Molecular Systems Design & Engineering最新文献

Field-based simulations can be challenging in multi-component polymer systems and are highly sensitive to the choice of relaxation coefficients (λ) used in the field update algorithms. Judiciously chosen relaxation coefficients are critical for both the stability and convergence of field-based simulations, yet their selection is challenging when the number of unique chemical species in the system is large. In this work, we develop a new method to automatically and efficiently locate optimal relaxation coefficients in systems with large numbers of species. We begin by analyzing the effects of relaxation coefficients in two- and three-species systems and demonstrate that regions of high-performance are both narrow and system-specific. Based on these findings, we next develop a method based on Bayesian optimization that automatically locates relaxation coefficients that are stable and exhibit good performance. We demonstrate that our method is considerably faster than naive search methods and becomes particularly efficient as the system complexity increases. This work demonstrates that Bayesian optimization can be used to stabilize and accelerate field-based simulations that contain many different chemical species.

Conjugation elongation of squaraines is a potential approach to optimize their performance as nonlinear optical (NLO) chromophores and TiO₂-photosensitizers in dye-sensitized solar cells (DSCs). This study investigates the impact of integrating π-conjugated heteroaromatic spacers on the optoelectronic properties of four modeled unsymmetrical squaraine derivatives. Density functional theory (DFT) and time-dependent TD-DFT computations revealed the dual functionality of all four π-extended squaraine dyes, with the capability to sensitize TiO₂ for far-red light harvesting and amplify second-order NLO response at the molecular-level. Dye SQ-N incorporating an ethyl-dithienopyrrole π-spacer emerged as the optimal photosensitizer for TiO₂-based DSCs, exhibiting a hyperchromic S₁ transition and a light harvesting efficiency (LHE) of 98% at 697 nm (λ_max), the most thermodynamically driven electron injection (ΔG_inj), robust adsorption (E_ads) onto the TiO₂ nanocluster, enhanced orbital coupling (ΔE_oi) and hybridization between virtual molecular π* orbitals of SQ-N and 3d-orbitals of Ti atoms, in addition to superior charge transfer at the SQ-N–TiO₂ interface, under deep red-to-NIR photoexcitation. Conversely, the P-acetyl dithienophosphole oxide π-linker in SQ-P led to a sixfold enhancement in off-resonant hyperpolarizability (β₀) compared to the π-spacer-free parent dye, in addition to manifesting the maximal dynamic electro-optic Pockels (EOP) β₁₀₆₄ and β₁₄₆₀, second-harmonic generation (SHG) β₁₀₆₄ and hyper-Rayleigh scattering β₁₀₆₄. Analytical DFT-predicted SHG activity of the modeled dyes showed simultaneous potential for NIR-to-green and telecom E-band (1460 nm) to red light conversion. β scans demonstrated dual EOP and optical rectification functionality, while dyes SQ-N and SQ-Th further displayed significant sum/difference frequency generation (SFG/DFG) output at ω₁ ± ω₂. Polarization-resolved SHG analysis revealed a hybrid dipolar–octupolar NLO symmetry across all the dyes, with maximal harmonic intensity at Ψ = ±90°—a signature of synergistic dipole alignment and 3D charge delocalization.

Cholesteric liquid crystals (CLCs) confined in curved geometries exhibit a rich spectrum of defect-mediated morphologies governed by the interplay between chirality, curvature, surface anchoring, and confinement. This study systematically investigates structural transitions in highly chiral CLC shells under asymmetric anchoring conditions, focusing on the effects of shell thickness and curvature on pitch axis reorientation and defect formation. Utilizing microfluidic techniques, we generate core–shell droplets with independently tunable anchoring at inner and outer aqueous interfaces. Transitioning from planar–planar to planar-homeotropic boundary conditions via surfactant-mediated modulation induces profound reorganizations in the director field, giving rise to focal conic domains (FCDs), stripe patterns, and hybrid textures. Optical microscopy reveals that thicker shells favor coherent FCD nucleation, while thinner shells exhibit asymmetric, fragmented domains due to increased spatial frustration and constrained elastic relaxation. In small-diameter shells, high curvature suppresses defect nucleation, promoting the emergence of periodic stripe textures as an energetically favorable alternative. Complementary continuum simulations based on the Landau–de Gennes framework reproduce experimental trends, highlighting anchoring energy thresholds that delineate morphological regimes and confirm the dominance of curvature in stabilizing non-defect-based modulations. The ability to engineer defect architectures and direct pitch axis orientation via geometrical and boundary condition control can open new avenues for designing responsive and reconfigurable optical materials and photonic elements.

A green synthesis method was employed to obtain cobalt ferrite nanoparticles (NPs) from orange extract in three different volumes (100, 150, and 200 mL). This provides an eco-friendly and convenient method to produce nanoparticles. The phytochemicals present in the extract act as reducing and stabilizing agents in the formation of cobalt ferrite nanoparticles. The orange extract has proved to be effective in modifying the crystallite size; a higher extract volume of orange juice produced smaller-sized crystallite nanoparticles. X-ray diffraction (XRD), simultaneous thermal analysis (STA), UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM) were used to characterize the effects of varying amounts of chelating agents on the morphological, structural, and optical characteristics of the produced CoFe₂O₄. FTIR analysis proved the synthesized samples' spinel structure and the force constant for the Fe–O bond was calculated to be 262.398 N m⁻¹ and for the Co–O bond was 156.047 N m⁻¹. The distribution of chemical components among the particles with varying quantities of O, Fe, and Co was determined using energy-dispersive X-ray (EDX) spectroscopy. According to the XRD analysis, the NPs' crystallite sizes range from 17 to 28 nm. The NPs' agglomerated shape and average particle size of 47–74 nm was observed by SEM. VSM studies show that the 100 mL extract-based sample exhibited the highest saturation magnetization of 65.71 emu g⁻¹. The band gap was measured using the Kubelka–Munk technique and increased from 2.261 to 2.475 eV with increasing extract volume. This study confirms that orange fruit extract can effectively synthesize nanoparticles of cobalt ferrite.

Quantum mechanical tunneling effects cannot be neglected when studying the kinetics of chemical reactions involving light atoms at low temperatures. Rate theories such as variational transition state theory with multidimensional tunneling (VTST/MT) can be computationally intensive as they need nuclear Hessian information along the entire minimum energy path (MEP) of the reaction step. We report an improved selection strategy for a small number of points on the MEP that are necessary for a low-cost reconstruction of Hessian eigenvalues via the polynomial variety-based matrix completion (PVMC) algorithm [S. J. Quiton, J. Chae, S. Bac, K. Kron, U. Mitra and S. Mallikarjun Sharada, J. Chem. Theory Comput., 2022, 18, 4327–4341]. We combine chemically informed sampling of points on the MEP that correspond to crossings between critical bond distances with a Euclidean distance-based approach that identifies points on the MEP that are most dissimilar from already sampled ones. We examine the performance of PVMC with the new sampling approach in predicting zero-curvature tunneling transmission coefficients, VTST/MT-based kinetic isotope effects (KIEs), and their trends for two possible CH activation mechanisms catalyzed by dioxo-dicopper complexes. PVMC reduces Hessian evaluations by over 58% while maintaining high predictive fidelity, offering a computationally efficient approach for quantum chemical rate predictions. While the approach is accurate for small KIEs (≤10), the prediction of very large tunneling transmission coefficients and consequently KIEs (between 10 and 60) depends very strongly on the underlying sampling strategy. PVMC also assumes an approximate polynomial structure for Hessian eigenvalues, which cannot always capture sharp changes in eigenspectra in the vicinity of the transition state. Going forward, we aim to (1) identify alternative structures to the quasi-polynomial approximation and (2) MEP characteristics in addition to bond crossings, to develop a universal sampling and matrix completion scheme for inexpensive VTST/MT calculations.

Corrosion inhibitors play a crucial role in mitigating metal degradation, yet their performance varies significantly depending on environmental conditions and application methods. This study employs a high-throughput methodology utilising volume loss measurements via optical profilometry to assess corrosion inhibitor efficiency. A comparative analysis between the droplet-on-plate and full-immersion testing methods is conducted to evaluate their impacts on inhibitor performance using optical profilometry. The research delves into the chemistry of corrosion inhibitors specifically designed for droplet corrosion, where benzothiazole derivatives performed well in both environments, whereas thiazole derivatives exhibited weaker performance under droplet conditions, whilst focusing on how pH gradients evolve within a droplet over time and influence corrosion inhibitor effectiveness. Results indicate that localised pH variations significantly alter the adsorption behaviour and stability of corrosion inhibitors, affecting their protective capabilities. Furthermore, the interactions between corrosion inhibitors and oxide layers are explored, revealing that anodic inhibitors tend to accumulate around corrosion pits, suggesting a selective protection mechanism. Those findings provide critical insights into optimising corrosion inhibitor formulations and testing methodologies for sound corrosion assessments.

Separation of carbon dioxide (CO₂) from acetylene (C₂H₂) represents a significant challenge in the petrochemical industry, primarily due to their similar physicochemical properties. By synergizing molecular simulation (MS) and machine learning (ML), in this study, we aim to discover top-performing metal–organic frameworks (MOFs) for inverse CO₂/C₂H₂ separation. Initially, the adsorption of a CO₂/C₂H₂ mixture in MOFs from the Cambridge Structural Database (CSD) is evaluated through MS, structure–performance relationships are constructed, and top-performing CSD MOFs are shortlisted. Subsequently, ML models are trained by utilizing pore geometry, framework chemistry, as well as adsorption heat and Henry's constant as descriptors. The significance of these descriptors is quantitatively assessed through Gini impurity measures and Shapley additive explanations. Finally, the transferability of the ML models is evaluated through out-of-sample predictions for CO₂/C₂H₂ separation in the computation-ready experimental (CoRE) MOFs. Notably, a handful of CoRE MOFs are found to outperform the best CSD MOFs and their performance is further compared with existing literature. The synergized MS and ML approach in this study is anticipated to accelerate the discovery of MOFs in a large chemical space for CO₂/C₂H₂ separation and other important separation processes.

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With the world swiftly evolving towards technology, the relentless quest for sustainable energy sources has garnered significant attention. Amidst the scientific advancements, triboelectric nanogenerators (TENGs) have emerged as a beacon of hope, providing a promising solution through energy generation from the ambient environment. This paper focuses on the development of a freestanding triboelectric layer (FTL) TENG for increasing output power energy by incorporating a PTFE layer. A comprehensive investigation is performed that involves mathematical modeling and COMSOL simulation of the FTL TENG. Experimentally, the novel FTL TENG is designed and fabricated using fur and PTFE/Cu electrodes. The results show a two-fold enhancement in the performance of the FTL TENG upon incorporating a PTFE layer over copper electrodes. The simulation results accurately predict voltage build up under open-circuit conditions and substantial current flow under short-circuit conditions, closely mirroring experimental results. The study also demonstrates the practicality of the FTL TENG in powering electronic devices through successful capacitor charging. This research underscores the FTL TENG's reliability as a clean and sustainable energy harvesting solution with potential applications across various fields, thereby illuminating the path towards self-powered electronic devices.

In this study, we report an investigation of the impact of molecular engineering through asymmetrical side chain substitution on the semiconducting performance of benzo[1,2-b:5,4-b′]dithiophene (BDT) derivatives in solution-processable organic field-effect transistors (OFETs). Pristine (2-(thiophen-2-yl)benzo[1,2-b:5,4-b′]dithiophene; compound 1), linear octyl-substituted (2-(5-octylthiophen-2-yl)benzo[1,2-b:5,4-b′]dithiophene; compound 2), and branched 2-ethylhexyl-substituted (2-(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:5,4-b′]dithiophene; compound 3) BDT derivatives were synthesized and characterized to evaluate the role of alkyl side chains in modulating thermal, optical, electrochemical, and charge transport properties. Despite the improved solubility and thermal stability observed for the alkylated derivatives, compound 1 without any side chains exhibited the highest field-effect mobility of up to 0.024 cm² V⁻¹ s⁻¹ and superior thin-film crystallinity. Our results demonstrate that excessive steric hindrance induced by bulky side chains can disrupt molecular packing and degrade OFET performance. This work highlights the importance of precise side chain engineering for optimizing the balance between solution-processability and charge transport in organic semiconductors.