nan Harsojo

Study of parallel oriented electrospun polyvinyl alcohol (PVA) nanofibers using modified electrospinning method

Parallel orientedpolyvinyl alcohol (PVA) nanofibershasbeen successfully prepared by using modified electrospinning method. This method uses two pairs of copper (Cu) electrodes which are set apart at a certain distance and applied voltage of 15 kV. The concentrations of PVA were varied from 11%, 13%, 15%, 17%, and 19%. The width of gap collector were varied from 5 mm, 10 mm, 15 mm, and 20 mm. The diameter of nanofibers increase as increasing concentration of PVA. As the width of gap collector increase, first diameter of nanofibers decrease and reach a minimum value at 355 ± 7nm in 15 mm of gap, then the diameters increase again. We also calculated the alignment parameter (S) for given aligned nanofiber. The result showed that alignment parameters (S) were on values around 0,9-1.

Synthesis of copper nanorods by aqueous solution method without heating external

So far, synthesizing Cu nanorods (CuNRs) are complicated, expensive, and needs a long time. In this study, We report a simple way to synthesized CuNRs by the aqueous solution method without external heating. Instead of external heating, we used internal heating from the exothermic reaction of NaOH and water. Copper (II) nitrate trihydrate Cu (NO3)2.3H2O, sodium hydroxide (NaOH), ethylenediamine (EDA), and hydrazine (N2H4) were used in our work. The morphology and formation structure of CuNRs have been investigated using Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy (SEM-EDXS), and X-ray Diffraction (XRD). The SEM analysis confirmed the formation of CuNRs with a diameter of 200-300 nm and length of 3-7 µm.

Optical properties of planar nematic liquid crystals samples which are parallel oriented by nanofibers

Optical properties of two nematic liquid crystals, i.e., 4-methoxybenzylidene-4-butylaniline (MBBA) and 4-cyano-4’-pentylbiphenyl (5 CB) which are parallel oriented by nanofibers has been successfully performed. Planar samples of liquid crystals were made using polyvinyl alcohol (PVA) nanofiber from electrospinning process. Electrospinning method was modified using copper (Cu) as gap collector. These planar samples area are 15 mm x 25 mm. Optical characteristic of these samples were studied by using optical polarizing microscope. The optical intensity changes by a rotationof crossed polarizers is observed. The sinusoidal intensity change was observedin these samples as such as in the planar sample prepared by the rubbing method.

Microscopic Characterization of Cellulose Nanocrystals Isolated from Sisal Fibers

Isolation of cellulose nanocrystals (CNCs) was carried out by unrepeated or repeated alkalization and bleaching followed by sulfuric acid hydrolysis and air cooling (unrepeated) or ice cooling (repeated). The influence of unrepeated and repeated alkalization and bleaching, and cooling rate (cooling medium) after hydrolysis on the morphology and crystallinity of the isolated micro- and nano-celluloses were characterized. Scanning electron microscopy (SEM) showed that repeated alkalization and bleaching led to a higher degree of fibrillated microcellulose (~10 mm) with higher surface roughness than unrepeated alkalization and bleaching. Transmission electron microscopy (TEM) revealed that air and ice cooling after acid hydrolysis producing different CNCs morphologies; heterogeneous CNCs nanowhisker and nano-spherical (~50 nm), and homogenous CNCs nanowhiskers (~50 nm width and ~500 nm length), respectively. The homogeneous nano whisker was related to single phase monoclinic b-cellulose. Residual lignin agglutinating between the nanoparticles was observed in TEM image as well as in Fourier transform infrared (FTIR) spectra. The existence of residual lignin after hydrolysis is comparable in crystalinity (crystallinity index, Ic: ~91%) with that of isolated CNCs, as confirmed by x-ray diffraction (XRD) analysis.

Building Up of Surface Plasmon Resonance Instrument Using Spreeta 2000 and Arduino Mega 2560

A system to monitor the signal produced by surface plasmon resonance (SPR) has been designed and tested. The built-in sensor consists of a polarized light source having a wave length 840 nm and a built in 128 photodiodes constructed around the maximum SPR angle to detect the reflection light from the gold surface. The signal produced from the diodes is then amplified and digitized. We use 5173 Hz clock to sample the signal generated by the diode array pixel during the reflection process producing SPR signal around the maximum angle. We program Arduino Mega 2560 to process the signals and transfer it using Lab View to present the data versus sampling time. Doing this, we can record the SPR signal versus time, known as the SPR dynamic signal. To test the performance of the system and to know the properties of the SPR signal, we test the system using ethyl alcohol with concentration of 10% (v/v) up to 90% (v/v). The result shows that the system can be used to monitor the dynamics of SPR signal during the reaction process and it indicates the possibility of using the instrument to detect various kinds of SPR signal related to the chemical and or biological process in the samples.

The Roles of Polyvinyl Alcohol (PVA) as the Capping Agent on the Polyol Method for Synthesizing Silver Nanowires

We report our investigation of roles of polyvinyl alcohol (PVA) as a high-performance capping agent in synthesizing silver nanowires (AgNWs) using polyol method. For this purpose, we varied the concentration of silver nitrate (AgNO3), from 0.3 M to 1.0 M, and molar ratios of [PVA:AgNO3] from 2 to 6. The UV-vis spectra show the AgNWs growth optimally at a molar ratio of 4.5 with the absorbance peaks of 378 nm and 380 nm. Meanwhile, from XRD patterns, it was found that the crystal structure of the AgNWs can be identified as a face-centered cubic (fcc) with a lattice constant according to the spacing distance between the {111} planes of 4.087 Å. Finally, scanning electron microscopy (SEM) and transmission electron microscopy TEM images show the diameter and length of the AgNRs are 150 to 230 nm and 50 to 120 µm, respectively. These results show that the AgNWs synthesized using PVA having a long size.

High-Performance Silver Nanowire Film on Flexible Substrate Prepared by Meyer-rod Coating

Flexible and transparent conducting (FTC) films based on silver nanowires (AgNWs) were fabricated onto a polycarbonate (PC) substrate by a simple Meyer-rod coating process. AgNWs were synthesized using polyvinyl alcohol by polyol process with a diameter and length of 500 nm and 10 µm, respectively. The FTC film was fabricated by varying the number of layers. The FTC film exhibited a sheet resistance of 12.1 Ω.sq-1 with a transparency of 89.5%. The optical conductivity of FTC films was obtained about 4.7 - 13.1 × 105 S.m-1 with a refractive index about 1.2 to 1.7. The number of layers is an important to influence on the sheet resistance and transmittance of the FTC films. The sheet resistance and transmittance decreases with the number of layers.

Study of the stability coated and uncoated nanosilver colloid

The stability of nanosilver colloids made using electrochemical process and chemical process were investigated. In the process using a DC generator cell, two silver electrodes under a DC voltage were used to generate the colloid. In the chemical process the colloid was made using the dilution of AgNO3 in deionized water with the addition of sodium citrate. To increase the stability to this colloid was added polyvinyl alcohol. The stability In those three colloids were investigated using UV-Vis spectrometer. The size of the nano Ag was measured using transmission electron microscope (TEM). The study reveals that within period of two weeks the trend toward a stable colloid is shown by colloid using DC generator. The addition of PVA may stabilize the unstable colloid made using the chemichal process and reduce the size particle to significantly smaller particle compared to the one made using DC generator cell. The condition of obtaining the stable nano colloid silver with smaller particle size was discussed.

The Critical Current of the Superconductor Having an Array of Hole with de Gennes Boundary Condition

We determine the critical current density of the superconductor having an array of hole exposed under electric current and under a perpendicular magnetic field. It is assumed that the inner holes sides are accounted in the de Gennes boundary condition while outer edge is in contact with vacuum. The critical current calculation was done after solving time dependent Ginzburg-Landau equation and evaluating the electric voltage. The enhancement factor of the critical currents due to the boundary condition is discussed.