Biomedical subjects

Yufeng Hao

Publications and source records attributed to Yufeng Hao.

3 recordsLinked to original sources

PubMed2006

Periodically twinned nanowires and polytypic nanobelts of ZnS: The role of mass diffusion in vapor-liquid-solid growth.

There are two mass diffusion processes regarding the vapor-liquid-solid (VLS) growth of nanostructures: one is inside the catalyst droplet toward the liquid-solid interface; the other is along the side surface planes of the growing nanostructures. In this letter, microscale, modulated mass diffusion scenarios are exhibited through the synthesis of two types of ZnS nanostructures in an Au-catalyzed VLS process: periodically twinned nanowires originated from periodical fluctuation between diffusion rate inside the catalytic droplet and the growth rate on the liquid-solid interface; the formation of asymmetrically polytypic nanobelts is related to one certain side surface bounded by high surface-energy plane, which serves as a preferential diffusion direction of reactant adatoms. The results may have important impact on the understanding of the physical and chemical process of the VLS mechanism. These longitudinally and latitudinally tunable crystalline structures enrich the family of one-dimensional nano-building blocks, and may find potential applications in nanotechnology.

Computer Simulation↗

PubMed2005

Zinc oxide nanostructures: morphology derivation and evolution.

Zinc oxide nanostructures of various types, including nanobelts, nanoplatelets, nanowires, and nanorods, have been synthesized via well-developed routes by many research groups. However, so far, the underlying mechanism for the morphology derivation and evolution of the nanostructures has not been elucidated in depth. In this article, we report the systematic investigation of the morphology evolution characteristics of ZnO nanostructures from dense rods to dense nanoplatelets, nanoplatelet flowers, dense nanobelt flowers, and nanowire flowers in an evaporation-physical transport-condensation approach. Through the use of crystal growth theory, the determining factors for the formation of different nanostructural morphologies were found to be gas-phase supersaturation and the surface energy of the growing surface planes. Other experimental parameters such as the temperature at the source and the substrate, the temperature difference and the distance between the source and the substrate, the heating rate of the furnace, the gas flow rate, the ceramic tube diameter, and the starting material are all correlated with supersaturation and impose an effect on the morphology evolution. This finding may have an important impact on the qualitative understanding of the morphology evolution of nanostructures and the achieving of desired nanostructures controllably.

Journal Article↗

PubMed2005

Kinetics-driven growth of orthogonally branched single-crystalline magnesium oxide nanostructures.

Orthogonally branched single-crystalline magnesium oxide nanostructures were synthesized through a simple chemical vapor transport and condensation process in a flowing Ar/O(2) atmosphere. Other morphologies, such as cubes and nanowires, can also be obtained under different controlled conditions. The formation of different types of nanostructures can be tuned by modifying oxygen partial pressure during the synthesis. All the nanostructures are cubic single-crystalline enclosed by low-index {100} facets. Growth mechanisms for the nanostructures are discussed in detail: different supersaturation ratios, relatively high substrate temperatures, and surface defects in certain crystallographic planes cooperatively take important effects on determining the product morphologies. Structural defect-related blue light emission of the three types of MgO nanostructures was investigated. The MgO nanostructures with abundant morphologies may find applications in various nanodevices, and the kinetics-driven methodology might be exploited to synthesize similar nanostructures of other functional oxide materials.

Journal Article↗