Advanced Materials Research Vol. 364

Abstract: Nanostructured zinc oxide (ZnO) thin films were deposited on glass substrates using radio frequency (RF) magnetron sputtering system at different oxygen flow rates ranges between 0 to 40 sccm. Field emission scanning electron microscopy (FESEM) images was revealed that nanocolumnar ZnO structure thin films are produced on the substrates using high purity ZnO as the target at RF power of 250 W in the argon and oxygen gas mixture ambient. The XRD spectra reveal that the deposited films are preferentially grown along the c-axis indicating high ZnO crystallinity. The ultraviolet-visible (UV-Vis) spectra show that all samples are very transparent in the visible region (400 – 800 nm) with average transparency above 80 %. The photocurrent properties indicate that ZnO thin film prepared at oxygen flow rate of 20 sccm has the optimum characteristic for ultraviolet sensor applications. This finding suggested that the oxygen flow rates play important role and has critical value for semiconducting nanocolumnar ZnO growth in the sputtering system, which can produce ZnO thin film with high sensitivity of ultraviolet detection.

Abstract: In this research, formation mechanism of a Cu/10 wt.% Cr-10 wt.% Al₂O₃ nanocomposite via mechanical alloying and subsequent heat treatment has been investigated. It was found that during milling process, Cu (Al) solid solution and Cu₉Al₄ phase were formed as intermediate products. Further heat treatment carried out under argon atmosphere at 900°C for 8 hours resulted in completion of Cr₂O₃ reduction by Al. The mechanism of in-situ formation of Al₂O₃ reinforcement in the copper matrix was also discussed as a two stages process. The SEM and TEM results confirmed the proposed mechanism and showed that the Cr dispersoids surrounded by Al₂O₃, in the nanometric scale. Also, the Cu matrix with mean crystallite size of 30 nm was stable at high temperature.

Abstract: Titanium dioxide (TiO₂) thin films deposited on quartz substrate by spin-coating method using titanium (IV) butoxide has been studied. The aim of this paper is to investigate the effect of annealing in oxygen ambient on the morphology and optical properties of thin films. The distinct variations in the morphology of the thin films were observed from atomic force microscope (AFM) images. The transmission spectra obtained from UV-VIS-NIR showed the TiO₂ thin films exhibited average transmittance value up to 80% in the visible region. Raman spectra of thin films annealed in O₂ shifted from 142 cm^-1 to 179 cm^-1.

Abstract: Development of technology in synthesizing a novel nanoscale material has been the main concern in the current material science. This study investigates the effect of two different carbon sources on the formation of carbon nanotubes (CNTs) via catalytic chemical vapour deposition (CCVD) method. Two types of carbon source i.e. acetylene gas and ethanol liquid were used for the synthesis of CNTs. The catalysts used in the synthesis of CNTs were formulated from nickel (Ni), copper (Cu) and praseodymium (Pr) using the wet impregnation method. The as-synthesized CNTs obtained were characterized using field emission-scanning electron microscope (FE-SEM), Thermal gravimetric analysis (TGA) and transmission electron microscope (TEM). The analysis result confirmed that the prepared catalysts were active for the production of CNTs. TEM analysis revealed that different morphologies of CNTs were formed when different carbon source was used. FE-SEM micrographs confirmed that acetylene proficient in producing multi walled carbon nanotubes (MWCNTs) and ethanol in producing heterojunctions CNTs with diameter range of 60 to 120 nm and 10 to 40 nm, respectively. Meanwhile, TGA analysis revealed thermal stability of each type of CNTs at different temperature of decomposition. Generally, this research has successful produced different types of CNTs when different carbon source is used.

Abstract: Raman analysis is one of the main methods use to investigate type of graphitized carbon nanomaterials. It provides information on the vibration of crystal lattice, electron structure and regularity of crystal structure of the graphitized carbon materials. In this work the single step chemical vapour deposition (CVD) method was introduced for the direct growth of all as-synthesized carbon nanomaterials; carbon nanotubes (CNTs), carbon nanofiber (CNF), carbon nanosphere chain (CNSC) and CNT heterojunctions (HJCNTs). Series of metal catalysts were formulated from Ni, Fe, Cr and Cu, and were used in the synthesis of the respected carbon nanomaterials (CNMs). By introducing the right combination of the reaction conditions consisting of the formulated catalyst, reaction temperature and flow rate as well as type of carbon source resulted in the formation of different types of carbon nanomaterials. Raman spectra analysis revealed that the used of acetylene and ethanol as the carbon precursors are proficient to produce different form of carbon nanomaterials as depicted by the evolution of the G-band and D-band intensities. The FESEM micrographs obtained confirmed the morphology and types of the respected carbon nanomaterials synthesized in this study.

Abstract: A series of six nanostructures vanadium phosphorus oxide catalysts were synthesized through the starting material vanadium pentoxide which subjected to high intensity ultrasound irradiation with different duration of time. XRD patterns of all nanostructure vanadium phosphorus oxide catalyst were indexed to (VO)₂P₂O₇ with one additional small peak which corresponds to the present of small amount of V⁵⁺ phase except for the catalyst that undergo 120 min of ultrasound irradiation time. The surface morphologies of the catalysts are uniform, well defined shapes and surface structures in nanoscale range but tend to agglomerate with each other to form larger particles. Furthermore, high amount of active oxygen species were released from V⁴⁺ phase (O^--V⁴⁺ pair) for the nanostructures VPO catalyst which were synthesized with 30 min of ultrasound irradiation time and drastic increment in n-butane conversion (9 %) in catalytic evaluation test, suggested that these nanostructure VPO is an active catalyst for partial oxidation of n-butane towards malefic anhydride.

Abstract: In this study, the synthesis of iron oxide nanoparticles (IONPs) and immunochromatographic (ICG) strip test of iron oxide conjugated with monoclonal antibody (IONPs-Ab) have been developed. The IONPs were synthesised using precipitation method and dispersed in water by applying polyethylene glycol coating. Several parameters that affected conjugations of the IONPs-Ab were studied namely iron oxide concentration, antibody volume, stabilizer concentration and the amount of SiPEG coating. From the transmission electron microscopy (TEM) image, the size of IONPs obtained was ~14 nm. Conjugate was tested with the ICG strip test lined with the antigen. The results showed 1.0μl SiPEG coating, 1 M IONPs concentration, 20μl of 1mg/ml antibody volume and 1% bovine serum albumin (BSA) were the optimum. Moreover, the IONPs-Ab was also tested with the Brugian filariasis positive and negative serum samples. The results showed positive result for the patient serum and negative result for the non-patient serum in just 15 minutes.

Abstract: Rectifying behavior more than 3 orders of aligned zinc oxide (ZnO) nanorods grown on Mg_0.3Zn_0.7O thin film template using chemical bath deposition method was observed, giving a barrier height of 0.75 eV, and the ideality factor achieved was almost 6, which was analyzed using thermionic emission theory. Field emission scanning electron microscope (FESEM) images revealed that the grown ZnO was in hexagonal shape, uniformly distributed and in vertically aligned form. The crystallinity of the sample being studied using X-ray diffraction (XRD), where the highest peak was found at (002) phase, confirming that high crytallinity of ZnO was attained. The effect of metal/semiconductor junction between metal and aligned ZnO nanorods was discussed in further details.

Abstract: Arsenic (As), Cadmium (Cd) and Lead (Pb) are the heavy metal and categorized as high toxicity compound. This element can be found in the animal and plant from bio accumulation mechanism. This bio accumulation will lead to the toxicity when its concentration surpasses regulated value. Centella asiatica is a plant belonging to the Umbelliferae family, hydrocotyle order, which has been used for curing of venous ulcers and venous hypertension for its activity on connective tissue metabolism and endothelial integrity. This plant also widely used in formulation of drugs and cosmetic. In order to produce high quality herbal product, the characterization and standardization of heavy metal content using modern technique must be carried out. Centella asiatica nanopowders were produced at different grinding condition and analyzed for As content using ICP-OES (Optima 7300 DV, Perkin Elmer). The confirmations of size were carried out using nanoZeta Sizer S (Malvern Instrument) and Field Emission Scanning Electron Microscope. The results obtained show that As, Cd and Pb presence in all type of grinding below the acceptable daily intake by the world health organization (WHO).