Melek Kiristi

RF hydrazine plasma modification of chitosan for antibacterial activity and nanofiber applications

Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66Pa) with 13.56MHz frequency at a power of 100W for 30min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436cm(-1) that confirmed increasing functional groups based on H-bonding. The number of NH(2) groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.

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.

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.

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.

A Comparison Study of Microwave and Radio Frequency Plasma Polymerized PEDOT Thin Films

PEDOT films were deposited by microwave (MW) and radio frequency (RF) plasma in a medium pressure of 0.02 Torr without precursor. In-situ optical emission spectroscopy (OES) measurement was carried out to determine plasma phase and to adjust discharge parameters. The other spectroscopic methods were used to characterize deposited thin films and to compare the effect of discharge parameters on the process. Conductivity values were found to be around up to 10−5 S/cm for MW plasma, and 10−8 S/cm for RF plasma deposited PEDOT films, without the addition of a doping agent. It was found that both plasma polymerization methods resulted in crosslinked PEDOT structures.

Platinum-free counter electrodes of plasma-modified hybrid nanomaterials for dye-sensitised solar cells

ABSTRACT Molybdenum disulphide (MoS2) nanotube and tungsten oxide (W18O49) nanowire were coated with poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene) (PEDOT) by a radio frequency (RF: 13.56 MHz)-rotating plasma-modification method as alternative counter electrodes for dye-sensitised solar cells (DSSCs). Surface analysis showed the homogenous plasma nanocoating of inorganic nanostructures by P3HT and PEDOT. It was demonstrated that the plasma-modified hybrid platinum-free counter electrodes increased the efficiencies of the DSSCs. The DSSCs based on hybrid nanostructure materials showed a short circuit current density of 9.49, 7.95, 2.59 and 2.57 mAcm−2 for MoS2/P3HT, MoS2/PEDOT, W18O49/PEDOT and W18O49/P3HT samples, respectively. The plasma nanocoating with the nanostructured materials approach for obtaining hybrid counter electrodes in the photovoltaic action shows an alternative route towards cost-effective, green energy conversion.

Surface properties of radio frequency plasma treated wool and denim fabrics

Purpose The purpose of this paper was to investigate the effects of hydrochloric acid (HCl), hydrazine, methyl methacrylate, styrene and hexamethyldisiloxane by radio-frequency (rf) plasma graftings on surface properties of wool and denim fabrics. Design/methodology/approach During plasma treatments, processing time was varied under optimized plasma conditions (50 W, rf: 13.56 MHz). All fabrics were comprehensively investigated by means of scanning electron microscopy-energy dispersive X-ray spectroscopy and contact angle measurements. Findings The experimental data shows that the rf-plasma processing has important effect on the wettability properties of wool and denim fabrics. The results indicated that HCl plasma treatment significantly improves the hydrophilicity of wool and denim fabrics. Originality/value The research on wool and denim fabric treatment by plasma is original.

Improving photovoltaic efficiency by RF rotating plasma modified nanotubes

Lower energy efficiency and higher cost are main challenges of current photovoltaics (PVs) and limit their using in widespread area. Nanostructure hybrid PVs that combined organic and inorganic nanoparticles, showed excellent performance with the intent of incorporating the advantages nano-scale materials1,2.

Atmospheric pen plasma sterilizing help paper surface

Cleaning process applied to microorganisms on any substance is called as sterilization. This process can be applied with different methods such as chemical (EtO), filtration (gases, liquids), temperature sterilizations etc. However, these methods have some drawbacks. Plasma sterilization is one of the rapidly developing technique in the study of disinfection because of its cheap, healthy and useful method. In this study, He aid-atmospheric plasma sterilizing is applied onto paper surface. We studied the use of non thermal helium plasma for sterilization of S. aureus and P. aeruginosa cells when applied the filter paper. The bacterial survival was evaluated in terms of the number of colony-forming units on agar plates. All of the S. aureus and P. aeruginosa cells (106 CFU/mL) are sterilized by helium plasma treatment for 5 minutes.