Younan Xia

Bio: Younan Xia is an academic researcher from The Wallace H. Coulter Department of Biomedical Engineering. The author has contributed to research in topics: Nanocages & Nanowire. The author has an hindex of 216, co-authored 943 publications receiving 175757 citations. Previous affiliations of Younan Xia include Washington University in St. Louis & University of Texas at Dallas.

Noble-Metal Nanocrystals with Controlled Shapes for Catalytic and Electrocatalytic Applications.

Abstract: The successful synthesis of noble-metal nanocrystals with controlled shapes offers many opportunities to not only maneuver their physicochemical properties but also optimize their figures of merit in a wide variety of applications. In particular, heterogeneous catalysis and surface science have benefited enormously from the availability of this new class of nanomaterials as the atomic structure presented on the surface of a nanocrystal is ultimately determined by its geometric shape. The immediate advantages may include significant enhancement in catalytic activity and/or selectivity and substantial reduction in materials cost while providing a well-defined model system for mechanistic study. With a focus on the monometallic system, this review article provides a comprehensive account of recent progress in the development of noble-metal nanocrystals with controlled shapes, in addition to their remarkable performance in a large number of catalytic and electrocatalytic reactions. We hope that this review article offers the impetus and roadmap for the development of next-generation catalysts vital to a broad range of industrial applications.

Solvent‐assisted microcontact molding: A convenient method for fabricating three‐dimensional structures on surfaces of polymers

Abstract: Registered names. trademarks. etc. used in this journal. even without specific, indications thereof, are not to be considered unprotected by law. Printed in the Federal Republic of Germany

One-dimensional nanostructures of trigonal tellurium with various morphologies can be synthesized using a solution-phase approach

Abstract: This article describes a solution-phase, self-seeding approach to the large-scale synthesis of one-dimensional (1D) nanostructures of trigonal tellurium (t-Te) with diameters ranging from 50 to hundreds of nanometers, and lengths up to tens of micrometers. These highly anisotropic nanostructures were formed through the reduction of orthotelluric acid (or tellurium dioxide) by hydrazine at various refluxing temperatures. Nuclei formed in the reduction process had a strong tendency to grow along the c-axis due to the inherently anisotropic structure of t-Te. Depending on the solvent and refluxing temperature, the growth of t-Te nanostructures was found to follow two distinct paths. When the reaction was refluxed in water and at temperatures below 100 °C, the initial reduction products were a mixture of nanocrystallites of t-Te and spherical colloids of amorphous tellurium (a-Te). When this mixture was aged at room temperature, the a-Te colloids slowly dissolved into the solution and grew into nanowires on the nanocrystallites of t-Te. When the reaction was carried out in pure ethylene glycol (or mixtures with water) and refluxed at temperatures above 100 °C, the 1D nanostructures of t-Te were directly formed in the reduction process. The exact morphology of these anisotropic nanostructures was mainly controlled by the refluxing temperature (Tr); typical examples include spines (Tr < 100 °C), filaments (Tr = 100–160 °C), needles (Tr = 160–180 °C), and tubular structures (Tr > 180 °C). These uniform, relatively monodispersed 1D nanostructures could form stable dispersions in ethylene glycol or water, and be used as the building blocks or templates to generate more complex nanostructured materials.

Shape-Controlled Synthesis of Silver and Gold Nanostructures

Abstract: This article provides a brief account of solution-phase methods that generate silver and gold nanostructures with well-controlled shapes. It is organized into five sections: The first section discusses the nucleation and formation of seeds from which nanostructures grow. The next two sections explain how seeds with fairly isotropic shapes can grow anisotropically into distinct morphologies. Polyol synthesis is selected as an example to illustrate this concept. Specifically, we discuss the growth of silver nanocubes (with and without truncated corners), nanowires, and triangular nanoplates. In the fourth section, we show that silver nanostructures can be transformed into hollow gold nanostructures through a galvanic replacement reaction. Examples include nanoboxes, nanocages, nanotubes (both single- and multi-walled), and nanorattles. The fifth section briefly outlines a potential medical application for gold nanocages.We conclude with some perspectives on areas for future work.

Microcontact printing of octadecylsiloxane on the surface of silicon dioxide and its application in microfabrication

Abstract: This paper describes the use of microcontact printing ({mu}CP) for patterning self-assembled monolayers (SAMs) of alkylsiloxanes on the surface of silicon dioxide. {mu}CP is a convenient technique for generating patterned SAMs of alkanethiolates on gold, but it has not been applied to Si/SiO{sub 2} and glass. The SAMs of alkyltrichlorosilanes on the hydroxyl-terminated surfaces are less ordered than those of alkanethiolates on gold, and they form more slowly. Here we demonstrate that {mu}CP can, nonetheless, be used to produce patterned SAMs of alkylsiloxanes on Si/SiO{sub 2}. We believe this technique will prove valuable for many other applications: for example, studies of protein absorption and cell attachment where high edge resolution is not critical. 17 refs., 2 figs., 1 tab.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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。

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346