Peidong Yang

Bio: Peidong Yang is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Nanowire & Perovskite (structure). The author has an hindex of 183, co-authored 562 publications receiving 144351 citations. Previous affiliations of Peidong Yang include Max Planck Society & University of California, Santa Barbara.

Efficient hydrogen peroxide generation using reduced graphene oxide-based oxygen reduction electrocatalysts

Abstract: Electrochemical oxygen reduction has garnered attention as an emerging alternative to the traditional anthraquinone oxidation process to enable the distributed production of hydrogen peroxide. Here, we demonstrate a selective and efficient non-precious electrocatalyst, prepared through an easily scalable mild thermal reduction of graphene oxide, to form hydrogen peroxide from oxygen. During oxygen reduction, certain variants of the mildly reduced graphene oxide electrocatalyst exhibit highly selective and stable peroxide formation activity at low overpotentials (<10 mV) under basic conditions, exceeding the performance of current state-of-the-art alkaline catalysts. Spectroscopic structural characterization and in situ Raman spectroelectrochemistry provide strong evidence that sp2-hybridized carbon near-ring ether defects along sheet edges are the most active sites for peroxide production, providing new insight into the electrocatalytic design of carbon-based materials for effective peroxide production. Electrochemical routes for the production of hydrogen peroxide would reduce the waste inherent in the current anthraquinone process, and also make distributed and on-site production more feasible. Here, inexpensive reduced graphene oxide is proven to be a stable and selective catalyst for oxygen reduction at remarkably low overpotentials.

ZnO nanowire transistors.

Abstract: ZnO nanowire field-effect transistors (FETs) were fabricated and studied in vacuum and a variety of ambient gases from 5 to 300 K. In air, these n-type nanowire transistors have among the highest mobilities yet reported for ZnO FETs (Ie ) 13 ( 5c m 2 V -1 s -1 ), with carrier concentrations averaging 5.2 ( 2.5 10 17 cm -3 and on-off current ratios ranging from 10 5 to 10 7 . Four probe measurements show that the resistivity of the Ti/Au-ZnO contacts is 0.002-0.02 ?‚cm. The performance characteristics of the nanowire transistors are intimately tied to the presence and nature of adsorbed surface species. In addition, we describe a dynamic gate effect that seems to involve mobile surface charges and causes hysteresis in the transconductance, among other effects.

Thermochromic halide perovskite solar cells

Abstract: Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

Langmuir-Blodgett nanorod assembly.

Abstract: Techniques for directing the assembly of metal or semiconductor quantum dots into novel superstructures have been extensively pursued over the past decades.1-3 Recent interest has been drawn toward 1-dimensional nanoscale building blocks such as nanotubes, nanowires, and nanorods.4-14 If these one-dimensional nanoscale building blocks can be ordered and rationally assembled into appropriate 2-dimensional architectures, they will offer fundamental scientific opportunities for investigating the influence of size and dimensionality with respect to their collective optical, magnetic, and electronic properties, as well as many other technologically important applications. Currently, efforts have been focused on the development of new synthetic methodologies for making nanorods with uniform sizes and aspect ratios.4-14 Few studies addressed the organization of these anisotropic building blocks except the 3-dimensional spontaneous superlattice formation of BaCrO4, FeOOH,13 CdSe,4 Ag,6 and Au12 nanorods. Herein, we report 2-dimensional nanorod monolayer assembly using the Langmuir-Blodgett technique. Pressure-induced isotropic-nematic-smectic phase transitions as well as transformation from monolayer to multilayer nanorod assembly were observed. Uniform BaCrO4 nanorods were prepared by using published procedures.7 Briefly, Barium bis(2-ethylhexyl)sulfosuccinate (Ba(AOT)2) reverse micelles were added to sodium chromate (Na2CrO4)-containing NaAOT microemulsion droplets, to give final molar ratios of [Ba]:[CrO4] ) 1 and water content [H2O]: [NaAOT] ) 10. The as-made yellow precipitate consists of ribbonlike and rectangular superstructures made of uniform nanorods. The nanorods were uniform in length (∼20 nm) and diameter (∼5 nm). Energy-dispersive X-ray analysis and electron diffraction patterns indicated that the nanorods were single crystalline BaCrO4 with an orthorhombic unit cell (a ) 0.91 nm, b ) 0.55 nm, c ) 0.73 nm). These as-made nanorods generally are stabilized with AOT surfactant molecules. They were diluted and redispersed into isooctane to make a stable nanorod colloidal suspension, which is used as stock solution for subsequent Langmuir-Blodgett studies. The nanorod colloidal suspension was spread dropwise (typically 1 mL of 2.5 mg/mL concentration) on the water surface of a Langmuir-Blodgett trough (Nima Technology, M611). The nanorod surface layer was then compressed slowly while the surface pressure was monitored with a Wilhelmy plate. Due to the presence of noncovalently bonded surfactant molecules, the compression starts with a nonzero surface pressure. In addition, since AOT is partially soluble in subphase water, the surface pressure decays with the time. In general, it was observed that the surface pressure increases during the compression. At different stages of compression, the nanorod assemblies at the water-air interface were transferred carefully onto transmission electron microscope (TEM) grids covered with continuous carbon thin film using the Langmuir-Schäffer horizontal liftoff procedure. Nanorod assemblies were examined systematically by using TEM. Initially, at low surface pressure, individual nanorods (generally 3 to 5 rods) form raft-like aggregates. These aggregates disperse on the subphase surface in a mostly isotropic state (Figure 1a). The surface pressure remains unchanged until the nanorods start forming a monolayer and when the monolayer was compressed to a surface pressure of ∼30 mN/m.15 During this process, monolayer of nanorods in a nematic arrangement are first obtained where the directors of these nanorods (or nanorod rafts) are qualitatively aligned presumably dictated by the barrier of the trough. Figure 1b shows such a partial nematic region with an orientational order parameter S of 0.83. The regularity of sideby-side inter-rod distance is reflected in the Fourier transform of the region (Figure 1b, inset). This nematic ordering, however, only occurs within a quite narrow pressure range. With further compression (surface pressure about ∼35 mN/m), nanorod (1) Collier, C. P.; Vossmeyer, T.; Heath, J. R. Annu. ReV. Phys. Chem. 1998, 49, 371-404. (2) Sun, S.; Murray, C. B.; Weller, D.; Folks, L.; Moser, A. Science 2000, 287, 1989-1992. (3) Chung, S. W.; Markovich, G.; Heath, J. R. J. Phys. Chem. B 1998, 102, 6685-6687. (4) Peng, X.; Manna, L.; Yang, W.; Wickham, J.; Scher, E.; Kadavanich, A.; Alivisatos, A. P. Nature 2000, 404, 59-61. (5) Chang, S.; Shih, C.; Chen, C.; Lai, W.; Wang, C. R. C. Langmuir 1999, 15, 701-709. (6) Korgel, B. A.; Fitzmaurice, D. AdV. Mater. 1998, 10, 661-665. (7) Li, M.; Schnablegger, H.; Mann, S. Nature 1999, 402, 393-395. (8) Park, S. J.; Kim, S.; Lee, S.; Khim, Z. G.; Char, K.; Hyeon, T. J. Am. Chem. Soc. 2000, 35, 8581-8582. (9) Tanori, J.; Pileni, M. P. Langmuir 1997, 13, 639-646. (10) Martin, B. R.; Dermody, D. J.; Reiss, B. D.; Fang, M.; Lyon, A.; Natan, M. J.; Mallouk, T. E. AdV. Mater. 1999, 11, 1021-1025. (11) Chen, C.; Chao, C.; Lang, Z. Chem. Mater. 2000, 12, 1516-1519. (12) Nikoobakht, B.; Wang, Z. L.; El-Sayed, M. A. J. Phys. Chem. B 2000, 104, 8635-8640. (13) Maeda, H.; Maeda, Y. Langmuir 1996, 12, 1446-1452. (14) Gabriel, J. C. P.; Davidson, P. AdV. Mater. 2000, 12, 9-20. (15) The free surfactants in the system can form Langmuir films themselves and may interfere with the formation of the nanorod monolayers. Consequently, the actual surface pressure during the compression may differ from the observed value. Figure 1. Transmission electron microscopy images of the nanorod assemblies at the water/air interface at different stages of compression: (a) isotropic distribution at low pressure; (b) monolayer with partial nematic arrangement; (c) monolayer with smectic arrangement; and (d) nanorod multilayer with nematic configuration. Insets in panels b and c are the Fourier transform of the corresponding image. 4360 J. Am. Chem. Soc. 2001, 123, 4360-4361

Microemulsion Templating of Siliceous Mesostructured Cellular Foams with Well-Defined Ultralarge Mesopores

Abstract: Siliceous mesostructured cellular foams (MCFs) with well-defined ultralarge mesopores and hydrothermally robust frameworks are described. The MCFs are templated by oil-in-water microemulsions and are characterized by small-angle X-ray scattering, nitrogen sorption, transmission electron microscopy, scanning electron microscopy, thermogravimetry, and differential thermal analysis. The MCFs consist of uniform spherical cells measuring 24−42 nm in diameter, possess BET surface areas up to 1000 m2/g and porosities of 80−84%, and give, because of their pores with small size distributions, higher-order scattering peaks even in the absence of long-range order. Windows with diameters of 9−22 nm and narrow size distribution interconnect the cells. The pore size can be controlled by adjusting the amount of the organic swelling agent that is added and by varying the aging temperature. Adding ammonium fluoride selectively enlarges the windows by 50−80%. In addition, the windows can be enlarged by postsynthesis treatm...

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。

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

A comprehensive review of zno materials and devices

Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...