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.

Synthesis and application of RuSe2 + δnanotubes as a methanol tolerant electrocatalyst for the oxygen reduction reaction

Abstract: This article describes an electrochemical study on the use of RuSe2 + δnanotubes as a catalyst for the oxygen reduction reaction (ORR). Uniform RuSe2 + δnanotubes were synthesized via a facile template-engaged reaction between Ru(acac)3 and t-Se nanowires at 80 °C, followed by selective removal of the unreacted t-Se cores. The resultant RuSe2 + δnanotubes were ∼55 nm in outer diameter, together with a wall thickness of ∼9 nm. These nanotubes were active for ORR and displayed high tolerance to 0.1 M methanol. While the mass-specific ORR activities at 0.7 V were ∼30 times lower than those reported for commercial Pt/C (TKK) catalysts, no detrimental effect over the ORR activity was observed upon the addition of 0.1 M methanol. In the presence of 0.1 M methanol, the mass-specific ORR activity for RuSe2 + δ was ∼12 times lower than that for Pt/C (TKK) at 0.7 V. Durability tests by chronoamperometry showed that 0.1 M methanol led to significant performance loss for Pt/C (TKK), while RuSe2 + δ was completely tolerant to 0.1 M methanol even after 1,800 s of operation.

Au@Cu Core–Shell Nanocubes with Controllable Sizes in the Range of 20–30 nm for Applications in Catalysis and Plasmonics

Abstract: Predominantly covered by a single type of {100} facets, Cu nanocubes are attractive catalytic material toward reactions such as electrochemical reduction of CO2. Here we report a seed-mediated approach to the facile synthesis of Au@Cu core–shell nanocubes with hexadecylamine and Cl– serving as capping agents toward the {100} facets of Cu and glucose as a reducing agent. The large (12%) lattice mismatch between Cu and Au led to the localized epitaxial growth of Cu shells on the Au seeds and the formation of nanocubes with randomly distributed Au cores. Compared to the same synthesis in the absence of Au seeds, the reduction of Cu(II) ions was greatly accelerated in the presence of Au seeds because of the autocatalytic surface reduction. It was also found that the structure and morphology of the products were highly dependent on the concentration of Cu(II) precursor in the reaction solution. Nanoplates rather than nanocubes were obtained when the concentration of Cu(II) precursor was reduced down to a certa...

On the Thermodynamics and Experimental Control of Twinning in Metal Nanocrystals

Abstract: This work demonstrates a new strategy for controlling the evolution of twin defects in metal nanocrystals by simply following thermodynamic principles. With Ag nanocrystals supported on amorphous SiO2 as a typical example, we establish that twin defects can be rationally generated by equilibrating nanoparticles of different sizes through heating and then cooling. We validate that Ag nanocrystals with icosahedral, decahedral, and single-crystal structures are favored at sizes below 7 nm, between 7 and 11 nm, and greater than 11 nm, respectively. This trend is then rationalized by computational studies based on density functional theory and molecular dynamics, which show that the excess free energy for the three equilibrium structures correlate strongly with particle size. This work not only highlights the importance of thermodynamic control but also adds another synthetic method to the ever-expanding toolbox used for generating metal nanocrystals with desired properties.

Bifunctional Janus Particles as Multivalent Synthetic Nanoparticle Antibodies (SNAbs) for Selective Depletion of Target Cells.

Abstract: Monoclonal antibodies (mAb) have had a transformative impact on treating cancers and immune disorders. However, their use is limited by high development time and monetary cost, manufacturing complexities, suboptimal pharmacokinetics, and availability of disease-specific targets. To address some of these challenges, we developed an entirely synthetic, multivalent, Janus nanotherapeutic platform, called Synthetic Nanoparticle Antibodies (SNAbs). SNAbs, with phage-display-identified cell-targeting ligands on one "face" and Fc-mimicking ligands on the opposite "face", were synthesized using a custom, multistep, solid-phase chemistry method. SNAbs efficiently targeted and depleted myeloid-derived immune-suppressor cells (MDSCs) from mouse-tumor and rat-trauma models, ex vivo. Systemic injection of MDSC-targeting SNAbs efficiently depleted circulating MDSCs in a mouse triple-negative breast cancer model, enabling enhanced T cell and Natural Killer cell infiltration into tumors. Our results demonstrate that SNAbs are a versatile and effective functional alternative to mAbs, with advantages of a plug-and-play, cell-free manufacturing process, and high-throughput screening (HTS)-enabled library of potential targeting ligands.

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