Many nanoscale biopolymer building blocks with defectfree molecular structure and exceptional mechanical properties have the potential to surpass the performance of existing fossil-based materials with respect to barrier properties, load-bearing substrates for advanced functionalities, as well as light-weight construction. Comprehension and control of performance variations of macroscopic biopolymer materials caused by humidity-driven structural changes at the nanoscale are imperative and challenging. A long-lasting challenge is the interaction with water molecules causing reversible changes in the intrinsic molecular structures that adversely affects the macroscale performance. Using in situ advanced X-ray and neutron scattering techniques, we reveal the structural rearrangements at the nanoscale in ultrathin nanocellulose films with humidity variations. These reversible rearrangements are then correlated with wettability that can be tuned. The results and methodology have general implications not only on the performance of cellulosebased materials but also for hierarchical materials fabricated with other organic and inorganic moisture-sensitive building blocks.

Some of the most remarkable materials in nature are made from proteins. The properties of these materials are closely connected to the hierarchical assembly of the protein building blocks. In this perspective, amyloid-like protein nanofibrils (PNFs) have emerged as a promising foundation for the synthesis of novel bio-based materials for a variety of applications. Whereas recent advances have revealed the molecular structure of PNFs, the mechanisms associated with fibril-fibril interactions and their assembly into macroscale structures remain largely unexplored. Here, we show that whey PNFs can be assembled into microfibers using a flow-focusing approach and without the addition of plasticizers or cross-linkers. Microfocus small-angle X-ray scattering allows us to monitor the fibril orientation in the microchannel and compare the assembly processes of PNFs of distinct morphologies. We find that the strongest fiber is obtained with a sufficient balance between ordered nanostructure and fibril entanglement. The results provide insights in the behavior of protein nanostructures under laminar flow conditions and their assembly mechanism into hierarchical macroscopic structures.protein nanofibrils | amyloid | hierarchical assembly | flow focusing | small-angle X-ray scattering P roteins are widely used in nature to create high-performance materials that can have both extraordinary mechanical properties (similar to muscles, silks) and sophisticated functionalities (e.g., adhesion, biological signaling) (1). The characteristics of these materials are intimately connected to the hierarchical assembly of the protein building blocks with well-defined organization at all structural levels (2). Improved knowledge about how to control the assembly of protein molecules into higher-order structures would open the possibilities to create novel bio-based materials for a variety of applications. In this perspective, the ability of protein molecules to undergo nonnative self-assembly into protein nanofibrils (PNFs) with highly organized supramolecular structures is of significant interest (3). The formation of PNFs was initially observed in association with diseases, such as Alzheimer's and Parkinson's diseases, and type II diabetes, where human organs are impaired by fibrous protein inclusions referred to as amyloid (4). However, several non-disease-related proteins have also been shown to form amyloid-like fibrils, e.g., the bovine whey protein β-lactoglobulin (5), hen-egg lysozyme (6), and soybean proteins (7). The unique fibrous structures of PNFs have the potential for being the building block of protein-based nanomaterials and to be used as scaffolds for applications such as tissue engineering, drug delivery systems, and biosensors (3). PNFs are characterized by intermolecular β-sheet structures, where the peptide backbones are oriented perpendicularly to the fibril axis and connected through a network of hydrogen bonds (4,8). This provides them with stiffness equivalent to silk and strength comparable to steel (2, 8). Moreo...

Tailoring the optical and electronic properties of nanostructured polymer−metal composites demonstrates great potential for efficient fabrication of modern organic optical and electronic devices such as flexible sensors, transistors, diodes, or photovoltaics. Self-assembled polymer−metal nanocomposites offer an excellent perspective for creating hierarchical nanostructures on macroscopic scales by simple bottom-up processes. We investigate the growth processes of nanogranular silver (Ag) layers on diblock copolymer thin film templates during sputter deposition. The Ag growth is strongly driven by self-assembly and selective wetting on the lamella structure of polystyrene-block-poly-(methyl methacrylate). We correlate the emerging nanoscale morphologies with collective optical and electronic properties and quantify the difference in Ag growth on the corresponding homopolymer thin films. Thus, we are able to determine the influence of the respective polymer template and observe substrate effects on the Ag cluster percolation threshold, which affects the insulator-to-metal transition (IMT). Optical spectroscopy in the UV−vis regime reveals localized surface plasmon resonance for the metal−polymer composite. Their maximum absorption is observed around the IMT due to the subsequent long-range electron conduction in percolated nanogranular Ag layers. Using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy, we identify the oxidation of Ag at the acrylate side chains as an essential influencing factor driving the selective wetting behavior in the early growth stages. The results of polymer-templated cluster growth are corroborated by atomic force microscopy and field emission scanning electron microscopy.

We investigated the fabrication and functional behaviour of conductive silver-nanowire-polymer composites for prospective use in printing applications. Silver-nanowires with an aspect ratio of up to 1000 were synthesized using the polyol route and embedded in a UV-curable and printable polymer matrix. Sheet resistances in the composites down to 13 Ω/sq at an optical transmission of about 90% were accomplished. The silver-nanowire composite morphology and network structure was investigated by electron microscopy, atomic force microscopy, profilometry, ellipsometry as well as surface sensitive X-ray scattering. By implementing different printing applications, we demonstrate that our silver nanowires can be used in different polymer composites. On the one hand, we used a tough composite for a 2D-printed film as top contact on a solar cell. On the other hand, a flexible composite was applied for a 3D-printed flexible capacitor.

Latex colloids are among the most promising materials for broad thin film applications due to their facile surface functionalization. Yet, the effect of these colloids on chemical film and wetting properties cannot be easily evaluated. At the nanoscale, core-shell particles can deform and coalesce during thermal annealing, yielding fine-tuned physical properties. Two different core-shell systems (soft and rigid) with identical shells but with chemically different core polymers and core sizes are investigated. The core-shell nanoparticles (NPs) are probed during thermal annealing in order to investigate their behavior as a function of nanostructure size and rigidity. X-ray scattering allows to follow the re-arrangement of the NPs and the structural evolution in situ during annealing. Evaluation by real-space imaging techniques reveals a disappearance of the structural integrity and a loss of NP boundaries. The possibility to fine-tune the wettability by tuning the core-shell NPs morphology in thin films provides a facile template methodology for repellent surfaces.

We investigate the layer formation of enzymatic cellulose by airbrush spray coating on silicon oxide surfaces. The layer structure and morphology of enzymatic cellulose films in the thickness range between 86 nm and 2.1 lm is determined as a function of the spray coating procedures. For each spray coating step, layer buildup, surface topography, crystallinity as well as the nanoscale structure are probed with atomic force microscopy and surfacesensitive X-ray scattering methods. Without intermittent drying, the film thickness saturates; with intermittent drying, a linear increase in layer thickness with the number of spray pulses is observed. A closed cellulose layer was always observed. The crystallinity remains unchanged; the nanoscale structures show three distinct sizes. Our results indicate that the smallest building blocks increasingly contribute to the morphology inside the cellulose network for thicker films, showing the importance of tailoring the cellulose nanofibrils. For a layer-bylayer coating, intermittent drying is mandatory.

y Contributed equally.To identify optimal deposition conditions and morphologies for ZnO nanorod arrays (NRA) for photovoltaic applications, ZnO NRA were electrochemically grown onto transparent conducting oxide (TCO) substrates pre-covered with an intrinsic zinc oxide (i-ZnO) seed layer (SL) at different cathodic potentials, deposition times and temperatures. The morphology and the optical properties of the ZnO NRA were investigated with respect to application in thin film solar cells. The NRA morphology was found to be strongly correlated with the amount of electrochemically deposited ZnO, irrespective of the reaction conditions for a wide range of parameters. It was demonstrated that also the optical reflectance and transmittance of the NRA were closely connected to the electrochemically deposited amount of ZnO and the NRA morphology. Also the relative amount of defects determined by room temperature (RT) photoluminescence (PL) measurements correlated with the amount of electrochemically deposited ZnO, higher defect densities were however found for high cathodic potentials and low temperatures presumably due to excessive deposition rates and preferential formation of Zn(OH) 2 , respectively. A range of reaction conditions was identified yielding both fast growth and ZnO NRA with morphological and optical properties suited for thin film solar cell applications.

The interaction between a graphene layer and pentacene (PEN) molecules leads to the formation of a lyingdown phase, which can improve charge transport for organic vertical field effect transistors and enhance the optical absorption for increased light harvesting in organic solar cells. Here, we present a comprehensive study of PEN growth on epitaxial graphene on silicon carbide (SiC). Simultaneous grazing-incidence small-and wide-angle X-ray scattering (GISAXS/GIWAXS) were used in situ for real-time monitoring of the PEN crystal growth with millisecond time resolution to identify two distinct anisotropic growth stages after the nucleation of the first monolayer (ML). In the first stage up to 1.5 nm, we observe rapid growth of pentacene domains along the ( 010) and ( 001) facets. This growth behavior is saturating after 1.5 nm. In a second stage, this is followed by continuous lateral crystal growth in only one in-plane direction (100) forming needle-shaped domains. In the second stage, an uninterrupted linear growth of the lying-down PEN phase is found based on the (001) diffraction up to 15 nm. Ex situ atomic force microscopy and polarized confocal Raman microscopy were used to further support the real-time observations of aligned PEN films on graphene.