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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.


Papers
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TL;DR: In this paper, femtosecond extreme-ultraviolet measurements suggest that small polaron localization is responsible for the ultrafast trapping of photoexcited carriers in haematite (α-Fe2O3).
Abstract: Small polaron formation is known to limit ground-state mobilities in metal oxide photocatalysts. However, the role of small polaron formation in the photoexcited state and how this affects the photoconversion efficiency has yet to be determined. Here, transient femtosecond extreme-ultraviolet measurements suggest that small polaron localization is responsible for the ultrafast trapping of photoexcited carriers in haematite (α-Fe2O3). Small polaron formation is evidenced by a sub-100 fs splitting of the Fe 3p core orbitals in the Fe M2,3 edge. The small polaron formation kinetics reproduces the triple-exponential relaxation frequently attributed to trap states. However, the measured spectral signature resembles only the spectral predictions of a small polaron and not the pre-edge features expected for mid-gap trap states. The small polaron formation probability, hopping radius and lifetime varies with excitation wavelength, decreasing with increasing energy in the t2g conduction band. The excitation-wavelength-dependent localization of carriers by small polaron formation is potentially a limiting factor in haematite’s photoconversion efficiency. The effect of polaron formation on photoconversion efficiency for oxide photocatalysts is not well known. Femtosecond extreme-ultraviolet measurements suggest that polaron localization is responsible for ultrafast trapping of photoexcited carriers in haematite.

172 citations

Journal ArticleDOI
TL;DR: In this article, a cobalt pentapyridine complex (CF3PY5Me2)Co(H2O)](CF3SO3)2 (1) was shown to operate in neutral water as an electrocatalyst for hydrogen generation under soluble, diffusion-limited conditions on a glassy carbon electrode.
Abstract: Recently, a family of cobalt pentapyridine complexes of the type [(R-PY5Me2)Co(H2O)])(CF3SO3)2, (R = CF3, H, or NMe2; PY5Me2 = 2,6-bis(1,1-di(pyridin-2-yl)ethyl)pyridine) were shown to catalyze the electrochemical generation of hydrogen from neutral aqueous solutions using a mercury electrode. We now report that the CF3 derivative of this series, [(CF3PY5Me2)Co(H2O)](CF3SO3)2 (1), can also operate in neutral water as an electrocatalyst for hydrogen generation under soluble, diffusion-limited conditions on a glassy carbon electrode, as well as a photocatalyst for hydrogen production using either molecular or semiconductor nanowire photosensitizers. Owing to its relatively low overpotential compared to other members of the PY5 family, complex 1 exhibits multiple redox features on glassy carbon, including a one-proton, one-electron coupled oxidative wave. Further, rotating disk electrode voltammetry measurements reveal the efficacy of 1 as a competent hydrogen evolution catalyst under soluble, diffusion-limited conditions. In addition, we establish that 1 can also generate hydrogen from neutral water under photocatalytic conditions with visible light irradiation (λirr ≥ 455 nm), using [Ru(bpy)3]2+ as a molecular inorganic chromophore and ascorbic acid as a sacrificial donor. Dynamic light scattering measurements show no evidence for nanoparticle formation for the duration of the photolytic hydrogen evolution experiments. Finally, we demonstrate that 1 is also able to enhance the hydrogen photolysis yield of GaP nanowires in water, showing that this catalyst is compatible with solid-state photosensitizers. Taken together, these data establish that the well-defined cobalt pentapyridine complex [(CF3PY5Me2)Co(H2O)]2+ is a versatile catalyst for hydrogen production from pure aqueous solutions using either solar or electrical input, providing a starting point for integrating molecular systems into sustainable energy generation devices.

171 citations

Journal ArticleDOI
TL;DR: In this paper, the coordination of carbon as a function of nitrogen concentration in carbon nitride films has been systematically studied and a structural transformation from primarily carbon 3 to carbon 2 was observed.
Abstract: The coordination of carbon as a function of nitrogen concentration in energetically deposited carbon nitride films has been systematically studied. A structural transformation from primarily ${\mathrm{sp}}^{3}$-bonded to ${\mathrm{sp}}^{2}$-bonded carbon and a density decrease from 3.3 to $2.1 {\mathrm{g}/\mathrm{c}\mathrm{m}}^{3}$ were observed as the nitrogen concentration increases from 11 to 17 %. Calculations on nitrogen-substituted carbon clusters indicate that there is a preference to form ${\mathrm{sp}}^{2}$-bonded carbon when the nitrogen concentration is larger than 12%. The implications for these results to the synthesis of superhard carbon nitride materials are discussed.

170 citations

Journal ArticleDOI
TL;DR: These observations reflect the interplay between the competing effects of charge and size of streptavidin on nanochannel conductance.
Abstract: Conductance characteristics of nanofluidic channels (nanochannels) fall into two regimes: at low ionic concentrations, conductance is governed by surface charge while at high ionic concentrations it is determined by nanochannel geometry and bulk ionic concentration. We used aminosilane chemistry and streptavidin-biotin binding to study the effects of surface reactions on nanochannel conductance at different ionic concentrations. Immobilization of small molecules such as aminosilane or biotin mainly changes surface charge, affecting conductance only in the low concentration regime. However, streptavidin not only modifies surface charge but also occludes part of the channel, resulting in observable conductance changes in both regimes. Our observations reflect the interplay between the competing effects of charge and size of streptavidin on nanochannel conductance.

170 citations

Journal ArticleDOI
TL;DR: A new synthetic approach, using tris(trimethylsilyl)silane as a mild reducing reagent, for synthesizing high-quality, ultrathin, and monodispersed copper nanowires, with an average diameter of 17.5 nm and a mean length of 17 μm is reported.
Abstract: Colloidal metal nanowire based transparent conductors are excellent candidates to replace indium–tin–oxide (ITO) owing to their outstanding balance between transparency and conductivity, flexibility, and solution-processability. Copper stands out as a promising material candidate due to its high intrinsic conductivity and earth abundance. Here, we report a new synthetic approach, using tris(trimethylsilyl)silane as a mild reducing reagent, for synthesizing high-quality, ultrathin, and monodispersed copper nanowires, with an average diameter of 17.5 nm and a mean length of 17 μm. A study of the growth mechanism using high-resolution transmission electron microscopy reveals that the copper nanowires adopt a five-fold twinned structure and evolve from decahedral nanoseeds. Fabricated transparent conducting films exhibit excellent transparency and conductivity. An additional advantage of our nanowire transparent conductors is highlighted through reduced optical haze factors (forward light scattering) due to t...

169 citations


Cited by
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01 May 1993
TL;DR: 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.
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.

29,323 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组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�ly.
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。

18,940 citations

Journal ArticleDOI
TL;DR: This work reviews the historical development of Transition metal dichalcogenides, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

13,348 citations

Journal ArticleDOI
TL;DR: 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.
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. ...

10,260 citations