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.

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.

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.

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.

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.

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

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.

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.

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.

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.