Aysegul Uygun Oksuz

Electrospun chitosan/PEDOT nanofibers.

Plasma-modified chitosan and poly(3,4-ethylenedioxythiophene) were blended to obtain conducting nanofibers with polyvinyl alcohol as a supporting polymer at various volumetric ratios by electrospinning method. Chemical compositions and molecular interactions among nanofiber blend components were determined using Fourier transform infrared spectroscopy (FTIR). The conducting blends containing plasma-modified chitosan resulted in a superior antibacterial activity and thinner fiber formation than those containing chitosan without plasma-modification. The obtained nanofiber diameters of plasma-modified chitosan were in the range of 170 to 200 nm and those obtained from unmodified chitosan were in the range of 190 to 246 nm. The electrical and electrochemical properties of nanofibers were also investigated by four-point probe conductivity and cyclic voltammetry measurements.

Poly(3,4-ethylenedioxythiophene) coated chitosan modified disposable electrodes for DNA and DNA-drug interaction sensing.

The need for sensitive, selective, rapid and low-cost detection systems for DNA and DNA-drug interactions are in crucial demand for diagnostics and real-world applications. This work details the preparation of poly(3,4-ethylenedioxythiophene) (PEDOT) coated chitosan (CHIT) and the use of PEDOT coated CHIT modified disposable pencil graphite electrodes (PGEs) for DNA and DNA-anticancer drug interaction sensing. PEDOT coated CHIT (PEDOT/CHIT) was prepared with rotating plasma polymerization using radio frequency (RF: 13.56 MHz) power generator. Then, modification of PEDOT/CHIT onto PGE was performed. The use of the prepared electrode was carried out using differential pulse voltammetry (DPV). Cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the PEDOT/CHIT/PGE. The performance of the electrode was compared with CHIT/PGE and unmodified PGE. The electrode exhibited high sensitivity for the investigation of DNA sensing and DNA-anticancer drug interaction. Such disposable sensing platform hold considerable promise for diverse bioapplications.

Highly conductive polymer materials based multi-walled carbon nanotubes as counter electrodes for dye-sensitized solar cells

ABSTRACT Poly(3,4-ethylenedioxxythiophene) (PEDOT), polyaniline (PANI) and polythiophene (PTh) based multi-walled carbon nanotube (MWCNT) composites were successfully prepared using RF-rotating plasma grafting method. Morphological characterizations of composites were determined using scanning electron microscopy (SEM), which showed that conducting polymers (CPs) of PEDOT, PANI and PTh were coated on the surface of CNTs. The surface properties of the Carbon Nanotube (CNT) composites were also determined by using Infrared Spectra (FT-IR), X-ray Photon Spectra (XPS), and Scanning Electron Microscopy-Energy Dispersive X-ray Spectra (SEM-EDX) analysis. X-ray photon spectra results confirmed the formation of the composites. Composites of MWCNT were used in dye-sensitized solar cells (DSSCs) as counter electrodes and exhibited short-circuit photocurrent densities of 11.19, 10.70 and 8.54 mA/cm2 for PANI/MWCNT, PTh/MWCNT and PEDOT/CNT, respectively. GRAPHICAL ABSTRACT

Complementary all Solid State Electrochromic Devices Using Carboxymethyl Cellulose Based Electrolytes

The paper presents the results of the research on a new polymer-membrane and gel electrolytes for electrochromic devices. A complementary solid-state electrochromic device consisting of cathodically coloring working electrode of WO3 and anodically coloring counter electrode of NiO films is prepared to compare the effects of gel or membrane forms of carboxymethyl cellulose (CMC) polymer electrolyte on the electrochromic properties of devices. The performance evaluations of the complementary solid-state electrochromic devices indicate good reversibility, low power consumption of ±3 V in colored state, high variation of transmittance changing of 64% in gel electrolyte, and lower 7% in membrane electrolyte and good memory effect under open-circuit conditions. CMC based electrolytes can be used as an ion-conducting medium and be a good candidate for complementary electrochromic devices owing to, the improved properties as well as its cheapness.

Biosensing applications of titanium dioxide coated graphene modified disposable electrodes.

In the present work, preparation of titanium dioxide coated graphene (TiO2/graphene) and the use of this nanocomposite modified electrode for electrochemical biosensing applications were detailed. The nanocomposite was prepared with radio frequency (rf) rotating plasma method which serves homogeneous distribution of TiO2 onto graphene. TiO2/graphene was characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Then, this nanocomposite was dissolved in phosphate buffer solution (pH 7.4) and modified onto disposable pencil graphite electrode (PGE) by dip coating for the investigation of the biosensing properties of the prepared electrode. TiO2/graphene modified PGE was characterized with SEM, EDS and cyclic voltammetry (CV). The sensor properties of the obtained surface were examined for DNA and DNA-drug interaction. The detection limit was calculated as 1.25mgL(-1) (n=3) for double-stranded DNA (dsDNA). RSD% was calculated as 2.4% for three successive determinations at 5mgL(-1) dsDNA concentration. Enhanced results were obtained compared to the ones obtained with graphene and unmodified (bare) electrodes.

RF sputtered electrochromic wool textile in different liquid media

A flexible e-textile has growing curiosity in the NEMS and MEMS of science and technology. This work has been done fabrication of electrochromic device based on wool textile substrates. Indium tin oxide (ITO) or platinum (Pt) and tungsten oxide WO3 film layers were used as conductive and the electrochromic material, respectively. All active layers were coated onto the wool textile surface by using Radio Frequency (RF) magnetron sputtering technique. The surface morphologies of all samples were investigated by using Scanning Electron Microscopy/Energy-dispersive X-ray spectroscopy (SEM/EDX) analysis. Characteristic properties of electrochromic electrodes were compared for two type electrolyte systems including Li+ cation source effect lithium perchlorate/Propylene Carbonate (LiClO4/PC) and lithium trifluoromethane sulfonate/Propylene Carbonate (LiTRIF/PC). Promising experimental results were obtained.

QCM-DNA biosensor based on plasma modified PT/TiO2 nanocomposites

ABSTRACT A quartz crystal microbalance DNA biosensor based on plasma prepared polythiophene /titanium dioxide (PT/TiO2) nanocomposite was developed for the detection of genetically modified organisms (GMOs). DNA hybridization was studied by quartz crystal microbalance (QCM) and cyclic voltammetry (CV) measurements. Single stranded DNA probes were immobilized on the PT/TiO2 coated quartz crystal electrode and the hybridization between the immobilized probe and the target complementary sequence in solution was monitored. The developed QCM-DNA biosensor represented promising results for a real-time, label-free, direct detection of DNA samples for the screening of genetically modified organisms.

Chemical synthesis and characterization of poly(3,4-ethylenedioxythiophene)/tungsten composite materials in the presence of ionic liquids

Abstract Poly(3,4-ethylenedioxythiophene)/tungsten (PEDOT/W) composites were prepared by an in situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene in different ionic liquids; 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl- 3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI). These polymer/metal hybrids (PEDOT/W) were subsequently characterized for their structural, crystalline, thermal and morphological properties by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The significant enhancement in properties can be attributed to the nanoscale particle size and uniform size distribution of PEDOT/W and the synergistic effect between the inorganic nano-W and organic PEDOT material.

Controlled Release of Ibuprofen From Electrospun Biocompatible Nanofibers With In Situ QCM Measurements

A series of drug-incorporating electrospun biocompatible nanofibers were fabricated by using the electrospinning process. A hydrophobic drug (ibuprofen, IBU) was directly dissolved with biopolymer systems such as polyvinyl alcohol/plasma modified chitosan (PVA/PMCh), polyvinyl alcohol/chitosan (PVA/Ch) and cellulose acetate (CA) into an organic solvent prior to electrospinning. The release of IBU from drug-loaded electrospun fibers was monitored using a quartz crystal microbalance (QCM). The results were compared with utilizing UV/Vis spectroscopy results. The biocompatible fibers were Fourier transform infrared spectroscopy (FTIR). The IBU-loaded PVA/Ch and PVA/PMCh fibers demonstrated more effective and uniform release profiles than the IBU–loaded CA fibers.

Poly(vinylferrocene)/Cellulose Acetate Fibers: A New Approach for In-Situ Monitoring Process Through QCM and Electrospinning Studies

A poly(vinylferrocene) (PVFc)/cellulose acetate (CA) fibers were obtained using an electrospinning method. The electrospinning process was controlled in situ with a quartz crystal microbalance (QCM) system. Fiber formation was observed through adjusting PVFc concentration. Morphological characteristics depending on the changes of atomic % ratio value of PVFc/CA electrospun fibers was investigated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis. Electrochemical behavior of PVFc/CA electrospun fibers was investigated by using cyclic voltammetry measurements based on the Fc+/Fc redox couple. The results indicated that PVFc deployed in/on the CA fibers and aggregated arbitrarily on the QCM electrode. The new PVFc/CA electrospun fibers were used for anion sensing.