The Experts below are selected from a list of 213132 Experts worldwide ranked by ideXlab platform
Justin M Hoffman - One of the best experts on this subject based on the ideXlab platform.
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long periodic ripple in a 2d hybrid halide perovskite structure using branched organic spacers
Chemical Science, 2020Co-Authors: Justin M Hoffman, Ido Hadar, Christos D Malliakas, Siraj Sidhik, Rebecca Mcclain, Aditya D Mohite, Mercouri G KanatzidisAbstract:Two-dimensional (2D) halide perovskites have great promise in optoelectronic devices because of their stability and optical tunability, but the subtle effects on the inorganic layer when modifying the organic spacer remain unclear. Here, we introduce two homologous series of Ruddlesden–Popper (RP) structures using the branched isobutylammonium (IBA) and isoamylammonium (IAA) cations with the general formula (RA)2(MA)n−1PbnI3n+1 (RA = IBA, IAA; MA = methylammonium n = 1–4). Surprisingly, the IAA n = 2 member results in the first modulated 2D perovskite structure with a ripple with a periodicity of 50.6 A occurring in the inorganic slab diagonally to the [101] direction of the basic unit cell. This leads to an increase of Pb–I–Pb angles along the direction of the wave. Generally, both series show larger in-plane bond angles resulting from the additional bulkiness of the spacers compensating for the MA's small size. Larger bond angles have been shown to decrease the bandgap which is seen here with the bulkier IBA leading to both larger in-plane angles and lower bandgaps except for n = 2, in which the modulated structure has a lower bandgap because of its larger Pb–I–Pb angles. Photo-response was tested for the n = 4 compounds and confirmed, signaling their potential use in solar cell devices. We made films using an MACl additive which showed good crystallinity and preferred orientation according to grazing-incidence Wide-Angle Scattering (GIWAXS). As exemplar, the two n = 4 samples were employed in devices with champion efficiencies of 8.22% and 7.32% for IBA and IAA, respectively.
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in situ grazing incidence wide angle Scattering reveals mechanisms for phase distribution and disorientation in 2d halide perovskite films
Advanced Materials, 2020Co-Authors: Justin M Hoffman, Joseph Strzalka, Nathan C Flanders, Ido Hadar, Shelby A Cuthriell, Qingteng Zhang, Richard D Schaller, William R Dichtel, Lin X ChenAbstract:2D hybrid halide perovskites with the formula (A')2 (A)n-1 Pbn I3n+1 have remarkable stability and promising efficiency in photovoltaic and optoelectronic devices, yet fundamental understanding of film formation, key to optimizing these devices, is lacking. Here, in situ grazing-incidence Wide-Angle X-ray Scattering (GIWAXS) is used to monitor film formation during spin-coating. This elucidates the general film formation mechanism of 2D halide perovskites during one-step spin-coating. There are three stages of film formation: sol-gel, oriented 3D, and 2D. Three precursor phases form during the sol-gel stage and transform to perovskite, first giving a highly oriented 3D-like phase at the air/liquid interface followed by subsequent nucleations forming slightly less oriented 2D perovskite. Furthermore, heating before crystallization leads to fewer nucleations and faster removal of the precursors, improving orientation. This outlines the primary causes of phase distribution and perpendicular orientation in 2D perovskite films and paves the way for rationally designed film fabrication techniques.
Luca Poletto - One of the best experts on this subject based on the ideXlab platform.
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coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source
Nature Communications, 2017Co-Authors: Daniela Rupp, Nils Monserud, Bruno Langbehn, Mario Sauppe, Julian Zimmermann, Y Ovcharenko, T Moller, Fabio Frassetto, Luca PolettoAbstract:Coherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using extreme ultraviolet pulses from a femtosecond-laser-driven high harmonic source. We obtain bright Wide-Angle Scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.Diffraction imaging studies of free individual nanoparticles have so far been restricted to XUV and X-ray free - electron laser facilities. Here the authors demonstrate the possibility of using table-top XUV laser sources to image prolate shapes of superfluid helium droplets.
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coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source
arXiv: Atomic and Molecular Clusters, 2016Co-Authors: Daniela Rupp, Nils Monserud, Bruno Langbehn, Mario Sauppe, Julian Zimmermann, Y Ovcharenko, T Moller, Fabio Frassetto, Luca PolettoAbstract:Coherent diffractive imaging of individual free nanoparticles has opened novel routes for the in-situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet (XUV) and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using XUV pulses from a femtosecond-laser driven high harmonic source. We obtain bright Wide-Angle Scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.
Y Ovcharenko - One of the best experts on this subject based on the ideXlab platform.
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coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source
Nature Communications, 2017Co-Authors: Daniela Rupp, Nils Monserud, Bruno Langbehn, Mario Sauppe, Julian Zimmermann, Y Ovcharenko, T Moller, Fabio Frassetto, Luca PolettoAbstract:Coherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using extreme ultraviolet pulses from a femtosecond-laser-driven high harmonic source. We obtain bright Wide-Angle Scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.Diffraction imaging studies of free individual nanoparticles have so far been restricted to XUV and X-ray free - electron laser facilities. Here the authors demonstrate the possibility of using table-top XUV laser sources to image prolate shapes of superfluid helium droplets.
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coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source
arXiv: Atomic and Molecular Clusters, 2016Co-Authors: Daniela Rupp, Nils Monserud, Bruno Langbehn, Mario Sauppe, Julian Zimmermann, Y Ovcharenko, T Moller, Fabio Frassetto, Luca PolettoAbstract:Coherent diffractive imaging of individual free nanoparticles has opened novel routes for the in-situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet (XUV) and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using XUV pulses from a femtosecond-laser driven high harmonic source. We obtain bright Wide-Angle Scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.
Yoshiharu Nishiyama - One of the best experts on this subject based on the ideXlab platform.
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water induced crystallization and nano scale spinodal decomposition of cellulose in nmmo and ionic liquid dope
Cellulose, 2019Co-Authors: Yoshiharu Nishiyama, Shirin Asaadi, Patrik Ahvenainen, Herbert SixtaAbstract:We followed the cellulose structure formation induced by water diffusion into Lyocell dopes based on both N-Methylmorpholine N-oxide (NMMO) and 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc], by using scanning simultaneous small- and Wide-Angle Scattering (SAXS-WAXS) experiment along the diffusion gradient. The water content at each point was estimated from the Wide-Angle Scattering profile, giving a binary diffusion constant of the order of 5 × 10−10 m2/sec. In the case of the cellulose solution in NMMO monohydrate, diffraction peaks corresponding to cellulose II appeared concomitantly with the increase in small angle Scattering features indicative of nanofibril formation. In the cellulose solution in the ionic liquid, an increase in small angle Scattering intensity with the progression of water content appeared at Scattering vector q = 0.015 A−1 corresponding to a correlation length of about 40 nm, indicative of nanometric spinodal decomposition preceding the coagulation process, though no crystalline peak appeared in the Wide-Angle Scattering.
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Structural coarsening of aspen wood by hydrothermal pretreatment monitored by small- and Wide-Angle Scattering of X-rays and neutrons on oriented specimens
Cellulose, 2014Co-Authors: Yoshiharu Nishiyama, Paul Langan, Hugh O’neill, Sai Venkatesh Pingali, Shane HartonAbstract:Structural changes across multiple length scales associated with hydrothermal pretreatments of biomass were investigated by using small- and Wide-Angle X-ray and neutron Scattering on oriented specimens. Isotropic and anisotropic Scattering components were numerically separated and then interpreted as contributions from matrix and cellulose components, respectively. Equatorial diffraction peaks present in the isotropic component became sharper after hydrothermal treatments or ammonia treatment. Before pretreatment the wet cell wall was found to be homogeneous in the 10–100 nm range and Scattering below Q = 0.5 (nm^−1) was dominated by surface Scattering from the lumen. After pretreatment with acid or steam at 160 or 180 °C, density fluctuation developed in the cell wall at length scales above 10 nm, most likely due to lateral coalescence of microfibrils that partially co-crystallize to give larger apparent crystal sizes. A density fluctuation up to about 100 nm appeared in the isotropic component after acid and steam pretreatments due to morphological changes in the hemicellulose and lignin matrix.
Lin X Chen - One of the best experts on this subject based on the ideXlab platform.
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in situ grazing incidence wide angle Scattering reveals mechanisms for phase distribution and disorientation in 2d halide perovskite films
Advanced Materials, 2020Co-Authors: Justin M Hoffman, Joseph Strzalka, Nathan C Flanders, Ido Hadar, Shelby A Cuthriell, Qingteng Zhang, Richard D Schaller, William R Dichtel, Lin X ChenAbstract:2D hybrid halide perovskites with the formula (A')2 (A)n-1 Pbn I3n+1 have remarkable stability and promising efficiency in photovoltaic and optoelectronic devices, yet fundamental understanding of film formation, key to optimizing these devices, is lacking. Here, in situ grazing-incidence Wide-Angle X-ray Scattering (GIWAXS) is used to monitor film formation during spin-coating. This elucidates the general film formation mechanism of 2D halide perovskites during one-step spin-coating. There are three stages of film formation: sol-gel, oriented 3D, and 2D. Three precursor phases form during the sol-gel stage and transform to perovskite, first giving a highly oriented 3D-like phase at the air/liquid interface followed by subsequent nucleations forming slightly less oriented 2D perovskite. Furthermore, heating before crystallization leads to fewer nucleations and faster removal of the precursors, improving orientation. This outlines the primary causes of phase distribution and perpendicular orientation in 2D perovskite films and paves the way for rationally designed film fabrication techniques.
