Amalina M. Afifi

Chitosan/(polyvinyl alcohol)/zeolite electrospun composite nanofibrous membrane for adsorption of Cr(6+), Fe(3+) and Ni(2).

In this study, chitosan/polyvinyl alcohol (PVA)/zeolite nanofibrous composite membrane was fabricated via electrospinning. First, crude chitosan was hydrolyzed with NaOH for 24h. Afterward, hydrolyzed chitosan solution was blended with aqueous PVA solution in different weight ratios. Morphological analysis of chitosan/PVA electrospun nanofiber showed a defect-free nanofiber material with 50:50 weight ratio of chitosan/PVA. Subsequently, 1wt.% of zeolite was added to this blended solution of 50:50 chitosan/PVA. The resulting nanofiber was characterized with field emission scanning electron microscopy, X-Ray diffraction, Fourier transform infrared spectroscopy, swelling test, and adsorption test. Fine, bead-free nanofiber with homogeneous nanofiber was electrospun. The resulting membrane was stable in distilled water, acidic, and basic media in 20 days. Moreover, the adsorption ability of nanofibrous membrane was studied over Cr (VI), Fe (III), and Ni (II) ions using Langmuir isotherm. Kinetic parameters were estimated using the Lagergren first-order, pseudo-second-order, and intraparticle diffusion kinetic models. Kinetic study showed that adsorption rate was high. However, the resulting nanofiber membrane showed less adsorption capacity at high concentration. The adsorption capacity of nanofiber was unaltered after five recycling runs, which indicated the reusability of chitosan/PVA/zeolite nanofibrous membrane. Therefore, chitosan/PVA/zeolite nanofiber can be a useful material for water treatment at moderate concentration of heavy metals.

Synthesis of chitosan/polyvinyl alcohol/zeolite composite for removal of methyl orange, Congo red and chromium(VI) by flocculation/adsorption

A chitosan/polyvinyl alcohol (PVA)/zeolite composite was fabricated in this study. The composite was analyzed through field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, and weight loss test. FTIR and XRD results revealed a strong interaction among chitosan, PVA, and zeolite. Weight loss test results indicated that the composite was stable in acidic and basic media. Congo red was removed through flocculation, and the removal rate was 94% at an initial concentration of 100mg/L for a dose of 1g/L. The removal rate of methyl orange was controlled by adsorption at an initial concentration of less than 100mg/L. Flocculation occurred at high concentrations. The removal rate was also 94% at an initial concentration of 500mg/L for a dose of 5g/L. The adsorption behavior of the composite for the removal of methyl orange and Cr(VI) was described by using a pseudo-second-order kinetic model. The adsorption capacity of the composite for Cr(VI) was 450mg/g. Therefore, the synthesized composite exhibited versatility during the removal of dyes and heavy metals.

Chitosan (PEO)/bioactive glass hybrid nanofibers for bone tissue engineering

A novel hybrid nanofibrous scaffold prepared with chitosan [containing 1.2 wt% polyethylene oxide (PEO)] and bioactive glass (BG) was fabricated by an electrospinning technique. The morphological and physicochemical properties of scaffolds were studied by scanning electron microscopy (SEM) and spectroscopy. The measurements of tensile strength and water-contact angles suggested that the incorporation of BG into the nanofibers improves the mechanical properties and hydrophilicity of the scaffolds. Biomineralization of the nanofibers was evaluated by soaking them in simulated body fluid (SBF), and the formation of hydroxycarbonate apatite (HCA) layer was determined by EDX and FE-SEM. The results showed that BG-containing nanofibers could induce the formation of HCA on the surface of the composite after 14 days of immersion in SBF. In vitro-cell viability of human mesenchymal stromal cells (hMSCs) on nanofibers was assessed by using the MTT assay. The cell-adhesion results showed that hMSCs were viable at variable time points on the chitosan/PEO/BG nanofiber scaffolds. In addition, the presence of BG enhanced the alkaline phosphatase (ALP) activity of hMSCs cultured on composite scaffolds at day 14 compared to that on pure chitosan/PEO scaffolds. Our results suggest that a chitosan/PEO/BG nanofibrous composite could be a potential candidate for application in tissue engineering.

Adsorption and photocatalytic degradation of anionic dyes on Chitosan/PVA/Na-Titanate/TiO2 composites synthesized by solution casting method.

Chitosan/PVA/Na-titanate/TiO2 composite was synthesized by solution casting method. The composite was analyzed via Fourier Transform Infrared Spectroscopy, X-ray diffraction, Field Emission Scanning Electron Microscopy, Thermal gravimetric analysis and water stability test. Incorporation of Na-titanate shown decrease of crystallinity for chitosan but increase water stability. However, the composite structure was deteriorated with considerable weight loss in acidic medium. Two anionic dyes, methyl orange and congo red were used for the adsorption test. The adsorption behavior of the composites were described by pseudo-second-order kinetic model and Lagergren-first-order model for methyl orange and congo red, respectively. For methyl orange, adsorption was started with a promising decolorization rate. 99.9% of methyl orange dye was removed by the composite having higher weightage of chitosan and crystalline TiO2 phase. On the other hand, for the congo red the composite having higher chitosan and Na-titanate showed an efficient removal capacity of 95.76%. UV-vis results showed that the molecular backbone of methyl orange and congo red was almost destroyed when equilibrium was obtained, and the decolorization rate was reaching 100%. Kinetic study results showed that the photocatalytic degradation of methyl orange and congo red could be explained by Langmuir-Hinshelwood model. Thus, chitosan/PVA/Na-titanate/TiO2 possesses efficient adsorptivity and photocatalytic property for dye degradation.

Fabrication and in vitro biological activity of βTCP-Chitosan-Fucoidan composite for bone tissue engineering

We developed tricalcium phosphate-chitosan-fucoidan biocomposite scaffold (TCP-Ch-Fu) by using the freeze-drying technique. The fabricated biocomposite scaffolds were analyzed by spectroscopy and porosity measurement. The biomechanical properties of scaffolds were assessed by compression test and the results suggested that the incorporation of Fucoidan into the biocomposite improves the compression strength of scaffolds. Biomineralization of scaffolds was evaluated by soaking them in simulated body fluid and the results revealed that the addition of Fucoidan into the scaffolds enhanced the formation of apatite layer on the surface of biocomposite after 7 days of immersion. Alamar Blue assay confirmed that the cell viability of human-derived bone marrow stromal cell was superior in the TCP-Ch-Fuscaffold. The addition of Fucoidan to TCP-Ch increased the release of osteocalcin, confirming that it can support osteogenic differentiation of human mesenchymal stromal cells in in vitro culture. Thus, TCP-Ch-Fu could be a potential candidate for bone-tissue engineering applications.

Electrospinning of polymethyl methacrylate nanofibers: optimization of processing parameters using the Taguchi design of experiments

The effects of polymer concentration and electrospinning parameters on the diameter of electrospun polymethyl methacrylate (PMMA) fibers were experimentally investigated. It was also studied how the controlled factors would affect the output with the intention of finding the optimal electrospinning settings in order to obtain the smallest PMMA fiber diameter. Subsequently the solution feed rate, needle gauge diameter, supply voltage, polymer concentration and tip-to-collector distance were considered as the control factors. To achieve these aims, Taguchi’s mixed-level parameter design (L18) was employed for the experimental design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio that was calculated from the electrospun PMMA fiber diameter according to “the-smaller-the-better” approach. Accordingly, the smallest fiber diameter observed was 228 (±76) nm and it was yielded at 15 wt% polymer concentration, 20 kV of supply voltage, 1 ml/h feed rate, 15 cm tip-to-distance and 19 needle gauge. Moreover, the S/N ratio response showed that the polymer concentration was the most effective parameter on determination of fiber diameter followed by feed rate, tip-to distance, needle gauge and voltage, respectively. The Taguchi design of experiments method has been found to be an effective approach to statistically optimize the critical parameters used in electrospinning so as to effectively tailor the resulting electrospun fiber diameters and morphology.

Effect of deacetylation on property of electrospun chitosan/PVA nanofibrous membrane and removal of methyl orange, Fe(III) and Cr(VI) ions

In this study, effect of degree of deacetylation on property and adsorption capacity of chitosan/polyvinyl Alcohol electrospun membrane has been investigated. Resulting nanofibers were characterized by FESEM, FTIR, XRD, TGA, tensile testing, weight loss test and adsorption test. FESEM result shows, finer nanofiber was fabricated from 42h hydrolyzed chitosan and PVA blend solution. FTIR and XRD result showed a strong interaction between chitosan and polyvinyl alcohol. Higher tensile strength was observed for the nanofiber having 42h hydrolyzed chitosan. Blend solution of chitosan/PVA having low DD chitosan had higher viscosity. The nanofibrous membrane was stable in distilled water, acidic and basic medium. The isotherm study shows that the adsorption capacity (qm) of nanofiber containing higher DD chitosan was higher for Cr(VI). In contrary, the membrane containing chitosan with lower DD showed the higher adsorption capacity for Fe(III) and methyl orange. Moreover, the effect of DD on removal percentage of adsorbate was dependent on the initial concentration of the adsorbate.

Fabrication and characterisation of chitosan/ poly vinyl alcohol nanofibres via electrospinning

Abstract In this study, chitosan nanofibres were fabricated using electrospinning process. Initially, chitosan powders were further deacetylated with sodium hydroxide to deprotonate the polymer chains and decrease the molecular weight. Subsequently, the treated chitosan (5 wt-% in 90:10 acetic acid/water ratio) were mixed with poly vinyl alcohol (8 wt-% in water) at different ratios in order to facilitate the electrospinning through cross-links formation. Field-emission scanning electron microscopic images showed that 60:40 (chitosan/poly vinyl alcohol) ratio was the threshold for formation of beads (chitosan/poly vinyl alcohol >50:50 contains imperfections) and that increasing chitosan/poly vinyl alcohol ratio from 20:80 to 60:40 decreased the average diameter of fibres from 80 to 40 nm. Fourier transform infrared spectra proved the formation of chitosan/poly vinyl alcohol cross-linked nanofibres.

Ionic liquid entrapment by an electrospun polymer nanofiber matrix as a high conductivity polymer electrolyte

Through external doping, novel conductive polymer nanofibers were successfully fabricated using ionic liquids. In this study, a polymer blend of polyvinyl alcohol (PVA) and chitosan (CS) in a 4 : 1 weight ratio was fabricated in the form of nanofibers through electrospinning and used as a scaffold membrane to capture room-temperature ionic liquids (RTILs), such as 1-ethyl-3-methylimidazolium chloride (EMIMCl) and 1-butyl-3-methylimidazolium bromide (BMIMBr). Morphological analysis using scanning electron microscopy (SEM) showed that the scaffold structure of the electrospun membrane facilitated sufficient trapping of RTILs. This membrane demonstrated significantly increased conductivity from 6 × 10−6 S cm−1 to 0.10 S cm−1, interestingly surpassing the value of pure ionic liquids, where the polymer chain breathing model has been suggested as a hypothesis to explain this phenomena. The dominance of ions as charge carriers was explained using an ionic transference number measurement. The interaction between the polymer nanofiber matrix and an ionic liquid has been explained using Fourier-transform infrared spectroscopy (FTIR), where the ionic liquid was found to be physically dispersed in the polymer nanofiber matrix. These materials have also shown some thermoelectric (TE) activity, by demonstrating Seebeck coefficients up to 17.92 μV K−1. The existence of freely movable ions in this type of membrane shows their applications as energy storage/conversion devices such as organic thermoelectrics (TEs), sensors, and dye-sensitised solar cells.

Preparation and characterisation of electrospun silica nanofibres

Abstract In this study, the silica electrospun nanofibres were fabricated using silica sol containing tetraethylorthosilicate, polyvinylpyrrolidone and butanol (solvent). The perfect concentration for silica sol to undergo the electrospinning was found to be 0·095 gr(pvp)/mL (butanol, tetraethyl orthosilicate), where the tetraethyl orthosilicate/butanol volume ratio was 3:2. Later with the intention of achieving the silica nanofibres, the electrospun samples afterwards were put in a furnace at 700°C for 3 hours. After that the morphological studies on the fibres before and after the thermal treatment were done employing the scanning electron microscopy. The results showed that fibre diameter before thermal treatment fits the micrometre scale, while it decreases dramatically to the 260–360 nm range when it goes through the thermal stage. Furthermore, Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy spectrums proved that polyvinylpyrrolidone and butanol were removed from the fibres after calcination and that the silica nanofibres were fabricated.