ACS Publications最新文献

The exceptional physicochemical and mechanical properties of mucus have inspired the development of dynamic mucus-based materials for a wide range of applications. Mucus’s combination of noncovalent interactions and rich liquid phases confer a range of properties. This perspective explores the synergy between dynamic networks and functional liquids in mucus-inspired supramolecular adhesives. It delves into the biological principles underlying mucus’s dynamic regulation and adhesive properties, the fundamentals of supramolecular adhesive design, and the transformative potential of these materials in biomedical applications. Finally, this perspective proposes potential directions for the molecular engineering of mucus-inspired supramolecular materials, emphasizing the need for interdisciplinary approaches to harness their full potential for biomedical and sustainable applications.

We use unsupervised machine learning to construct a phase diagram of a simple 2D rose water model. The machine learning method that we use is a combination of dimensionality reduction methods and clustering algorithms. Two different data sets from the same simulations are used as input data for machine learning. These are angular distribution functions and a set of different thermodynamic, dynamic, and structural properties. To evaluate the efficiency of the method, the machine learning results are compared to manually determined phase diagrams. We show that the methods successfully predict the phase diagram of the rose water model. Furthermore, the phase diagrams obtained from the two data sets are in semiquantitative agreement with each other. Four different solid phases, one liquid phase, and one gaseous phase were determined. The method we have presented is straightforward and easy to implement. It requires almost no prior knowledge of the system to obtain a phase diagram. The method can also be used to distinguish between the different parts of the same phase that have different properties or a sufficiently different structure, and in this way find local differences and anomalies.

Charge transfer due to a water–air contact line moving over a fluoropolymer hydrophobic surface is investigated for an aqueous solution containing surface-active molecules. It is found that anionic (SDS) and neutral (Triton X-100) surfactants exhibit a two-stage charge transfer reduction with concentration. At low concentrations, a layer of surfactant molecules accumulates near the hydrophobic surface and partially quenches the charge transfer. Surprisingly, after this first stage, the charge transfer remains nearly constant or weakly increasing, while the concentration of surfactants increases several orders of magnitude. Eventually, for large enough concentrations, the charge transfer continues to decrease, eventually resulting in almost zero charge transfer before reaching the critical micelle concentration. For the cationic surfactant (CTAB), the behavior is entirely different and a single quenching mechanism can explain the observed reduction in charge transfer due to positively charged surface-active molecules forming a layer that electrostatically screens the water-induced negative charge residing on the hydrophobic interface. A similar behavior is observed for poly(vinyl alcohol), which is attributed to its known and strong interaction with the hydrophobic surface used in this study.

Willemite is a low dielectric constant ceramic that is well suited for millimeter-wave applications. This study explores the improvement of the dielectric properties of Zn_1.8SiO_3.8 ceramics by doping with Nd₂O₃ at molar fractions of 2%, 4%, 6%, and 8%, with the goal of enhancing their application in microwave filters. The phase structure, morphology, and vibrational modes of the samples were analyzed by using XRD, SEM, Raman, and IR spectroscopy. Additionally, their dielectric constants, quality factors, and temperature coefficients were measured. The results indicate that the ceramic sample doped with 6 mol % Nd₂O₃ and sintered at 1225 °C maintains a stable dielectric constant and achieves a high Q × f value of approximately 130,000 GHz, exhibiting significantly enhanced dielectric properties compared to pure Zn_1.8SiO_3.8 ceramics. Based on the optimized Zn_1.8SiO_3.8 −6 mol % Nd₂O₃ ceramic system, a band-pass filter with a center frequency of 5.15 GHz and a bandwidth of 200 MHz was designed and fabricated. Experimental results demonstrate that the filter exhibits a low insertion loss of −0.62 dB and a return loss exceeding −20 dB, highlighting its strong potential for 5G communication applications. This study demonstrates the effectiveness of rare earth doping in optimizing the performance of microwave dielectric materials and provides new ideas for the design of high-performance dielectric filters.

Hydrogels have emerged as a versatile class of materials with broad applications in biomedical engineering, drug delivery, and tissue engineering. Understanding their intricate structures and morphologies is crucial for tailoring their properties to meet specific biomedical needs. It has been clearly established that the composition and microarchitecture of the materials play a critical role in essential cellular mechanisms such as mechanosensing, adhesion, and remodeling. This question is essential in tissue engineering, where precisely characterizing the microarchitecture of the materials used to model the cell microenvironment is a critical step to ensure the reproducibility and relevance of reconstructed tissues. In this study, we present a comprehensive comparison of four advanced electron microscopy techniques, namely, scanning electron microscopy, cryo-scanning electron microscopy, environmental scanning electron microscopy, and transmission electron microscopy, to observe the hydrogel microarchitecture, including a comparison of the sample preparation methods for each technique. Each technique’s specific advantages and limitations are discussed in detail, highlighting their unique capabilities in characterizing the hydrogel structures. We illustrate this study with two semisynthetic hydrogels, such as gelatin methacrylate and hyaluronic acid methacrylate. Moreover, we delve into the critical sample preparation steps necessary for each method, emphasizing the need to preserve the hydrogel’s native state while obtaining high-resolution images. This comparative analysis aims to select the most suitable electron microscopy technique for their hydrogel studies, fostering deeper insights into the design and development of advanced biomaterials for tissue engineering applications.

Hydrolysis reactions comprise a widely studied class of abiotic transformation processes that impact the environmental fate of many organic contaminants. While hydrolysis rates are typically measured in buffered solutions in order to predict transformation rates in the environment, rate constants measured in laboratory buffers are often higher than values in corresponding natural water samples. In this Perspective, we summarize these discrepancies and prior explanations provided for their occurrence. Through modeling using two linear free energy relationships (i.e., the Swain–Scott and the Bro̷nsted relationships), we propose a simple but overlooked alternative explanation─namely, that hydrolysis reactions are often much more sensitive to constituents in laboratory buffers than often assumed. We suggest that buffers employed in standard practices (e.g., at 50 mM or higher concentrations recommended by regulatory guidelines) are expected to significantly catalyze many hydrolysis reactions by acting as nucleophiles or bases. Finally, we recommend strategies to successfully measure hydrolysis rates for more accurate predictions of contaminant transformation in environmental systems.

Long-range ordered supercrystals (SCs) built up by colloidal nanocrystals (NCs) represent a class of novel metamaterials with unique collective properties. While great attention has been paid to the ligand-controlled assembly of NCs, the contribution of the inorganic core is considered limited because of the weak core–core interactions. Here, we report the spontaneous assembly of Ag₂S quantum dots (QDs) into three-dimensional SCs in solution, driven by pronounced dipole–dipole interactions. Dielectric spectroscopy shows a large permanent dipole moment of 516.7 D in 4.2 nm Ag₂S QDs, and multiscale molecular simulation proves the dipole–dipole interaction-driven crystallization of Ag₂S QDs. Moreover, we demonstrate that tuning the dipole–dipole interactions facilitates the formation of diverse nanostructures, including SCs, nanochains, and monodisperse nanoparticles. These findings offer a straightforward strategy for SC synthesis and establish the dipole–dipole interactions as a key driving force of NC self-assembly with broad implications for colloidal nanomaterials and their emergent functionalities.

Cu-based multinary selenide nanomaterials have garnered significant attention in photocatalytic and photovoltaic applications, owing to their unique electronic and optical properties. However, the high-yield and scalable synthesis of wurtzite colloidal Cu-based multinary selenide nanocrystals via a versatile and simple colloidal method has not yet been achieved. In this work, we report a general hot-injection colloidal method for the high-yield synthesis of a diverse library of wurtzite Cu-based quaternary selenide nanocrystals, including Cu₂CdSnSe₄, Cu₂ZnSnSe₄, Cu₂FeSnSe₄, Cu₂CoSnSe₄, Cu₂MnSnSe₄, Cu₃InSnSe₅, Cu₃GaSnSe₅, CuZnInSe₃, CuZnGaSe₃, CuCdInSe₃, and Cu(InGa)Se₂. As a proof of concept, the wurtzite Cu₂CdSnSe₄ nanocrystals are used as photocatalysts for solar-to-hydrogen production, displaying a good photocatalytic hydrogen evolution performance. Moreover, this approach has broad applicability for the high-yield synthesis of other wurtzite nanomaterials, which show significant potential for a wide range of applications.

Although the synthesis of low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (LMW-PPO) has been widely studied, preparing metal-free LMW-PPO with high thermal stability and satisfactory dielectric properties is still challenging. In this study, a new method for synthesizing metal-free LMW-PPO by nonmetal catalysts has been developed. In the absence of Cu(II) catalysts, amines can catalyze benzoyl peroxide (BPO) to produce metal-free LMW-PPO in CH₃CN (M_n in the range of 4.0 × 10³–6.0 × 10³), and N,N-dimethyl-p-toluidine (DMT) exhibits high reactivity in the yield of PPO (68.4%) with a low 3,3′,5,5′-tetramethyl-4,4’diphenoquinone (DPQ) yield (2.6 × 10^–2%) and PDI (1.50). The low dielectric constant (D_k = 1.96) and low dielectric loss factor (D_f = 1.57 × 10^–3) of the obtained PPO indicate that amines are more appropriate for the synthesis of metal-free LMW-PPO with superior dielectric properties. Meanwhile, the M_n values of PPO can be successfully mediated by regulating the contents of the catalyst or mixing appropriate contents of toluene in CH₃CN, and the decreased T_g values from 209.3 to 170.8 °C with decreasing M_n values from 1.7 × 10⁴ to 4.1 × 10³ indicate the improved processability of the LMW-PPO while maintaining high thermal stability (T_d5% = 420.8–434.2 °C). Density functional theory (DFT) calculations further reveal the formation of oxidizing radicals from BPO by DMT, which then initiate H-abstraction from DMP to form the DMP radical. The produced DMP radicals then polymerize to LMW-PPO. This study provides new insight into synthesizing highly qualified LMW-PPO by metal-free catalysts.

Aqueous zinc–iodine batteries (AZIBs) are attractive energy storage systems with the features of low cost, sustainability, and efficient multielectron transfer mechanism. However, the I₂ cathodes face obstacles due to the sluggish redox kinetics and severe shuttle effect. Herein, the atomically dispersed selenium single atoms (Se SAs) are embedded in ZIF-8-derived nitrogen-doped carbon. This design not only triggers the rapid redox conversion of I₂ but also enhances the anchoring of polyiodides, thereby enabling the excellent lifespan and rate capability of the Zn–I₂ battery. Specifically, the Se SAs and N dopants on carbon achieve a rapid I₂/I^– couple conversion reaction via modulation of the conversion energy barrier, as revealed by in situ results coupled with density functional theory analysis. This work demonstrates the application of atomic synergy in facilitating the reversible conversion of iodine species and provides valuable insights into designing efficient I₂ hosts for next-generation AZIBs.