Christopher B. Murray

Bio: Christopher B. Murray is an academic researcher from University of Pennsylvania. The author has contributed to research in topics: Nanocrystal & Quantum dot. The author has an hindex of 88, co-authored 336 publications receiving 54410 citations. Previous affiliations of Christopher B. Murray include Universal Display Corporation & Lawrence Berkeley National Laboratory.

Efficient Removal of Organic Ligands from Supported Nanocrystals by Fast Thermal Annealing Enables Catalytic Studies on Well-Defined Active Phases

Abstract: A simple yet efficient method to remove organic ligands from supported nanocrystals is reported for activating uniform catalysts prepared by colloidal synthesis procedures. The method relies on a fast thermal treatment in which ligands are quickly removed in air, before sintering can cause changes in the size and shape of the supported nanocrystals. A short treatment at high temperatures is found to be sufficient for activating the systems for catalytic reactions. We show that this method is widely applicable to nanostructures of different sizes, shapes, and compositions. Being rapid and effective, this procedure allows the production of monodisperse heterogeneous catalysts for studying a variety of structure-activity relationships. We show here results on methane steam reforming, where the particle size controls the CO/CO2 ratio on alumina-supported Pd, demonstrating the potential applications of the method in catalysis.

Shape-dependent plasmonic response and directed self-assembly in a new semiconductor building block, indium-doped cadmium oxide (ICO).

Abstract: The influence of particle shape on plasmonic response and local electric field strength is well-documented in metallic nanoparticles. Morphologies such as rods, plates, and octahedra are readily synthesized and exhibit drastically different extinction spectra than spherical particles. Despite this fact, the influence of composition and shape on the optical properties of plasmonic semiconductor nanocrystals, in which free electrons result from heavy doping, has not been well-studied. Here, we report the first observation of plasmonic resonance in indium-doped cadmium oxide (ICO) nanocrystals, which exhibit the highest quality factors reported for semiconductor nanocrystals. Furthermore, we are able to independently control the shape and free electron concentration in ICO nanocrystals, allowing for the influence of shape on the optical response of a plasmonic semiconductor to be conclusively demonstrated. The highly uniform particles may be self-assembled into ordered single component and binary nanocrystal...

Synthesis and Oxygen Storage Capacity of Two‐Dimensional Ceria Nanocrystals

Abstract: Shape-controlled synthesis of inorganic nanomaterials has received great attention due to their unique shapedependent properties and their various applications in catalysis, electronics, magnetics, optics, and biomedicine. Among these nanomaterials, ultrathin twodimensional (2D) anisotropic nanomaterials are especially attractive due to their high surface-to-volume ratio and potential quantum size effects. A variety of approaches have been developed to prepare such nanomaterials. Typical methods include vapor deposition, templated synthesis, electrochemical deposition, sol–gel processing, and solvothermal/hydrothermal treatments. Solution-phase chemical synthesis has proven particularly effective in controlling the size and morphology of the nanomaterials. Ceria has been widely used in catalysis, optics, sensors, and solid oxide fuel cells. Due to its high oxygen storage capacity (OSC), which originates from easy conversion between CeO2 and CeO2 x, ceria has found its primary utilization in catalysis as an oxygen carrier. Ceria nanomaterials with various morphologies, mainly polyhedra, have been reported. Recently, 1D ceria nanostructures, such as nanowires, have also been reported. However, with the exception of one report on the preparation of nanosheets, well-controlled 2D ceria nanomaterials have not been explored and the comparison of the OSC properties between 3D and 2D structures has not been possible. On the other hand, the different properties of the (100), (110), and (111) ceria facets has been debated. There is no consensus on whether crystallographic orientation or particle size affects reactivities. Therefore, high-quality ceria nanocrystals selectively exposing different low Miller-index surfaces, are crucial to enabling experiments that resolve the controversy. Here we report a simple, robust solution-phase synthesis of ultrathin ceria nanoplates in the presence of mineralizers. The morphology of nanoplates can be easily controlled by changing reaction parameters, such as precursor ratio, reaction time, etc. In addition, we also prepare ceria nanomaterials in various 3D morphologies by hydrothermal and combustion methods. The OSC of our 2D ceria materials have been tested and compared to the OSC of their 3D counterparts. In brief, the synthesis of ceria nanoplates involves the thermal decomposition of cerium acetate at 320–330 8C in the presence of oleic acid and oleylamine as stabilizers and employs sodium diphosphate or sodium oleate as mineralizers. Transmission electron microscopy (TEM) images of ceria nanoplates are shown in Figure 1. Square ceria nanoplates (S-nanoplates, Figure 1a) with an edge length of 11.9 nm (s= 7%), are synthesized with sodium diphosphate as the mineralizer while elongated ceria nanoplates (Lnanoplates, Figure 1e) with a length of 151.6 nm (s= 9%) and a width of 14.3 nm (s= 12%), are produced with sodium oleate as the mineralizer. The nanoplates in both samples have a thickness of about 2 nm. As shown in Figure 1c and g, the stacks of nanoplates confirm that the sample consists of 2D plates rather than 3D cubes or rods. S-nanoplates readily form the demonstrated stacking arrays as seen in drop-cast TEM samples. L-nanoplates only form stacks by a selfassembly at a liquid–liquid (e.g. hexane–ethylene glycol) interface. The S-nanoplates also self-assemble to a ceria nanosheet at a hexane–acetonitrile interface, as shown in Figure 3a. High-resolution TEM (HRTEM) images of both nanoplates (Figures 1d,h and S1c in the Supporting Information) reveal an interplanar distance of 0.27 nm, consistent with the (200) lattice spacing of the ceria crystal. The fast Fourier transform (FFT) patterns confirm the {100} textures of ceria nanoplates. Plates (e.g. square plates) could be enclosed by either six (100) facets or a combination of two (100) facets and four (110) facets. As illustrated in Figure S1, our HRTEM images and simulations of HRTEM images suggest that our ceria nanoplates are enclosed by six (100) [*] D. Y. Wang, Y. J. Kang, Prof. C. B. Murray Department of Chemistry University of Pennsylvania, Philadelphia, PA 19104 (USA) E-mail: cbmurray@sas.upenn.edu

Design of Pt–Pd Binary Superlattices Exploiting Shape Effects and Synergistic Effects for Oxygen Reduction Reactions

Abstract: Large-area icosahedral-AB(13)-type Pt-Pd binary superlattices (BNSLs) are fabricated through self-assembly of 6 nm Pd nanocrystals (NCs) and 13 nm Pt octahedra at a liquid-air interface. The Pt-Pd BNSLs enable a high activity toward electrocatalysis of oxygen reduction reaction (ORR) by successfully exploiting the shape effects of Pt NCs and synergistic effects of Pt-Pd into a single crystalline nanostructure. The Pt-Pd BNSLs are promising catalysts for the oxygen electrode of fuel cells.

Highly active Pt3Pb and core-shell Pt3Pb-Pt electrocatalysts for formic acid oxidation.

Abstract: Formic acid is a promising chemical fuel for fuel cell applications. However, due to the dominance of the indirect reaction pathway and strong poisoning effects, the development of direct formic acid fuel cells has been impeded by the low activity of existing electrocatalysts at desirable operating voltage. We report the first synthesis of Pt3Pb nanocrystals through solution phase synthesis and show they are highly efficient formic acid oxidation electrocatalysts. The activity can be further improved by manipulating the Pt3Pb–Pt core–shell structure. Combined experimental and theoretical studies suggest that the high activity from Pt3Pb and the Pt–Pb core–shell nanocrystals results from the elimination of CO poisoning and decreased barriers for the dehydrogenation steps. Therefore, the Pt3Pb and Pt–Pb core–shell nanocrystals can improve the performance of direct formic acid fuel cells at desired operating voltage to enable their practical application.

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。

Semiconductor Clusters, Nanocrystals, and Quantum Dots

Abstract: Current research into semiconductor clusters is focused on the properties of quantum dots-fragments of semiconductor consisting of hundreds to many thousands of atoms-with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.

Quantum Dot Bioconjugates for Ultrasensitive Nonisotopic Detection

Abstract: Highly luminescent semiconductor quantum dots (zinc sulfide-capped cadmium selenide) have been covalently coupled to biomolecules for use in ultrasensitive biological detection. In comparison with organic dyes such as rhodamine, this class of luminescent labels is 20 times as bright, 100 times as stable against photobleaching, and one-third as wide in spectral linewidth. These nanometer-sized conjugates are water-soluble and biocompatible. Quantum dots that were labeled with the protein transferrin underwent receptor-mediated endocytosis in cultured HeLa cells, and those dots that were labeled with immunomolecules recognized specific antibodies or antigens.