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.

Self-Assembled Magnetic Nanoparticle Arrays

Abstract: Advances in magnetic recording technology have resulted primarily from proportional scaling of each individual storage bit [1]. To control the signal to noise ratio and other important recording parameters, it is essential to maintain a large number of independent ferromagnetic grains per bit. These trends have driven the development of new magnetic thin film media with smaller grains, high coercivity, low magnetization and minimal magnetic exchange coupling between neighboring grains [2–6]. Today, the grain size of Co-alloy based advanced recording media has been reduced to dimensions close to the onset of superparamagnetic behavior. At such dimensions the magnetization of individual grains tends to fluctuate randomly with ambient thermal energy, resulting in irreversible thermal decay of stored information [7] (Chaps. 5 and 6).

Synthesis and Properties of Lead Selenide Nanocrystal Solids

Abstract: We present results of our investigation of the synthesis, structural properties and electrical transport properties of lead selenide (PbSe) nanoparticle-derived solids. Stable colloidal solutions containing crystalline PbSe particles with sizes on the order of 5–10 nm were synthesized using an organometallic lyothermal growth method in high-temperature organic solvents (100∼200 ◦ C). The nanoparticle powders have been characterized by X-ray scattering (WAXS/SAXS), electron microscopy and optical absorption. Thin films were formed by controlled precipitation of the nanoparticles from solution onto insulating substrates. Electrical resistance (R) and Seebeck coefficient (S) for conductive PbSe films from different annealing conditions were studied and compared. We were able to obtain conductive PbSe films from colloids by low temperature annealing which did not disturb the nanoparticle self-assembly.

MO-G-BRF-07: Optical Characterization of Novel Terbium-Doped Nanophosphors Excited by Clinical Electron and Photon Beams for Potential Use in Molecular Imaging Or Photodynamic Therapy

Abstract: Purpose: Optical properties of terbium (Tb3+)-doped gadolinium trifluoride (GdF3) nanoplates irradiated by electron and photon beams were investigated for their potential as optical probes. The contribution of induced Cerenkov radiation in exciting the nanophosphors was investigated as well. Methods: The emission spectra of Terbium-doped GdF3 dispersed in hexane, embedded in tissue mimicking phantoms were collected by an optical fiber connected to a CCD-coupled spectrograph, while the samples were irradiated by a medical linear accelerator with electron beams of energies 6, 9, 12, 16, and 20 MeV or X-ray beams of energies of 6, and 15 MV. The contribution of induced Cerenkov radiation in exciting the nanophosphores was investigated in a dedicated experimental apparatus through optical isolation of the samples and also by using 125 kVp X-ray beams whose energy is below the threshold for generating Cerenkov radiation in that medium. Results: Terbium-doped GdF3 nanoplates show characteristic cathodoluminescence emission peaks at 488, 543, 586, and 619 nm, which are responsible for the characteristic f-f transition of terbium ion. In a series of experiments, the contribution of Cerenkov radiation in the luminescence of such nanophosphors was ruled out. Conclusion: We have characterized the optical properties of Terbium-doped GdF3 nanoplates. Such nanocrystals with emission tunability and high surface area that facilitates attachment with targeting reagents are promising in situ light source candidates for molecular imaging or exciting a photosensitizer for ultralow fluence photodynamic therapy. This work is supported by the Department of Radiation Oncology at the University of Pennsylvania, the American Cancer Society through IRG-78-002-28, and the University of Pennsylvania's Nano/Bio Interface Center through NSEC DMR08-32802.

Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

Abstract: Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

Designing Strong Optical Absorbers via Continuous Tuning of Interparticle Interaction in Colloidal Gold Nanocrystal Assemblies

Abstract: We program the optical properties of colloidal Au nanocrystal (NC) assemblies via an unconventional ligand hybridization (LH) strategy to precisely engineer interparticle interactions and design ma...

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.