Ahmad Kusumaatmaja

Electrospun Nanofibers Based on Polyvinyl Alcohol/Chitosan and its Stability in KOH Solution

Fabrication of nanofibers based on polyvinyl alcohol and chitosan (PVA/chitosan) has been carried out by means of electrospinning with focusing on beads formation and diameter variation due to effects of weight ratio variations of PVA/chitosan. For electrospinning solution, the PVA/chitosan with artios of 10:1, 10:2 and 10:3 w/w were dissolved in 1% acetic acid. In addition, stability testing of PVA/chitosan nanofibers in an electrolyte solution was performed by soaking the nanofiber mat in KOH solution. As results, the addition of chitosan concentration increased the pH, conductivity, and viscosity of the solution. Beads were potentially generated for low chitosan concentration. Furthermore, the effect of viscosity and conductivity on diameter of electrospun nanofibers is very significant and need to be optimized. The average diameter of electrospun nanofibers were found to be 160 ± 18 nm, 120 ± 12 nm, and 148 ± 26 nm, for weight ratios of PVA and chitosan 10:1, 10:2 and 10:3, respectively. In addition, no significant change in morphology after being soaked the electrospun PVA/chitosan nanofibers in KOH 40 wt% solution for 24 hours. It indicates that the electrospun PVA/chitosan nanofibers is stable in electrolyte solution which shows a high potential for electrolyte membrane in fuel cells application.

Solvent vapor treatment improves mechanical strength of electrospun polyvinyl alcohol nanofibers

Electrospun nanofibers of polyvinyl alcohol (PVA) have poor mechanical strength. As such their use has often been avoided, particularly in applications that require high mechanical properties. The objective of this study is to increase the mechanical properties of PVA nanofiber mats via physical crosslinking with solvent vapor treatment using organic solvents, dimethyl sulfoxide (DMSO), N, N-dimethyl formamide (DMF), and methanol. The effect of solvent vapor treatment on PVA nanofibers is clearly observed by scanning electron microscope (SEM). The tensile strength increased by over 60%, 90%, and 115% after solvent vapor treatment with DMF at a temperature of 40 °C for 2 h, 4 h, and 8 h, respectively, compared to untreated PVA nanofibers. In addition, Youngs modulus of PVA nanofiber mats also increased after DMF treatment. As a comparison, DMSO and methanol were also used in solvent vapor treatment because of differences in their polymer-solvent affinity. Results showed that the highest improvement (100%) in mechanical strength was obtained using DMF. This study shows that solvent vapor treatment offers a simple and inexpensive method that provides excellent results and is a promising alternative treatment for use in increasing the mechanical properties of electrospun nanofibers.

Application of polyvinyl alcohol nanofiber membrane for smoke filtration

Polyvinyl alcohol (PVA) nanofiber have been prepared by an electrospinning method and applied as a smoke filter. Three sources of smoke were used to investigate the filtration efficiency of PVA membrane qualitatively by observing the morphology of PVA membrane after filtration. Filtration test was done by designing a special device to obtain the gas before and after filtration. The results show that PVA nanofiber was promising as a smoke filter that could be observed from the morphology of nanofiber after filtration. Almost all small particles from smoke are inhibited on the PVA membrane not only caused by porous properties but also the adsorbent properties of the membrane.

Polyacrylonitrile Nanofiber-Based Quartz Crystal Microbalance for Sensitive Detection of Safrole

Safrole is the main precursor for producing the amphetamine-type stimulant (ATS) drug, N-methyl-3,4-methylenedioxyamphetamine (MDMA), also known as ecstasy. We devise a polyacrylonitrile (PAN) nanofiber-based quartz crystal microbalance (QCM) for detecting safrole. The PAN nanofibers were fabricated by direct electrospinning to modify the QCM chips. The PAN nanofiber on the QCM chips has a diameter of 240 ± 10 nm. The sensing of safrole by QCM modified with PAN nanofiber shows good reversibility and an apparent sensitivity of 4.6 Hz·L/mg. The proposed method is simple, inexpensive, and convenient for detecting safrole, and can be an alternative to conventional instrumental analytical methods for general volatile compounds.

Polyacrylonitrile nanofiber as polar solvent N,N-dimethyl formamide sensor based on quartz crystal microbalance technique

Here, we describe an N,N-dimethyl formamide (DMF) vapour sensor fabricated by coating polyacrylonitrile (PAN) nanofiber structured on quartz crystal microbalance (QCM). The PAN nanofiber sensors with an average diameter of 225 nm to 310 nm were fabricated via electrospinning process with different mass deposition on QCM substrate. The nanostructured of PAN nanofiber offers a high specific surface area that improved the sensing performance of nanofiber sensors. Benefiting from that fine structure, and high polymer-solvent affinity between PAN and DMF, the development of DMF sensors presented good response at ambient temperature. Since there is no chemical reaction between PAN nanofiber and DMF vapour, weak physical interaction such absorption and swelling were responsible for the sensing behavior. The results are indicating that the response of PAN nanofiber sensors has more dependency on the nanofiber structure (specific surface area) rather than its mass deposition. The sensor also showed good stability after a few days sensing. These findings have significant implications for developing DMF vapour sensor based on QCM coated polymer nanofibers.

Effect of Blend Ratio on Morphology and Swelling Properties of PVA/Chitosan Nanofibers

PVA/chitosan nanofibers have been prepared by electrospinning method. A novel nanofibers mat was prepared in a various blend ratio of PVA to chitosan. The structure of PVA/chitosan nanofibers was examined by FTIR and SEM. The results showed that PVA/chitosan nanofibers were successfully formed. The result of FTIR indicates that PVA and chitosan exist in PVA/chitosan Nanofibers. SEM observation showed that the fiber has several hundred nanometers with a smooth surface. It also observed that fibers diameters decreased by increase percentage of chitosan, this occurs because of the conductivity of electrospun solution increase and the viscosity decrease. Reduction of fiber diameter followed by a decrease in pore size, this is a very important property of a membrane having a small pore size with high porosity. PVA/chitosan nanofibers have pH sensitive of swelling properties and better-swelling properties in acid conditions.

Preparation of PVA/TiO2 Composites Nanofibers by using Electrospinning Method for Photocatalytic Degradation

PVA/TiO2 composites nanofibers have been prepared by using electrospinning method. Electrospinning was performed at a voltage of 15 kV, with a tip-collector distance of 14 cm. The PVA/TiO2 composites nanofibers were characterized by FTIR, SEM, and EDAX. The results showed that PVA/TiO2 composites nanofibers were successfully formed. SEM observation showed that the nanofibers has several hundred nanometers with a smooth surface and have TiO2 nanoparticle distributed in the nanofibers. FTIR result shows a functional group of PVA and EDAX result demonstrates the presence of TiO2 in the nanofibers. The photocatalytic activity of PVA/TiO2 composites nanofibers were investigated for the degradation of methylene blue under UV light. The PVA/TiO2 composite nanofibers suspending in the dye solution have dye removal of 70% dye was degraded in 5 h. As a comparison, the TiO2 powder that has dye removal of 95% dye was degraded in 5 h. Photocatalytic activity of PVA/TiO2 nanofiber was lower than TiO2 powder, but PVA/TiO2 nanofiber was more efficient than TiO2 powder regarding process treatments photocatalytic.

Effect of heat treatment on morphology and crystallinity of electrospun Poly(vinyl alcohol) nanofibers

Four temperatures of heat treatment had been used (110 °C, 135 °C, 150 °C, and 160 °C) to give different effects on the morphology of PVA nanofibers. Heat treatment changed the crystallinity of PVA nanofibers which was indicated by the changes of XRD FWHM spectral peaks, and the crystallite size. The changes in the intensity of FTIR spectral transmittance were also observed which might be caused by the differences temperature of heat treatment. The larger crystallite size and the smaller XRD FWHM spectral values indicated greater crystallinity of PVA nanofibers that was expected to increase the stability and physical properties of PVA nanofibers.

Study of thermal degradation of PVA/Chitosan/Gelatin electrospun nanofibers

Electrospinning of PVA/Chitosan, PVA/Gelatin, and PVA/Gelatin/Chitosan Blend were prepared to study thermal characteristic by using thermogravimetric analysis (TGA). Electrospinning processes were controlled by applied voltage 16 kVA and tip-to-collector distance (TCD) 0f 14 cm. The morphology and structure of the fiber were characterized by using scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The influence of PVA addition showed in an image of SEM. Thermal behavior was showed by comparing thin film of PVA/Gelatin/Chitosan Blend in fiber and dip coating. Thermal stability of these samples showed the different melting temperature and phase transition. Fiber sample indicated to begin earlier at melting temperature than dip coating sample.

Study on Photocatalytic Properties of TiO2 Nanoparticle in various pH condition

Titanium dioxide has been widely studied for its ability to photocatalytic and applications have high performance for photovoltaic applications. In this paper TiO2 nanoparticle was investigated for the degradation of methylene blue under UV light in various pH condition. The TiO2 nanoparticle was characterized by SEM and XRD. The results showed that TiO2 nanoparticle has the structure of anatase and have a particle size of 27 nm. The photocatalytic activity of TiO2 nanoparticle show that the degradation of methylene blue under UV light have dye removal of 97% dye was degraded in 3 h, but the degradation of methylene blue without UV light have dye removal of 15% dye was degraded in 3 h. It indicated that The photocatalytic activity of TiO2 nanoparticle could occur if there the UV light. If not UV light the photocatalytic activity cannot occurs, the degradation of Methylene Blue 15% is not a photocatalytic activity but it is adsorption of Methylene Blue by TiO2 nanoparticle. The photocatalytic activity of TiO2 nanoparticle has pH-sensitive. The photocatalytic activity of TiO2 nanoparticle in acid condition (pH 4.1) is 40%, in neutral condition (pH 7.0) is 90%, and in base condition (pH 9.7) is 97%. The highest photocatalytic activity occurs in base condition, it causes in base condition OH- can be direct reaction with a hole to produce hydroxyl radical (OH*).