Experimental Characterization Research Articles

Mechanical Bond Induced Enhancement and Purification of Pyrene Emission in the Solid State.

To address key concerns on solid-state pyrene-based luminescent materials, we propose a novel and efficient mechanical bond strategy. This strategy results in a transformation from aggregation-caused quenching (ACQ) to aggregation-induced emission (AIE) effect and a remarkable enhancement of pyrene emission in the solid state. More importantly, an unusual purification of emission is also achieved. Through computational calculation and experimental characterization, finally determined by X-ray diffraction analysis, we prove that the excellent emissions result from the refined molecular arrangements, including reduced π-π stacking, well-ordered packing and enhanced structural stability. This work demonstrates the potential of mechanical bond in the field of organic luminescent molecules, providing a new avenue for developing high-performance organic luminescent materials and beyond.

Genotype sampling for deep-learning assisted experimental mapping of a combinatorially complete fitness landscape.

Experimental characterization of fitness landscapes, which map genotypes onto fitness, is important for both evolutionary biology and protein engineering. It faces a fundamental obstacle in the astronomical number of genotypes whose fitness needs to be measured for any one protein. Deep learning may help to predict the fitness of many genotypes from a smaller neural network training sample of genotypes with experimentally measured fitness. Here I use a recently published experimentally mapped fitness landscape of more than 260,000 protein genotypes to ask how such sampling is best performed. I show that multilayer perceptrons, recurrent neural networks (RNNs), convolutional networks, and transformers, can explain more than 90 percent of fitness variance in the data. In addition, 90 percent of this performance is reached with a training sample comprising merely ≈103 sequences. Generalization to unseen test data is best when training data is sampled randomly and uniformly, or sampled to minimize the number of synonymous sequences. In contrast, sampling to maximize sequence diversity or codon usage bias reduces performance substantially. These observations hold for more than one network architecture. Simple sampling strategies may perform best when training deep learning neural networks to map fitness landscapes from experimental data. The fitness landscape data analyzed here is publicly available as described previously (Papkou, et al., 2023). All code used to analyze this landscape is publicly available at https://github.com/andreas-wagner-uzh/fitness_landscape_sampling. Supplementary data are available at Bioinformatics online.

Effect of corrosion pit on fatigue damage and failure in powder bed fusion AlSi10Mg

AbstractThis paper is concerned with environmental corrosion during service of load‐bearing aluminum alloys fabricated by additive manufacturing (AM) with a focus on damage evolution characterization and identification of dominated failure mechanisms of pre‐corroded selective laser melted aluminum alloy. An experimental strategy for analysis of the damage and failure process is presented, combining 3D surface measurement, 3D digital image correlation, and scanning electron microscopy, to provide a multi‐source experimental characterization of corrosion morphology, strain field evolution, and fracture morphology. Statistics and machine learning methods were employed to process the measured multi‐source experimental data, showing that local average roughness has a strong influence on macro‐crack initiation position. The analysis focuses on four primary types of fatigue micro‐crack initiation, namely, internal defect, diffuse corrosion, corrosion micro‐pit, and corrosion jut; internal defect and diffuse corrosion are unique features for powder bed fusion (PBF) AlSi10Mg. The micro‐crack initiation mechanisms for all four types are (i) local stress concentrations due to adjacent material micro‐structural defects, (ii) interaction of underlying alloy microstructure and corrosion‐induced stress/strain, and (iii) local stress/strain concentration at corrosion micro‐pit and jut, respectively.

Dual‐ and triple‐passband coupled‐complementary FSSs based on the four‐arms star geometry

AbstractThe authors propose a system of closely coupled‐complementary frequency‐selective surfaces (FSSs) based on the four‐arms star geometry with dual‐ and triple‐passbands responses for 5G applications. Four complementary structure configurations are presented, and depending on the chosen configuration, the structure can create two or three transmission bands in one or both polarisations of the electromagnetic waves. The designed FSSs are compact and have stable behaviour at different incident angles. The complementary FSS passes signals around 2.6 and 6.2 GHz, and a structural offset allows the transmission at a third frequency (4.2 GHz). To validate the proposed designs, four prototypes are fabricated and measured. Numerical and experimental characterisations are in good agreement.

Tailoring the Electronic Structures and Spectral Properties of ZnO with Irradiation Defects Generated Under Intense Electronic Excitation: A Combined Experimental and DFT Approach

AbstractThe relationship between the composition of the internal defect states, spectral properties, and correlated electronic structures of wurtzite zinc oxide (ZnO) crystals under 645 MeV Xe35+ irradiation is systematically investigated, employing experimental characterizations combined with first‐principle calculations. Based on the ion irradiation‐induced thermal expansion and relaxation processes, the high concentration of vacancy/interstitial defects produced from the transient disordered phase in molten track states trigger photoelectric changes, as follows: i) the generation of internal defect states effectively reduces the intrinsic bandgap (3.25 eV → 2.66 eV); ii) a large number of defective active sites inhibits the recombination between electron–hole pairs, causing dark conductance and photoconductance to increase with increasing damage levels until optimal fluence is achieved. Based on the density functional theory (DFT) with the GGA + U (GGA = generalized gradient approximation) method, the defective models associated with the different electronic structures, density of states, formation energy, and the nature of the chemical bonding are established. The narrowing of the bandgap observed experimentally and the enhancement of carrier concentration originating from the internal electron defect states are qualitatively verified, therefore laying the foundation for designing future nanoscale photoelectronic devices and microelectronics applications.

Development of sunflower husk reinforced polypropylene based sustainable composites: An experimental investigation of mechanical and thermal performance

AbstractClimate change, shrinking resources, and rising raw material costs have pushed the industry to create more sustainable, and lightweight materials. Natural fiber composites are materials of interest for replacing conventional materials such as steel. Sunflower husks (SH), among many other natural fibers, are readily accessible as agricultural waste and have advantageous properties. In this study, sunflower husks were mixed with polypropylene (PP) matrix using a twin‐screw extruder, and then tests specimens for experimental characterizations were manufactured through injection molding. The tensile tests revealed that the inclusion of SH into PP decreased the load‐bearing capacity of the composites by around 20% and increased their impact resistance by over 200%, while reducing the ductility by about eight times. Moreover, magnesium hydroxide (Mg(OH)2) was incorporated into the composites as a flame retardant, and it has improved the stiffness and impact resistance of the composites. Besides, incorporation of SH and Mg(OH)2 elevated significantly the glass transition temperature of the composites. The use of Mg(OH)2 delayed 60% the flame retention of the composites observed from UL‐94 HB flammability testing. In summary, they could be suitable for components such as spare wheel wells, seat backs, trunk floor, the acoustic panel behind the door, and airbag housing.

Synergistic Catalysis of SO42–/TiO2–CNT for the CO2 Desorption Process with Low Energy Consumption

Synergistic Catalysis of SO₄^2–/TiO₂–CNT for the CO₂ Desorption Process with Low Energy Consumption

Thermally compensated common-path differential interferometer with reduced long-term zero-drifts

Abstract Laser interferometers have served as the workhorses in the metrology of length for several decades. Their broader application brings further challenges, especially for longer measurement time-frames or outside the laboratory environment with strictly controlled conditions. As a part of our team's activities aiming at characterizing and eliminating the effects of unstable temperature on interferometric length measurements, we report on successfully remodelling a differential interferometer's optical arrangement focused on increasing resilience against temperature changes. The experimental characterization under constant temperature and subsequently under thermal load proved a tenfold decrease in short-term fluctuations and reduced sensitivity to temperature changes by a factor of 100.

Conformations of a highly expressed Z19 α-zein studied with AlphaFold2 and MD simulations.

α-zeins are amphiphilic maize seed storage proteins with material properties suitable for a multitude of applications e.g., in renewable plastics, foods, therapeutics and additive manufacturing (3D-printing). To exploit their full potential, molecular-level insights are essential. The difficulties in experimental atomic-resolution characterization of α-zeins have resulted in a diversity of published molecular models. However, deep-learning α-zein models are largely unexplored. Therefore, this work studies an AlphaFold2 (AF2) model of a highly expressed α-zein using molecular dynamics (MD) simulations. The sequence of the α-zein cZ19C2 gave a loosely packed AF2 model with 7 α-helical segments connected by turns/loops. Compact tertiary structure was limited to a C-terminal bundle of three α-helices, each showing notable agreement with a published consensus sequence. Aiming to chart possible α-zein conformations in practically relevant solvents, rather than the native solid-state, the AF2 model was subjected to MD simulations in water/ethanol mixtures with varying ethanol concentrations. Despite giving structurally diverse endpoints, the simulations showed several patterns: In water and low ethanol concentrations, the model rapidly formed compact globular structures, largely preserving the C-terminal bundle. At ≥ 50 mol% ethanol, extended conformations prevailed, consistent with previous SAXS studies. Tertiary structure was partially stabilized in water and low ethanol concentrations, but was disrupted in ≥ 50 mol% ethanol. Aggregated results indicated minor increases in helicity with ethanol concentration. β-sheet content was consistently low (∼1%) across all conditions. Beyond structural dynamics, the rapid formation of branched α-zein aggregates in aqueous environments was highlighted. Furthermore, aqueous simulations revealed favorable interactions between the protein and the crosslinking agent glycidyl methacrylate (GMA). The proximity of GMA epoxide carbons and side chain hydroxyl oxygens simultaneously suggested accessible reactive sites in compact α-zein conformations and pre-reaction geometries for methacrylation. The findings may assist in expanding the applications of these technologically significant proteins, e.g., by guiding chemical modifications.

Probing the activated complex of the F + NH3 reaction via a dipole-bound state

Experimental characterization of the transition state poses a significant challenge due to its fleeting nature. Negative ion photodetachment offers a unique tool for probing transition states and their vicinity. However, this approach is usually limited to Franck-Condon regions. For example, high-lying Feshbach resonances with an excited HF stretching mode (vHF = 2-4) were recently identified in the transition-state region of the F + NH3 → HF + NH2 reaction through photo-detaching FNH3− anions, but the direct photodetachment failed to observe the lower-lying vHF = 0,1 resonances and bound states due apparently to negligible Franck-Condon factors. Indeed, these weak transitions can be resonantly enhanced via a dipole-bound state (DBS) formed between an electron and the polar FNH3 species. In this study, we unveil a series of Feshbach resonances and bound states along the F + NH3 reaction path via a DBS by combining high-resolution photoelectron spectroscopy with high-level quantum dynamical computations. This study presents an approach for probing the activated complex in a reaction by negative ion photodetachment through a DBS.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance.

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

Texture and Twinning Evolution of Cold-Rolled Industrial Pure Zirconium

Industrial pure zirconium plays an essential role as a structural material in the nuclear energy sector. Understanding the deformation mechanisms is crucial for effectively managing the plasticity and texture evolution of industrial pure zirconium. In the present study, the texture and microstructure evolution of industrial pure zirconium during the cold-rolling process have been characterized by XRD, EBSD, and TEM. The influences of various twins on texture evolution have also been simulated by the reaction stress model. The effects of slip and twinning on the deformation behavior and texture evolution have been discussed based on crystallographic and experimental considerations. Cold rolling yields a typical bimodal texture, resulting in the preferential <21-1-0>//RD orientation. The activation of the deformation mechanisms during cold rolling follows the sequential trend of slip, twinning, local slip. Experimental characterization and reaction stress simulation illustrate that T1 twins dominate in the early stage, whereas C2 twins develop at the later stage of the cold-rolling process. Twinning, especially the T1 twin, contributes to the formation of the {0001}<101-0> orientation.

Novel modification strategy via GO and polyurethane for epoxy nanocomposites: Simultaneous enhancements of fracture toughness and liquid oxygen compatibility for cryotank applications

Fracture toughness and liquid oxygen (LOX) compatibility of epoxy nanocomposites for liquid oxygen composite cryotank applications are two main concerns. In this work, a novel rigid-and-soft hybrid-microstructure modification strategy is proposed to improve these two properties simultaneously. Graphene oxide (GO) nanosheets are physically incorporated, and polyurethane (PU) particles are formed through phase-separation process. When 10 parts of PU and 0.1 parts of GO are added into 100 parts of epoxy (i.e., 10 phr PU and 0.1 phr GO), the fracture toughness is enhanced by 207.26 % at room temperature and 243.02 % at 90 K, respectively. Meanwhile, no sensitivity phenomena such as explosion, burning, flash, or charring for the nanocomposite are observed during liquid oxygen impact testing. Consequently, experimental characterizations and multiscale finite element models are utilized to reveal the synergistic effects of GO and PU on fracture behaviors and impact energy absorption.

Porous Aromatic Frameworks Enabling Polyiodide Confinement toward High Capacity and Long Lifespan Zinc-Iodine Batteries.

Aqueous zinc-iodine batteries (AZIBs) are attracting increasing attention because of their high safety and abundance of resources. However, the performance of AZIBs is compromised by inadequate confinement of soluble polyiodides, the undesired shuttle effect, and slow reaction kinetics. In this study, a porous aromatic framework (PAF) with abundant benzene motifs and a well-organized pore structure is adopted as the iodine host, which exhibits high iodine adsorption capacity and robust polyiodide confinement. Both experimental characterizations and theoretical simulations indicate that the interactions between iodine species and the PAF-1 facilitate the redox reaction by coupling the electronic structures of the active species in the framework. A comparison of PAF-1, PAF-5, and PAF-11 also emphasizes the structural advantages of the high surface area and interconnected three-dimensional channels of PAF-1. Consequently, the I2@PAF-1 cathode can deliver a high capacity of 328 mAh g-1 at 0.5 C, outstanding rate performance (86% retention at 10 C), and a stable cycling life of 20000 cycles. The robust polyiodide confinement and superb electrochemical performance of Zn-I2@PAF-1 provide insights into the practical application of PAFs as excellent electrode materials for AZIBs. This article is protected by copyright. All rights reserved.

Experimental and numerical mechanical characterisation of additively manufactured polymeric lattice structures under uniaxial tensile load

AbstractAdditive manufacturing enables the production of lighter, more robust components with intricate features like lattice structures. However, since the mechanical behaviour of lattice structures is not fully characterized, the application of such potential is limited today. The challenge with lattice structures tensile tests is defining a suitable design that fits the standard requirements and process characteristics. In the polymeric powder bed fusion process, the problem is to produce powder-free geometries and to avoid stress concentrations zones, adapting the specimen accordingly. In this regard, numerical simulation may provide insightful information and support the analysis of the deformation mechanisms. This paper analyses a new tensile sample for lattice structures using finite element analysis. The sample is designed following the EN ISO 527 standard prescriptions. An area with a controlled gradation of the lattice relative density is designed to ensure both powder-free voids and fracture localization within the lattice specimen gauge length. Experimental tests are performed to validate the numerical results using a modified body cubic centred topology with two different strut diameters. The specimens are produced in polyamide by powder bed AM process. Due to the complexity of the lattice design, a digital image correlation is used to compute the full range of strains at the macroscopic level. Experimental and numerical strain maps results showed a good agreement. The recorded deviation was attributed to the process-induced defect, such as the geometrical accuracy that, if compensated, boosted the capability of the numerical model to predict the mechanical behaviour of the lattice structure.

Characterization of Freezing Processes in Drug Substance Bottles by Ice Core Sampling

Freezing of biological drug substance (DS) is a critical unit operation that may impact product quality, potentially leading to protein aggregation and sub-visible particle formation. Cryo-concentration has been identified as a critical parameter to impact protein stability during freezing and should therefore be minimized. The macroscopic cryo-concentration, in the following only referred to as cryo-concentration, is majorly influenced by the freezing rate, which is in turn impacted by product independent process parameters such as the DS container, its size and fill level, and the freezing equipment. (At-scale) process characterization studies are crucial to understand and optimize freezing processes. However, evaluating cryo-concentration requires sampling of the frozen bulk, which is typically performed by cutting the ice block into pieces for subsequent analysis. Also, the large amount of product requirement for these studies is a major limitation. In this study, we report the development of a simple methodology for experimental characterization of frozen DS in bottles at relevant scale using a surrogate solution. The novel ice core sampling technique identifies the axial ice core in the center to be indicative for cryo-concentration, which was measured by osmolality, and concentrations of histidine and polysorbate 80 (PS80), whereas osmolality revealed to be a sensitive read-out. Finally, we exemplify the suitability of the method to study cryo-concentration in DS bottles by comparing cryo-concentrations from different freezing protocols (-80°C vs -40°C). Prolonged stress times during freezing correlated to a higher extent of cryo-concentration quantified by osmolality in the axial center of a 2 L DS bottle.Graphical

Removing the Barrier in O-O Bond Formation Via the Combination of Intramolecular Radical Coupling and the Oxide Relay Mechanism.

The Ru(tda) catalyst has been a major milestone in the development of molecular water oxidation catalysts due to its outstanding performance at neutral pH. The role of the noncoordinating carboxylate group is to act as a nucleophile, donating an oxygen atom to the oxo group, thereby acting as an oxide relay (OR) mechanism for O-O bond formation. A substitution of the carboxylates for phosphonate groups has been proposed, resulting in the Ru(tPaO) catalyst, which has shown even more efficient performance in experimental characterization. In this study, we explore the feasibility of the OR mechanism in the newly reported Ru(tPaO) molecular catalyst. We investigated the catalytic cycle using density functional theory and identified a variation of the OR mechanism that involves radical oxygen atoms in O-O bond formation. We have also determined that the subsequent hydroxide nucleophilic attack is the sole rate-limiting step in the catalytic cycle. All activation free energies are very low, with a free-energy barrier of 2.1 kcal/mol for O-O bond formation and 4.2 kcal/mol for OH- nucleophilic attack.

Experimental and Theoretical Insights on the Structural, Electronic, and Magnetic Properties of the Quaternary Selenides EuPrCuSe3 and EuNdCuSe3.

Magnetic semiconductors EuPrCuSe3 and EuNdCuSe3 were obtained by using the halide flux method. Their crystal structures and magnetic properties were studied and discussed. Optical properties of the obtained selenides were studied by the means of diffuse reflectance spectroscopy, which revealed the values of 1.92/1.97 and 0.90/0.94 eV for the direct and indirect band gaps of Ln = Nd/Pr, respectively. The structural, electronic, and magnetic properties of the obtained compounds were additionally studied with spin-polarized density functional theory calculations, wherein both systems were found to be two new examples of semiconducting quaternary selenides with disperse conduction bands of Nd/Pr 5d character. The modeling showed that various magnetic orderings in the systems have subtle influences on the alignments/overlaps between the Se/Cu, Eu, and Pr/Nd bands, and that the spin-state energetics are very dependent upon the treatment of electron correlation, but a distinguishing feature in the case of ferromagnetic coupling is that the spin density on the Se atoms is maximized. Overall, the calculations are in good agreement with the experimental characterization of ferromagnetism in the bulk crystals, wherein the ferromagnetic transition occurs at temperatures of about 2.5 K for EuPrCuSe3 and about 3 K for EuNdCuSe3.

Understanding Spin‐Triplet Excited States in Carbene‐Metal‐Amides

Understanding Spin‐Triplet Excited States in Carbene‐Metal‐Amides

Understanding Spin-Triplet Excited States in Carbene-Metal-Amides.

Carbene-metal-amides (CMAs) are emerging delayed fluorescence materials for organic light-emitting diode (OLED) applications. CMAs possess fast, efficient emission owing to rapid forward and reverse intersystem crossing (ISC) rates. The resulting dynamic equilibrium between singlet and triplet spin manifolds distinguishes CMAs from most purely organic thermally activated delayed fluorescence emitters. However, direct experimental triplet characterization in CMAs is underutilized, limiting our detailed understanding of the ISC mechanism. In this work, we combine time-resolved spectroscopy with tuning of state energies through environmental polarity and metal substitution, focusing on the interplay between charge-transfer (3CT) and local exciton (3LE) triplets. Unlike previous photophysical work, we investigate evaporated host:guest films of CMAs and small-molecule hosts for increased device relevance. Transient absorption reveals an evolution in the triplet excited-state absorption (ESA) consistent with a change in orbital character between hosts with differing dielectric constants. Using quantum chemical calculations, we simulate ESAs of the lowest triplet states, highlighting the contribution of only 3CT and donor-moiety 3LE states to spectral features, with no strong evidence for a low-lying acceptor-centered 3LE. Thus, our work provides a blueprint for understanding the role of triplet excited states in CMAs which will enable further intelligent optimization of this promising class of materials.