3D Flower-Like Hierarchitectures Constructed by SnS/SnS 2

Sn chalcogenides, including SnS, Sn2S3, and SnS2, have been extensively studied as anode materials for lithium batteries. In order to obtain one kind of high capacity, long cycle life lithium batteries anode materials, three-dimensional (3D) flower-like hierarchitectures constructed by SnS/SnS2 heterostructure nanosheets with thickness of ~20 nm have been synthesized via a simple one-pot solvothermal method. The obtained samples exhibit excellent electrochemical performance as anode for Li-ion batteries (LIBs), which deliver a first discharge capacity of 1277 mAhg−1 and remain a reversible capacity up to 500 mAhg−1 after 50 cycles at a current of 100 mAg−1

Drude Conductivity of Dirac Fermions in Graphene

Electrons moving in graphene behave as massless Dirac fermions, and they exhibit fascinating low-frequency electrical transport phenomena. Their dynamic response, however, is little known at frequencies above one terahertz (THz). Such knowledge is important not only for a deeper understanding of the Dirac electron quantum transport, but also for graphene applications in ultrahigh speed THz electronics and IR optoelectronics. In this paper, we report the first measurement of high-frequency conductivity of graphene from THz to mid-IR at different carrier concentrations. The conductivity exhibits Drude-like frequency dependence and increases dramatically at THz frequencies, but its absolute strength is substantially lower than theoretical predictions. This anomalous reduction of free electron oscillator strength is corroborated by corresponding changes in graphene interband transitions, as required by the sum rule. Our surprising observation indicates that many-body effects and Dirac fermion-impurity interactions beyond current transport theories are important for Dirac fermion electrical response in graphene

Electrical Control of Plasmon Resonance with Graphene

Surface plasmon, with its unique capability to concentrate light into sub-wavelength volume, has enabled great advances in photon science, ranging from nano-antenna and single-molecule Raman scattering to plasmonic waveguide and metamaterials. In many applications it is desirable to control the surface plasmon resonance in situ with electric field. Graphene, with its unique tunable optical properties, provides an ideal material to integrate with nanometallic structures for realizing such control. Here we demonstrate effective modulation of the plasmon resonance in a model system composed of hybrid graphene-gold nanorod structure. Upon electrical gating the strong optical transitions in graphene can be switched on and off, which leads to significant modulation of both the resonance frequency and quality factor of plasmon resonance in gold nanorods. Hybrid graphene-nanometallic structures, as exemplified by this combination of graphene and gold nanorod, provide a general and powerful way for electrical control of plasmon resonances. It holds promise for novel active optical devices and plasmonic circuits at the deep subwavelength scale

Intraband Optical Transitions in Graphene

Abstract: We measured tunable interband and intraband transitions in graphene using infrared spectroscopy. Graphene electrons have strong intraband absorption at terahertz frequency range. The absorption spectra are described by a Drude-like frequency dependence

A Tunable Phonon-Exciton Fano System in Bilayer Graphene

Interference between different possible paths lies at the heart of quantum physics. Such interference between coupled discrete and continuum states of a system can profoundly change its interaction with light as seen in Fano resonance. Here we present a unique many-body Fano system composed of a discrete phonon vibration and continuous electron-hole pair transitions in bilayer graphene. Mediated by the electron-phonon interactions, the excited state is described by new quanta of elementary excitations of hybrid phonon-exciton nature. Infrared absorption of the hybrid states exhibit characteristic Fano lineshapes with parameters renormalized by many-body interactions. Remarkably, the Fano resonance in bilayer graphene is continuously tunable through electrical gating. Further control of the phonon-exciton coupling may be achieved with an optical field exploiting the excited state infrared activity. This tunable phonon-exciton system also offers the intriguing possibility of a 'phonon laser' with stimulated phonon amplification generated by population inversion of band-edge electrons.Comment: 21 pages, 3 figure

X-ray diffraction data

X-ray diffraction data for wild type and mutant Y99L.The coordinates have been deposited in the Research Collaboration for Structural Bioinformatics (RCSB) Protein Data Bank with the following accession codes: 3TN3 for wild-type GkaP, and 3TN5 for Y99L

Data from: Active site loop conformation regulates promiscuous activity in a lactonase from Geobacillus kaustophilus HTA426

Enzyme promiscuity is a prerequisite for fast divergent evolution of biocatalysts. A phosphotriesterase-like lactonase (PLL) from Geobacillus kaustophilus HTA426 (GkaP) exhibits main lactonase and promiscuous phosphotriesterase activities. To understand its catalytic and evolutionary mechanisms, we investigated a “hot spot” in the active site by saturation mutagenesis as well as X-ray crystallographic analyses. We found that position 99 in the active site was involved in substrate discrimination. One mutant, Y99L, exhibited 11-fold improvement over wild-type in reactivity (kcat/Km) toward the phosphotriesterase substrate ethyl-paraoxon, but showed 15-fold decrease toward the lactonase substrate δ-decanolactone, resulting in a 157-fold inversion of the substrate specificity. Structural analysis of Y99L revealed that the mutation causes a ~6.6 Å outward shift of adjacent loop 7, which may cause increased flexibility of the active site and facilitate accommodation and/or catalysis of organophosphate substrate. This study provides for the PLL family an example of how the evolutionary route from promiscuity to specificity can derive from very few mutations, which promotes alteration in the conformational adjustment of the active site loops, in turn draws the capacity of substrate binding and activity

Controlling inelastic light scattering quantum pathways in graphene,”

Inelastic light scattering spectroscopy has, since its first discovery Graphene, a two-dimensional carbon sheet The excitation pathways in graphene samples are controlled through electrostatic doping using a high-capacitance ion-gel gate dielectric To determine the gate-induced Fermi energy shift in graphene samples, we use infrared transmission spectroscop

Active Site Loop Conformation Regulates Promiscuous Activity in a Lactonase from <i>Geobacillus kaustophilus</i> HTA426

<div><p>Enzyme promiscuity is a prerequisite for fast divergent evolution of biocatalysts. A phosphotriesterase-like lactonase (PLL) from <i>Geobacillus kaustophilus</i> HTA426 (<i>Gka</i>P) exhibits main lactonase and promiscuous phosphotriesterase activities. To understand its catalytic and evolutionary mechanisms, we investigated a “hot spot” in the active site by saturation mutagenesis as well as X-ray crystallographic analyses. We found that position 99 in the active site was involved in substrate discrimination. One mutant, Y99L, exhibited 11-fold improvement over wild-type in reactivity (<i>k_cat</i>/<i>K_m</i>) toward the phosphotriesterase substrate <i>ethyl</i>-paraoxon, but showed 15-fold decrease toward the lactonase substrate δ-decanolactone, resulting in a 157-fold inversion of the substrate specificity. Structural analysis of Y99L revealed that the mutation causes a ∼6.6 Å outward shift of adjacent loop 7, which may cause increased flexibility of the active site and facilitate accommodation and/or catalysis of organophosphate substrate. This study provides for the PLL family an example of how the evolutionary route from promiscuity to specificity can derive from very few mutations, which promotes alteration in the conformational adjustment of the active site loops, in turn draws the capacity of substrate binding and activity.</p></div

Primary data

Primary data(table1, table2 and table3 in the maintext were extracted from these data, it also contains screening data for tyr99 saturation mutagenesis