Richard J. Saykally

Bio: Richard J. Saykally is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Spectroscopy & Absorption spectroscopy. The author has an hindex of 94, co-authored 457 publications receiving 40997 citations. Previous affiliations of Richard J. Saykally include University of California & Lawrence Berkeley National Laboratory.

Characterization of Domain Ordering in Polymer and Dendrimer Thin Films Using Photoluminescence and Third Harmonic Generation (THG) Near-field Scanning Optical Microscopy (NSOM)

Abstract: We have utilized the high spatial resolution of near-field scanning optical microscopy (NSOM) to characterize nanoscopic electronic inhomogeneity in as-cast thin films of a light-harvesting dendrimer consisting of coumarin-343 (core) and coumarin-2 (peripheral) chromophores and in thermally annealed thin films of the semiconductive polymer poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV). Using photoluminescence (PL) and third harmonic generation (THG) NSOM techniques, we have observed nanoscopic domains in these films that exhibit increased delocalization in the excited (using PL) and ground states (using THG). In addition, we have developed a procedure for examining NSOM images via calculation of radial distribution functions (RDFs). RDF analysis of the PL and THG NSOM images indicates that the domains exhibit correlated structure in annealed MEH-PPV films while the light-harvesting dendrimeric material does not. The existence or absence of such nanoscopic amorphous structure can be understood in terms of the molecular structure of each material.

Infrared Single Photon Counting Fluorescence Spectroscopy (IRSPCES) of UV Excited Naphthalene: The Mechanism of Interstellar Infrared Emission Bands

Abstract: Polycyclic aromatic hydrocarbons (PAH's) are hypothesized to be the carriers of the ubiquitous diffuse intersellar bands (DIB's) and the unidentified infrared bands (UIR's) $^{1, 2, 3, 4}$ which are found in interstellar dust clouds that are irradiated by starlight. The UIR's occur principally at 3.3, 3.4, 6.2, 7.7, 8.6 and $11.3 \mu m$. The mechanism for the IR emission is postulated to be UV excitation of electronic transitions followed by intermolecular energy transfer and subsequent IR fluorescence. A new experiment has been designed in order to test this hypothesis. A 5\% mixture of naphtalene in argoin is expanded through a pulsed nozzle into a vaccuum where it is intersected with either 193 nm or 248 nm radiation 20 nozzle diameters downstream from the orifice. IR fluorescence is collected with an f/7 lens and dispersed by a 0.5m monochromator. A blocked impurity band $detector^{2}$ is used to detect the radiation. This solid state detector employes a gain mechanism to produce a measurable discrere current pulse for single incident infrared photons. The fast time response of the detector and following photon-counting electronics allow observation times shorter than the time between gas kinetic collisions following the UV excitation pulse. Thus, collision free spectra are observed.

Catalytic Mechanism of Interfacial Water in the Cycloaddition of Quadricyclane and Diethyl Azodicarboxylate.

Abstract: "On-water" catalysis, the unusual activity of water molecules at the organic solvent-water interface, has been demonstrated in many organic reactions. However, the catalytic mechanism has remained unclear, largely because of the irreproducibility of the organic-water interface under the common stirring condition. Here, the interfacial area was controlled by employing adsorbed water on mesoporous silica nanoparticles as the catalyst. Reliable kinetics of the cycloaddition reaction of quadricyclane and diethyl azodicarboxylate (DEAD) at the toluene-water interface within the nanoparticle pores were measured. Data reveal an Eley-Rideal mechanism, wherein DEAD adsorbs at the toluene-water interface via hydrogen bonds formed with interfacial water, which lower the activation energy of the cycloaddition reaction. The mechanistic insights gained and preparation of surface water in silica pores described herein may facilitate the future design of improved "on-water" catalysts.

A Crystallographic Analysis of C60 (Buckminsterfullerene).

Abstract: Crystallographic analysis of C60 grown from a hexane solution revealed a structure which is neither hexagonal nor cubic closest packed [space group P63/m, a= 33.54(1), c= 10.113(8)A]; packing models which are consistent with the Patterson map are described.

Poled polymer thin film gratings studied by near-field second harmonic optical microscopy and far-field optical diffraction

Abstract: Electrical poling induces polar ordering of molecules in a grating that has been holographically inscribed on a thin film of polymer functionalized with azobenzene side chains. Depending on the surface relief amplitude, the resulting χ (2) grating, seen by second harmonic generation (SHG) near-field scanning optical microscopy (NSOM), can have a periodic structure significantly different from the topographical image. The far-field linear and SHG diffraction patterns correlate well with the grating structures. Poling of the thin-film grating, which presumably has photo-driven non-uniform material properties within each period, leads to the more complex structure of the χ (2) grating.

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。

The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment

Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...

Dye-Sensitized Solar Cells

Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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.