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Your search keyword '"Hsu, Wei‐Hao"' showing total 128 results
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128 results on '"Hsu, Wei‐Hao"'

1. Formation of highly stable interfacial nitrogen gas hydrate overlayers under ambient conditions

Author

Fang, Chung-Kai, Chuang, Cheng-Hao, Yang, Chih-Wen, Guo, Zheng-Rong, Hsu, Wei-Hao, Wang, Chia-Hsin, and Hwang, Ing-Shouh

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Chemical Physics
Abstract

Surfaces (interfaces) dictate many physical and chemical properties of solid materials and adsorbates considerably affect these properties. Nitrogen molecules, which are the most abundant constituent in ambient air, are considered to be inert. Our study combining atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) revealed that nitrogen and water molecules can self-assemble into two-dimensional domains, forming ordered stripe structures on graphitic surfaces in both water and ambient air. The stripe structures of this study were composed of approximately 90% and 10% water and nitrogen molecules, respectively, and survived in ultra-high vacuum (UHV) conditions at temperatures up to approximately 350 K. Because pure water molecules completely desorb from graphitic surfaces in a UHV at temperatures lower than 200 K, our results indicate that the incorporation of nitrogen molecules substantially enhanced the stability of the crystalline water hydrogen bonding network. Additional studies on interfacial gas hydrates can provide deeper insight into the mechanisms underlying formation of gas hydrates.

Published
2024

2. Observation of Mesoscopic Clathrate Structures in Ethanol-Water Mixtures

Author

Hsu, Wei-Hao, Yen, Tzu-Chieh, Chen, Chien-Chun, Yang, Chih-Wen, Fang, Chung-Kai, and Hwang, Ing-Shouh

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Water-alcohol mixtures exhibit many abnormal physicochemical properties, the origins of which remain controversial. Here we use transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and atomic force microscopy (AFM) to study ethanol-water mixtures. TEM reveals mesoscopic clathrate structures with water molecules forming a crystalline matrix hosting a high density of tiny cells. The presence of these mesoscopic clathrate structures is further supported by a refractive index of 1.27+-0.02 at 405 nm measured via NTA and the hydrophilic nature of the mesoscopic structures implied by AFM observations, explaining many long-standing puzzles related to water-alcohol mixtures.

Published
2022

6. Three-dimensional surface topography of graphene by divergent beam electron diffraction

Author

Latychevskaia, Tatiana, Hsu, Wei-Hao, Chang, Wei-Tse, Lin, Chun-Yueh, and Hwang, Ing-Shouh

Subjects
Physics - Instrumentation and Detectors, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

There is only a handful of scanning techniques that can provide surface topography at nanometre resolution. At the same time, there are no methods that are capable of non-invasive imaging of the three-dimensional surface topography of a thin free-standing crystalline material. Here we propose a new technique - the divergent beam electron diffraction (DBED) and show that it can directly image the inhomogeneity in the atomic positions in a crystal. Such inhomogeneities are directly transformed into the intensity contrast in the first order diffraction spots of DBED patterns and the intensity contrast linearly depends on the wavelength of the employed probing electrons. Three-dimensional displacement of atoms as small as 1 angstrom can be detected when imaged with low-energy electrons (50 - 250 eV). The main advantage of DBED is that it allows visualisation of the three-dimensional surface topography and strain distribution at the nanometre scale in non-scanning mode, from a single shot diffraction experiment.

Published
2017
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7. Preferential Gas Adsorption at the Graphene-Water interface

Author

Ko, Hsien-Chen, Hsu, Wei-Hao, Yang, Chih-Wen, Fang, Chung-Kai, Lu, Yi-Hsien, and Hwang, Ing-Shouh

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The contact of water with graphene is of fundamental importance and of great interest for numerous promising applications, but how graphene interacts with water remains unclear. Here we used atomic force microscopy to investigate hydrophilic mica substrates with some regions covered by mechanically exfoliated graphene layers in water. In water containing air gas close to the saturation concentration (within ~40%), cap-shaped nanostructures and ordered stripe domains were observed on graphene-covered regions, but not on pure mica regions. These structures did not appear on graphene when samples were immersed in highly degassed water, indicating that their formation was caused by adsorption of gas dissolved in water. Thus, atomically thin graphene, even at a narrow width of 20 nm, changes the local surface chemistry of a highly hydrophilic substrate. Further, surface hydrophobicity significantly affects gas adsorption, which has broad implications for diverse phenomena in water.

Published
2016

8. Low-voltage coherent electron imaging based on a single-atom electron

Author

Chang, Wei-Tse, Lin, Chun-Yueh, Hsu, Wei-Hao, Chang, Mu-Tung, Chen, Yi-Sheng, Hwu, En-Te, and Hwang, Ing-Shouh

Subjects
Physics - Instrumentation and Detectors, Condensed Matter - Materials Science
Abstract

It has been a general trend to develop low-voltage electron microscopes due to their high imaging contrast of the sample and low radiation damage. Atom-resolved transmission electron microscopes with voltages as low as 15-40 kV have been demonstrated. However, achieving atomic resolution at voltages lower than 10 kV is extremely difficult. An alternative approach is coherent imaging or phase retrieval imaging, which requires a sufficiently coherent source and an adequately small detection area on the sample as well as the detection of high-angle diffracted patterns with a sufficient resolution. In this work, we propose several transmission-type schemes to achieve coherent imaging of thin materials (less than 5 nm thick) with atomic resolution at voltages lower than 10 kV. Experimental schemes of both lens-less and lens-containing designs are presented and the advantages and challenges of these schemes are discussed. Preliminary results based on a highly coherent single-atom electron source are presented. The image plate is designed to be retractable to record the transmission patterns at different positions along the beam propagation direction. In addition, reflection-type coherent electron imaging schemes are also proposed as novel methods for characterizing surface atomic and electronic structures of materials.

Published
2015

16. Evidence of synergistic electrocatalysis at a cobalt oxide–graphene interface through nanochemical mapping of scanning transmission X-ray microscopy

Author

Vélez, Juan-Jesus Velasco, primary, Chin, Yi-Ying, additional, Tsai, Meng-Hsua, additional, Burton, Oliver James, additional, Wang, Ruizhi, additional, Hofmann, Stephan, additional, Hsu, Wei-Hao, additional, Ohigashi, Takuji, additional, Pong, Way-Faung, additional, and Chuang, Cheng-Hao, additional

Published
2022
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48. Greater HbA1c variability is associated with increased cardiovascular events in type 2 diabetes patients with preserved renal function, but not in moderate to advanced chronic kidney disease.

Author

Lee, Mei-Yueh, Hsiao, Pi-Jung, Huang, Yu-Ting, Huang, Jiun-Chi, Hsu, Wei-Hao, Chen, Szu-Chia, and Shin, Shyi–Jang

Subjects
GLYCEMIC control, BLOOD sugar monitoring, TYPE 2 diabetes, CARDIOVASCULAR diseases, CORONARY disease
Abstract

Emerging evidence suggests that glycemic variability may be a more reliable measure of glycemic control than mean HbA1c in type 2 diabetes mellitus. This study aimed to determine if HbA1c variability is associated with cardiovascular events in type 2 diabetic patients and if different renal functions affect such association. This longitudinal study enrolled 8259 diabetic patients from the Kaohsiung Medical University Research Database in 2009 and were followed-up until 2015. Intra-individual HbA1C variability was defined as the standard deviation (SD) of HbA1c and cardiovascular events were defined as hospitalization for coronary artery disease, unstable angina, myocardial infarction, stroke, peripheral artery disease, and cardiovascular death. The patients were grouped into two based on their estimated glomerular filtration rate (eGFR) ≥ 60 or < 60 min/ml/1.73m2. In a mean follow-up period of 6.3 years, cardiovascular events were recorded in 8.9% of the patients. In an adjusted Cox model, high HbA1c SD (hazard ratio, 1.290; 95% confidence interval, 1.008–1.650; p = 0.043), but not mean HbA1c, was associated with significantly increased risk of cardiovascular events in patients with eGFR ≥ 60 min/ml/1.73m2. This association was not seen in patients with eGFR < 60 min/ml/1.73m2. In this study, greater HbA1c variability is associated with increased risk of cardiovascular among patients with preserved renal function, but not in those with moderate to advanced chronic kidney disease. [ABSTRACT FROM AUTHOR]

Published
2017
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