Molecular Systems Design & Engineering最新文献

Conjugated macrocycles can exhibit concealed antiaromaticity; that is, despite not being antiaromatic, under specific circumstances, they can display properties typically observed in antiaromatic molecules due to their formal macrocyclic 4n π-electron system. Paracyclophanetetraene (PCT) and its derivatives are prime examples of macrocycles exhibiting this behaviour. In redox reactions and upon photoexcitation, they have been shown to behave like antiaromatic molecules (requiring type I and II concealed antiaromaticity, respectively), with such phenomena showing potential for use in battery electrode materials and other electronic applications. However, further exploration of PCTs has been hindered by the lack of halogenated molecular building blocks that would permit their integration into larger conjugated molecules by cross-coupling reactions. Here, we present two dibrominated PCTs, obtained as a mixture of regioisomers from a three-step synthesis, and demonstrate their functionalisation via Suzuki cross-coupling reactions. Optical, electrochemical, and theoretical studies reveal that aryl substituents can subtly tune the properties and behaviour of PCT, showing that this is a viable strategy in further exploring this promising class of materials.

Steam electrolysis is one of the most efficient approaches for producing green hydrogen. This method is based on the application of solid oxide electrolysis cells (SOECs) fabricated from functional ceramic composites for water splitting at high temperatures. Gadolinium doped ceria (GDC) is a promising electrolyte material for the fabrication of SOECs. However, the effective sintering temperature for GDC composites is usually above 1250 °C, which makes it impossible to use conventional supporting materials like ferritic steel for stack fabrication. In this work, for the first time, we have developed a lithium–bismuth–copper co-doped GDC composite capable of sintering at ～750 °C. The physicochemical and electrochemical characteristics of the co-doped GDC electrolyte were systematically analysed using thermogravimetric analysis (TG/DTA), Raman spectroscopy, SEM/EDX, XRD, EIS, XPS and dilatometry analysis. The fabricated electrolyte pellets sintered at 750 °C for 6 hours in an inert atmosphere (argon) showed high densification, obtaining 96.70% relative density. Also, the electrical conductivity obtained for the synthesised composite Ce_0.712Gd_0.178Li_0.05Bi_0.05Cu_0.01O_1.801 (sintered at 950 °C for 6 h) was 29.6 mS cm^?1 at 750 °C with activation energy as low as 0.13 eV. The result of this study helps to understand better the properties of co-doped electrolyte materials for the fabrication of more efficient steam electrolysers for environmentally-friendly hydrogen generation.

Hydrogen bonded multi-component crystalline solids with desired physicochemical properties owing to their diverse potential applications have attracted great research attention. Minor differences in hydrogen bond interactions manipulate the molecular arrangements in the crystal lattice, leading to changes in physicochemical properties, such as solubility, stability, pharmaceutical, luminescence, etc. In this study, thorough understanding of the formation of different hydrogen bond patterns between the –COOH group and some specific but identical solvent molecules is presented. To this end, structural studies on six solvates of two isomeric pyromellitic diimide carboxylic acid host compounds (1 and 2) with dimethylformamide; DMF, (1a and 2a), dimethyl sulphoxide; DMSO, (1b and 2b) and 1,4-dioxane; Diox, (1c and 2c) guest solvent molecules were carried out. SCXRD structure analyses revealed that various types of donor–acceptor intermolecular interactions between the host–host, host–guest, and guest–guest molecules resulted in the formation of 3D supramolecular architectures of these solvates. Subtle differences in hydrogen bond patterns between the –COOH groups of isomeric host molecules and similar guest solvent molecules were observed in the structures of these solvates. DFT calculations on these different types of hydrogen bond motifs, either intermolecular rings (R) or non-cyclic intermolecular dyads (D), suggest that the same guest molecule can interact with the –COOH groups of isomeric host molecules in different ways. TGA for each solvate was consistent for the weight loss of solvent molecules according to the host–guest ratio which was further confirmed by the appearance of an endothermic peak in the same temperature region in each DSC diagram. The solid state fluorescence emission properties of both host compounds were found almost similar to their solvates, respectively, except for solvate 1c, which possesses two sets of symmetry non-equivalent guest Diox molecules in its crystal lattice, making a 3D channel architecture by the combination of hosts and one set of symmetry independent guest molecules. Overall, this study provides helpful insight into the formation of different hydrogen bond motifs between the two identical host–guest binding entities under the influence of steric orientations and other weak interactions.

Directed self-assembly (DSA) of nanoparticles onto templated substrates facilitates the design of plasmonic, photovoltaic, and semiconducting devices. It is commonly thought that the wedge-mechanism of DSA of micrometer sized particles onto templated surfaces would apply to DSA of sub-10 nm particles. Using many-body dissipative particle dynamics simulations, we present a model to understand the mechanisms of DSA of sub-10 nm particles onto an array of nanocavities as a template. The simulation results suggest that the random hopping mechanism ahead of the receding meniscus plays the major role in DSA of sub-10 nm particles. The simulation results provide a phase diagram of DSA yield as a function of liquid film thickness (confinement) and nanoparticle density. Furthermore, we find that the DSA yield of sub-10 nm particles varies with the nanoparticle diameter to cavity size ratio. The impact of template geometry, cavity size and spacing, and nanoparticle ordering in the bulk on the DSA yield will also be discussed. Overall, the present study provides new insights into the potential mechanisms of DSA of nanoparticles onto templated substrates and the relevant driving factors, which help future experimental design of DSA onto templated surfaces at sub-10 nm scales.

Metal–organic frameworks (MOFs) are promising materials with various applications, and machine learning (ML) techniques can enable their design and understanding of structure–property relationships. In this paper, we use machine learning (ML) to cluster the MOFs using two different approaches. For the first set of clusters, we decompose the data using the textural properties and cluster the resulting components. We separately cluster the MOF space with respect to their topology. The feature data from each of the clusters were then fed into separate neural networks (NNs) for direct learning on an adsorption task (methane or hydrogen). The resulting NNs were then used in transfer learning (TL) where only the last NN layer was retrained. The results show significant differences in TL performance based on which cluster is chosen for direct learning. We find TL performance depends on the Euclidean distance in the decomposed feature space between the clusters involved in the direct and TL. Similar results were found when TL was performed simultaneously across both types of clusters and adsorption tasks. We note that methane adsorption was a better source task than hydrogen adsorption. Overall, the approach was able to identify MOFs with the most transferable information, leading to valuable insights and a more comprehensive understanding of the MOF landscape. This highlights the method's potential to generate a deeper understanding of complex systems and provides an opportunity for its application in alternative datasets.

We construct a reduced, data-driven, parameter dependent effective stochastic differential equation (eSDE) for electric-field mediated colloidal crystallization using data obtained from Brownian dynamics simulations. We use diffusion maps (a manifold learning algorithm) to identify a set of useful latent observables. In this latent space we identify an eSDE using a deep learning architecture inspired by numerical stochastic integrators and compare it with the traditional Kramers–Moyal expansion estimation. We show that the obtained variables and the learned dynamics accurately encode the physics of the Brownian dynamic simulations. We further illustrate that our reduced model captures the dynamics of corresponding experimental data. Our dimension reduction/reduced model identification approach can be easily ported to a broad class of particle systems dynamics experiments/models.

Preventing ice formation and accumulation on solid surfaces has been a great challenge to address for various engineering and technological applications. Recently, the new development of zwitterionic polymer coatings attracted a lot of attention due to their excellent anti-icing performance (i.e., effectively reducing ice formation and adhesion), making them ideal material candidates for anti-icing coating applications. In this study, we employ density functional theory (DFT) to explore the hydration behaviors of two representative zwitterionic polymers, i.e., poly(sulfobetaine-methacrylate) (polySB) and poly(2-methacryloxoethyl-phosphorylcholine) (polyMPC). Through detailed bonding analysis by crystal orbital Hamilton populations (COHP), our results indicate strong interaction and covalent-nature bonds between the hydrogen atoms in water molecules and polymers' oxygen atoms of the anionic group of the polymer. Electron partial density of states (PDOS), Bader charge analysis, and energy calculations further demonstrate the physical and chemical nature of the water–polymer bonds. Interestingly, our modeling results also reveal that the addition of more water molecules will decrease the bonding stability of the bond between adsorbed water molecules to the polymer. Such induced bond instability, along with the polymer's hydrophilic character, suggests that continuous association and dissociation of bonded water molecules serve as the key mechanism which explains the inhibition of water clustering of the hydration layer. Our findings provide valuable insights into the physiochemical nature of water–polymer interaction by unveiling the molecular mechanism of hydration behavior, paving the way for design of next-generation anti-icing materials.

A classic technique in semiconductors but new to polymers, rapid thermal annealing (RTA) offers numerous opportunities in polymer processing. Infrared/visible light in RTA allows uniform rapid heating (typically ～100–150 °C s^?1; up to 1200 °C) with the capability of finely tuned temperature and atmosphere, unlike other flash heating methods, such as photothermal annealing. This review first summarizes the recent advances in RTA of polymers in the areas of doping/templating of hard materials and accessing non-equilibrium structures. The review of these previous studies elucidates emerging research opportunities in the field of polymer synthesis, characterization, and synergistic study for other flash heating methods that are relevant for various applications, from healthcare to electronics.

This study reports a simple protocol for the synthesis of ferrocene substituted benzoic acid and an efficient synthetic approach towards a ferrocene appended peptide mimetic with a high reaction rate, yield and purity. From X-ray single crystal analysis, the ferrocene appended peptide mimetic adopts an extended conformation and self-aggregates to form a dimer structure by intermolecular hydrogen bonds. The dimer formation is also supported by mass spectrometry. In higher order packing, the dimeric subunits further self-assembled to form a complex sheet-like structure stabilized by multiple π–π stacking interactions between the phenyl and cyclopentandienyl rings of ferrocene. Moreover, the ferrocene appended peptide mimetic forms a stimulus-responsive metallogel in DMF–water. The rheology experiments support the formation of a strong gel. The metallogel burst on addition of other salts such as Cu(OAc)₂·4H₂O, Pb(OAc)₂, Zn(OAc)₂·2H₂O, Cd(OAc)₂·4H₂O, and Mn(OAc)₂·4H₂O. The metallogel is responsive to pH. On addition of triethylamine the metallogel turned into a golden yellow solution. However, on further addition of trifluoroacetic acid the metallogel reappeared.