Single-crystal hexagonal disks and rings of ZnO: low-temperature, large-scale synthesis and growth mechanism.
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Biomedical subjects
Publications and source records attributed to Yong Ding.
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Freestanding single-crystal complete nanorings of zinc oxide were formed via a spontaneous self-coiling process during the growth of polar nanobelts. The nanoring appeared to be initiated by circular folding of a nanobelt, caused by long-range electrostatic interaction. Coaxial and uniradial loop-by-loop winding of the nanobelt formed a complete ring. Short-range chemical bonding among the loops resulted in a single-crystal structure. The self-coiling is likely to be driven by minimizing the energy contributed by polar charges, surface area, and elastic deformation. Zinc oxide nanorings formed by self-coiling of nanobelts may be useful for investigating polar surface-induced growth processes, fundamental physics phenomena, and nanoscale devices.
Vapor-liquid-solid (VLS) is a well-established process in catalyst-guided growth of nanowires. The catalyst particle is generally believed to be in liquid state during growth, and it is the site for adsorbing incoming molecules; the crystalline structure of the catalyst may not have any influence on the structure of the grown one-dimensional nanostructures. In this paper, using tin particle guided growth of ZnO nanostructures as a model system, we show that the interfacial region of the tin particle with the ZnO nanowire/nanobelt could be ordered (or partially crystalline) during the VLS growth, although the local growth temperature is much higher than the melting point of tin, and the crystallographic lattice structure at the interface is important in defining the structural characteristics of the grown nanowires and nanobelts. The interface prefers to take the least lattice mismatch; thus, the crystalline orientation of the tin particle may determine the growth direction and the side surfaces of the nanowires and nanobelts. This result may have important impact on the understanding of the physical chemical process in the VLS growth.
We report the first successful synthesis and characterization of single-crystal wurtzite CdSe nanoribbons through a simple thermal evaporation process. Asymmetric growth of the nanoribbons occurs, yielding a sawlike shape with sharp teeth on one side. This asymmetric growth is suggested to be induced by the polarization of the c-plane in the wurtzite crystal structure.
AIM: The value of vesicant 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the detection and staging of primary gastric malignancies was studied prospectively. METHODS: Thirty-eight patients with suspected gastric tumour were imaged with three-dimensional PET after the injection of 18F-FDG. During the PET study, vesicant was given orally in order to extend the stomach with CO(2) gas. Surgical operation (n=31) or gastric endoscopy with biopsy (n=7) was undertaken 3-26 days after the PET study. The PET results were compared with clinical (computed tomography/magnetic resonance imaging/ultrasound), surgical and histological staging. RESULTS: PET correctly diagnosed 83.3% of primary malignant (25/30) and benign (7/8) lesions, and corrected 11 clinically and five surgically mis-staged cases. Five primaries were false-negatives in quantitative analysis, but qualitative PET readings revealed positive lymph nodes, thereby providing a correct diagnosis in two of the five. PET misdiagnosed seven N1, one N2 and one false-positive case. The focal uptake of 18F-FDG was correlated with the differentiation, size and depth of invasion of the gastric tumours. CONCLUSIONS: 18F-FDG PET is useful for the detection and staging of primary gastric malignancies, and the administration of vesicant may improve the diagnostic confidence.
OBJECTIVE: To study the change of the activity of protective enzyme to avoid sprout tumble of Pinellia ternata. METHOD: A high temperature stress was given to P. ternata. Then the activity of protective enzyme (SOD, POD and CAT) and the content of membrane lipid peroxidation (MDA) were detected after different treating days. RESULT AND CONCLUSION: By stress time increasing, the content of MDA in lamina and petiole increased obviously, but it increased invisibly in tuber. After high temperature stress, the activity of both SOD and CAT decreased gradually. The activity of POD increased at first but then decreased rapidly.