Browsing by Author "Lee, M."
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Item A Fermi-Level-Pinning-Free 1D Electrical Contact at the Intrinsic 2D MoS₂–Metal Junction(Wiley-VCH Verlag, 2019-05-08) Yang, Z.; Kim, C.; Lee, K. Y.; Lee, M.; Appalakondaiah, S.; Ra, C. -H; Watanabe, K.; Taniguchi, T.; Cho, Kyeongiae; Hwang, E.; Hone, J.; Yoo, W. J.; 0000-0003-2698-7774 (Cho, K); Cho, KyeongiaeCurrently 2D crystals are being studied intensively for use in future nanoelectronics, as conventional semiconductor devices face challenges in high power consumption and short channel effects when scaled to the quantum limit. Toward this end, achieving barrier-free contact to 2D semiconductors has emerged as a major roadblock. In conventional contacts to bulk metals, the 2D semiconductor Fermi levels become pinned inside the bandgap, deviating from the ideal Schottky–Mott rule and resulting in significant suppression of carrier transport in the device. Here, MoS₂ polarity control is realized without extrinsic doping by employing a 1D elemental metal contact scheme. The use of high-work-function palladium (Pd) or gold (Au) enables a high-quality p-type dominant contact to intrinsic MoS₂, realizing Fermi level depinning. Field-effect transistors (FETs) with Pd edge contact and Au edge contact show high performance with the highest hole mobility reaching 330 and 432 cm² V⁻¹ s⁻¹ at 300 K, respectively. The ideal Fermi level alignment allows creation of p- and n-type FETs on the same intrinsic MoS₂ flake using Pd and low-work-function molybdenum (Mo) contacts, respectively. This device acts as an efficient inverter, a basic building block for semiconductor integrated circuits, with gain reaching 15 at V_{D} = 5 V. ©2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem Regulation of Acetate Utilization by Monocarboxylate Transporter 1 (MCT1) in Hepatocellular Carcinoma (HCC)(Cognizant Communication Corporation, 2018-10-22) Jeon, J. Y.; Lee, M.; Whang, S. H.; Kim, Jung-whan; Cho, A.; Yun, M.; 0000-0002-7829-1480 (Kim, J-w); Kim, Jung-whanAltered energy metabolism is a biochemical fingerprint of cancer cells. Hepatocellular carcinoma (HCC) shows reciprocal [¹⁸F]fluorodeoxyglucose (FDG) and [¹¹C]acetate uptake, as revealed by positron emission tomography/computed tomography (PET/CT). Previous studies have focused on the role of FDG uptake in cancer cells. In this study, we evaluated the mechanism and roles of [¹¹C]acetate uptake in human HCCs and cell lines. The expression of monocarboxylate transporters (MCTs) was assessed to determine the transporters of [¹¹C]acetate uptake in HCC cell lines and human HCCs with different [¹¹C]acetate uptake. Using two representative cell lines with widely different [¹¹C]acetate uptake (HepG2 for high uptake and Hep3B for low uptake), changes in [¹¹C]acetate uptake were measured after treatment with an MCT1 inhibitor or MCT1- targeted siRNA. To verify the roles of MCT1 in cells, oxygen consumption rate and the amount of lipid synthesis were measured. HepG2 cells with high [¹¹C]acetate uptake showed higher MCT1 expression than other HCC cell lines with low [¹¹C]acetate uptake. MCT1 expression was elevated in human HCCs with high [¹¹C] acetate uptake compared to those with low [¹¹C]acetate uptake. After blocking MCT1 with AR-C155858 or MCT1 knockdown, [¹¹C]acetate uptake in HepG2 cells was significantly reduced. Additionally, inhibition of MCT1 suppressed mitochondrial oxidative phosphorylation, lipid synthesis, and cellular proliferation in HCC cells with high [¹¹C]acetate uptake. MCT1 may be a new therapeutic target for acetate-dependent HCCs with high [¹¹C]acetate uptake, which can be selected by [¹¹C]acetate PET/CT imaging in clinical practice.