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.

Interpreting the Energy-Dependent Anisotropy of Colloidal Nanorods Using Ensemble and Single-Particle Spectroscopy

Abstract: We report the use of polarized excitation spectroscopy in the study of the polarized optical properties of II–VI semiconducting nanorods. This technique provides a quantitative measure for analyzing the polarization-dependent electronic structure of ensembles of semiconducting nanoparticles in colloidal solutions. We develop a procedure to quantify the anisotropy of nanorod excitations and the influence of the dielectric environment which yields results in qualitative agreement with theoretical predictions of nanorod absorption properties. Excitation measurements of nanorod ensembles and single-particle excitation and emission polarization measurements are used to interpret ensemble measurements on the molecular frame. At the single-particle level, we find a large dispersion in the angles between excitation and emission polarization curves. This contrasts with the conventional picture of CdSe electronic transitions, in which the crystal axes dictate the symmetry of excitations. Such geometrically heteroge...

Resonant energy transfer within a colloidal nanocrystal polymer host system

Abstract: The authors report on resonant energy transfer of nonequilibrium excitons in an amorphous polyfluorene donor CdSe∕ZnS core-shell nanocrystal acceptor system. By time-resolved photoluminescence (PL) spectroscopy, they have investigated the PL decay behavior of the primarily excited polyfluorene in dependence of the concentration of the nanocrystals. The authors are able to demonstrate that the finite rise time of the PL transient monitored at the spectral position of the acceptor PL directly reflects the PL decay of the donor.

Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films

Abstract: The dispersion, local orientation and optical absorption of polystyrene (PS, degree of polymerization P) nanocomposites containing PS-grafted gold nanorods (Au NRs, PS degree of polymerization N), with aspect ratios (ν = length/diameter) ranging from 2.5 to 6.3, are studied using quantitative scanning electron microscopy (SEM) and optical spectroscopy. The experimentally observed nanorod assemblies and optical absorptions are compared with predictions from self-consistent field theory (SCFT) and finite difference time domain (FDTD) calculations, respectively. A pair correlation function for Au NRs is calculated from SEM images, and contains no correlation peaks for P/N = 0.9, indicating nanorods are dispersed within the nanocomposite. Large correlation peaks are observed for P/N = 7.6, representative of interparticle separation distances within nanorod aggregates, which do not vary with ν. On the basis of SCFT calculations, aggregation is attributed to significant depletion-attraction forces in the composite for P/N > 1. When Au NRs disperse, the longitudinal surface plasmon resonance (LSPR) peak red shifts from the visible into the near-IR as ν increases. No shift in the dispersed LSPR position is observed for v = 2.5 and 3.3 upon aggregation because the ratio of the interparticle distance to the nanorod length is too large for surface plasmon coupling. However, for v = 6.3, significant coupling between surface plasmons leads to a blue shift of the LSPR by approximately 140 nm, in agreement with FDTD calculations.

Supported platinum–zinc oxide core–shell nanoparticle catalysts for methanol steam reforming

Abstract: Platinum–zinc oxide (Pt@ZnO) and palladium–zinc oxide (Pd@ZnO) core–shell nanoparticles were synthesized in solution using a method based on self-assembly and deposited onto a functionalized alumina (Si–Al2O3) support. TEM investigations of the samples confirm the formation of core–shell structures of approximately 6 nm of diameter following calcination to remove the ligands. In situ TEM and coulometric titration experiments suggest that Pt–Zn alloys are formed upon reduction and that these are highly tunable in size. While methanol steam reforming (MSR) measurements on conventional Pt/Al2O3 and Pd/Al2O3 catalysts show poor CO2 selectivities, a Pt (1 wt%)@ZnO (9 wt%)/Si–Al2O3 system showed comparable activity and selectivity for CO2 as a conventional Pt/ZnO catalyst, providing further indication that Pt@ZnO forms a Pt–Zn alloy upon reduction due to the intimate contact between the two materials. The Pd@ZnO/Si–Al2O3 exhibited lower CO2 selectivities than Pt@ZnO/Si–Al2O3.

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.