Author
Hengzhong Zhang
Other affiliations: Central South University, University of Wisconsin-Madison, Planetary Science Institute
Bio: Hengzhong Zhang is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Nanoparticle & Nanocrystalline material. The author has an hindex of 41, co-authored 83 publications receiving 11140 citations. Previous affiliations of Hengzhong Zhang include Central South University & University of Wisconsin-Madison.
Topics: Nanoparticle, Nanocrystalline material, Anatase, Particle size, Particle
Papers published on a yearly basis
Papers
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TL;DR: High-resolution transmission electron microscopy of biomineralization products of iron-oxidizing bacteria revealed an alternative coarsening mechanism in which adjacent 2- to 3-nanometer particles aggregate and rotate so their structures adopt parallel orientations in three dimensions.
Abstract: Crystals are generally considered to grow by attachment of ions to inorganic surfaces or organic templates. High-resolution transmission electron microscopy of biomineralization products of iron-oxidizing bacteria revealed an alternative coarsening mechanism in which adjacent 2- to 3-nanometer particles aggregate and rotate so their structures adopt parallel orientations in three dimensions. Crystal growth is accomplished by eliminating water molecules at interfaces and forming iron-oxygen bonds. Self-assembly occurs at multiple sites, leading to a coarser, polycrystalline material. Point defects (from surface-adsorbed impurities), dislocations, and slabs of structurally distinct material are created as a consequence of this growth mechanism and can dramatically impact subsequent reactivity.
1,620 citations
TL;DR: In this paper, the impact of particle size on phase stability and phase transformation during growth of nanocrystalline aggregates was investigated using titania (TiO2) samples consisting of anatase and brookite.
Abstract: To understand the impact of particle size on phase stability and phase transformation during growth of nanocrystalline aggregates we conducted experiments using titania (TiO2) samples consisting of nanocrystalline anatase (46.7 wt %, 5.1 nm) and brookite (53.3 wt %, 8.1 nm). Reactions were studied isochronally at reaction times of 2 h in the temperature range 598−1023 K and isothermally at 723, 853, and 973 K by X-ray diffraction (XRD). A numerical deconvolution method was developed to separate overlapping XRD peaks, and an analytical method for determining phase contents of anatase, brookite, and rutile from XRD data was established. Results show that, in contrast to previous studies, anatase in our samples transforms to brookite and/or rutile before brookite transforms to rutile. Thermodynamic and kinetic analyses further support this conclusion. For general titania samples, the transformation sequence among anatase and brookite depends on the initial particle sizes of anatase and brookite, since partic...
1,408 citations
University of Washington1, Pacific Northwest National Laboratory2, University of Wisconsin-Madison3, Radcliffe Institute for Advanced Study4, Eindhoven University of Technology5, University of Minnesota6, Lawrence Berkeley National Laboratory7, Northwestern University8, University of California, Berkeley9, University of Houston10, University of California, Davis11, University of Delaware12, Virginia Tech13, University of Leeds14, University of Konstanz15
TL;DR: The current understanding of CPA is described, some of the nonclassical thermodynamic and dynamic mechanisms known to give rise to experimentally observed pathways are examined, and the challenges to the understanding of these mechanisms are highlighted.
Abstract: Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments.
1,357 citations
TL;DR: In this article, the phase stability of anatase and rutile was analyzed thermodynamically, and it was shown that anatase becomes more stable than rutsile when the particle size decreases below 14 nm.
Abstract: The phase stability of nanocrystalline anatase and rutile was analyzed thermodynamically. According to the present analysis, anatase becomes more stable than rutile when the particle size decreases belowca. 14 nm. The calculated phase boundary between nanocrystalline anatase and rutile coincides with the experimental data for appearance of rutile during coarsening of nanocrystalline anatase. Both surface free energy and surface stress play important roles in the thermodynamic phase stability, which is a function of particle size.
1,212 citations
TL;DR: The closely balanced energetics of the TiO2 polymorphs directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7).
Abstract: The energetics of the TiO2 polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 ± 0.38 kJ/mol (6) and bulk anatase is 2.61 ± 0.41 kJ/mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 ± 0.2 J/m2, 1.0 ± 0.2 J/m2, and 0.4 ± 0.1 J/m2, respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m2/mol is 24.25 ± 0.88 kJ/mol higher in enthalpy than bulk rutile.
502 citations
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations
9,432 citations
TL;DR: This review discusses the synthetic chemistry, fluid stabilization and surface modification of superparamagnetic iron oxide nanoparticles, as well as their use for above biomedical applications.
6,207 citations
TL;DR: Probing the various interfaces of nanoparticle/biological interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings.
Abstract: Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.
6,075 citations
TL;DR: The field of photocatalysis can be traced back more than 80 years to early observations of the chalking of titania-based paints and to studies of the darkening of metal oxides in contact with organic compounds in sunlight as discussed by the authors.
5,729 citations