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Annealing Effects on the Photoluminescence of Amorphous Silicon-Nitride Films
Changhun Ko,Moonsup Han,Byoung Youl Park,Jiho Joo,Jung Hyun Sok,Kyoungwan Park 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
Amorphous silicon-nitride films were deposited at low temperature (350 C) and with high deposition rates (220 . 280 °A/min) by using plasma-enhanced chemical-vapor deposition (PECVD). The optical and the structural properties of these films have been characterized by using photoluminescence (PL) and atomic force microscopy (AFM). Five broad emission peaks, one each at 3.1, 2.4, 2.15, 1.9, and 1.75 eV, were observed in the PL spectra by adjusting the flow rate of the nitrogen gas. As the nitrogen gas flow was increased, the wavelength of the emitted light shifted from blue to red in the PL spectra. After the films were annealed at 700 . 1000 C for 10 min in ultra-high vacuum (UHV) condition, the PL intensity became 4 . 10 times stronger while the positions of the PL peaks were not changed. These experimental results show that the PL of amorphous silicon nitride films is closely related to the formation of optically active defect states. According to this interpretation, we will explain the PL enhancement after the thermal annealing process.p#?
Park, Changhun,Yun, Seokhun,Lee, Sang Yup,Park, Kyungmoon,Lee, Jinwon Humana Press 2012 Applied biochemistry and biotechnology Vol.167 No.3
<P>The global pool of intracellular metabolites is a reflection of all the metabolic functions of an organism. In the absence of in situ methods capable of directly measuring metabolite pools, intracellular metabolite measurements need to be performed after an extraction procedure. In this study, we evaluated the optimization of technologies for generation of a global metabolomics profile for intracellular metabolites in Klebsiella oxytoca. Intracellular metabolites of K. oxytoca were extracted at the early stationary phase using six different common extraction procedures, including cold methanol, boiling ethanol, methanol/chloroform combinations, hot water, potassium hydroxide, and perchloric acid. The metabolites were subsequently collected for further analysis, and intracellular metabolite concentration profiles were generated using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. During analysis, the stability of metabolites extracted using cold methanol was clearly higher than that obtained by other extraction methods. For the majority of metabolites, extracts generated in this manner exhibited the greatest recovery, with high reproducibility. Therefore, the use of cold ethanol was the best extraction method for attaining a metabolic profile. However, in another parallel extraction method, perchloric acid may also be required to maximize the range of metabolites recovered, particularly to extract glucose 1-phosphate and NADPH.</P>
Changhun Park,이진원,Youn-jin Lee,오한빈,이상엽 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.2
In the present study, we demonstrate that SRM LC-MS/MS method developed by Luo et al. (ref. 10) can be successfully applied to the quantitative analysis of intracellular metabolites in E. coli that are collected at the exponential and stationary growth phases. A focus is given on measuring the changes in the concentrations of intracellular metabolites in batch cultures, which were induced during both the dynamically changing exponential and stationary growth phases.The following intracellular metabolites are quantified in the exponential and stationary phases of E. coli growth, using the SRM mode of a triple quadrupole mass spectrometer: glucose-1-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate,pyruvate, acetyl-coenzyme A, 6-phosphogluconate, ribulose-5-phosphate, xylulose-5-phosphate,erythrose-4-phosphate. The determined intracellular metabolite concentration profiles are shown to be in a good agreement with the growth profiles of E. coli, which clearly indicates that SRM LC-MS/MS can be successfully used for following the metabolite changes induced at different growth stages.