Serhat Koçyiğit

Synthesis and Characterization of Poly(vinyl alcohol)/Poly(vinyl pyrrolidone)-Iodine Nanofibers with Poloxamer 188 and Chitosan

This study focuses on the fabrication of poly(vinyl alcohol)/ poly(vinyl pyrrolidone)-Iodine nanofibers via electrospinning. Electrospun fibers were characterized by FT-IR, DSC and SEM techniques. DSC results indicated that the thermal stability of nanofibers were improved after the addition of chitosan and poloxamer 188. SEM images showed that the spongiform structure is much more compact and fibrous in the case of added chitosan, with an average fiber diameter of 374 nm, whereas the addition of poloxamer 188 resulted in a more porous and beaded composition, with average fiber diameter of 489 nm.

PVA/PAA-Based Antibacterial Wound Dressing Material with Aloe Vera

The incorporation of drugs into the dressings make these dressings antimicrobial and help in control of infection around the wound. The wound dressing materials based on PVA/PAA, ciprofloxacin HCl, and aloe vera have been designed and developed so that the wound undergoes proper healing and scar formation is minimal. These wound dressing materials are produced using the electrospinning method. The wound dressing materials are characterized using the FT-IR, DSC, DTA, TGA, and SEM techniques. The wound dressing materials are tested for microbial activity tests and drug release experiments. Controlled ciprofloxacin HCl release is observed.

Preparation and Characterization of Polyvinyl Alcohol Based Copolymers as Wound Dressing Fibers

Biocompatible polyvinyl alcohol/polyethylene glycol and polyvinyl alcohol/polypropylene glycol copolymer mats were prepared by electrospinning. The composite fiber mats were subjected to detailed physical analysis complemented by scanning electron microscopy and Fourier transformations infrared spectroscopy. Scanning electron microscopy images showed that the morphology and diameters of the fibers were mainly affected by the types of polymers and their copolymer compositions. Microbial culture results showed that among the tested fibrous mats polyvinyl alcohol/50% polyethylene glycol gave the best results in preventing the cell attachment and proliferation. This novel electrospun matrix would be used as potential wound dressing material for skin regeneration. GRAPHICAL ABSTRACT

On double exponential forward bias current-voltage (I–V) characteristics of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures in temperature range of 80–340 K

Current transport mechanisms (CTMs) of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures were investigated using current–voltage (I–V) characteristics in the temperature range of 80–340 K. Semilogarithmic I–V plots show two linear regions corresponding to low (0.075–0.250 V) and moderate (0.27–0.70 V) biases, respectively. Zero-bias barrier height (ΦB0) was observed to increase with increase in the temperature, whereas opposite behaviour was observed for ideality factor (n). ΦB0 and (n−1–1) vesus q/2kT and ΦB0 versus n plots were drawn to get an evidence of Gaussian distribution (GD) of the barrier heights. These plots, too, show two linear regions corresponding to low (80–160 K) and high (200–340 K) temperature ranges (LTR and HTR), respectively. Mean value of barrier height (B0) and standard deviation (σs) were extracted from the intercept and slope of ΦB0 versus q/2kT plots for two linear regions as 0.382 eV, 0.0060 V for LTR and 0.850 eV, 0.135 V for HTR at low biases and 0.364 eV, 0.0059 V for LTR and 0.806 eV, 0.132 V for HTR at high biases, respectively. B0 and Richardson constant (A*) values were also obtained from the intercept and slope of the modified Richardson (Ln(Io/T2)−(q2σs2/2k2T2) versus q/kT) plots as 131.81 Acm−2 K−2, 0.381 eV for LTR and 129.35 Acm−2 K−2, 0. 854 eV for HTR at low biases and 148.01 Acm−2 K−2, 0.377 eV for LTR and 143.77 Acm−2 K−2, 0.812 eV for HTR at high biases, respectively. In conclusion, CTM in the structure can be successfully explained in terms of thermionic emission theory with the double GD of barrier heights.

Synthesis and Characterization of PVA/Calix[4]arene Fibers

In this study, both boron-doped and -undoped poly(vinyl alcohol)/Calix[4]arene fibers were prepared by using an electrospinning technique. Obtained fibers were characterized by FT-IR, DSC, and SEM techniques. The DSC results show that the degradation of the boron-doped fibers started at much higher temperatures. This result indicates the addition of boron increased the thermal stability of the fibers. SEM pictures show that both of the fiber samples are nonbeaded with diameters ranging from 0.5 to 1 µm. The fiber diameters are not homogeneous and uniformly distributed for boron-undoped samples.

Fabrication and characterisation of boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic composite

Abstract In this paper, the fabrication and characterisation processes of both boron doped and undoped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders using polymeric precursor were reported. Obtained boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders, which have been synthesised by polymeric precursor technique at temperatures below 900°C and at atmospheric condition, were characterised by X-ray diffraction, Fourier transform infrared and scanning electron microscopy techniques. According to X-ray results, fcc and bcc phases coexist in the samples of the nanocrystalline ceramic powders. Crystallite sizes for body centred cubic structure were calculated using Scherrer equation for both boron doped and undoped samples. In addition, lattice parameters were calculated for all samples.

Thermoelectric Properties of Nickel and Boron Co-Substituted NaCo2O4 Prepared by Electrospinning Technique

In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0≤x≤0.3, 0≤y≤0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15–300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25×10-5, 5.3×10-6, 8.6×10-5 and 9×10-6 for sintered powders from undoped, Ni and B doped powders, respectively.