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William W. Yu

Bio: William W. Yu is an academic researcher from Louisiana State University in Shreveport. The author has contributed to research in topics: Quantum dot & Perovskite (structure). The author has an hindex of 56, co-authored 213 publications receiving 23000 citations. Previous affiliations of William W. Yu include Worcester Polytechnic Institute & University of Arkansas.


Papers
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TL;DR: In this article, the extinction coefficient per mole of nanocrystals at the first exitonic absorption peak, e.g., for high-quality CdTe, CdSe, and CdS, was found to be strongly dependent on the size of the nanocrystal, between a square and a cubic dependence.
Abstract: The extinction coefficient per mole of nanocrystals at the first exitonic absorption peak, e, for high-quality CdTe, CdSe, and CdS nanocrystals was found to be strongly dependent on the size of the nanocrystals, between a square and a cubic dependence. The measurements were carried out using either nanocrystals purified with monitored purification procedures or nanocrystals prepared through controlled etching methods. The nature of the surface ligands, the refractive index of the solvents, the PL quantum yield of the nanocrystals, the methods used for the synthesis of the nanocrystals, and the temperature for the measurements all did not show detectable influence on the extinction coefficient for a given sized nanocrystal within experimental error.

4,802 citations

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TL;DR: In this paper, it was shown that a "nanofluid" consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure or pure glycol or even polyethylene glycol containing the same volume fraction of dispersed oxide nanoparticles.
Abstract: It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.

3,551 citations

Journal ArticleDOI
TL;DR: It is shown that noncoordinating solvents not only are compatible with the synthesis of semiconductor nanocrystals, but also provide tunable reactivity of the monomers by simply varying the concentration of ligands in the solution.
Abstract: Semiconductor nanocrystals are of great interest for both fundamental research and industrial development.[1, 2] The lack of adequate synthetic methods for nanocrystals of the desired quality is currently a bottleneck in this field.[3] The relatively successful approaches, including the organometallic approach[4±8] and its alternatives,[9±13] are exclusively performed in coordinating solvents. Evidently, only a few compounds can act as the coordinating solvents,[11] and this makes it extremely challenging to identify a suitable reaction system for growing high-quality nanocrystals in most cases. Here we show that noncoordinating solvents not only are compatible with the synthesis of semiconductor nanocrystals, but also provide tunable reactivity of the monomers by simply varying the concentration of ligands in the solution. The tunable reactivity of the monomers provides a necessary balance between nucleation and growth, which is the key for control over the size and size distribution of the resulting nanocrystals.[5] In practice, such tunability has great potential to promote the synthesis of various semiconductor nanocrystals to the level of that of the well-developed CdSe N N

1,231 citations

Journal ArticleDOI
10 Nov 2006-Science
TL;DR: Using the high specific surface area of Fe3O4 NCs that were 12 nanometers in diameter, the mass of waste associated with arsenic removal from water was reduced by orders of magnitude and the size dependence of magnetic separation permitted mixtures of 4- and 12-nanometer–sized Fe3Os to be separated by the application of different magnetic fields.
Abstract: Magnetic separations at very low magnetic field gradients (<100 tesla per meter) can now be applied to diverse problems, such as point-of-use water purification and the simultaneous separation of complex mixtures. High-surface area and monodisperse magnetite (Fe3O4) nanocrystals (NCs) were shown to respond to low fields in a size-dependent fashion. The particles apparently do not act independently in the separation but rather reversibly aggregate through the resulting high-field gradients present at their surfaces. Using the high specific surface area of Fe3O4 NCs that were 12 nanometers in diameter, we reduced the mass of waste associated with arsenic removal from water by orders of magnitude. Additionally, the size dependence of magnetic separation permitted mixtures of 4- and 12-nanometer-sized Fe3O4 NCs to be separated by the application of different magnetic fields.

1,170 citations

Journal ArticleDOI
TL;DR: In this article, the formation of nearly monodisperse CdTe nanocrystals was studied, and the ligand effects on the monomers were found to play a more important role than ligand effect on the nanocrystal and the bonding strength and steric effects of ligands dramatically affect the reactivity of monomers and are considered as contributors to the activity coefficients of monomer.
Abstract: The formation of nearly monodisperse CdTe nanocrystalsdots (either zinc blende or wurtzite crystal structure), rods, and tetrapodsin a noncoordinating solvent was studied Several strong ligand effects were observed, and the ligand effects on the monomers were found to play a more important role than the ligand effects on the nanocrystals Experimental results suggest that, instead of monomer concentrations, monomer activities is a more relevant term for understanding the formation of nanocrystals because strong ligands always exist in the reaction solutions The bonding strength and the steric effects of ligands dramatically affect the reactivity of monomers and are considered as contributors to the activity coefficients of monomers The overall optical properties of the as-prepared CdTe nanocrystals are better than those reported in the literature and comparable to the standard CdSe nanocrystal system The configuration of the hydrocarbon chains of the ligands on the surface of each nanocrystal also pla

753 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
28 Jan 2005-Science
TL;DR: The new generations of qdots have far-reaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.
Abstract: Research on fluorescent semiconductor nanocrystals (also known as quantum dots or qdots) has evolved over the past two decades from electronic materials science to biological applications. We review current approaches to the synthesis, solubilization, and functionalization of qdots and their applications to cell and animal biology. Recent examples of their experimental use include the observation of diffusion of individual glycine receptors in living neurons and the identification of lymph nodes in live animals by near-infrared emission during surgery. The new generations of qdots have farreaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.

7,499 citations

Journal ArticleDOI
20 Mar 2008-Nature
TL;DR: Some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water are highlighted.
Abstract: One of the most pervasive problems afflicting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally, even in regions currently considered water-rich. Addressing these problems calls out for a tremendous amount of research to be conducted to identify robust new methods of purifying water at lower cost and with less energy, while at the same time minimizing the use of chemicals and impact on the environment. Here we highlight some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water.

6,967 citations