Advanced Materials Research Vol. 364

Abstract: In this research, new chemistry is explored through a simple, efficient and cheap method to synthesize new surfactants from palm oil fatty acids. Oleic acid, which is one of the major fatty acids in palm oil, has been used as a starting material for the synthesis of surfactants. This study focuses on the synthesis and characterization of bolaform surfactants from oleic acid. For this purpose, two steps reaction will be carried out: Firstly, consisted of hydrobromination of oleic acid followed by reaction of 10-bromo-octadecanoic acid with ethane-1,2-dithiol and butane-1,2-dithiol. During the first stage of the reaction, hydrobromination of oleic acid was carried out by adding hydrobromic acid into the oleic acid. The reaction was carried out in benzene as solvent at 30°C and atmospheric pressure. This reaction gives 73% yield of 10-bromo-octadecanoic acid and it yield a black brownish liquid which have the m/z 363.2056 by ESI-MS(ToF) and –CH2-CHBr-CH2-shift (4.02 ppm) was well defined in ¹H-NMR. The separation of 10-bromo-octadecanoic acid was done through thin layer chromatography (TLC) with chloroform and methanol as the eluent and silica plate grade 60 F₂₅₄ as the stationary phase. The second stage of reaction was reacting the 10-bromo-octadecanoic acid with ethane-1,2-dithiol and butane-1,2-dithiol in THF as the solvent and 1,8-Diazabicyclo [5.4.0] undec-7-ene (DBU) as the catalyst respectively. These reactions were carried out at 30°C and atmospheric pressure. Product obtained was a two layers black brownish liquid with white colour precipitate gives m/z: 659.4813 for ethane-1,2-dithiol and m/z:686.5278 for butane-1,4-dithiol respectively using ESI-MS (ToF) mass spectroscopy. Separation was done on both bolaform surfactants through thin layer chromatography (TLC) with hexane and ethyl acetate as eluent and silica plate grade 60 F₂₅₄ as stationary phase, and finally followed by column chromatography. These two new surfactants will be tested for their physical-chemical properties as well as apply on nanomaterial stabilizer.

Abstract: The science of biomimicry has served as a fusion point between nature and technology where one could adopt nature’s best solution for human’s use. Lotus leaf, for example, possesses self-cleaning capability due to the unique physical and chemical properties of its surface structural features. In this work, we aimed to mimic these features on glass surface using ZnO nanostructures to achieve the self-cleaning functionality. A series of ZnO films were electrochemically deposited on indium-doped tin oxide (ITO) conducting glass substrates from different aqueous electrolytes at systematically varied deposition potentials and electrolyte conditions. The surface morphology, density, orientation and aspect ratio of the ZnO micro/nanostructures obtained were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). ZnO ranging from two dimensional plate-like to one-dimensional needle-like micro/nanostructures were observed. Results from these studies show that lower electrolyte concentrations tend to favor one-dimensional growth of ZnO nanostructures that self-assembled into micron-size flower-like clusters at higher deposition temperatures. The ZnO-modified hierarchical dual-structured surface exhibits superhydrophobic property with water contact angle as high as 170^o.

Abstract: Sol-gel spin coated PMMA:TiO₂ nanocomposite thin films on glass substrates were studied by comparing two types of the sol-gel solutions. Two types of PMMA:TiO₂ nanocomposite sol-gel solutions were prepared; one using Degusa (P25), and the other one is using self-prepared TiO₂ powder. The self-prepared nanosized TiO₂ powder is obtained by drying the TiO₂ sol-gel using solvothermal method followed by grinding the TiO₂ crystal using ball miller. Triton-X was used as surfactant to stabilize the composite. Besides comparing the nanocomposite solution, we also studied the effect of the thin films thickness on the optical properties and their surface morphology. The optical properties and surface morphology were measured with UV-VIS spectrometer and atomic force microscopy (AFM). The result showed that nanocomposite PMMA with self-prepared TiO₂ give high optical transparency than that of with Degusa (P25). The results also indicate that as the thickness is increased the optical transparency are decreased. Both AFM images showed that the agglomerations of TiO₂ particles occurred on top of the thin film and the surface roughness increased when the thickness is increased. AFM results show that nanocomposited PMMA with P25 has high agglomeration particles compared to the other one.

Abstract: In this work, different thicknesses of silver (Ag) thin films were prepared on flexible polyethylene terephthalate (PET) plastic substrates by screen printing technology. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize morphology and surface roughness of the Ag thin films. Crystallinity and crystallites sizes of the films were verified on High resolution X-ray diffraction (HR-XRD) system. From the AFM, rough surfaces were revealed with root mean square surface roughness (RMS) ranging from 20 to 40 nm for different thicknesses of the films and were found to be strongly dependent on the film thickness. The HR-XRD spectra showed different crystalline orientations of Ag thin films (with various thicknesses) produced by the screen printing technique. All the experimental findings were subsequently discussed.

Abstract: Concrete is the most widely used building material all around the world which has been undergoing many changes aligned with technological advancement. The most recent available type of concrete is high performance concrete which is produced employing different admixtures both chemical and mineral to enhance mechanical and durability qualities. As sustainability emerged as an indispensable factor in concrete industry, many researchers targeted micro sized mineral admixtures such as silica fume, fly ash, rice husk ash, slag and so on in order to replace Portland cement which is known to be responsible for almost 7% of carbon dioxide emission into atmosphere.Recently, technology has made it easy for scientist to study nanoscale admixtures and their effect on structure of concrete. This paper reviews nanomaterials in cement composites and how they can improve different properties of concrete.

Abstract: The effect of radio frequency (R.F) power to the properties of zinc oxide (ZnO) thin films deposited by magnetron sputtering is presented. This project has been focused on electrical, optical and structural properties of ZnO thin films. The effect of variation R.F power at 100 watt ~ 400 watt on the ZnO thin films has been investigated. The thin films were examined using current-voltage (I-V) measurement, UV-Vis-NIR spectrophotometer, x-ray diffraction (XRD) and atomic force microscope (AFM). ZnO thin films were prepared at room temperature in pure argon atmosphere by a R.F magnetron sputtering using ZnO target. I-V measurement indicates that at 300 watt R.F power show the highest conductivity. All films have showed high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). Highly oriented ZnO thin films [002] direction was obtained by using Rigaku Ultima IV. The root means square (rms) roughness for ZnO thin film were about (<2nm) was measured using AFM (Park System XE-100). Keywords-ZnO thin films, R.F power, electrical properties, optical properties, structural properties

Abstract: Thin films of conducting unsaturated polymer of red color poly [2-methoxy-5(2’-ethyl hexyloxy)-phenylene vinylene] (MEH-PPV) containing different weight percent of ZnO nanoparticles were deposited by spin coating techniques. The MEH-PPV: ZnO solutions were spin coated onto 2 × 2 cm glass substrates. The spun MEH-PPV: ZnO thin films were used for investigating the optical properties by using Ultraviolet-Visible Spectrometer (UV-Vis). The structural properties of the thin films were investigated by Scanning Electron Microscopy (SEM). For MEH-PPV: ZnO nanocomposites, the UV-Vis absorption bands increases and showing slight blue shift compared to the pure MEH-PPV. The optical bandgap of MEH-PPV: ZnO nanocomposites slightly decrease when the amount of ZnO nanoparticles increase. ZnO nanoparticles apparently no effect on conjugation segments of MEH-PPV. From the SEM images of MEH-PPV: ZnO nanocomposites, it can be seen that ZnO nanoparticles form agglomerated regions.

Abstract: CdS/ZnO quantum dots (QDs) were prepared at a temperature of 293 K by the sol-gel method with Triethanolamine (TEA) as a capping agent. The effect of CdS/ZnO mixture ratio of 1:9, 1:1 and 9:1 on the optical absorption and fluorescence spectra were investigated by UV-Vis and Fluorescence spectroscopy. By increasing ZnO composition, a blue-shift of absorption edge and emission spectra were observed. The band gap for 1:9, 1:1 and 9:1 were found to be 4.13, 3.93 and 3.11 eV, respectively. The morphology of the CdS/ZnO QDs for each mixing ratio was obtained by transmission electron microscope (TEM). The size of the QDs was found to be in the range of 5-10 nm with some agglomerated particles.

Abstract: This work describes the properties of silica drug delivery system (DDS) produced using micelles entrapment approach. Isoniazid, which is a water soluble drug for tuberculosis was used in the system. The effects of synthesis parameters were systematically studied such as synthesis temperature (38-70°C), amount of butanol co-solvent (6-18 ml), and amount of Si organic precursor (2-8 ml). From transmission electron microscope (TEM) images, the size of DDS could be tuned from 21-104 nm by changing the reaction temperature. The increase of butanol co-solvent enlarged the size of DDS in the range of 40-94 nm. A similar trend was observed for DDS with increasing organic Si precursor whereby the particle size could be tuned from 40-132 nm. However, at high organic Si precursor of > 2 ml, a bimodal structure of DDS was observed. Stability study in biological media at 37°C of selected sample showed that the produced DDS had acceptable degree of agglomeration.

Abstract: In this report, the growth of GaN p-n junction on Si (111) substrate by plasma-assisted molecular beam epitaxy (PAMBE) is demonstrated. Doping of the GaN p-n junction has been carried out using Si and Mg as n-type and p-type dopants, respectively. Silicon substrate is used to grow the GaNpn-junction. In order to improve the crystalline quality of the nitride based junction, AlN is used as a buffer layer. The optical properties of the sample have been characterized by photoluminescence (PL) and Raman spectroscopy.PL spectrum shows a strong band edge emission of GaN at ~364nm, indicating good quality of the sample.The presence of peak ~657cm^-1 in Raman measurement has exhibited asuccessful doping of Mg in the sample. The structural properties are measured by high-resolution x-ray diffraction (HR-XRD) and scanning electron microscopy (SEM). The cross section of the SEM image of the sample has shown sharp interfaces.