Emine Akar

Preparation of pH- and ionic-strength responsive biodegradable fumaric acid crosslinked carboxymethyl cellulose

A novel biodegradable sodium carboxymethyl cellulose (NaCMC)-based hydrogel was synthesized by using fumaric acid (FA) as a crosslinking agent at various ratios. Hydrogels (CMCF) were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Swelling behaviors of hydrogels were investigated in distilled water, various salt, and pH solutions. The FTIR results indicated the crosslinking between carboxyl groups of FA with hydroxyl group of NaCMC through ester formation. AFM analyses showed that roughness of hydrogel surface decreased with increasing crosslinker concentration. The swelling capacity decreased with an increase in charge of the metal cation (Al(3+)<Ca(2+)<Na(+)). In order to investigate reversible pH sensitivity of CMCF hydrogels, pH-dependent swelling was studied at pH 2 and 10. Reversible pH-responsiveness of CMCF hydrogels was achieved. CMCF hydrogels containing the greatest ratio of FA exhibited the longest biodegradation time with a half life of 21 h using cellulase.

Application of carboxymethylcellulose hydrogel based silver nanocomposites on cotton fabrics for antibacterial property

In this study, fumaric acid (FA) crosslinked carboxymethylcellulose (CMC) hydrogel (CMCF) based silver nanocomposites were coated on cotton fabric for antibacterial property for the first time. The performance of the nanocomposite treated cotton fabric was tested for different mixing times of hydrogel solution, padding times and concentrations of silver. The cotton fabrics treated with CMC hydrogel based silver nanocomposites demonstrated 99.9% reduction for both Staphylococcus aureus (Sa) and Klebsiella pneumonia (Kp). After one cycle washing processes of treated cotton fabric, there is no significant variation observed in antibacterial activity. From SEM and AFM analyses, silver particles in nano-size, homogenously distributed, were observed. The treated samples were also evaluated by tensile strength, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) analysis, fluid absorbency properties, and whiteness index. The treatment of cotton fabric with CMCF hydrogel did not affect the whiteness considerably, but increased the absorbency values of cotton.

Evaluating of Agave americana fibers for biosorption of dye from aqueous solution

Fibers extracted from Agave americana were evaluated as a low cost sorbent for the removal of Malachite Green (MG) from aqueous solution. Agave fiber was characterized by using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and determining chemical content such as cellulose and hemicellulose. The crystallinity index and average size of crystals of agave fibers were obtained to be 53.29 % and 1.4 nm, respectively. The effects of temperature, amount of sorbent and ionic strength on biosorption behavior were investigated. By using Langmuir, Freundlich, and Dubinin-Radushkevich equations, equilibrium biosorption data were analyzed. Based on R2 values, the best fit was provided with Langmuir isotherm. The results showed that the largest biosorption capacity was obtained as 33 mg g−1 at 318 K. According to the thermodynamic studies, biosorption was determined to be endothermic and spontaneous in nature. Biosorption kinetics was investigated by equations such as Elovich rate equations, intraparticle diffusion models, pseudo-second-order, and pseudo-first-order models.

Electromechanical characterization of multilayer graphene-reinforced cellulose composite containing 1-ethyl-3-methylimidazolium diethylphosphonate ionic liquid

Abstract In this study, multilayer graphene (Gr)-reinforced cellulose composites were synthesized by using 1-ethyl-3-methylimidazolium diethylphosphonate ionic liquid. The composites were fabricated via dissolving the cellulose in 1-ethyl-3-methylimidazolium diethylphosphonate and Gr loading at different ratios (0.2, 0.4, and 0.6 wt.%). Both sides of the composites were coated with gold leaf to generate electrodes. The effect of Gr loading on chemical functional groups, crystallographic properties, thermal stability, and morphological and mechanical properties of cellulose film was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and tensile test, respectively. Electromechanical behavior of the cellulose composite films reinforced with Gr (0.2, 0.4, and 0.6 wt.%) was investigated under DC excitation voltages of 1, 3, 5 and 7 V. Gr loading of 0.2 wt.% increased maximum tip displacement by 400% when the actuator is excited with 3 V.

Investigation of the effects of PWM parameters on ionic polymer metal composite actuators

The effects of the PWM excitation signal parameters, such as frequency and magnitude, on the Nafion-based ionic polymer metal composite (IPMC) actuator response were found out. The first set of experiments was designed to observe the actuator response when the actuators were biased with constant DC voltages. These experimental results were exploited to build an experimental data based dynamic model. The model and these results were also used as references to evaluate the experimental results in the proceeding experiments. The second set of experiments was designed to observe the actuator response when the DC square wave signals at different frequencies (0 to 1000 Hz) were applied. The third set of experiments was designed to observe the actuator response when the PWM signals at different magnitudes (6, 8 and 10 V) were applied. It is observed that back relaxation reduces with increasing frequency, but after a certain frequency value, it remains approximately constant. It is seen that the input output relationship of the actuators are linear only for a range of PWM signal magnitudes. The observations in both the PWM frequency and the magnitude experiments indicated that the performance of the Nafion-based IPMC actuator could be improved by selecting a magnitude of PWM signals between 6–8 Volts and by selecting a frequency between 400–1000 Hz.

Development of a traceable molecular hygiene control method (TMHCM) for human DNA content in foods.

The aim of this study was to develop a molecular technique to determine the level of human originated DNA contamination in unhygienic food products. In the study, four model foods were prepared under both hygienic (H) and non-hygienic (NH) conditions and the human originated microbial loads of these products were determined. DNA was extracted from the model foods and human buccal samples by GIDAGEN Multi-fast DNA isolation kit. A primer specific region of human mitochondrial D-Loop was designed. The level of human DNA contamination in the model foods was determined by real-time PCR. The sensitivity of the technique developed here was 0.00001ng DNA/PCR. In addition, the applicability of the traceable molecular hygiene control method (TMHCM) was tested in 60 food samples from the market. The results of this study demonstrate that DNA based TMHCM can be used to predict to what extent foods meet the human oriented hygienic conditions.