Advanced Materials Research Vol. 832

Abstract: Carbon nanotubes (CNTs) are widely used in fields as diverse as engineering, physics and medicine. CNTs unique physical properties and strength play a major part in such a wide application. However, there have been concerns on the deleterious effects of CNTs as a delivery tool for therapeutic proteins, peptides and genes in biomedicine. CNTs disturb normal neuronal function, and accumulate and cause brain damage. Unfunctionalized CNTs were reported to cause toxicity in cells rather than functionalized CNTs. Thus, effects of CNTs on cells should be rigorously tested. In the present study, unfunctionalized multiwall CNTs were introduced to human neuroblastoma (SH-SY5Y) cells to investigate the toxicity effect. The neurotoxicity test showed that cell viability was above 80 % for CNT at 100 pg/ ml 1 mg/ ml. The neuroprotective test revealed that viability of cells was less than 40 % and 50 % at 1 μg/ ml - 1 mg/ ml and 1 pg/ml - 100 ng/ ml concentration range, respectively. The number of viable cells was decreased, with increase in the concentration of CNT using a reactive oxygen species (ROS) test. These findings provide useful information in elucidating the inhibitory effect of CNTs as a tool of drug delivery.

Abstract: The application of carbon nanotubes as a catalyst support has received considerable attention recently. The influence of acid and thermal treatments on the properties of multi-walled carbon nanotubes (MWCNTs) is presented in this paper. MWCNTs were treated with 65 wt% HNO₃ at the 120 °C for 14 h in order to open the caps and introduce functional groups on the MWCNTs. Then thermal treatment was carried out at 600, 700, 800, 900 °C for 3 h in flowing Ar gas in a tubular furnace. The MWCNTs were characterized by N₂- adsorption, FESEM and Raman spectroscopy. The thermal treatment resulted in slight morphological changes of the MWCNTs. The acid and thermal treatments also increased the BET surface areas and pore volumes of the MWCNTs.

Abstract: Bulk heterojunction solar cell has received significant attention over the past decade due to low cost power generation and the potential to develop a clean renewable energy source [. We investigated the effect of different type of metal cathodes on the power conversion efficiency of bulk heterojunction solar cell based on a blend of conjugated polymer poly [2-methoxy 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with titanium dioxide (TiO₂). In this case of study, Aluminum (Al) and gold (Au) has been chosen as the metal cathode due to the difference of work function and their wide application in hybrid solar cell. We show that the choice of metal cathode plays a role in determining overall device efficiency through their impact on short-circuit current, open circuit voltage and fill factor due to the influence of work function. It is found that the device employing Al metal cathode which has low work function is showing a comparable performance to the Au metal electrode with fill factor of over 20 % and a power conversion efficiency of 3.3x10^-3 %. Overall it is demonstrated that the matching between the work function of the cathode and photoactive layer MEH-PPV: TiO₂ is the most important factor towards best bulk heterojunction solar cell performance.

Abstract: In recent years, the research on organic solar cells systems based on nanocomposite containing conjugated polymers has lead to great attention with the aim or replacing conventional inorganic solar cells. This nanocomposite can be processed at lower cost, low weight and ease of synthesis with greater versatility than todays solar cell. In this study, we investigated the dependence of physical, optical and electrical properties on the thickness of MEH-PPV: TiO₂ nanocomposite thin films for organic solar cell application. It was found the optical properties of photo-active layer MEH-PPV: TiO₂ nanocomposite thin films improved with increasing its thickness however the electrical properties decreased. The absorption coefficients of photoactive layer are high in the visible region (400-600 nm) with optimum absorption region at 500 nm. The shift of absorption edge toward longer wavelength with increased of nanocomposite photoactive layer thickness due to narrowing band gap caused by the effects of electron-electron and electron-impurity scattering. In addition the study of illuminated current-voltage (I-V) characteristics revealed the increment of recombination process with increased of photoactive layer thicknesses. It was found such increased in resistivity from 136x10³ to 1600x10³ Ω.cm is closely related to the electric field and exciton dissociation which is decreased with increased photoactive thickness.

Abstract: Recently, nanomaterial based biosensor application has drawn a lot attention among researchers because of specialty to enhance the sensor signal for increasing the sensitivity for detecting and identification of pathogen, viruses and toxic compound in controlling plant disease outbreak effectively. Rice tungro disease (RTD) causes a major problem in rice production and also will effect in the economic loss in the country. Therefore, early detection system is needed to monitor the disease at the early stage of the infection for preventing the disease outbreak in planting area. Lastly, this paper will discuss the current findings in rapid diagnostics using immunosensors technologies with nanomaterial application in enhancing the sensor signal for increasing the detection sensitivity

Abstract: A simple method for the fabrication of silicon nanowires using Electron Beam Lithography (EBL) combined with thermal oxidation size reduction method is presented. EBL is used to define the initial silicon nanowires of dimensions approximately 100 nm. Size-reduction method is employed for reaching true nanoscale of dimensions approximately 20 nm. Dry oxidation of silicon is well investigated process for self-limited size-reduction of silicon nanowires. In this paper, successful size reduction of silicon nanowires is presented and surface topography characterizations using Atomic Force Microscopy (AFM) are reported.

Abstract: In this work, we report the used of Negative Pattern Scheme (NPS) by Electron Microscope Based Electron Beam Lithography (EBL) Technique in connection with scanning electron microscope (SEM) for creating extremely fine nanowires. These patterns have been designed using GDSII Editor and directly transferred on the sample coated with ma-N 2400 Series as the negative tone e-beam resist. The NPS designs having line width of approximately 100 nm are successfully fabricated at our lab. The profile of the nanowire can be precisely controlled by this technique. The optical characterization that is applied to check the nanowires structure using SEM and Atomic Force Microscopy (AFM).

Abstract: Amorphous carbon (a-C) thin films have been prepared by a simple thermal CVD using camphor oil as precursor. The effects of argon gas flow rate on electrical, optical and structural properties of a-C thin films have been investigated. The a-C thin films were characterized by using current-voltage (I-V) measurement, UV-Vis-NIR spectroscopy, Raman and FTIR spectroscopy. The I-V study reveals that the electrical conductivity was increased with increasing argon gas flow rate. It was found that the optical band gap decreased from 0.88 to 0.42 eV as gas flow rate increased which indicates a microstructural disorder at different gas flow rate. Raman and FTIR studies reveal the amorphous structures which consist of a mixture of sp² and sp³ bonded carbon atoms.

Abstract: We investigated the growth of zinc oxide (ZnO) nanotetrapods on a crystallized ZnO seed layer. The seed layer was deposited by RF magnetron sputtering and etched by HF solution before the deposition of ZnO nanotetrapods by thermal chemical vapor deposition. The HF etching was done to roughen the seed layer surface to facilitate the nucleation sites for the nanostructures growth. We found that the shapes of the nanostructures on the HF-etched seed layers and those on un-etched seed layer are different, in which the nanostructures on the etched layers are in the form of plates with needles grown at the edge, whereas the nanostructures on the un-etched layers are in the shape of typical nanotetrapods. This is believed to be the result of different growth mechanisms associated with the different conditions of the growth surface.

Abstract: Malaysian is among the most diverse plant resource country in the world especially with its richesnest flora and fauna. It has about 12,000 species of flowering plants of which about 1,300 species were said to be medicinal plant and have been investigated for their therapeutic potential. Spies have been known to be a valuable source of bioactive compound which are being used to treat various diseases and improved health for a thousand years ago. The beneficial health effects of medicinal plants come from polyphenols group which is often attributed to their potent antioxidant activities. This paper reviews the antioxidant potential of selected plants from Malaysia as Persicaria hydropiper, Cosmos caudatus and Melicope ptelefolia based on reported from several researchers.