Showing papers on "Amorphous solid published in 2016"
TL;DR: This review attempts to address the critical molecular and thermodynamic aspects governing the physicochemical properties of amorphous solid dispersion systems and potential advantage of polymers as inert, hydrophilic, pharmaceutical carrier matrices.
680 citations
TL;DR: The discovery of switchable lithiophobic-lithiophilic surfaces to improve the Li metal/SSE interface opens opportunities for improving many other SSEs.
Abstract: All-solid-state Li-batteries using solid-state electrolytes (SSEs) offer enhanced safety over conventional Li-ion batteries with organic liquid electrolytes due to the nonflammable nature of SSEs. The superior mechanical strength of SSEs can also protect against Li dendrite penetration, which enables the use of the highest specific capacity (3861 mAh/g) and lowest redox potential (−3.04 V vs standard hydrogen electrode) anode: Li metal. However, contact between the Li metal and SSEs presents a major challenge, where a large polarization occurs at the Li metal/SSE interface. Here, the chemical properties of a promising oxide-based SSE (garnet) changed from “super-lithiophobicity” to “super-lithiophilicity” through an ultrathin coating of amorphous Si deposited by plasma-enhanced chemical vapor deposition (PECVD). The wettability transition is due to the reaction between Li and Si and the in situ formation of lithiated Si. As a result, symmetric cells composed of a Si-coated garnet-structured SSE and Li met...
485 citations
TL;DR: In this article, a simple and scalable synthesis route is developed to prepare amorphous FeOOH quantum dots (QDs) and FeOH QDs/graphene hybrid nanosheets.
Abstract: Previous research on iron oxides/hydroxides has focused on the crystalline rather than the amorphous phase, despite that the latter could have superior electrochemical activity due to the disordered structure. In this work, a simple and scalable synthesis route is developed to prepare amorphous FeOOH quantum dots (QDs) and FeOOH QDs/graphene hybrid nanosheets. The hybrid nanosheets possess a unique heterostructure, comprising a continuous mesoporous FeOOH nanofilm tightly anchored on the graphene surface. The amorphous FeOOH/graphene hybrid nanosheets exhibit superior pseudocapacitive performance, which largely outperforms the crystalline iron oxides/hydroxides-based materials. In the voltage range between −0.8 and 0 V versus Ag/AgCl, the amorphous FeOOH/graphene composite electrode exhibits a large specific capacitance of about 365 F g−1, outstanding cycle performance (89.7% capacitance retention after 20 000 cycles), and excellent rate capability (189 F g−1 at a current density of 128 A g−1). When the lower cutoff voltage is extended to −1.0 and −1.25 V, the specific capacitance of the amorphous FeOOH/graphene composite electrode can be increased to 403 and 1243 F g−1, respectively, which, however, compromises the rate capability and cycle performance. This work brings new opportunities to design high-performance electrode materials for supercapacitors, especially for amorphous oxides/hydroxides-based materials.
412 citations
TL;DR: The Segal method estimates the amorphous fraction of cellulose Iβ materials simply based on intensity in an X-ray diffraction pattern and was extended to cellulose II using 16° 2θ intensity, which resulted in relatively good agreement with the simulation for mercerized cotton.
367 citations
TL;DR: These experiments provide the first mechanistic insight into the mechanism of imine-linked 2D COF formation, which is distinct from that of boronate-ester linked COFs.
322 citations
TL;DR: The proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods and foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.
Abstract: Optically rewritable surface phonon–polariton resonators are demonstrated in a system combining phase-change materials that can reversibly switch between amorphous and crystalline phases, with polar crystals that support surface phonon–polaritons.
316 citations
TL;DR: This work proposes and demonstrates facile solution synthesis of a series of colloidal organometal halide perovskite CH3NH3PbX3 (X = halides) nanoparticles with amorphous structure, which exhibit high quantum yield and tunable emission from ultraviolet to near-infrared in light-emitting devices.
Abstract: Organometal halide perovskite has recently emerged as a very promising family of materials with augmented performance in electronic and optoelectronic applications including photovoltaic devices, photodetectors, and light-emitting diodes. Herein, we propose and demonstrate facile solution synthesis of a series of colloidal organometal halide perovskite CH3NH3PbX3 (X = halides) nanoparticles with amorphous structure, which exhibit high quantum yield and tunable emission from ultraviolet to near-infrared. The growth mechanism and photoluminescence properties of the perovskite amorphous nanoparticles were studied in detail. A high-efficiency green-light-emitting diode based on amorphous CH3NH3PbBr3 nanoparticles was demonstrated. The perovskite amorphous nanoparticle-based light-emitting diode shows a maximum luminous efficiency of 11.49 cd/A, a power efficiency of 7.84 lm/W, and an external quantum efficiency of 3.8%, which is 3.5 times higher than that of the best colloidal perovskite quantum-dot-based lig...
310 citations
TL;DR: In situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone.
Abstract: Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.
306 citations
TL;DR: In this article, a solution-based fabrication and characterization of the lead-free perovskite-related methylammonium antimony iodide (CH3NH3)3Sb2I9 compound was presented.
Abstract: We present solution-based fabrication and characterization of the lead-free perovskite-related methylammonium antimony iodide (CH3NH3)3Sb2I9 compound. By photothermal deflection spectroscopy (PDS), we determined a peak absorption coefficient α ≈ 105 cm–1 and an optical band gap of 2.14 eV for amorphous films of (CH3NH3)3Sb2I9. Compared to the related Bi compound, the Sb-perovskite shows no exciton peak in its absorption spectrum. The photoluminescence emission (PL) is observed at 1.58 eV, and the Urbach tail energy of this amorphous compound is Eu = 62 meV, indicating a substantial amount of energetic disorder. We fabricate a planar heterojunction solar cell with a (CH3NH3)3Sb2I9 absorber layer that yields a power conversion efficiency of η ≈ 0.5%, already featuring a decent fill factor (FF) of 55% and open-circuit voltage of 890 mV but low photocurrent densities. The result of this basic study on (CH3NH3)3Sb2I9 shows that this compound is a possible starting point for further research into Sb-based lead-...
290 citations
TL;DR: A unified method using persistence diagrams for studying the geometry of atomic configurations in amorphous solids, which suggests that the PDs provide a unified method that extracts greater depth of geometric information in amortized solids than conventional methods.
Abstract: This article proposes a topological method that extracts hierarchical structures of various amorphous solids. The method is based on the persistence diagram (PD), a mathematical tool for capturing shapes of multiscale data. The input to the PDs is given by an atomic configuration and the output is expressed as 2D histograms. Then, specific distributions such as curves and islands in the PDs identify meaningful shape characteristics of the atomic configuration. Although the method can be applied to a wide variety of disordered systems, it is applied here to silica glass, the Lennard-Jones system, and Cu-Zr metallic glass as standard examples of continuous random network and random packing structures. In silica glass, the method classified the atomic rings as short-range and medium-range orders and unveiled hierarchical ring structures among them. These detailed geometric characterizations clarified a real space origin of the first sharp diffraction peak and also indicated that PDs contain information on elastic response. Even in the Lennard-Jones system and Cu-Zr metallic glass, the hierarchical structures in the atomic configurations were derived in a similar way using PDs, although the glass structures and properties substantially differ from silica glass. These results suggest that the PDs provide a unified method that extracts greater depth of geometric information in amorphous solids than conventional methods.
276 citations
TL;DR: In this paper, the electronic structure of iridium oxide was investigated using synchrotron-based X-ray photoemission and absorption spectroscopies with theoretical calculations.
Abstract: Iridium-based materials are among the most active and stable electrocatalysts for the oxygen evolution reaction. Amorphous iridium oxide structures are found to be more active than their crystalline counterparts. Herein, we combine synchrotron-based X-ray photoemission and absorption spectroscopies with theoretical calculations to investigate the electronic structure of Ir metal, rutile-type IrO2, and an amorphous IrOx. Theory and experiment show that while the Ir 4f line shape of Ir metal is well described by a simple Doniach–Sunjic function, the peculiar line shape of rutile-type IrO2 requires the addition of a shake-up satellite 1 eV above the main line. In the catalytically more active amorphous IrOx, we find that additional intensity appears in the Ir 4f spectrum at higher binding energy when compared with rutile-type IrO2 along with a pre-edge feature in the O K-edge. We identify these additional features as electronic defects in the anionic and cationic frameworks, namely, formally OI− and IrIII, which may explain the increased activity of amorphous IrOx electrocatalysts. We corroborate our findings by in situ X-ray diffraction as well as in situ X-ray photoemission and absorption spectroscopies. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In the present paper, laboratorial and industrial scale processes were reviewed, and guidelines for a rationale selection of manufacturing processes were proposed to ensure an adequate development and production according to the good manufacturing practices (GMP) (industrial scale) of amorphous solid dispersions.
TL;DR: Amorphous fish-scale-like FeOOH and Co-Ni double hydroxides (Co-Ni-DH) have been synthesized through one-step electrodeposition in this article.
TL;DR: For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation.
Abstract: Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation.
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TL;DR: In situ electron microscopy is used to show how gold and silver nanocrystals nucleate from supersaturated aqueous solutions in three distinct steps: spinodal decomposition into solute-rich andsolute-poor liquid phases, nucleation of amorphous nanoclusters within the metal-rich liquid phase, followed by crystallization of theseAmorphous clusters.
Abstract: Nucleation and growth of solids from solutions impacts many natural processes and are fundamental to applications in materials engineering and medicine. For a crystalline solid, the nucleus is a nanoscale cluster of ordered atoms, which forms through mechanisms that are still poorly understood. These mechanisms have important consequences on the morphology and nucleation rates of the resultant crystals but it is unclear whether a nucleus forms spontaneously from solution in a single step or through multiple steps. Using in-situ electron microscopy, we observe and quantify how gold and silver nanocrystals nucleate from a supersaturated aqueous gold and silver solution in three distinct steps: (I) spinodal decomposition into solute-rich and solute-poor liquid phases, (II) nucleation of amorphous gold nanoclusters within the gold-rich liquid phase, followed by (III) crystallization of these amorphous clusters. Our ab-initio calculations on gold nucleation suggest that these steps might be associated with strong gold-gold atom coupling and water-mediated metastable gold complexes. The understanding of intermediate steps in nuclei formation has important implications for the formation and growth of both crystalline and amorphous materials.
TL;DR: In this paper, amorphous MoS x (a-MoS x ) nanoparticles were directly anchored on the g-C 3 N 4 surface by an adsorption-in situ transformation method with the aim of improving photocatalytic H 2 -evolution activity.
Abstract: Exploiting novel and high-performance electron-cocatalysts without noble metallic element is of great significance for photocatalytic H 2 -evolution reaction. Molybdenum sulfide is one of the promising candidates of such electron-cocatalysts, but its present performance is intrinsically restrained by the scarce active sites of unsaturated S atoms. In this study, amorphous MoS x (a-MoS x ) nanoparticles were directly anchored on the g-C 3 N 4 surface by an adsorption-in situ transformation method with the aim of improving photocatalytic H 2 -evolution activity. It was found that compared with the crystalline molybdenum sulfide (c-MoS 2 ), the a-MoS x cocatalyst clearly exhibited more unsaturated active S atoms due to its highly irregular arrangement structure. Photocatalytic experimental results suggested that the H 2 -evolution activity of g-C 3 N 4 photocatalyst could be obviously improved by loading a-MoS x cocatalyst, which is obviously higher than that of unmodified g-C 3 N 4 and c-MoS 2 /g-C 3 N 4 . More importantly, in addition to the g-C 3 N 4 , the amorphous MoS x could also work as the efficient electron cocatalyst to greatly enhance the photocatalytic performance of conventional H 2 -evolution materials such as TiO 2 (a typical UV-light photocatalyst) and CdS (a typical Vis-light photocatalyst). On the basis of the present results, an electron-cocatalyst mechanism of amorphous MoS x was proposed to account for the improved photocatalytic H 2 -evolution activity, namely, the amorphous MoS x can provide more unsaturated active S atoms as the efficient active sites to rapidly capture protons from solution, and then promote the direct reduction of H + to H 2 by photogenerated electrons. Considering its low cost and high efficiency, the amorphous MoS x cocatalyst would have great potential for the development of high-performance photocatalytic materials used in various fields.
TL;DR: The findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic, in ferromagnetic resonance (FMR), which is the lowest value for ultrathin films published so far.
Abstract: We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10−5 is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10−5 is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials.
TL;DR: In this article, the influence of the addition of more Se on dielectric properties, opto-electrical parameters and electronic polarizability of amorphous chalcogenide Cd 50 S 50−x Se x thin films was studied.
TL;DR: In this paper, the authors investigate several polymer-fullerene systems, which present short circuit current (Jsc) loss to varying degrees, in order to determine under which conditions dimerization occurs.
Abstract: Fullerene dimerization has been linked to short circuit current (Jsc) losses in organic solar cells comprised of certain polymer–fullerene systems. We investigate several polymer–fullerene systems, which present Jsc loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the Jsc loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of Jsc. In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from Voc to Jsc also significantly reduces the amount of dimerization-related Jsc loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at Voc instead of Jsc. The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism via excitons.
TL;DR: A scalable and catalyst-free method to deposit stoichiometric molybdenum disulfide (MoS2) films over large areas is reported, with the maximum area limited by the size of the substrate holder.
Abstract: A scalable and catalyst-free method to deposit stoichiometric molybdenum disulfide (MoS2) films over large areas is reported, with the maximum area limited by the size of the substrate holder. The method allows deposition of MoS2 layers on a wide range of substrates without any additional surface preparation, including single-crystal (sapphire and quartz), polycrystalline (HfO2), and amorphous (SiO2) substrates. The films are deposited using carefully designed MoS2 targets fabricated with excess sulfur and variable MoS2 and sulfur particle size. Uniform and layered MoS2 films as thin as two monolayers, with an electrical resistivity of 1.54 × 104 Ω cm–1, were achieved. The MoS2 stoichiometry was confirmed by high-resolution Rutherford backscattering spectrometry. With the method reported here, in situ graded MoS2 films ranging from ∼1 to 10 monolayers can be deposited.
TL;DR: In this article, the significant effects of SnO2 crystallinity on sodium storage performance were studied in detail, and it was shown that amorphous nanocomposite is more effective than c-SnO2/GA in overcoming electrode degradation from large volume changes associated with charge discharge processes.
Abstract: The exploration of sodium ion batteries (SIBs) is a profound challenge due to the rich sodium abundance and limited supply of lithium on earth. Here, amorphous SnO2/graphene aerogel (a-SnO2/GA) nanocomposites have been successfully synthesized via a hydrothermal method for use as anode materials in SIBs. The designed annealing process produces crystalline SnO2/graphene aerogel (c-SnO2/GA) nanocomposites. For the first time, the significant effects of SnO2 crystallinity on sodium storage performance are studied in detail. Notably, a-SnO2/GA is more effective than c-SnO2/GA in overcoming electrode degradation from large volume changes associated with charge–discharge processes. Surprisingly, the amorphous SnO2 delivers a high specific capacity of 380.2 mAh g−1 after 100 cycles at a current density of 50 mA g−1, which is almost three times as much as for crystalline SnO2 (138.6 mAh g−1). The impressive electrochemical performance of amorphous SnO2 can be attributed to the intrinsic isotropic nature, the enhanced Na+ diffusion coefficient, and the strong interaction between amorphous SnO2 and GA. In addition, amorphous SnO2 particles with the smaller size better function to relieve the volume expansion/shrinkage. This study provides a significant research direction aiming to increase the electrochemical performance of the anode materials used in SIBs.
TL;DR: In this paper, a 3D carbonized aerogel derived from biomass bacterial cellulose (BC) is introduced as a flexible framework for iron oxides in Li-ion batteries (LIBs).
TL;DR: The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.
Abstract: The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx ) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.
TL;DR: Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes and is linked to the different reactivity of these networks.
Abstract: Operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3–xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks...
TL;DR: In this article, a comparative study of six common carbon interatomic potentials: Tersoff, REBO-II, ReaxFF, EDIP, LCBOP-I and COMB3 is performed.
TL;DR: Iron oxide was employed to demonstrate a concept that rationally designing an amorphous structure should be useful to enhance Na-ion storage performance of a metal oxide to facilitate preparation of various amorphously nanostructure of other metal oxides and improve their Na-ions storage performance.
Abstract: With the increasing use of sodium-ion batteries (SIBs), developing cost-effective anode materials, such as metal oxide, for Na-ion storage is one of the most attractive topics Due to the obviously larger ion radius of Na than that of Li, most metal oxide electrode materials fail to exhibit the same high performance for SIBs like that of Li-ion batteries Herein, iron oxide was employed to demonstrate a concept that rationally designing an amorphous structure should be useful to enhance Na-ion storage performance of a metal oxide Amorphous Fe2O3/graphene composite nanosheets (Fe2O3@GNS) were successfully synthesized by a facile approach as anodes for SIBs It reveals that amorphous Fe2O3 nanoparticles with an average diameter of 5 nm were uniformly anchored on the surface of graphene nanosheets by the strong C–O–Fe oxygen-bridge bond Compared to well-crystalline Fe2O3, amorphous Fe2O3@GNS exhibited superior sodium storage properties such as high electrochemical activity, high initial Coulombic efficienc
TL;DR: The authors used fifth-order dielectric susceptibility measurements to show that the real reason behind the stiffness of glass is more complicated. But the emerging amorphous order is only weakly dependent on the specific molecular properties, suggesting a more universal governing behavior for making glasses The authors.
Abstract: Glasses are often thought of as frozen liquids without long-range order. Albert et al. used fifth-order dielectric susceptibility measurements to show that the real reason behind the stiffness of glass is more complicated. Measuring the response of two traditional glass formers to very high electric fields is challenging, but reveals the growth of compact domains across the glass transition. The emerging amorphous order is only weakly dependent on the specific molecular properties, suggesting a more universal governing behavior for making glasses.
Science , this issue p. [1308][1]
[1]: /lookup/doi/10.1126/science.aaf3182
TL;DR: It is shown by using transmission electron microscopy that 100-300 nm amorphous calcium phosphate regions are present in the disordered phase of trabecular bone, and postulate that this transition in failure mechanism is caused by the suppression of extrafibrillar shearing in the smaller samples, and that the emergent smaller-is-stronger size effect is related to the sample-size scaling of the distribution of flaws.
Abstract: In human bone, an amorphous mineral serves as a precursor to the formation of a highly substituted nanocrystalline apatite. However, the precise role of this amorphous mineral remains unknown. Here, we show by using transmission electron microscopy that 100–300 nm amorphous calcium phosphate regions are present in the disordered phase of trabecular bone. Nanomechanical experiments on cylindrical samples, with diameters between 250 nm and 3,000 nm, of the bone’s ordered and disordered phases revealed a transition from plastic deformation to brittle failure and at least a factor-of-2 higher strength in the smaller samples. We postulate that this transition in failure mechanism is caused by the suppression of extrafibrillar shearing in the smaller samples, and that the emergent smaller-is-stronger size effect is related to the sample-size scaling of the distribution of flaws. Our findings should help in the understanding of the multi-scale nature of bone and provide insights into the biomineralization process.
TL;DR: In this article, the authors review the different parameters that influence the dewetting and illustrate how these parameters can be tuned by varying the thickness of the film, the annealing temperature, or the state of strain in the film.