RESUMEN
This work demonstrates the enhancement of light extraction of polymer light-emitting diodes (PLEDs) by incorporating a 12-fold photonic quasi crystal (PQC) in the device structure. Multi-exposure two-beam interference technique combined with inductively coupled plasma etching was employed to pattern a 12-fold PQC structure on the ITO film on a glass substrate of the diode. The air-hole coverage (AHC) and etching depth dependences of the light emitting performance of the 12-fold PQC patterned PLEDs were investigated. For AHC within the range between 6.4% and 32.3%, a nearly constant enhancement of the luminance efficiency of the PQC PLEDs was observed. On the other hand, the light emitting performance of the PQC PLEDs is very sensitive to the etching depth. The photoluminescence intensity of the PQC PLEDs increases monotonically with the etching depth. In contrast, the electro luminance efficiency shows a non-monotonic dependence on etching depth with a maximum occurring at 55 nm etching depth. The maximum improvement of luminance efficiency of the 12-fold PQC PLEDs reaches nearly 95% compared with an un-patterned PLED at an injection current of 110 mA.
RESUMEN
The objective of this study is to investigate the nano-fabrication method for ginseng extract powders (GEPs) and detect the differences in physical and chemical properties, and cytotoxicity of GEPs before and after fabrication. White ginseng was used as the raw material to produce the GEPs (Sample A). After grinding, the GEPs passed a 40-mesh sieve (particle size < 105 microm) and was named as Sample B. The residue (particle size > 105 microm) was named as Sample C. Samples A and B were used for nanofabrication though the use of a high-energy ball mill. Sample B was ground for 3 hr (Sample D) and 1 hr (Sample E), while Sample A was ground for 3 hr (Sample F) and 1 hr (Sample G). Nanoparticles of GEPs with ranges of 300 nm approximately 1 microm and 500 nm approximately 3 microm were produced. The heavy metal content (As, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb, Se and W) of Samples A-G were all under the maximum residue limit. Sample C contained a higher amount of yellow crystal material and had the highest ginsenoside contents and antioxidant capacity. There were enrichments of ginsenosides (approximately 1.3 fold) and antioxidant capacities (approximately 1.6 fold) in Sample C compared to Sample A. Moreover, after nano-fabrication, the antioxidant capacity was not changed significantly. However, the cellular growth enhancement ability was increased significantly. Samples F and G had the higher cellular growth enhancement ability and improved the cellular growth of L929 cells about 1.3 times as compared to Sample A. In future studies, Sample C will be used for nanofabrication in order to enhance the curative efficiency of ginseng.