic liquid to the oxygen sensitivity and to surface characteristics were examined. EMIMBF 4 doped sol-gel slides exhibited enhanced O 2 sensitivity, larger Stern-Volmer constants, linear Stern-Volmer plots with respect to classical acid catalyzed sol-gel monoliths and completely crack-free surfaces. The utilization of EMIMBF 4 in sol-gel matrix also caused a red shift of 23 nm in the emission wavelength and an enhanced Stoke's shift value of (Ru(bipy) 3 2+) with respect to ionic liquid free sol-gel composites. The response and regeneration times were 5 and 10 s after exposure to 100% O 2 and 100% N 2 , respectively. The offered composite is only available for gas phase measurements.

Sensors and Actuators B-chemical, Sep 1, 2006

ABSTRACT A new optical CO2 sensor based on the spectrophotometric signal changes of the bromothym... more ABSTRACT A new optical CO2 sensor based on the spectrophotometric signal changes of the bromothymol blue/tetraoctylammonium (BTB−/TOA+) ion pair in room temperature ionic liquids (RTILs) has been proposed. Ionic liquids, also known as green chemistry reagents, have been used for the first time as a matrix material in the optical CO2 sensor design. In the first stage of the study, determination of the acidity constant (pKa) of the modified BTB has been performed in the employed ionic liquids. In the second stage, response of the sensor composition to gaseous and dissolved CO2 has been evaluated. It should be noted that the solubility of CO2 in water miscible ionic liquids is about 10–20 times as that observed in the conventional solvents, polymer matrices or in water and enhance the response of the sensing agent. The detection limits were 1.4% for gaseous, and 10−6M [HCO3−] for dissolved CO2. CO2 can be completely extruded from the ionic liquid by heating, under vacuum or sonification. The regenerated ionic liquid has been used for CO2 sensing without any loss of efficiency.

Talanta, Jul 30, 2008

In this study emission-based ratiometric response of ion pair form of 1-hydroxy-3,6,8-pyrenetrisu... more In this study emission-based ratiometric response of ion pair form of 1-hydroxy-3,6,8-pyrenetrisulfonate (HPTS) to gaseous CO 2 has been evaluated in ionic liquid (IL) containing ethyl cellulose (EC) matrix. The ionic liquid: 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4); provided longer storage time and highly stable microenvironment for the HPTS molecule due to the buffering effect. The utilization of ionic liquid in ethyl cellulose matrix resulted with superior spectral characteristics. The excitation spectra of HPTS exhibited an atypical isoemmissive point in modified EC matrix at 418 nm which allows ratiometric processing of the signal intensities. EMIMBF 4-doped sensor films exhibited enhanced linear working range between 0 and 100% pCO 2. The signal changes were fully reversible and the shelf life of the EMIMBF 4-doped films was extended from 15 to 95 days.

Analytical and Bioanalytical Chemistry, Jul 29, 2006

We describe the characterization of a new optical CO 2 sensor based on the change in the fluoresc... more We describe the characterization of a new optical CO 2 sensor based on the change in the fluorescence signal intensity of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) in green chemistry reagents-roomtemperature ionic liquids (RTILs). As far as we are aware, this is the first time RTILs, 1-methyl-3-butylimidazolium tetrafluoroborate (RTIL-I) and 1-methyl-3-butylimidazolium bromide (RTIL-II), have been used as matrix materials with HPTS in an optical CO 2 sensor. It should be noted that the solubility of CO 2 in water-miscible ionic liquids is approximately 10 to 20 times that in conventional solvents, polymer matrices, or water. The response of the sensor to gaseous and dissolved CO 2 has been evaluated. The luminescence intensity of HPTS at 519 and 521 nm decreased with the increasing concentrations of CO 2 by 90 and 75% in RTIL-I and RTIL-II, respectively. The response times of the sensing reagents were in the range 1-2 min for switching from nitrogen to CO 2 , and 7-10 min for switching from CO 2 to nitrogen. The signal changes were fully reversible and no significant hysteresis was observed during the measurements. The stability of HPTS in RTILs was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.

Talanta, Oct 16, 2002

In recent years squarines received attention as fluorescent labels. Their very promising spectral... more In recent years squarines received attention as fluorescent labels. Their very promising spectral properties such as long wavelength absorption and emission, high extinction coefficients and quantum yields could lead novel sensing technologies. In this work newly synthesized fluoroinophores named bis[4-N-(1-aza-4,7,10,13-tetraoxacyclopentadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-1 and 2 bis[4-N-(1-aza-4,7,10,13,16-pentaoxacyclooctadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-2 have been used for sodium and potassium sensing in plasticized PVC matrix. The squaraine derivatives exhibited fluorescence emission based optical responses to sodium and potassium with a detection limit of 1.10 (9 M. The sensor compositions exhibited wide response ranges between 10 (9 and 10 (5 M Na ' or K ' , and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2 Á/7.3. Throughout fiber optic based studies a relative signal change of 54 Á/56% has been achieved. The azacrown dyes have the advantage that they can be excited with long wavelength light and, are, therefore, LED compatible. The cross sensitivity of azacrown-1 and-2 to Ba 2' , Ca 2' and NH 4 ' were also tested in separate solutions.

Journal of Fluorescence, Mar 27, 2019

Correct measurement of the pH in highly acidic environments is still a challenge. In such conditi... more Correct measurement of the pH in highly acidic environments is still a challenge. In such conditions most of the pH indicators suffer from instability in air or leaching from host matrices due to the solubility considerations. In this work, two different fluorescent probes were used along with silver nanoparticles (AgNPs) and ionic liquid (IL) in the polymeric matrices for sensing of the pH in harsh conditions. The pH sensitivities of the probes were tested after exposure to strong acid vapors by steady-state, lifetime based and kinetic mode measurements. The sensing materials were fabricated in form of thin films and electrospun nanofibers. The ionic liquid; 1-butyl-3-methylimidazolium tetrafluoroborate was exploited as additive to enhance the stability as well as response towards pH. Spectral changes were tested in a large scale; between pH 3.00-12.00. Utilization of the dyes in ethyl cellulose and polymethyl methacrylate along with AgNPs in form of electrospun fibers resulted in many advantages such as enhanced long term stability, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered designs were tested after exposed to vapors of HCl, H 2 SO 4 and HNO 3 , respectively.

Journal of Luminescence, Dec 1, 2015

In this study, pH induced spectral response of the newly synthesized carbazole derivative (9butyl... more In this study, pH induced spectral response of the newly synthesized carbazole derivative (9butyl-bis-3-(4-(dimethylamino) phenyl) allylidene)-9H-carbazole-3,6-diamine) has been declared. We utilized silver nanoparticles (AgNPs) along with ionic liquid as additives for manipulation of the spectral response. Plasticized ethyl cellulose (EC) was used as matrix material. Fibers and porous films were produced by electrospinning technique. The emission intensity at 631 nm has been followed as the analytical signal. Utilization of silver nanoparticles in electrospun polymeric fibers for pH sensing purposes resulted with many 2 advantages such as tuned sensitivity, linear calibration plot for larger pH ranges, increased surface area and enhancement in all sensor dynamics. Additionally, we performed manipulation of the pKa within the same matrix exploiting the silver NPs. Characteristics of the pH induced response for the offered composition was superior with respect to the previously reported ones. When stored at the ambient air of the laboratory there was no significant drift in the signal intensity after 16 months. Our sensitivity and stability tests are still in progress.

Turkish Journal of Chemistry, 2016

Eosin-Y exhibits high affinity and emission based spectral response to most of the major ions in ... more Eosin-Y exhibits high affinity and emission based spectral response to most of the major ions in water samples. In the present study we performed selective spectrofluorimetric analysis of manganese with eosin-Y in the presence of potential interferents. We employed green chemistry reagents, ionic liquids (ILs) and two different micelles, to suppress the effect of conventional cations and anions on the response of eosin-Y. The experimental data revealed that different test moieties caused enhanced analytical response to Mn 2+. The highest analytical signal of eosin-Y was obtained in the presence of Triton X-100 at a concentration of 2.0 × 10 −3 mol L −1. Presence of the green chemistry reagents ILs enhanced the limit of quantification for Mn 2+ 10-fold with respect to the IL-free moieties. The interfering effects of the metal ions of Ca 2+ , Cu 2+ , Hg + , Hg 2+ , As 5+ , Li + , Al 3+ , Cr 3+ , Co 2+ , Ni 2+ , and the anionic groups were completely suppressed in the presence of the ILs and micelles. Additionally, the tolerance limit of Na + and Zn 2+ ions increased 6-fold in the presence of IL and sodium dodecyl sulfate. The presented method did not use any harmful conventional solvents and was employed successfully for the detection of Mn 2+ ions in real water samples.

Spectroscopy Letters, Aug 17, 2010

Photoinduced switch behaviors of two dimethylamino-bearing azometine derivatives (AZM-I and AZM-I... more Photoinduced switch behaviors of two dimethylamino-bearing azometine derivatives (AZM-I and AZM-II) were investigated in conventional solvents, polyvinyl chloride (PVC) and ethyl cellulose (EC) by means of absorption and emission spectroscopy. The fluorescence modulation of the molecular switches arises from increasing response of the exploited molecules to pH between pH = 6.00 and 11.00 in emission intensity at 590 and 582 nm. In the