Bragg coherent diffraction imaging (BCDI), a well-established technique for imaging the internal strain of nanoparticles, was used to image the internal compositional distribution of binary alloys in ...thermal equilibrium. The images experimentally obtained for Pd-Rh alloy nanoparticles are presented and discussed. A direct correspondence between the lattice strain and the compositional deviation is discussed with the derivation of the BCDI displacement field aided by illustrations. The correspondence suggests that the longitudinal derivative of the displacement field, the strain induced by compositional heterogeneity, can be quantitatively converted to 3D images of the compositional deviation from the particle average by using Vegard’s law. It also suggests that the transverse derivative can be qualitatively associated with the disorder of Bragg planes. The studied Pd-Rh alloy nanoparticle exhibited internal composition heterogeneity; the Rh composition tends to be high at edges and corners between facets and gradually decreases from the surface to the core of the particle.
We synthesized a series of acceptor–donor–acceptor-type small molecules (SIDPP-EE, SIDPP-EO, SIDPP-OE, and SIDPP-OO) consisting of a dithienosilole (SI) electron-donating moiety and two ...diketopyrrolopyrrole (DPP) electron-withdrawing moieties each bearing linear n-octyl (O) and/or branched 2-ethylhexyl (E) alkyl side chains. X-ray diffraction patterns revealed that SIDPP-EE and SIDPP-EO films were highly crystalline with pronounced edge-on orientation, whereas SIDPP-OE and SIDPP-OO films were less crystalline with a radial distribution of molecular orientations. Near-edge X-ray absorption fine structure spectroscopy disclosed an edge-on orientation with a molecular backbone tilt angle of ∼22° for both SIDPP-EE and SIDPP-EO. Our analysis of the molecular packing and orientation indicated that the shorter 2-ethylhexyl groups on the SI core promote tight π–π stacking of the molecular backbone, whereas n-octyl groups on the SI core hinder close π–π stacking to some degree. Conversely, the longer linear n-octyl groups on the DPP arms facilitate close intermolecular packing via octyl–octyl interdigitation. Quantum mechanics/molecular mechanics molecular dynamics simulations determined the optimal three-dimensional positions of the flexible alkyl side chains of the SI and DPP units, which elucidates the structural cause of the molecular packing and orientation explicitly. The alkyl-chain-dependent molecular stacking significantly affected the electrical properties of the molecular films. The edge-on oriented molecules showed high hole mobilities in organic field-effect transistors, while the radially oriented molecules exhibited high photovoltaic properties in organic photovoltaic cells. These results demonstrate that appropriate positioning of alkyl side chains can modulate crystallinity and molecular orientation in SIDPP films, which ultimately have a profound impact on carrier transport and photovoltaic performance.
Hydrogen fuel cells and electrolyzers operating below 600 °C, ideally below 400 °C, are essential components in the clean energy transition. Yttrium‐doped barium zirconate BaZr0.8Y0.2O3‐d (BZY) has ...attracted a lot of attention as a proton‐conducting solid oxide for electrochemical devices due to its high chemical stability and proton conductivity in the desired temperature range. Grain interfaces and topological defects modulate bulk proton conductivity and hydration, especially at low temperatures. Therefore, understanding the nanoscale crystal structure dynamics in situ is crucial to achieving high proton transport, material stability, and extending the operating range of proton‐conducting solid oxides. Here, Bragg coherent X‐ray diffractive imaging is applied to investigate in situ and in 3D nanoscale dynamics in BZY during hydration over 40 h at 200 °C, in the low‐temperature range. An unexpected activity of topological defects and subsequent cracking is found on a nanoscale covered by the macroscale stability. The rearrangements in structure correlate with emergent regions of different lattice constants, suggesting heterogeneous hydration. The results highlight the extent and impact of nanoscale processes in proton‐conducting solid oxides, informing future development of low‐temperature protonic ceramic electrochemical cells.
Proton‐conducting ceramics open new horizons for hydrogen energy devices in the lower operating temperature ranges, promising higher energy efficiency. Nevertheless, nanostructure plays a more important role in lowering the operating temperature. Presented here are the results of in situ X‐ray imaging of nanostructure dynamics in BaZr0.8Y0.2O3‐d during hydration, exposing a unique degree of freedom in proton‐conducting solid oxide materials.
Palladium absorbs large volumetric quantities of hydrogen at room temperature and ambient pressure, making the palladium hydride system a promising candidate for hydrogen storage. Here, we use Bragg ...coherent diffraction imaging to map the strain associated with defects in three dimensions before and during the hydride phase transformation of an individual octahedral palladium nanoparticle, synthesized using a seed-mediated approach. The displacement distribution imaging unveils the location of the seed nanoparticle in the final nanocrystal. By comparing our experimental results with a finite-element model, we verify that the seed nanoparticle causes a characteristic displacement distribution of the larger nanocrystal. During the hydrogen exposure, the hydride phase is predominantly formed on one tip of the octahedra, where there is a high number of lower coordinated Pd atoms. Our experimental and theoretical results provide an unambiguous method for future structure optimization of seed-mediated nanoparticle growth and in the design of palladium-based hydrogen storage systems.
We characterized the electrical properties of a field-effect transistor (FET) and a nonvolatile memory device based on a solution-processable low bandgap small molecule, Si1TDPP-EE-C6. The small ...molecule consisted of electron-rich thiophene-dithienosilole-thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) units. The as-spun Si1TDPP-EE-C6 FET device exhibited ambipolar transport properties with a hole mobility of 7.3 × 10–5 cm2/(V s) and an electron mobility of 1.6 × 10–5 cm2/(V s). Thermal annealing at 110 °C led to a significant increase in carrier mobility, with hole and electron mobilities of 3.7 × 10–3 and 5.1 × 10–4 cm2/(Vs), respectively. This improvement is strongly correlated with the increased film crystallinity and reduced π–π intermolecular stacking distance upon thermal annealing, revealed by grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) measurements. In addition, nonvolatile memory devices based on Si1TDPP-EE-C6 were successfully fabricated by incorporating Au nanoparticles (AuNPs) as charge trapping sites at the interface between the silicon oxide (SiO2) and cross-linked poly(4-vinylphenol) (cPVP) dielectrics. The device exhibited reliable nonvolatile memory characteristics, including a wide memory window of 98 V, a high on/off-current ratio of 1 × 103, and good electrical reliability. Overall, we demonstrate that donor–acceptor-type small molecules are a potentially important class of materials for ambipolar FETs and nonvolatile memory applications.
The fused dithieno2,3-d:2′,3′-d′benzo1,2-b:4,5-b′dithiophene (DTBDT) structure was coupled with diketopyrrolopyrrole (DPP) moieties to generate highly planar ...bis(2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo3,4-cpyrrole-1,4-dione)dithieno2,3-d:2′,3′-d′benzo1,2-b:4,5-b′dithiophene (DTBDTDPP-EH) and bis(2,5-bis(2-butyloctyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo3,4-cpyrrole-1,4-dione)dithieno2,3-d:2′,3′-d′benzo1,2-b:4,5-b′dithiophene (DTBDTDPP-BO) molecules, where the EH and BO stands for 2-ethylhexyl and 2-butyloctyl groups respectively. The morphology of the DTBDTDPP-EH alone or DTBDTDPP-EH:6,6-phenyl-C61-butyric acid methyl ester (PCBM) blend film was controlled using post-thermal annealing at 130 °C or addition of 1,8-diiodooctane (DIO) additives. The DIO-additive treatment was more effective than thermal annealing at increasing crystallinity; the DIO-additives promoted the formation of nanoscopically well-connected molecular crystalline domains in the blend films. This observation well explained the ordering of the photovoltaic properties of DTBDTDPP-EH:PCBM devices: from worst to best, as-cast, thermally treated, and DIO-treated photoactive films. The DTBDTDPP-BO:PCBM device followed the similar trend with lower performances due to the presence of irregularly overgrown domains. Overall, we demonstrate that it is critical to optimize nanoscale film morphologies by engineering alkyl chains and selecting an appropriate processing method.
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•Dithienobenzodithiophene-core small molecules were synthesized.•The light absorption and HOMO/LUMO levels of DTBDTDPP molecules are appropriate for OPVs.•The morphology of photoactive layer was optimized by thermal annealing and diiodooctane-additive use.•DTBDTDPP-EH:PCBM blend exhibited optimal phase separation, yielding the high PCE of 4.35%.
The recent advent of hard x-ray free electron lasers (XFELs) opens new areas of science due to their exceptional brightness, coherence, and time structure. In principle, such sources enable studies ...of dynamics of condensed matter systems over times ranging from femtoseconds to seconds. However, the studies of "slow" dynamics in polymeric materials still remain in question due to the characteristics of the XFEL beam and concerns about sample damage. Here we demonstrate the feasibility of measuring the relaxation dynamics of gold nanoparticles suspended in polymer melts using X-ray photon correlation spectroscopy (XPCS), while also monitoring eventual X-ray induced damage. In spite of inherently large pulse-to-pulse intensity and position variations of the XFEL beam, measurements can be realized at slow time scales. The X-ray induced damage and heating are less than initially expected for soft matter materials.
Abstract
Strain and interactions at grain boundaries during solid-phase crystallization are known to play a significant role in the functional properties of polycrystalline materials. However, ...elucidating three-dimensional nanoscale grain morphology, kinetics, and strain under realistic conditions is challenging. Here, we image a single-grain growth during the amorphous-to-polycrystalline transition in technologically relevant transparent conductive oxide film of In
2
O
3
:Zr with in situ Bragg coherent X-ray diffraction imaging and transmission electron microscopy. We find that the Johnson-Mehl-Avrami-Kolmogorov theory, which describes the average kinetics of polycrystalline films growth, can be applied to the single grains as well. The quantitative analysis stems directly from imaging results. We elucidate the interface-controlled nature of the single-grain growth in thin films and reveal the surface strains which may be a driving force for anisotropic crystallization rates. Our results bring in situ imaging with coherent X-rays towards understanding and controlling the crystallization processes of transparent conductive oxides and other polycrystalline materials at the nanoscale.
Purpose
This study aims to explore the effects of consumer resilience and brand familiarity on the relationship between corporate social responsibility (CSR) and consumer attitudes toward the company ...conducting CSR in places that have suffered from traumatic events such as natural or anthropogenic disasters and uncertainty of public health issue.
Design/methodology/approach
This study collected survey-based data from 194 participants who suffered from natural and anthropogenic disasters in the state of Texas. Path analysis was used to test each structural relationship among variables after verifying the reliability and validity of each variable. Analysis of variance was used to investigate the difference in resilience between the two groups.
Findings
This study verified that there is a positive relationship between CSR and consumer attitude. More importantly, the results show that both resilience and familiarity play an important role as a mediator in the relationship between CSR and attitudes. In particular, it tells us that a group with high resilience shows a higher possibility of having positive attitudes toward the company than another group having low resilience.
Originality/value
This study empirically tested the impacts of CSR, resilience and brand familiarity on building consumer attitudes. Furthermore, this study explored the effects of resilience and brand familiarity on the relationship between CSR and attitudes. Thus, this study was able to contribute to understanding the effects of CSR, resilience and familiarity on building a positive attitude in the specific settings, in terms of traumatic events, theoretically and practically.
In this work, ferroelastic domain walls inside BaTiO3 (BTO) tetragonal nanocrystals are distinguished by Bragg peak position and studied with Bragg coherent x-ray diffraction imaging (BCDI). ...Convergence-related features of the BCDI method for strongly phased objects are reported. A ferroelastic domain wall inside a BTO crystal has been tracked and imaged across the tetragonal-cubic phase transition and proves to be reversible. The linear relationship of relative displacement between two twin domains with temperature is measured and shows a different slope for heating and cooling, while the tetragonality reproduces well over temperature changes in both directions. An edge dislocation is also observed and found to annihilate when heating the crystal close to the phase transition temperature.
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