GISAXS Research Articles

Influence of NaCl on the Structure and Dynamics of Phospholipid Layers

We present a structural and dynamical analysis of the influence of NaCl on multilayer stacks of phospholipids on a solid surface. To this end, multilayer stacks of phospholipids (L-α-phosphatidylcholine, abbreviated as SoyPC) are investigated with neutron reflectometry, grazing-incidence small-angle neutron scattering (GISANS) and grazing-incidence neutron-spin echo spectroscopy (GINSES). We show both that the NaCl influence on the structure is predominantly on water-head group interface and also, that the change in dynamics is restricted to an associated change in the inter-plane viscosity. Using this knowledge, it is possible to model the dynamical behavior of a phospholipid membrane in response to a salt concentration of the solvent using only a single parameter, namely the in-plane viscosity. The excellent agreement with our previously published model also strongly supports the existence of a thermally excited surface mode in phospholipid membranes for close-to-physiological conditions.

Flexible Sample Environment for the Investigation of Soft Matter at the European Spallation Source: Part II—The GISANS Setup

The FlexiProb project is a joint effort of three soft matter groups at the Universities of Bielefeld, Darmstadt, and Munich with scientific support from the European Spallation Source (ESS), the small-K advanced diffractometer (SKADI) beamline development group of the Jülich Centre for Neutron Science (JCNS), and the Heinz Maier-Leibnitz Zentrum (MLZ). Within this framework, a flexible and quickly interchangeable sample carrier system for small-angle neutron scattering (SANS) at the ESS was developed. In the present contribution, the development of a sample environment for the investigation of soft matter thin films with grazing-incidence small-angle neutron scattering (GISANS) is introduced. Therefore, components were assembled on an optical breadboard for the measurement of thin film samples under controlled ambient conditions, with adjustable temperature and humidity, as well as the optional in situ recording of the film thickness via spectral reflectance. Samples were placed in a 3D-printed spherical humidity metal chamber, which enabled the accurate control of experimental conditions via water-heated channels within its walls. A separately heated gas flow stream supplied an adjustable flow of dry or saturated solvent vapor. First test experiments proved the concept of the setup and respective component functionality.

Flexible Sample Environment for the Investigation of Soft Matter at the European Spallation Source: Part II—The GISANS Setup

The FlexiProb project is a joint effort of three soft matter groups at the Universities of Bielefeld, Darmstadt, and Munich with scientific support from the European Spallation Source (ESS), the small-K advanced diffractometer (SKADI) beamline development group of the Julich Centre for Neutron Science (JCNS), and the Heinz Maier-Leibnitz Zentrum (MLZ).Within this framework, a flexible and quickly interchangeable sample carrier system for small-angle neutron scattering (SANS) at the ESS was developed. In the present contribution, the development of a sample environment for the investigation of soft matter thin films with grazing-incidence small-angle neutron scattering (GISANS) is introduced. Therefore, components were assembled on an optical breadboard for the measurement of thin film samples under controlled ambient conditions, with adjustable temperature and humidity, as well as the optional in situ recording of the film thickness via spectral reflectance. Samples were placed in a 3D-printed spherical humidity metal chamber, which enabled the accurate control of experimental conditions via water-heated channels within its walls. A separately heated gas flow stream supplied an adjustable flow of dry or saturated solvent vapor. First test experiments proved the concept of the setup and respective component functionality.

Methyl-Branched Side Chains on Polythiophene Suppress Chain Mobility and Crystallization to Enhance Photovoltaic Performance

We synthesized a polythiophene with methyl-branched side chains, poly(3-2-methylpentylthiophene) (P3MPT), and studied the thermal properties, morphology, optoelectrical properties, and photovoltaic performance of P3MPT blended with the fullerene derivative, [6,6]-phenyl C₆₀-butyric acid methyl ester (PCBM). The results are compared to those of the commonly used poly(3-hexylthiopene) (P3HT) with linear side chains to investigate the effects of the methyl-branched side chain. Differential scanning calorimetry (DSC) shows a higher glass transition temperature, and both X-ray diffraction and UV–vis absorption reveal a lower crystallization rate for P3MPT as compared to P3HT, due to the methyl-branched side chains that more efficiently suppress the chain mobility. Such behaviors can create an optimal as well as a stable structure for bulk-heterojunction solar cells so that the P3MPT/PCBM-based device not only shows a higher power conversion efficiency (PCE) but can much more effectively maintain the efficiency with time than the P3HT/PCBM-based device does. The stable phase-separated structure in the P3MPT/PCBM blend is confirmed by the grazing-incidence small-angle X-ray scattering (GISAXS) technique, which explains the superior long-term stability of the P3MPT/PCBM solar cell.

Deep learning for x-ray or neutron scattering under grazing-incidence: extraction of distributions

Grazing-incidence small-angle scattering (GISAS) is a technique of significant importance for the investigation of thin multilayered films containing nano-sized objects. It provides morphology information averaged over the sample area. However, this averaging together with multiple reflections and the well-known phase problem make the data analysis challenging and time consuming. In the present paper we show that densely connected neural networks (DenseNets) can be applied for GISAS data analysis and deliver fast and plausible results. The extraction of the rotational distributions of hexagonal nanoparticle arrangements is taken as a case study.

Grazing Incidence Small-Angle Neutron Scattering: Background Determination and Optimization for Soft Matter Samples

Grazing incidence small-angle neutron scattering (GISANS) provides access to interfacial properties, e.g., in soft matter on polymers adsorbed at a solid substrate. Simulations in the frame of the distorted wave Born approximation using the BornAgain software allow to understand and quantify the scattering pattern above and below the sample horizon, in reflection and transmission, respectively. The small-angle scattering from the interfacial layer, visible around the transmitted beam, which might contribute also on the side of the reflected beam, can be understood in this way and be included into the analysis. Background reduction by optimized sample cell design is supported by simulations, paving the way for an optimized GISANS cell.

Tailoring the Optical Properties of Sputter-Deposited Gold Nanostructures on Nanostructured Titanium Dioxide Templates Based on In Situ Grazing-Incidence Small-Angle X-ray Scattering Determined Growth Laws.

Gold/titanium dioxide (Au/TiO2) nanohybrid materials have been widely applied in various fields because of their outstanding optical and photocatalytic performance. By state-of-the-art polymer templating, it is possible to make uniform nanostructured TiO2 layers with potentially large-scale processing methods. We use customized polymer templating to achieve TiO2 nanostructures with different morphologies. Au/TiO2 hybrid thin films are fabricated by sputter deposition. An in-depth understanding of the Au morphology on the TiO2 templates is achieved with in situ grazing-incidence small-angle X-ray scattering (GISAXS) during the sputter deposition. The resulting Au nanostructure is largely influenced by the TiO2 template morphology. Based on the detailed understanding of the Au growth process, characteristic distances can be selected to achieve tailored Au nanostructures at different Au loadings. For selected sputter-deposited Au/TiO2 hybrid thin films, the optical response with a tailored localized surface plasmon resonance is demonstrated.

Enhance the efficiency of polymer solar cells through regulating phase segregation and improving charge transport via non-toxic halogen-free additive

Conventional additives like 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN) play an essential role in optimization of blend film morphology of polymer solar cells (PSCs). However, they have halogenated elements in their end groups, which are harmful to the environment and humans, limiting large-scale applications. In this work, a novel non-toxic and non-halogen additive, dibenzyl ether (DE), was introduced into PTB7-Th:PC71BM based PSCs, and the role of the DE additive was systemically investigated. The results showed that DE additive can not only adjust phase separation and optimize the morphology of blend film, but also promote the mobility of hole and electron. The grazing-incidence small-angle X-ray scattering (GISAXS) showed that the introduction of DE increased the interface area between PTB7-Th and PC71BM, which can promote exciton dissociation, and achieve better charge transport. Transient photovoltage (TPV) and transient photocurrent (TPC) measurements show that carrier recombination of the additive-containing devices can be effectively inhibited with improved charge transport efficiency of the active layer. Consequently, the devices with DE additive achieve power conversion efficiency (PCE) of 9.53% and a fill factor (FF) of 70.41%. Our non-toxic and non-halogen additive provides a potential solution for the preparation of environmental-friendly PSCs in the future.

Structurally Asymmetric Porous Carbon Materials with Ordered Top Surface Layers from Nonequilibrium Block Copolymer Self-Assembly

Inorganic materials with asymmetric pore structures provide increased accessibility and flux, making them attractive for applications in energy conversion and storage, separations, and catalysis. Non-equilibrium-based block copolymer structure-directed self-assembly approaches provide routes to obtaining such materials. We report a one-pot synthesis using the co-assembly and non-solvent-induced phase separation (CNIPS) of poly(isoprene)-b-poly(styrene)-b-poly(4-vinylpyridine) (ISV) triblock terpolymer and phenol formaldehyde resols. After heat-treatment, carbon materials with asymmetric pore structures result. They have a mesoporous top surface atop a porous support with graded porosity along the film normal. The walls of the macroporous support are also mesoporous, providing an additional structural hierarchy and increased specific surface area. We demonstrate how successfully navigating the pathway complexity associated with the nonequilibrium approach of CNIPS enables switching from disordered to ordered top surfaces in the as-made organic–organic hybrids and resulting carbon materials after thermal treatments. To that end, a combination of ex situ transmission small-angle X-ray scattering (SAXS) of the membrane dope solutions, in situ grazing-incidence SAXS (GISAXS) after dope solution blading and during solvent evaporation, and scanning electron microscopy (SEM) of the final membrane structures was used. We expect the final porous carbon materials exhibiting a combination of asymmetric, hierarchical pore structures and well-defined mesoporosity throughout the material to be of interest for a number of applications, including batteries, fuel cells, electrochemical double-layer capacitors, and as catalyst supports.

In situ Grazing Incidence Small Angle X-ray Scattering on Roll-To-Roll Coating of Organic Solar Cells with Laboratory X-ray Instrumentation.

We present an in-house, in situ Grazing Incidence Small Angle X-ray Scattering (GISAXS) experiment, developed to probe the drying kinetics of roll-to-roll slot-die coating of the active layer in organic photovoltaics (OPVs), during deposition. For this demonstration, the focus is on the combination of P3HT:O-IDTBR and P3HT:EH-IDTBR, which have different drying kinetics and device performance, despite their chemical structure only varying slightly by the sidechain of the small molecule acceptor. This article provides a step-by-step guide to perform an in situ GISAXS experiment and demonstrates how to analyze and interpret the results. Usually, performing this type of in situ X-ray experiments to investigate the drying kinetics of the active layer in OPVs relies on access to synchrotrons. However, by using and further developing the method described in this paper, it is possible to perform experiments with a coarse temporal and spatial resolution, on a day-to-day basis to gain fundamental insight in the morphology of drying inks.

Photoinduced Resist-free Imprinting (PRI) in fullerene thin films as revealed by Grazing Incidence Small-angle X-ray scattering

In this article we explore the potential of synchrotron Grazing Incidence Small Angle X-ray Scattering (GISAXS) to evaluate the extension of a Photoinduced Resist-free Imprinting (PRI) effect for grating-like Laser Induced Periodic Surface Structures (LIPSS) on spin-coated thin films of the fullerene derivative [6,6]-phenyl C71-butyric acid methyl ester (PC71BM). Valuable information about the nature of both the original fullerene LIPSS and of the remaining resist-free nanostructure in terms of geometry, size distribution, lattice periodicity and degree of order can be achieved by simulations of the GISAXS patterns. One of the most interesting features provided by the GISAXS analysis is the estimation of the paracrystalline distortion factor, which can be useful to evaluate the level of order in the nanostructure. Data revealed that LIPSS in PC71BM films can be described as one-dimensional paracrystalline lattices with levels of order in accordance with those typically observed in LIPSS of other materials. The PRI effect leaves a qualitatively similar nanostructure but about two times more disordered than the original LIPSS one. Our results show that GISAXS is a powerful tool to characterize Resist-free Imprinting procedures of potential relevance in nanotechnology.

Alignment frustration in block copolymer films with block copolymer grafted TiO2 nanoparticles under soft‐shear cold zone annealing

AbstractBlock copolymers (BCPs) have received significant attention as promising candidates for sequestering nanoparticles and fabrication of aligned nanostructures with optimal optical or electrical properties. We investigate the influence of static and dynamic thermal field on the alignment of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) BCP morphology with the loading of novel poly(methyl methacrylate‐block‐Polystyrene) (PMMA‐b‐PS)‐grafted‐TiO2 nanoparticles (BCP‐g‐TiO2). Observation of characteristics IR peaks for PMMA and PS in BCP‐g‐TiO2 nanoparticles and Transmission Electron Microscopy (TEM) results of the outer coating of core nanoparticle, validate the grafting to approach in synthesizing BCP‐g‐TiO2. Here we report that under the sharp dynamic thermal field, at low loading of BCP‐g‐TiO2, there is good dispersion of nanoparticles in unidirectionally aligned BCP matrix in film interior probed by GISAXS, while, at high nanoparticle loading (~10 wt%), there is local frustration in the unidirectional alignment of the BCP matrix due to aggregation of BCP‐g‐TiO2 nanoparticles. However, Grazing incidence small angle X‐ray scattering (GISAXS) shows clearly that the BCP films remain largely locally ordered at the domain scale, despite these large perturbations to long‐range ordering even at high loading level, while bringing in new TiO2 functionality to the BCP films, such as UVO absorptivity or biofouling prevention, important to potential new applications of such membranes.

Influence of Additives on the In Situ Crystallization Dynamics of Methyl Ammonium Lead Halide Perovskites.

Understanding the kinetics of the crystallization process for organometal halide perovskite formation is critical in determining the crystalline, nanoscale morphology and therefore the electronic properties of the films produced during thin film formation from solution. In this work, in situ grazing incidence small-angle X-ray scattering (GISAXS) and optical microscopy measurements are used to investigate the processes of nucleation and growth of pristine mixed halide perovskite (MAPbI3–xClx) crystalline films deposited by bar coating at 60 °C, with and without additives in the solution. A small amount of 1,8-diiodooctane (DIO) and hydriodic acid (HI) added to MAPbI3–xClx is shown to increase the numbers of nucleation centers promoting heterogeneous nucleation and accelerate and modify the size of nuclei during nucleation and growth. A generalized formation mechanism is derived from the overlapping parameters obtained from real-time GISAXS and optical microscopy, which revealed that during nucleation, perovskite precursors cluster before becoming the nuclei that function as elemental units for subsequent formation of perovskite crystals. Additive-free MAPbI3–xClx follows reaction-controlled growth, in contrast with when DIO and HI are present, and it is highly possible that the growth then follows a hindered diffusion-controlled mechanism. These results provide important details of the crystallization mechanisms occurring and will help to develop greater control over perovskite films produced.

Effect of growth rate on quality of Alq3 films and Co diffusion

The quality of organic semiconductor tris-(8-hydroxyquinoline)aluminum (Alq3) thin films, deposited at the rate of 5.0 Å s−1, 2.5 Å s−1, and 1.0 Å s−1 respectively, have been investigated using x-ray reflectivity (XRR) and grazing incidence small angle x-ray scattering (GISAXS) studies. While XRR provides information about structural details, GISAXS provides information about the morphology of the films. The film quality is very good with a surface roughness of only 8 Å. The electron density of the film increases from 0.39 e Å−3 to 0.43 e Å−3 due to reduction of growth rate from 5 Å s−1 to 1 Å s−1. The higher electron density (0.43 e Å−3) of the film deposited at the lower deposition rate (1 Å s−1) indicates the presence of less defects and/or porosity in the film. Average separation between pores increases from 200 Å to 500 Å and simultaneously pore depth decreases from 300 Å to 120 Å due to reduction of growth rate from 5 Å s−1 to 1 Å s−1. The mixing between Alq3 and Co at the Alq3/Co interface and diffusion of Co into Alq3 layer through Co/Alq3 interface have been studied by combined XRR and grazing incidence x-ray standing wave (GIXSW) measurements for the three Alq3/Co/Alq3/W/Si multilayers in which Alq3 films were deposited at the above mentioned three different rates. It is found that there is about 30 Å thick (∼ two monolayer of Alq3) mixing region at the Alq3/Co interface in three multilayer samples, which suggests that mixing at this interface is independent of the growth rate of Alq3 films. The depth of diffusion of Co into Alq3 through Co/Alq3 interface reduces from 300 Å to 160 Å due to the reduction of deposition rate from 5 Å s−1 to 1 Å s−1. This study suggests that by controlling the growth rate of Alq3, porosity as well as the diffusion of ferromagnetic Co in an organic semiconductor Alq3 can be reduced, which plays an important role in the performance of organic spin valve devices.

Time-Resolved Morphology and Kinetic Studies of Pulsed Laser Deposition-Grown Pt Layers on Sapphire at Different Growth Temperatures by in Situ Grazing Incidence Small-Angle X-ray Scattering.

Optimizing and monitoring the growth conditions of Pt films, often used as bottom electrodes in multiferroic material systems, represents a highly relevant issue that is of importance for controlling the crystalline quality and performance of ferroelectric oxides such as, e.g. LuFeO3. We performed a time-resolved monitoring of the growth and morphology of Pt films during pulsed laser deposition (PLD) in dependence on the grown film effective thickness and on the growth temperature Tg using in situ grazing incidence small-angle X-ray scattering (GISAXS). Through real-time analysis and modeling of GISAXS patterns, we could fully characterize the influence of Tg on the morphology and on the growth kinetics of the Pt layers. Consequently, critical and characteristic effective thicknesses for the transitions nucleation phase (I)/coalescence phase (II) and coalescence phase (II)/coarsening phase (III) could be determined. In combination with complementary microscopic imaging and chemical mapping via combined SEM/EDXS, we demonstrate the occurrence of a morphological progression in the Pt PLD-grown Pt films, changing from grains at room temperature to a 3D-island morphology at 300 °C, further to a hole-free structure at 500 °C, and finally to a channel structure for 700 and 900 °C. The film topography, as characterized by atomic force microscopy (AFM), favors the PLD growth of Pt layers at temperatures beyond 700 °C where the film is homogeneous, continuous, and hole-free with a flat and smooth surface. The double dependency of the percolation transition on the film effective thickness and on the growth temperature has been established by measuring the electrical conductivity.

Layer-by-Layer Spray-Coating of Cellulose Nanofibrils and Silver Nanoparticles for Hydrophilic Interfaces

Silver nanoparticles (AgNPs) and AgNP-based composite materials have attracted growing interest due to their structure-dependent optical, electrical, catalytic, and stimuli-responsive properties. For practical applications, polymeric materials are often combined with AgNPs to provide flexibility and offer a scaffold for homogenous distribution of the AgNPs. However, the control over the assembly process of AgNPs on polymeric substrates remains a big challenge. Herein, we report the fabrication of AgNP/cellulose nanofibril (CNF) thin films via layer-by-layer (LBL) spray-coating. The morphology and self-assembly of AgNPs with increasing number of spray cycles are characterized by atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), and grazing-incidence wide-angle X-ray scattering (GIWAXS). We deduce that an individual AgNP (radius = 15 ± 3 nm) is composed of multiple nanocrystallites (diameter = 2.4 ± 0.9 nm). Our results suggest that AgNPs are assembled into large agglomerates on SiO2 substrates during spray-coating, which is disadvantageous for AgNP functionalization. However, the incorporation of CNF substrates contributes to a more uniform distribution of AgNP agglomerates and individual AgNPs by its network structure and by absorbing the partially dissolved AgNP agglomerates. Furthermore, we demonstrate that the spray-coating of the AgNP/CNF mixture results in similar topography and agglomeration patterns of AgNPs compared to depositing AgNPs onto a precoated CNF thin film. Contact-angle measurements and UV/vis spectroscopy suggest that the deposition of AgNPs onto or within CNFs could increase the hydrophilicity of AgNP-containing surfaces and the localized surface plasmon resonance (LSPR) intensity of AgNP compared to AgNPs sprayed on SiO2 substrates, suggesting their potential applications in antifouling coatings or label-free biosensors. Thereby, our approach provides a platform for a facile and scalable production of AgNP/CNF films with a low agglomeration rate by two different methods as follows: (1) multistep layer-by-layer (LBL) spray-coating and (2) direct spray-coating of the AgNP/CNF mixture. We also demonstrate the ability of CNFs as a flexible framework for directing the uniform assembly of AgNPs with tailorable wettability and plasmonic properties.

Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets.

Spray deposition is a scalable and cost-effective technique for the fabrication of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles. However, it is challenging to obtain spray-deposited anisotropic magnetic hybrid films without using external magnetic fields. In the present work, spray deposition is applied to prepare perpendicular anisotropic magnetic hybrid films by controlling the orientation of strontium hexaferrite nanoplatelets inside ultra-high-molecular-weight DBC polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films. During spray deposition, the evolution of DBC morphology and the orientation of magnetic nanoplatelets are monitored with in situ grazing-incidence small-angle X-ray scattering (GISAXS). For reference, a pure DBC film without nanoplatelets is deposited with the same conditions. Solvent-controlled magnetic properties of the hybrid film are proven with solvent vapor annealing (SVA) applied to the final deposited magnetic films. Obvious changes in the DBC morphology and nanoplatelet localization are observed during SVA. The superconducting quantum interference device data show that ferromagnetic hybrid polymer films with high coercivity can be achieved via spray deposition. The hybrid films show a perpendicular magnetic anisotropy before SVA, which is strongly weakened after SVA. The spray-deposited hybrid films appear highly promising for potential applications in magnetic data storage and sensors.

In Situ Study of Order Formation in Mesoporous Titania Thin Films Templated by a Diblock Copolymer during Slot-Die Printing.

Slot-die printing, a large-scale deposition technique, is applied to fabricate mesoporous titania films. Printing is interesting, for example, for scaling up solar cells where titania films with an interconnected mesoporous network and a large surface-to-volume ratio are desired as photoanodes. A fundamental understanding of the structure evolution during printing is of high significance in tailoring these films. In this work, we provide important insights into the self-assembly of the slot-die-printed titania/polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles into ordered hybrid structures in real time via in situ grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS allows for tracking both vertical and lateral structure development of the film formation process. In the hybrid film, a face-centered cubic (FCC) structure is preferentially formed at the interfaces with air and with the substrate, while a defect-rich mixed FCC and body-centered cubic (BCC) structure forms in the bulk. After calcination, the surface and inner morphologies of the obtained nanostructured titania films are compared with the spin-coated analogues. In the printed films, the initially formed nanoscale structure of the hybrid film is preserved, and the resulting mesoporous titania film shows a superior order as compared with the spin-coated thin films which can be beneficial for future applications.

Advanced Small-Angle Scattering Instrument Available in the Tokyo Area. Time-Of-Flight, Small-Angle Neutron Scattering Developed on the iMATERIA Diffractometer at the High Intensity Pulsed Neutron Source J-PARC

A method of time-of-flight, small-angle neutron scattering (TOF-SANS) has been developed based on the iMATERIA powder diffractometer at BL20, of the Materials and Life Sciences Facility (MLF) at the high-intensity proton accelerator (J-PARC). A large-area detector for SANS, which is composed of triple-layered 3He tube detectors, has a hole at its center in order to release a direct beam behind and to detect ultra-small-angle scattering. As a result, the pulsed-neutron TOF method enables us to perform multiscale observations covering 0.003 < q (Å−1) < 40 (qmax/qmix = 1.3 × 104) and to determine the static structure factor S(q) and/or form factor P(q) under real-time and in-situ conditions. Our challenge, using unique sample accessories of a super-conducting magnet and polarized neutron, is dynamic nuclear polarization (DNP) for contrast variation, especially for industrial use. To reinforce conventional SANS measurements with powder materials, grazing-incidence small-angle neutron scattering (GISANS) or reflectivity is also available on the iMATERIA instrument.

Analysis of Homopolymer Distribution in a Polymer Blend Thin Film by Anomalous Grazing Incidence Small-Angle X-ray Scattering at the Bromine K-Edge

Polystyrene-block-poly(4-hydroxystyrene) (PS–PHS)/poly(4-hydroxystyrene) brominated (Br-PHS) blend thin films were analyzed using anomalous grazing incidence small-angle X-ray scattering (anomalous...