Many membraneless organelles, or biological condensates, that play key roles in signal sensing and transcriptional regulation form through phase separation. While the functional importance of these condensates has inspired many studies to characterize their stability and spatial organization, the underlying principles that dictate these emergent properties are still being uncovered. In this review, we examine recent work on biological condensates, especially multicomponent systems. We focus on connecting molecular factors such as binding energy, valency, and stoichiometry with the interfacial tension, explaining the nontrivial interior organization in many condensates. We further discuss mechanisms that arrest condensate coalescence by lowering the surface tension or introducing kinetic barriers to stabilize the multidroplet state.

Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science. Molecular aggregation finds wide applications in the research of new physical effects; however, its value for chemical reaction development has been far less explored. Herein, we report the development of aggregation-enabled alkene insertion into carbon–halogen bonds. The spontaneous cleavage of C–X (X = Cl, Br, or I) bonds generates an intimate ion pair, which can be quickly captured by alkenes in the aggregated state. Additional catalysts or promoters are not necessary under such circumstances, and solvent quenching experiments indicate that the aggregated state is critical for initiating such sequences. The ionic insertion mode and the intimate ion pair mechanism are supported by mechanistic studies, density functional theory calculations, and symmetry-adapted perturbation theory analysis. Results show that the non-aggregated state may quench the transition state and terminate the insertion process.

Direct visualization of polymer crystalline structure remains challenging due to the lack of contrast across different microphases of polymers. Here we address this conundrum using an aggregation-induced emission luminogen (AIEgen) with confinement fluorescence effect, which could be used as a “built-in” sensor to label different crystalline phases. Computational simulations reveal that the confined space induces the AIEgens to take a more planar conformation, resulting in a red-shifted emission spectrum. With this property, the information of various polymer crystalline forms is converted into different fluorescence colors, which is attributed to the different spatial dimensions of the polymer amorphous layer between lamellar crystals where the AIEgens are located. Finally, polymer crystalline phases distinction, quantitative crystallinity determination, and stereocomplex crystals visualization are achieved, providing a relationship between crystalline microstructure and fluorescence signals. This work demonstrates the potential of AIE fluorescence technology in polymer science, providing a theoretical and experimental guideline for the materials processing and optimization of mechanical performance.

The development of green and simple chemiluminescence (CL) systems with intensive and long-lasting emission is highly desirable in lighting and extension of their applications. In this study, it is found that the involvement of aggregation-induced emission (AIE) surfactant could greatly enhance the CL of luminol–H2O2–Co2+ system. The inserted hydrophobic tetraphenylethylene fluorophore in AIE is able to increase the hydrophobicity of alkyl chain and decrease the critical micelle concentration (CMC) of surfactant. The synergistic effect of micelle-improved enrichment and CL resonance energy transfer endows luminol–H2O2–Co2+ system intensive and long-lasting emission under neutral pH conditions (pH 7.4). The visible emission is still observed even after 60 min. Our study has opened a new avenue for exploring green and simple effective CL systems through AIE surfactant with unltralow CMC toward various applications in lighting, optical sensing, and photocatalysis, etc.

Carbon dots (CDs) possess outstanding luminescence properties, leading to their use in a wide range of applications including optical displays, anti-counterfeiting systems, bioimaging and sensors. Presently, there is much debate about the classification of CDs, as well as their formation process, structure and fluorescence mechanisms. Aggregation plays an important role in both the formation of CDs and their fluorescence (e.g. aggregation-induced emission), yet is seldom studied in detail. This review aims fill this knowledge gap, by firstly exploring how aggregation leads to the formation of different types of CDs (e.g. graphene quantum dots, carbon quantum dots, and carbonized polymer dots), followed by a detailed examination of the effect of aggregation-induced morphology on the luminescence properties and application of CDs. Finally, opportunities and challenges for the application of CDs in various applications are discussed, with the need for better mechanistic understanding of aggregation-induced luminescence being an imperative.

Preparation of coemissive luminescent nanoparticles in continuous-flow microreactors for efficient light-harvesting systemsAndrea Pucci

Single-helical or double-helical structures are common in all living organisms, such as RNA and DNA. Helical assembly has been found in the artificial nanoparticles, but how they do so remains poorly understood. Here, we exploit atomically precise Au6Cu6 alloy nanoparticles (or called nanoclusters) as building blocks to construct a single-helical Au12Cu12 superstructure in an operative path, thereby providing access to currently elusive mechanistic pathways. We propose that the thermodynamically viable linear-to-bent process at a couple of Au6Cu6 nanoclusters imparted by the organic ligands seems to be critical for the helical-nanostructured arrangement of Au12Cu12. This study could help to offer new design rules for the exquisitely helical structure assembled from nanoparticles.

Stimulating and harnessing circularly polarized luminescence (CPL) is not only a sine qua non for fundamentally unveiling chirogenesis in physical chemistry, and also a pivotal prerequisite for implementation of such phenomenon in area of chiral optoelectronics and theranostics. Herein, red-emissive carbonized polymer dots (CPDs)-based helical structures were synthesized in this work via biomolecule-tailored organic-inorganic co-assembly strategy. The surface states related chirality exhibited enhanced circular dichroism (CD) and CPL activities with anisotropic factors as high as gCD,max=5.4×10-3 and glum,max=1.5×10-2 respectively. The obtained CPL signals can be further manipulated with an excitation-dependent manner indicating a synergistic-competition phenomenon is existed between configurational chirality and intermolecular energy-transfer dynamics, which is further supported by simulations based on density function theory (DFT). Such tunable CPL behaviors triggers revolutionary designs and applications of these chiral CPDs into the realm of chirality-related biological issues and next generation chiral optoelectronics.

In the wave of the Internet era created by computer and communication technology, flexible sensors play an important role in accurately collecting information owing to their excellent flexibility, ductility, freeform bending or folding, and versatile structural shapes. By endowing elastomeric polymers with conductivity, researchers have recently devoted extensive efforts toward developing high-performance flexible sensors based on elastomeric conductive layers and exploring their potential applications in diverse fields ranging from project manufacturing to daily life. This review reports the recent advancements in elastomeric polymers used to make conductive layers, as well as the relationships between elastomeric polymers and the performance and application of flexible sensors are comprehensively summarized. First, the principles and methods for using elastomeric polymers to construct conductive layers are provided. Then, the fundamental design, unique properties, and underlying mechanisms in different flexible sensors (pressure/strain, temperature, humidity) and their related applications are revealed. Finally, this review concludes with a perspective on the challenges and future directions of high-performance flexible sensors.

The co-assembly of charged nanoparticles with oppositely charged molecular ions has emerged as a promising technique in the fabrication of nanoparticle superstructures. However, the underlying mechanism behind these molecular ions in mediating the repulsion between these charged nanoparticles remains elusive. Herein, coarse-grained molecular dynamics simulations are used to elucidate the effects of valency, shape and size of molecular anions on their co-assembly with gold nanoparticles coated with positively charged ligands. The findings suggest that the valency, shape and size of molecular anions significantly influence the repulsion and aggregating dynamics among these positively charged nanoparticles. Moreover, the free energy calculations reveal that ring-shaped molecular anions with higher valencies and larger sizes are more effective at reducing the repulsion between these gold nanoparticles and thus enhance the stability of the aggregate. This study contributes to a better understanding of the critical roles of valence, shape and size of ions in mediating the electrostatic co-assembly of nanoparticles with oppositely charged ions and it also guides the future design of DNA templates and DNA origami in co-assembly with oppositely charged nanoparticles.

Gold nanoparticles (GNPs) are promising materials for many bioapplications. However, upon contacting with biological media, GNPs undergo changes. The interaction with proteins results in the so-called protein corona (PC) around GNPs, leading to the new bioidentity and optical properties. Understanding the mechanisms of PC formation and its functions can help us to utilise its benefits and avoid its drawbacks. To date, most of the previous works aimed to understand the mechanisms governing PC formation and focused on the spherical nanoparticles although non-spherical nanoparticles are designed for a wide range of applications in biosensing. In this work, we investigated the differences in PC formation on spherical and anisotropic GNPs (nanostars in particular) from the joint experimental (extinction spectroscopy, zeta potential and surface enhanced Raman scattering [SERS]) and computational methods (the finite element method and molecular dynamics [MD] simulations). We discovered that protein does not fully cover the surface of anisotropic nanoparticles, leaving SERS hot-spots at the tips and high curvature edges “available” for analyte binding (no SERS signal after pre-incubation with protein) while providing protein-induced stabilization (indicated by extinction spectroscopy) of the GNPs by providing a protein layer around the particle’s core. The findings are confirmed from our MD simulations, the adsorption energy significantly decreases with the increased radius of curvature, so that tips (adsorption energy: 2762.334 kJ/mol) would be the least preferential binding site compared to core (adsorption energy: 11819.263 kJ/mol). These observations will help the development of new nanostructures with improved sensing and targeting ability.

Transparent afterglow crystals are keenly desired for three-dimensional information storage. Herein, CsCdCl3 perovskite crystals were grown by a programmable cooling procedure in a hydrothermal reactor. The pristine crystal showed an abnormal optical behavior where the absorption increased by 2.3 folds at high temperature, leading to a 4-fold boost of PL intensity. After Mn2+ doping, the PL QY was improved to nearly unity. Importantly, the doped crystals exhibited an ultralong afterglow up to 12 hours after ceasing UV excitation and a high transmittance up to 75% in the visible region. This work brought a new member to the library of transparent afterglow crystal, opening up many possibilities to advanced applications such as volumetric display and three-dimensional information encryption.

Room-temperature phosphorescence (RTP) of purely organic materials is easily quenched with unexpected purposes because the excited triplet state is extremely susceptible to external stimuli. How to stabilize the RTP property of purely organic luminogens is still challenging and considered as the bottleneck in the further advancement of the bottom-up approach. Here, we describe a gated strategy that can effectively harness RTP by employing complexation/dissociation with proton. Due to the order-disorder transition orientation of intermolecular packing, the RTP of triazine derivative Br-TRZ will easily vanish upon mechanical force. Impressively, by enhancing its intramolecular charge transfer effect, the protonated Br-TRZ stubbornly possesses an obvious RTP under external grinding, whatever in the ordered or disordered intermolecular arrangement state. Consequently, the “Lock” gate of RTP was achieved in the protonated Br-TRZ molecule. Combined with theoretical calculation analysis, the enhanced charge transfer effect can narrow the singlet−triplet energy gap significantly, and stabilize the RTP property of triazine derivative sequentially. Furthermore, the locked RTP can be tuned via proton and counterions repeatedly and show excellent reversibility. This gated RTP concept provide an effective strategy for stabilizing the RTP emission of purely organic systems.

Flame retardants play a crucial role in improving the flame retardant properties of polymer materials. In recent years, environmental problems caused by flame retardants have attracted widespread attention. It is urgent to use green and effective methods to prepare flame retardant polymers. Bioinspired nanocomposites with layered structures seem to provide an effective idea, but in general, the hydrophilic properties of their raw materials limit their applications in certain fields. Here, we prepared biomimetic composites with a layered “brick-and-mortar” structure by gravity-induced deposition using polyimide as the polymer matrix and montmorillonite (MMT) as the filler. The well-arranged structures of the composite material could isolate oxygen and prevent combustible gases from escaping. The gas barrier performance has been greatly improved, in which the water vapor transmission rate (WVTR) and the oxygen transmission rate (OTR) decreased by 99.18% and three orders of magnitude, respectively. The flame retardant performance has also been improved, and its limiting oxygen index can reach 67.9%. More importantly, the polyimide matrix can be converted to water-insoluble by thermal imidization of water-soluble poly (amic acid) salt precursors, which endows the composites with low hygroscopicity. Such coating containing MMT can protect against polyurethane (PU) foam from fire. During the conical calorimetric test, the coated sample self-extinguished, and the peak heat release rate, total heat release, total smoke production is significantly decreased by 53.39%, 40.69%, and 53.03%, respectively. Taking advantage of these properties, this work utilizes a facile method to prepare biomimetic composites with low moisture absorption, excellent gas barrier properties, and flame retardancy, which have great application potential.

Antibiotic resistance is a major challenge in the clinical treatment of bacterial infectious diseases. Herein, we constructed a multifunctional DNA nanoplatform as a versatile carrier for bacteria-specific delivery of clinical antibiotic ciprofloxacin (CIP) and classic nanoantibiotic silver nanoparticles (AgNP). In our rational design, CIP was efficiently loaded in the self-assembly double-bundle DNA tetrahedron through intercalation with DNA duplex, and single-strand DNA-modified AgNP was embedded in the cavity of the DNA tetrahedron through hybridization. With the site-specific assembly of targeting aptamer in the well-defined DNA tetrahedron, the bacteria-specific dual-antibiotic delivery system exhibited excellent combined bactericidal properties. With enhanced antibiotic accumulation through breaking the out membrane of bacteria, the antibiotic delivery system effectively inhibited biofilm formation and promoted the healing of infected wounds in vivo. This DNA-based antibiotic delivery system provides a promising strategy for the treatment of antibiotic-resistant infections.

Crosslinking thermosets with hyperbranched polymers confers them superior comprehensive performance. However, it still remains a further understanding of polymer crosslinking from the molecular chains to the role of aggregates. In this study, three hyperbranched polysiloxane structures (HBPSi-R) are synthesized as model macromolecules, each featuring distinct terminal groups (R denotes amino, epoxy, and vinyl groups) while similar molecular backbone (Si-O-C). These structures were subsequently copolymerized with epoxy monomers to construct interpenetrating HBPSi-R/epoxy/anhydride co-polymer systems. The spatial molecular configuration and flexible Si-O-C branches of HBPSi-R endow them with remarkable reinforcement and toughening effects. Notably, an optimum impact strength of 28.9 kJ mol-1 is achieved with a mere 3% loading of HBPSi-V, nearly three times that of the native epoxy (12.9 kJ mol-1). By contrasting the terminal effects, the aggregation states and crosslinking modes were proposed, thus clarifying the supramolecular-dominant aggregation mechanism and covalent-dominant dispersion mechanism, which influences the resulting material properties. This work underscores the significance of aggregate science in comprehending polymer crosslinking and provides theoretical insights for tailoring material properties at a refined molecular level in the field of polymer science.

Aggregation-Induced Emission (AIE) is a unique phenomenon whereby aggregation of molecules induces fluorescence emission as opposed to the more commonly known Aggregation-Caused Quenching (ACQ). AIE has the potential to be utilized in the large-scale production of AIE-active polymeric materials because of their wide range of practical applications such as stimuli-responsive sensors, biological imaging agents, and drug delivery systems. This is evident from the increasing number of publications over the years since AIE was first discovered. In addition, the ever-growing interest in this field has led many researchers around the world to develop new and creative methods in the design of monomers, initiators and crosslinkers, with the goal of broadening the scope and utility of AIE polymers. One of the most promising approaches to the design and synthesis of AIE polymers is the use of the Reversible-Deactivation Radical Polymerization (RDRP) techniques, which enabled the production of well-controlled AIE materials that are often difficult to achieve by other methods. In this review, a summary of some recent works that utilize RDRP for AIE polymer design and synthesis is presented, including (1) the design of AIE-related monomers, initiators/crosslinkers; the achievements in preparation of AIE polymers using (2) Reversible Addition-Fragmentation Chain Transfer (RAFT) technique; (3) Atom Transfer Radical Polymerization (ATRP) technique; (4) other techniques such as Cu(0)-RDRP technique and Nitroxide-Mediated Polymerization (NMP) technique; (5) the possible applications of these AIE polymers and finally (6) a summary/perspective and the future direction of AIE polymers.

Macroscopic chiral spherulites prepared by hierarchical self-assembly have attracted considerable attention due to their excellent property as chiroptical materials. However, preparing controllable handedness spherulites in bulk film remains a challenge due to the absent knowledge of the evolution mechanism from the molecule to macroscopic crystal during chiral assembly. In this contribution, we constructed chiral controllable macroscopic spherulites with circularly polarized luminescence (CPL) using enantiomeric tartaric acid and Rhodamine B co-assembled with liquid crystal block copolymers, poly (ethylene oxide)-b-poly (methyl methacrylate) bearing azobenzene group side chains. It was found that the chiral liquid crystal field induced by exogenous chiral molecules was closely related to the formation of macroscopic chiral spherulites. Moreover, the transformation of azobenzene cis-trans isomerization under photo-thermal endows films with adjustable CPL. This facile strategy provides a platform to design large-scale chiral structures for chiroptical switching, encryption, and memory storage materials.