Solid State Phenomena Vol. 290

Abstract: The role of both zinc oxide (ZnO) and zinc (Zn) seed layers were evaluated for the growth of vertically aligned high-quality zinc oxide (ZnO) nanorods by the sonochemical method. A total of four samples categorized into two groups were evaluated, with a different type and thickness of seed layer for the first group - ZnO, 85 nm and the second group - Zn, 55 nm respectively. This was after depositing Ti (10 nm) as the adhesion layer on p-type Si (111) substrates for two samples, and without the adhesion layer on the others. All depositions were carried out using RF-sputtering. The effects of the seed layers on the growth of vertically aligned high-quality ZnO nanorods were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). Results show that the type and thickness of a seed layer are key parameters to the synthesis of high quality ZnO nanorods. Results also show that the Ti (10 nm) adhesion layer did not affect the growth surface-to-volume ratio of the ZnO nanorods and the ZnO nanorods synthesized using ZnO (85 nm) as seed layer has a better surface-to-volume ratio compared to that using Zn (55 nm) as seed layer, with and without the adhesion layer.

Abstract: In this study, we investigated in vitro toxicity of ZnO nanopowder on L929 fibroblast cell lines. The ZnO nanoparticles were observed to possess relatively more surficial zinc compared to oxygen. Field-emission scanning electron microscope (FESEM) data revealed that the particle morphologies consisted of nanorods, platelets and nodules between 40-100 nm size range. EDS confirmed that there were more zinc elements on the surfaces of the particles. XRD results showed that the calculated average crystallite size of ZnO nanopowder was 44.28 nm. The optical band gap calculated was 3.298 eV based on UV-visible absorption spectra. In vitro toxicity results showed that ZnO concentration at 0.3125mM, 0.625mM and 1.25 mM were considered non-toxic to L929 cell line since the cell viability was higher than 70 % after 72 hours treatment whereas the ZnO nanopowder concentration above 2.5mM was considered toxic. High surficial zinc atoms on ZnO particles could have been a significant factor in cell toxicity.

Abstract: The use of zinc oxide nanorods is a promising option to increase the specific area for efficient glucose oxidase immobilization which further enhance the signal performance of glucose detection. In this work ZnO nanorods were prepared via hydrothermal process on sol-gel ZnO seed layer. The effects of different temperature of annealed seed layer on the morphology and properties of grow ZnO nanorods were investigated. The ZnO seed layers were annealed at various temperatures ranging from 300 to 600 °C for 2 h. The study demonstrated that the process condition of ZnO seed layer had a strong influence on the morphology and crystallinity of ZnO nanorods grow. X-ray diffraction analysis and scanning electronic microscopy were employed to characterize the crystal structure and morphology of the prepared ZnO seed layer and grow ZnO nanorods. The performance of different aspect ratio of ZnO nanorods on glucose detection were measured by using electrochemical analysis. With optimized ZnO nanorods, the glucose biosensor exhibited an enhanced in signal performance with a high sensitivity of 11.36 μA mM^-1 cm^-2 in the range of 0.05-1 mM. Such high performance was due to more immobilization on the well-aligned ZnO nanorods array and direct electron conduction between the nanorods and the electrodes

Abstract: Apart from being a promising optoelectronic devices such as photodetector and sensors, ZnO has many dental and biomedical applications. ZnO has been known to possess strong toxicity towards bacteria, cancer and fungi. Cytotoxicity test of pharmaceutical grade of ZnO on L929 mouse fibroblast cell lines was carried out using trypan blue assay. ZnO was characterized for its morphology, structure and optical properties using FESEM, EDS, UV-Vis and XRD. ZnO exhibited various morphologies like rod, platelet, slab and irregular-shaped particles. EDS data showed the ZnO powder possessed relatively higher oxygen atomic percentage if compared to zinc atoms with an oxygen-to-zinc ratio of 1.219. The average crystallite size obtained was about 39 nm. The percentage of cell viability on L929 cell was decreased with increasing ZnO concentrations. The cells viability after 72h were achieved and the concentration of ZnO below 1 mM was summarized as non-toxic after treated with ZnO. The higher surficial oxygen on ZnO particle surface could have promoted higher generation of reactive oxygen species that caused lower L929 cell viability.

Abstract: Cotton fibre has been widely used for clothing applications since thousand years ago. However, the products made of cotton fibre can be easily deteriorated by microoganisms due to its natural feature and moisture affinity. This will lead to loss of mechanical strength as well as hygiene problems. Zinc oxide nanoparticles (ZnO NPs) have shown antimicrobial effects on many microorganisms. Due to the lack of bonding between ZnO and cotton fabric and improve mechanical strength, PVA is applied onto ZnO and cotton fabric by dip coating. In this study, the presence of ZnO NPs are determined by SEM and XRD. The crystal size of ZnO NPs are approximately 25 ~ 35 nm. The optimum tensile strength occurred at 0.20 M ZnO and 15 g PVA. The antibacterial efficiency against S. aureus is tested by disc diffusion test. It found that increased ZnO NPs and PVA concentration, increased inhibition zone and thus showed good antibacterial activity.

Abstract: Superparamagnetic iron oxide nanoparticles (SPION) were synthesized by one pot coprecipitation method at room temperature in the presence of Polyvinylpyrrolidone (PVP). X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Vibrating Sample Magnetometer (VSM) were used to analysis the physicochemical properties of PVP-SPION. The XRD patterns confirmed that the structure of as-synthesized sample is magnetite with cubic structure system. In TEM results, the image of PVP-SPION displayed that the size of particles was 14.05 nm with narrower size distribution and also the PVP played important role to minimize the agglomeration of SPION. Finally, the high saturation magnetization value of PVP-SPION (53.0 emu/g) indicate the as-synthesized sample has a great potential as a contrast agent for MRI.

Abstract: The capping of manganese–zinc ferrite nanoparticle by polyvinyl pyrrolidone agent has been carried out by a simple thermal treatment route. The obtained nanopowder samples have been given a screening investigation for its elemental composition, structural and morphological behaviour. The observed crystalline phase of manganese–zinc ferrite nanopowder was evidenced by X-ray diffractometer at a calcination temperature of 650 °C with no other impurity phases being detected. The average crystallite size determined from the XRD data and TEM micrographs showed an increasing trend with increasing calcination temperature. The morphological examination revealed that the manganese–zinc ferrite nanoparticle exhibits a uniform shape with enhancement in nanoparticles dispersion as the calcination temperature increased.

Abstract: The development of boundary layer flow problem which is involve of nanofluid for improve thermal efficiency in many applications is gaining momentum as most of base fluid are not very good thermal conductor. The enhancement of thermal conductivity can be improving when the magnetic fields is presented. Also, by using this material may encountered another problem such as separation flow. This research is study about magnetic fields effect on unsteady mixed convection flow on nanofluid past a sphere with heat flux as its boundary condition. This problem will consider its mathematical model where it can help to predict the solution in experimental method. The mathematical method that being used is Keller-box because of its ability to solve non-linear equation. The nanoparticles that being choose are copper and titanium oxide with water as based fluid. There will have three equation which is mass, momentum, and energy equation. All equations are transform into non-similarity ordinary differential equations by using appropriate variables. The effect of magnetic parameter on velocity and temperature profiles as well as skin friction and Nusselt number are studied. The results show that volume fraction affected the heat-transfer rate, and skin friction coefficient. This study also shows that magnetic parameter affected the separation times which is decelerated the flow.

Abstract: Doping of the materials with other metals or transition metals will modify the properties of the nanomaterials. In this work, MgO and Cu doped MgO which are Mg_0.95Cu_0.05O and Mg_0.90Cu_0.10O nanomaterials are synthesized using a self-propagating combustion method. The samples are annealed at 900 °C for 24 hours. The phase and purity of the synthesized samples are studied using X-Ray Diffraction (XRD) and the result revealed that the samples are pure and single phase. The morphology and crystallite size of the pure samples are examined using Field Emission Scanning Electron Microscope (FESEM). The result shows polyhedral morphology with agglomeration of crystallite and average crystallite size of the samples is between 40 to 210 nm. The band gap obtained for MgO nanostructures is 6.38 eV which is lower than bulk MgO of 7.8 eV. The presence of Cu causes the narrowing the band gap energy of Mg_0.95Cu_0.05O and Mg_0.90Cu_0.10O samples to 4.28 eV and 3.35 eV respectively.

Abstract: Titanium dioxide (TiO₂) nanoparticles thin film has been successfully prepared by a simple hydrothermal process using Hydrochloric Acid (HCl) as chelating agent and Titanium (IV) Chloride (TiCl₄) as precursor. In this study, the nanostructured TiO₂ thin films were prepared at different hydrothermal reaction times of 2 hours, 5 hours, and 10 hours, and then Ag₂S Quantum Dots (QDs) were deposited on the surface of TiO₂ nanoparticles using 6 cycles of Successive Ionic Layer Adsorption and Reaction Deposition (SILAR) method. The surface morphology, crystalline structure and optical characterizations of the films were carried out using Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscope (AFM), X-ray Diffraction (XRD) and Ultra-Violet-Visible Near Infrared Spectrophotometer (UV-Vis). For electrical properties, four-point probe investigated the sheet resistance, resistivity, and conductivity of these thin films. TiO₂ nanorods were formed with diameter ranged from 33.78 nm to 42.58 nm and the length of TiO₂ layer increased as the reaction time increased, from 2.84 μm to 3.93 μm (without Ag₂S QDs) and 2.88 μm to 4.85 μm (with Ag₂S QDs). When the reaction time reaches 10 hours, nanoflowers can be seen on the surface of film. The XRD results showed that with longer reaction time, the value of full-width at half maximum (FWHM) of the TiO₂/ Ag₂S QDs thin films decreased from 0.335° to 0.263 while the crystallite size increased from 22.73 nm to 35.39 nm. UV-Vis analysis indicated that the optical band gap of these thin films decreased from 2.68 eV to 2.00 eV (direct) and 2.94 eV to 2.40 eV (indirect) with increased in reaction time. The electrical properties of the films showed that the resistivity varied between 7 x 10⁷ Ω.cm and 5.07 x 10⁷ Ω.cm when the reaction time changed from 2 hours to 10 hours. The conductivity of the TiO₂/ Ag₂S QDs thin films increased with the increase in hydrothermal reaction time and further increased with the incorporation of Ag₂S QDs. Besides, the TiO₂ films synthesized hydrothermally for 10 hours showed higher surface roughness as compared to other thin films. The obtained results showed that the TiO₂ / Ag₂S QDs thin films are applicable as a photoanode for Quantum Dots Sensitized Solar Cell (QDSSCs) applications.