Papers by Keyword: Seeded-Growth

Abstract: Seeded growth of gallium nitride (GaN) crystals on a spontaneously nucleated small GaN by the Na flux method was performed. In this study, we attempted to control the growth habit by changing the flux composition (Ga/Na) and by introducing a small amount of additives (Ca and Li). Our experiment clarified that a low Ga composition was preferred to grow high-crystallinity prismatic GaN crystals with a high growth rate. Furthermore, the transparent GaN single crystals with prism shape could be grown by the addition of Ca and Li.

Abstract: Horseradish peroxidase (HRP) was successfully immobilized on vertically oriented TiO₂ nanotube arrays (NTAs), which was prepared by seeded-growth mechanism. The nanotubular structure of TiO₂ was characterized by scanning electron microscope (SEM). After encapsulated HRP on TiO₂ nanotube arrays, the direct electron transfer of HRP was observed.

Abstract: This work describes properties of 1-D ZnO nanorods arrays growth using low temperature hydrothermal method on a seeded substrate. The properties of ZnO seed were studied by varying thermal oxidation temperature from 250-450°C. The formation of ZnO nanorods was studied by varying the growth time during hydrothermal process. The optimum oxidation temperature to produce seeded ZnO template was 400°C. The formation of ZnO nanorods was further studied by varying hydrothermal reaction growth time from 1 to 24 hours. The optimum hydrothermal growth time of 4 hours produced blunt tip-like nanorods with length of ~735 nm and top diameter of ~66 nm. I-V characteristics of ZnO nanorods photodetector in dark, ambient light and UV light were also studied. The change in the photoconductivity under UV illumination was found to be 1 order of magnitude higher compared to dark and ambient light. With an incident wavelength of 370 nm and applied bias of 3V, the responsivity of photodetector was 5.0 mA/W, which was higher compared to other reported works. The increase of photosensitivity indicated that the produced ZnO nanorods were suitable for UV photodetector applications.

Abstract: This study describes the formation of spherical gold nanoparticles (AuNPs) using a simple seeded-growth technique. The size and surface morphology of AuNPs were investigated using transmission electron microscopy (TEM) and UV-Vis spectrophotometer was used to determine the wavelength and absorption of AuNPs. In the seed stage, the effect of trisodium citrate volume was studied. The size of AuNPs at seed stage was varied from 15 to 40 nm with decreasing volume of trisodium citrate. In the growth stage, the effects of seed solution volume and concentration of hydroxylamine were studied. The size of AuNPs produced became larger when the amount of seed solution was reduced. This approach was beneficial to produce AuNPs with the size range from 15 to 150 nm. The increase of hydroxylamine concentration increased the size of AuNPs. However, after the concentration of hydroxylamine reached supersaturation condition (3 M NH₂OH.HCl), the AuNPs formed in a bulk and clusters. Selected sizes of AuNPs were then conjugated to antibody and proved by testing on the immunoassay test strip. The observation using naked eyes for the appearance of red lines on the immunoassay test strip showed that AuNPs were successfully conjugated to antibody and specifically bound to the antigen drawn on the strip assay by tested with positive and negative serum of the disease.

Abstract: This work describes the formation of WO₃ nanostructures via seeded growth hydrothermal reaction. WO₃ seed formation was first studied using thermal oxidation of W substrate from 300-500°C for 30 minutes. The optimum seeded substrates were then subjected to hydrothermal reaction at 80°C by varying precursor concentration and pH of the solution. Optimum oxidation temperature to produce WO₃ seeds was at 400°C for 30 minutes. Below 400°C, no seed was formed while above that temperature the seeds became too compact and less uniform. The optimum hydrothermal reaction parameters were obtained after 24 hrs reaction time, concentration ratio of sodium tungstate dehydrate to cetyltrimethylammonium bromide (CTAB) of 6:1 and at pH 2. By lowering the pH and increasing the precursor concentration, the growth of WO₃ nanostructures was enhanced. X-ray diffraction analysis showed that WO₃ nanostructures formed were of hexagonal structure.