• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.52-52
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• 2018

Only approximately 30% of fossil fuel energy is used; therefore, it is desirable to utilize the huge amounts of waste energy. Thermoelectric (TE) materials that convert heat into electrical power are a promising energy technology. The TE materials can be formed either as thin films or as bulk semiconductors. Generally, thin-film TE materials have low energy conversion rates due to their thinness compared to that in bulk. However, an advantage of a thin-film TE material is that the efficiency can be smartly engineered by controlling the nanostructure and composition. Especially nanostructured TE thin films are useful for mitigating heating problems in highly integrated microelectronic devices by accurately controlling the temperature. Hence, there is a rising interest in thin-film TE devices. These devices have been extensively investigated. It is demonstrated that transparent amorphous oxide semiconductors (TAOS) can be excellent thermoelectric (TE) materials, since their thermal conductivity (${\kappa}$) through a randomly disordered structure is quite low, while their electrical conductivity and carrier mobility (${\mu}$) are high, compared to crystalline semiconductors through the first-principles calculations and the various measurements for the amorphous In-Zn-O (a-IZO) thin film. The calculated phonon dispersion in a-IZO shows non-linear phonon instability, which can prevent the transport of phonon. The a-IZO was measured to have poor ${\kappa}$ and high electrical conductivity compared to crystalline $In_2O_3:Sn$ (c-ITO). These properties show that the TAOS can be an excellent thin-film transparent TE material. It is suggested that the TAOS can be employed to mitigate the heating problem in the transparent display devices.

• The Korean Journal of Nuclear Medicine
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• v.36 no.6
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• pp.333-343
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• 2002

Purpose: A new linker, hydrazino nicotinamide (HYNIC), was recently introduced for labelling of liposome with $^{99m}Tc$. In this study we synthesized HYNIC derivatized PEG (polyethylene glycol)-liposomes radiolabeled with $^{99m}Tc$. Materials and Methods: In order to synthesize HYNIC-DSPE (distearoyl phosphatidyl ethanolamine) which is a crucial component for $^{99m}Tc$ chelation, first of all succinimidyl 6-BOC-hydrazinopyridine-3-carboxylic acid was synthesized from 6-chloronicotinic acid by three sequential reactions. A DSPE derivative of succinimidyl 6-BOC-hydrazinopyridine-3-carboxylic acid was transformed into HYNIC-DSPE by HCI/dioxane. HYNIC-PEG-liposomes were prepared by hydration of the dried lipid mixture of EPC (egg phosphatidyl choline): PEG-DSPE : HYNIC-DSPE:cholesterol (1.85:0.15:0.07:1, molar ratio). The HYNIC-PEG-liposomes were labeled with $^{99m}Tc$ in the presence of $SnCl_2{\cdot}2H_2O$ (a reducing agent) and tricine (a coligand). To investigate the level of in vivo transchelation of $^{99m}Tc$ in the liposomes, the $^{99m}Tc$-HYNiC-PES-liposomes were incubated with a molar excess of DTPA, cysteine or glutathione solutions at $37^{\circ}C$ for 1 hour. The radiolabeled liposomes were also incubated in the presence of human serum at $37^{\circ}C$ for 24 hours. Results: 6-BOC-hydrazinopyridine-3-carboxylic acid was synthesized with 77.3% overall yield. The HYNIC concentration in the PEG-coated liposome dispersion was 1.08 mM. In condition of considering the measured liposomal size of 106 nm, the phospholipid concentration of $77.5\;{\mu}mol/m{\ell}$ and the liposomal particle number of $5.2{\times}10^{14}$ liposomes/ml, it is corresponded to approximate 1,250 nicotinyl hydrazine group per liposome in HYNIC-PEG-liposome. The removal of free $^{99m}Tc$ was not necessary because the labeling efficiency were above 99%. The radiolabeled liposomes maintained 98%, 96% and 99%, respectively, of radioactivity after incubation with transchelators. The radiolabeled liposomes possessed above 90% of the radioactivity in serum. Conclusion: These results suggest that the HYNIC can be synthesized easily and applied in labelling of PEG-liposomes with $^{99m}Tc$.