nan Chotimah

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.

The Effect of Alkaline Ratios of NaOH to NH3 on the Formation of Nanostructured Titania

The effect of alkaline solvent of NaOH and NH3 in the synthesis of nanostructured titania (TiO2) has been studied. Powder of anatase titania as the precursor was mixed with various volume ratios of 10 M of NaOH and 15 M of NH3. The mixture was heated in Teflon-lined autoclave at 150 °C for 24 h. The as-synthesized TiO2 powders were then washed with 0.1 M HCl and calcined at 300 °C. The calcined samples were characterized using TEM (transmission electron microscope), and XRD (X-Ray diffraction). Raman spectroscopy was further used to determine the contributing crystalline phases for the synthesized TiO2. It is shown that varying the solvent ratios of NOH to NH3 resulted in nanotubes, nanosheets, and nanoparticle morphology of TiO2. The TEM images showed the formation of nanotube structure in alkaline ratio NaOH:NH3 of 1:0 and 3:1, with diameter of about 10 nm. At volume ratio of 1:1, the nanosheets and nanotubes both were formed and at volume ratio of NaOH:NH3 of 1:3, nanosheets contributed as its main morphology. While, at fully NH3 solvent, the nanospheres with anatase domain were produced. Raman spectra confirmed that the major contributor for hydrothermal synthesis employing less NaOH for volume ratio of NaOH:NH3 of 3:1 was predominantly anatase with slight presence of titanate. For volume ratio at higher NH3 the presence of titanate is not prominent, but the morphology has already changed into more nanosheet and then nanospheres. The crystallinity of TiO2 anatase crystalline phase was enhanced as more NH3 utilized.

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.

Post-Treatments to Enhance Vertical Alignment of ZnO Nanorods on Glass Substrates by Hydrothermal Deposition

Vertically aligned nanorods ZnO have been deposited hydrothermally on the pre-coated ZnO seeded-glass substrates. Enhanced vertical alignment is achieved as a result of combined film post-treatments. Dipped-drawn and immersed-washing the as-synthesized ZnO films in water as well as quenching of the hydrothermal were proposed to hinder excessive deposition and engineer the growth of ZnO nanorods. The XRD patterns shows suppressed growth of ZnO crystallite along (101) with increased textural coefficients on (002), TC002, from 3.94 to 5.23. Dense vertically aligned bundles of ZnO nanorods may reach up to 0.75 μm length. Bandgap energy of the resulted ZnO nanorod thin films were ranging from 3.69 to 3.79 eV, wider than those of bulk ZnO. Hydrothermal technique with simple post-treatments of immersed-washing and hydrothermal quenching has offered robust and efficient method to prepare vertically-aligned 1-D ZnO nanorods potential as photoanodes for dye-sensitized solar cells.

Effect of polyaniline polymerization methods on the preparation of electrospun polyaniline nanofiber

In this work, polyaniline was synthesized by conventional polymerization and rapid mixing polymerization method and confirmed by FTIR. Polyaniline nanofiber was successfully fabricated by electrospinning method in the presence of poly(vinyl alcohol) (PVA) due to the low solubility of polyaniline powder in the common solvents. Electrospinning solution was prepared in weight percent ratio 1:1 of PANI:PVA, and 11, 12 and 13% of PVA/total weight of a solution. The fibers obtained from spinning process then characterized by FTIR and SEM to determined their surface properties and morphology. In general, polyaniline resulted from conventional polymerization gave much larger diameter size of fibers and dispersed than from rapid mixing polymerization. The diameter of fibers was increasing accord with the increasing of polymer concentration. Fibers were decreasing in quantity and diameter due to PVA evaporation after being heated.

The electrical properties of PEDOT:PSS nanofibers

Fabrication of nanofibers based on conducting polymer of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(p-phenylene sulfide) or PEDOT:PSS has been carried out using electrospinning technique. In this study, poly (vinyl alcohol) (PVA) as a matrix was added. I addition, the dimethyl sulfoxide (DMSO) was also added to PEDOT:PSS/PVA nanofibers to improve the conductivity. The measurement of resistance a thin layer of done with the two-point probe method. A thin layer of PEDOT:PSS and blend PEDOT:PSS/PVA in preparation above the substrate by a method of spin coatings and electrospinning. The morphology and diameter of PEDOT:PSS:PVA nanofibers were determined with a scanning electron microscope or SEM (JEOL, JSM-6510LA), while the chemical compositions of nanofibers were determined using Fourier transform infrared (FTIR). The observation was made with variations of probe position of grids. The measurement result suggests contact between a probe and the PEDOT:PSS is ohmic contact, and the addition of D...

Determination of Band Gap Energy of Semiconductor in Homojunction Structure Devices by Using Customized Microcontroller Based Apparatus

We have successfully developed a customized apparatus based on microcontroller for simple band gap energy (Eg) measurement of semiconductors in homojunction structure devices. The apparatus consisted of a data acquisition system based on microcontroller AVR ATMega 128 and a thermos flask equipped with temperature controller. It permits recording of current-voltage (I-V) and temperature and subsequently sends data to a computer to enable the computer processing of such data. For samples under tested, we used two types of commercial diode, i.e. Silicon (1N4007) and Germanium (1N60). In this measurement, the voltage across the resistor was used to calculate the current while the voltage across the diode gave the forward bias voltage. The temperature of diode was varied from 5°C to 80°C. During each I-V measurement, the temperature of diode was maintained to be constant by employing a proportional-integral-derivative (PID) controller to the heater. Furthermore, by varying the temperature of diode, we could extract the saturation currents under reverse bias across the diode of each I-V measurement. For the two types of diode, it is found that the Eg of silicon is 1.13 ± 0.03 eV, while that of germanium is 0.71 ± 0.03 eV. This result is closed to the Eg value of each diode indicated in the respective datasheet. Therefore, it suggests for applying this apparatus for measuring Eg of semiconductor in most homojunction structure devices.

Sol-Gel Derived ZnO Nanorod Templated TiO2 Nanotube Synthesis for Natural Dye Sensitized Solar Cell

Natural dye sensitized solar cells (nDSSC) mostly suffer from low solar cell performance, that vertically aligned nanotube TiO2 as the photoanode is expected to increase the performance by providing higher surface area and direct electron transport. Nanostructured TiO2 films have been fabricated on glass substrates employing ZnO nanorod films as the template. First, vertically oriented ZnO nanorod on a glass substrate was prepared hydrothermally. Then, sol-gel dip-coating technique was used to deposit TiO2. The template films were dip-coated into sols of titanium tetraisopropoxide-ethanol-diethanol ammine with withdrawing rate of 2 cm/min for three- (Ti3) and seven-times (Ti7). After drying at 100 °C for 10 min, the films were calcined at 550 °C for 1h and washed with HCl 3% (v/v). The films were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It is observed that different coating cycles resulted in different film morphologies. Nanotube TiO2 with diameter of ~50 nm was identified for Ti3, while Ti7 displayed sheet-like structure. The diffraction patterns confirmed the presence of only anatase crystalline phase with crystallite size of 10.3 nm (Ti3) and 21.7 nm (Ti7). The dye absorption was red-shifted indicating dye monomeric adsorption on TiO2 via chelation. Enhanced absorption of anthocyanin dye extracted from pericarps of mangosteen (Garcinia mangostana l.) fruit on TiO2 nanotube compared to TiO2 nanoparticle (P25) was observed leading to improved photovoltaic performance of the constructed nDSSC.