Search

Phase plates (PPs) in transmission electron microscopy (TEM) improve the contrast of weakly scattering objects under in-focus imaging conditions. A well-established PP type is the Zernike (Z)PP, which consists of a thin amorphous carbon (aC) film with a microscaled hole in the centre. The mean inner potential of the aC film is exploited to shift the phase of the scattered electrons while the unscattered electrons in the zero-order beam propagate through the hole and remain unaffected. However, the abrupt thickness increase at the hole edge induces an abrupt change of the phase-shift distribution and leads to fringing, that is, intensity oscillations around imaged objects, in TEM images. In this work, we have used focused-ion-beam milling to fabricate ZPPs with abrupt and graded thickness profiles around the centre hole. Depending on the thickness gradient and inner hole radius, graded-ZPP-TEM images of an aC/vacuum interface and bundles of carbon nanotubes (CNTs) show strongly reduced fringing. Image simulations were performed with ZPP-phase-shift distributions derived from measured thickness profiles of graded ZPPs, which show good agreement with the experimental images., Fringing artefacts, that is, intensity oscillations around imaged objects, are strongly reduced for Zernike phase plates with a graded thickness profile around the centre hole., Focused-ion-beam milling is used to fabricate graded Zernike phase plates with specific inner hole radius and thickness gradients., The phase-shift distribution is obtained from measured thickness profiles around the centre hole., Image simulations based on experimentally measured thickness/phase-shift distributions show good agreement with experimental Zernike phase-plate TEM images., The authors acknowledge funding of this project by the German Research Foundation (Deutsche Forschungsgemeinschaft) under contract Ge 841/26. This work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – 2082/1–390761711 and by the Carl Zeiss Foundation. S.H. acknowledges funding from the German Research Foundation (HE 7675/1-1) and from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 889546., Open access funding enabled and organized by Projekt DEAL.

An asymmetric bis-phenol-β-diketone (H4L) has been designed as a ligand programmed to promote the assembly of a molecular arrangement composed of three magnetically exchanged [NiCu] pairs, each exhibiting an S = 1/2 spin. The latter are shown by EPR and magnetometry to be good qubit realizations and non-equivalent within the molecule in the solid state, as required for conditional quantum gates., This research was supported by Spanish MINECO (PGC2018-098630-B-I00, PID2020-118329B-I00), the Aragón government (E31_20R PLATON) and the EU (FET-OPEN grant 862893 FATMOLS). G. A. thanks the Generalitat de Catalunya for the prize ICREA Academia 2018. B. L. G. thanks French GENCI/IDRIS-CINES centers for high-performance computing resources. The authors thank the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DEAC02-05CH11231, and the Zeiss Foundation for funding.

We unravel the underlying near-field mechanism of the enhancement of the magneto-optical activity of bismuth-substituted yttrium iron garnet films (Bi:YIG) loaded with gold nanoparticles. The experimental results show that the embedded gold nanoparticles lead to a broadband enhancement of the magneto-optical activity with respect to the activity of the bare Bi:YIG films. Full vectorial near- and far-field simulations demonstrate that this broadband enhancement is the result of a magneto-optically enabled cross-talking of orthogonal localized plasmon resonances. Our results pave the way to the on-demand design of the magneto-optical properties of hybrid magneto-plasmonic circuitry., This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – TRR 173 – 268565370. E. Th. P. and S. D. P. acknowledge the Carl Zeiss Foundation. Ken-ichi Uchida (NIMS, Japan) is acknowledged for providing the Bi:YIG/AuNPs samples. Dipl.-Phys. Marc Vogel – AG von Freymann – TU Kaiserslautern is acknowledged for the introduction to CST software and his help with the installation of the package.

The relaxation of photoexcited nanosystems is a fundamental process of light–matter interaction. Depending on the couplings of the internal degrees of freedom, relaxation can be ultrafast, converting electronic energy in a few fs, or slow, if the energy is trapped in a metastable state that decouples from its environment. Here, we study helium nanodroplets excited resonantly by femtosecond extreme-ultraviolet (XUV) pulses from a seeded free-electron laser. Despite their superfluid nature, we find that helium nanodroplets in the lowest electronically excited states undergo ultrafast relaxation. By comparing experimental photoelectron spectra with time-dependent density functional theory simulations, we unravel the full relaxation pathway: Following an ultrafast interband transition, a void nanometer-sized bubble forms around the localized excitation (He∗) within 1 ps. Subsequently, the bubble collapses and releases metastable He∗ at the droplet surface. This study highlights the high level of detail achievable in probing the photodynamics of nanosystems using tunable XUV pulses., Funding from the Deutsche Forschungsgemeinschaft (MU 2347/8-1, STI 125/19-1, and the priority program 1840 QUTIF, the Carlsberg Foundation, National Science Foundation (DMR-1828019), Carl-Zeiss-Stiftung, Grant No. FIS2017-87801-P (AEI/FEDER, UE), and Swiss National Science Foundation (200020_162434) is gratefully acknowledged. O.G., D.M.N., and M.P.Z. were supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division, through Contract No. DE-AC02-05CH11231.

21 p.-9 fig.-2 tab., Focal adhesion kinase (FAK) is a key component of the membrane proximal signaling layer in focal adhesion complexes, regulating important cellular processes, including cell migration, proliferation, and survival. In the cytosol, FAK adopts an autoinhibited state but is activated upon recruitment into focal adhesions, yet how this occurs or what induces structural changes is unknown. Here, we employ cryo-electron microscopy to reveal how FAK associates with lipid membranes and how membrane interactions unlock FAK autoinhibition to promote activation. Intriguingly, initial binding of FAK to the membrane causes steric clashes that release the kinase domain from autoinhibition, allowing it to undergo a large conformational change and interact itself with the membrane in an orientation that places the active site toward the membrane. In this conformation, the autophosphorylation site is exposed and multiple interfaces align to promote FAK oligomerization on the membrane. We show that interfaces responsible for initial dimerization and membrane attachment are essential for FAK autophosphorylation and resulting cellular activity including cancer cell invasion, while stable FAK oligomerization appears to be needed for optimal cancer cell proliferation in an anchorage-independent manner. Together, our data provide structural details of a key membrane bound state of FAK that is primed for efficient autophosphorylation and activation, hence revealing the critical event in integrin mediated FAK activation and signaling at focal adhesions., I.A. acknowledges support from the José Castillejo Mobility Grant issued by the Spanish Ministry of Education, Culture and Sports. R.D.R. acknowledges funding from the Fellowships for Excellence program sponsored by the Werner-Siemens Foundation and the University of Basel.H.S. acknowledges support by the Swiss National Science Foundation(grants 205320_166164 and 185544 (NCCR TransCure)). M.C.F., A.B., J.C., and C.S. were supported by a Cancer Research UK Programme Grant (C157/ A24837) to M.C.F. F.G. acknowledges funding by the Klaus Tschira Foundation, by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – 2082/1 –390761711, and the state of Baden-Württemberg through bwHPC and the DFG through grant INST 35/11341 FUGG.S.d.B. thanks the Carl Zeiss Foundation for financial support. D.L. acknowledges support from the Spanish Ministry of Economy, Industry and Competitiveness for the Retos Grant BFU2016-77665-R and the Ministry of Science, Innovation and Universities for the Spanish State Research Agency Retos Grant RTI2018-099318-B-I00,both co-funded by the European Regional Development Fund (FEDER) and from an intramural grant from the Spanish National Research Council(CSIC, Ref: 201820I124). O.L. is funded by SAF2017-82632-P grant from the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI), cofunded by the European Regional Development Fund (ERDF), by the National Institute of Health Carlos III and by projects Y2018/BIO4747 and P2018/NMT4443 from the Autonomous Region of Madrid and co-funded by the European Social Fund and the European Regional Development Fund. C.F.R. is funded by a BES-2015-071348 PhD fellowship by the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI).

A combinatorial study of the effect of in-mixing of various guests on the thermoelectric properties of the host workhorse polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) is presented. Specifically, the composition and thickness for doped films of PBTTT blended with different polymers are varied. Some blends at guest weight fractions around 10–15% exhibit up to a fivefold increase in power factor compared to the reference material, leading to zT values around 0.1. Spectroscopic analysis of the charge-transfer species, structural characterization using grazing-incidence wide-angle X-ray scattering, differential scanning calorimetry, Raman, and atomic force microscopy, and Monte Carlo simulations are employed to determine that the key to improved performance is for the guest to promote long-range electrical connectivity and low disorder, together with similar highest occupied molecular orbital levels for both materials in order to ensure electronic connectivity are combined., The authors acknowledge financial support from the Spanish Ministry of Science and Innovation through the Severo Ochoa" Program for Centers of Excellence in R&D (No. CEX2019-000917-S) and projects PGC2018-095411- B-I00, PGC2018-094620-A-I00, and MAT2017-90024-P (TANGENTS)-EI/Fondo Europeo de Desarrollo Regional and from the European Research Council (ERC) under Grant Agreements Nos. 648901 and 963954. J.M. thanks Ministerio de Ciencia, Innovación y Universidades for the Ramón y Cajal contract. The authors are thankful to Dr. Agustín Mihi for access and support with the FTIR equipment. The authors acknowledge the European funding (European Regional Development Fund and European Social Fund). The authors thank Andrés Gómez Rodríguez from the Scanning Probe Microscopy Laboratory (ICMAB-CSIC) for a set of fine AFM measurements. GIWAXS experiments were performed at NCD-SWEET beamline at ALBA Synchrotron with the collaboration of ALBA staff. Finally, the authors acknowledge the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unidad de Recursos de Información Científica para la Investigación (URICI). M.K. thanks the Carl Zeiss Foundation for financial support. G.Z. acknowledges the support from Alexander von Humboldt Foundation., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Filling in the gaps In a plant seed, the embryo lies dormant surrounded by nutritive endosperm while awaiting suitable conditions to germinate. A hydrophobic cuticle around the embryo protects it from catastrophic water loss during the early days of growth. Doll et al. identified a back-and-forth signaling pathway that ensures an intact cuticle. The precursor of a signaling peptide is made in the embryo and transferred to the endosperm, where it is processed into an active form. The activated peptide diffuses back into the embryo to activate receptor-like kinases that drive cuticle development. Serve and return continues until all leaks in the cuticle are filled in and the peptide can no longer cross the barrier. Science , this issue p. 431

et al., Atmospheric contamination with organic compounds is undesired in industry and in society because of odor nuisance or potential toxicity. Resistive gas sensors made of semiconducting metal oxides are effective in the detection of gases even at low concentration. Major drawbacks are low selectivity and missing sensitivity toward a targeted compound. Acetaldehyde is selected due to its high relevance in chemical industry and its toxic character. Considering the similarity between gas-sensing and heterogeneous catalysis (surface reactions, activity, selectivity), it is tempting to transfer concepts. A question of importance is how doping and the resulting change in electronic properties of a metal-oxide support with semiconducting properties alters reactivity of the surfaces and the functionality in gas-sensing and in heterogeneous catalysis. A gas-phase synthesis method is employed for aerogel-like zinc oxide materials with a defined content of aluminum (n-doping), which were then used for the assembly of gas sensors. It is shown that only Al-doped ZnO represents an effective sensor material that is sensitive down to very low concentrations (, S.P. and K.H. gratefully acknowledge funding from the Carl-Zeiss Foundation (project REFINE). M.R.W. acknowledges the postdoctoral Marie Curie Fellowship (IEF) HeatProNano (Grant No. 628197)

International audience; Biodiversity monitoring is the standard for environmental impact assessment of anthropogenic activities. Several recent studies showed that high-throughput amplicon sequencing of environmental DNA (eDNA metabarcoding) could overcome many limitations of the traditional morphotaxonomy-based bioassessment. Recently, we demonstrated that supervised machine learning (SML) can be used to predict accurate biotic indices values from eDNA metabarcoding data, regardless of the taxonomic affiliation of the sequences. However, it is unknown to which extent the accuracy of such models depends on taxonomic resolution of molecular markers or how SML compares with metabarcoding approaches targeting well-established bioindicator species. In this study, we address these issues by training predictive models upon five different ribosomal bacterial and eukaryotic markers and measuring their performance to assess the environmental impact of marine aquaculture on independent data sets. Our results show that all tested markers are yielding accurate predictive models and that they all outperform the assessment relying solely on taxonomically assigned sequences. Remarkably, we did not find any significant difference in the performance of the models built using universal eukaryotic or prokaryotic markers. Using any molecular marker with a taxonomic range broad enough to comprise different potential bioindicator taxa, SML approach can overcome the limits of taxonomy-based eDNA bioassessment.

Solar cells based on organic–inorganic halide perovskites are now leading the photovoltaic technologies because of their high power conversion efficiency. Recently, there have been debates on the microstructure-related defects in metal halide perovskites (grain size, grain boundaries, etc.) and a widespread view is that large grains are a prerequisite to suppress nonradiative recombination and improve photovoltaic performance, although opinions against it also exist. Herein, we employ blends of methylammonium lead iodide perovskites with an insulating polymer (polyvinylpyrrolidone) that offer the possibility to tune the grain size in order to obtain a fundamental understanding of the photoresponse at the microscopic level. We provide, for the first time, spatially resolved details of the microstructures in such blend systems via Raman mapping, light beam-induced current imaging, and conductive atomic force microscopy. Although the polymer blend systems systematically alter the morphology by creating small grains (more grain boundaries), they reduce nonradiative recombination within the film and enhance its spatial homogeneity of radiative recombination. We attribute this to a reduction in the density of bulk trap states, as evidenced by an order of magnitude higher photoluminescence intensity and a significantly higher open-circuit voltage when the polymer is incorporated into the perovskite films. The solar cells employing blend systems also show nearly hysteresis-free power conversion efficiency ∼17.5%, as well as a remarkable shelf-life stability over 100 days.

The optical and magneto-optical behavior in periodically nanostructured surfaces at the threshold of surface continuity is revealed. We address Co films that evolve from an island-like array to a connecting network of islands that form a membrane pattern. The analysis of magneto-optical spectra as well as numerical simulations show significant differences between continuous and broken membranes that depend dramatically on the energy of the incoming radiation. Light localization increases the magneto-optical signal in the membranes. However, the generation of hot spots is not accompanied with magneto-optic enhancement. The electromagnetic field profile within the membrane system can explain the differences in the transmission and in the magneto-optic Kerr signal., E.Th.P acknowledges the collaborative research center SFB/TRR 173: SPIN+X: Spin in its collective environment-Project B07 of the Deutsche Forschungsgemeinschaft (DFG), and the Carl Zeiss Foundation. H.F. acknowledges the financial support by the China Scholarship Council (CSC). A.G.-M. and B.C. gratefully acknowledge support by the Spanish Ministry of Economy and Competitiveness through grant MAT2014-58860-P and by the Comunidad de Madrid through Contract No. S2013/MIT-2740. E. M. A. acknowledges the Guangdong Innovative and Entrepreneurial Team Program: Plasmonic Nanomaterials and Quantum Dots for Light Management in Optoelectronic Devices.

We reveal an explicit strategy to design the magneto-optic response of a magneto-plasmonic crystal by correlating near- and far-fields effects. We use photoemission electron microscopy to map the spatial distribution of the electric near-field on a nanopatterned magnetic surface that supports plasmon polaritons. By using different photon energies and polarization states of the incident light we reveal that the electric near-field is either concentrated in spots forming a hexagonal lattice with the same symmetry as the Ni nanopattern or in stripes oriented along the Γ−K direction of the lattice and perpendicular to the polarization direction. We show that the polarization-dependent near-field enhancement on the patterned surface is directly correlated to both the excitation of surface plasmon polaritons on the patterned surface as well as the enhancement of the polar magneto-optical Kerr effect. We obtain a relationship between the size of the enhanced magnetooptical behavior and the polarization and wavelength of optical excitation. The engineering of the magneto-optic response based on the plasmon-induced modification of the optical properties introduces the concept of a magneto-plasmonic meta-structure., E.Th.P. acknowledges Carl Zeiss Foundation for financial support. A.G.-M. acknowledges the Spanish Ministry of Economy and Competitiveness (Contract No. MAT2014- 58860-P) and the Comunidad de Madrid (Contract No. S2013/MIT-2740). P.T. acknowledges financial support through the Excellence Initiative (DFG/GSC 266). V.K. acknowledges financial support from the Knut and Alice Wallenberg Foundation. We thank Piotr Patoka for the preparation of the polystyrene bead template. We gratefully acknowledge the Deutsche Forschungsgemeinschaft program SFB/TRR 173: SPIN+X.

Large surface plasmon polariton assisted enhancement of the magneto-optical activity has been observed in the past, through spectral measurements of the polar Kerr rotation in Co hexagonal antidot arrays. Here, we report a strong thickness dependence, which is unexpected given that the Kerr effect is considered a surface sensitive phenomena. The maximum Kerr rotation was found to be -0.66 degrees for a 100 nm thick sample. This thickness is far above the typical optical penetration depth of a continuous Co film, demonstrating that in the presence of plasmons the critical lengthscales are dramatically altered, and in this case extended. We therefore establish that the plasmon enhanced Kerr effect does not only depend on the in-plane structuring of the sample, but also on the out-of-plane geometrical parameters, which is an important consideration in magnetoplasmonic device design., The authors acknowledge support from the Knut and Alice Wallenberg Foundation project “Harnessing light and spins through plasmons at the nanoscale” (2015.0060), the Swedish Research Council and the Swedish Foundation for International Cooperation in Research and Higher Education. This work is part of a project which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 737093. E. Th. P acknowledges the Deutsche Forschungsgemeinschaft (DFG) through the collaborative research center SFB TRR 173: SPIN+X Project B07 and the Carl Zeiss Foundation. A.G.-M. acknowledges funding from the Spanish Ministry of Economy and Competitiveness through grant MAT2014-58860-P, and from the Comunidad de Madrid through Contract No. S2013/MIT-2740.

The phonon dispersion of graphene on Ir(111) has been determined by means of angle-resolved inelastic electron scattering and density functional calculations. Kohn anomalies of the highest optical-phonon branches are observed at the $\overline{\ensuremath{\Gamma}}$ and $\overline{\text{K}}$ point of the surface Brillouin zone. At $\overline{\text{K}}$ the Kohn anomaly is weaker than observed for pristine graphene and graphite. This observation is rationalized in terms of a decrease of the electron-phonon coupling due to screening of graphene electron correlations by the metal substrate.

We present here a generalization of the scattering-matrix approach for the description of the propagation of electromagnetic waves in nanostructured magneto-optical systems. Our formalism allows us to describe all the key magneto-optical effects in any configuration in periodically patterned multilayer structures. The method can also be applied to describe periodic multilayer systems comprising materials with any type of optical anisotropy. We illustrate the method with the analysis of a recent experiment in which the transverse magneto-optical Kerr effect was measured in an Fe film with a periodic array of subwavelength circular holes. We show, in agreement with the experiments, that the excitation of surface plasmon polaritons in this system leads to a resonant enhancement of the transverse magneto-optical Kerr effect. © 2012 American Physical Society., B.C. and A.G.-M. acknowledge funding from the EU (NMP3-SL-2008-214107-Nanomagma), the Spanish MICINN (“MAPS” MAT2011-29194-C02-01, “MAGPLAS” MAT2008-06765-C02-01/NAN, and “FUNCOAT” CONSOLIDER INGENIO 2010 CSD2008-00023), and the Comunidad de Madrid (“MICROSERES-CM” S2009/TIC-1476). J.C.C. acknowledges financial support from the Spanish MICINN (Contract No. FIS2011-28851-C02-01) and from the German foundations Carl Zeiss Stiftung and Stifterverband für die Deutsche Wissenschaft via the award of an “InnoLecture-Gastdozentur.”