Interview with Professor Guoqing Zhang

The side-chain has a significant effect on the optical properties and aggregation behaviors of the organic small molecule acceptors, which becomes an important strategy to optimize the photovoltaic performance of organic solar cells (OSCs). In this work, we designed and synthesized three novel nonfused ring electron acceptors (NFREAs) OC4-4Cl-Ph, OC4-4Cl-Th and OC4-4Cl-C8 with hexylbenzene, hexylthiophene and octyl side chains on the π-bridge units. Compared with OC4-4Cl-Ph and OC4-4Cl-Th, OC4-4Cl-C8 with linear alkyl side chain has more red-shift absorption, which is conducive to obtaining higher short-circuit current density. Additionally, the OC4-4Cl-C8 film exhibits a longer exciton diffusion distance and the D18:OC4-4Cl-C8 blend film displays faster hole transfer, weaker bimolecular recombination, and more efficient exciton transport. Furthermore, the D18:OC4-4Cl-C8 blend films can form good nano fibril-like interpenetrating networks, which can facilitate exciton dissociation and charge transport. Finally, OC4-4Cl-C8 based devices can generate an excellent PCE of 16.56%, which is much higher than OC4-4Cl-Ph (12.29%) and OC4-4Cl-Th based (11.00%) ones, being the highest PCE among the NFREA based binary devices. All in all, we have demonstrated that side-chain engineering is an efficient way to achieve high-performance NFREAs.

Amyloid-β peptide (Aβ) oligomers, characteristic symptom of Alzheimer’s disease (AD), have been identified as the most neurotoxic species and significant contributors to neurodegeneration in AD. However, due to their transient and heterogeneous nature, the high-resolution structures and exact pathogenic processes of Aβ oligomers are currently unknown. Using light-controlled molecular tweezers (LMTs), we describe a method for precisely capturing specific Aβ oligomers produced from synthetic Aβ and AD animal models. Light irradiation can activate LMTs, which are composed of two Aβ-targeting pentapeptides (KLVFF) motifs and a rigid azobenzene (azo) derivative, to form a tweezer-like cis configuration that preferentially binds to specifc oligomers matching the space of the tweezers via multivalent interactions of KLVFF motifs with the oligomers. Surprisingly, cis-LMTs can immobilize the captured oligomers in transgenic Caenorhabditis elegans (C. elegans) in vivo under light irradiation. The LMTs may serve as spatiotemporally controllable molecular tools to extract specific native oligomers for the structure and function studies via their reversible photoisomerization, which would improve the understanding of the toxic mechanisms of Aβ oligomers and development of oligomer-targeted diagnosis and therapy.

Fluorescent-magneto nanoemitters have gained considerable attention for their applications in mechanical controlling-assisted optical signaling. However, the incompatibility between magnetic and fluorescent components often leads to functional limitations in traditional magneto@fluorescence nanostructure. Herein, we introduce a new compact-discrete spatial arrangement on a “fluorescence@magneto” core–shell nanostructure consisting of a close-packed aggregation-induced emission luminogen (AIEgen) core and a discrete magnetic shell. This structural design effectively eliminates the optical and magnetic interferences between the dual components by facilitating AIEgens loading in core region and reducing the magnetic feeding amount through effective exposure of the magnetic units. Thereby, the resulting magneto-AIEgen nanoparticle (MANP) demonstrates “win-win” performances: (i) high fluorescent intensity contributed by AIEgens stacking-enhanced photoluminescence and reduced photons loss from the meager magnetic shell; (ii) marked magnetic activity due to magneto extraposition-minimized magnetic shielding. Accordingly, the dual functions-retained MANP provides a proof of concept for construction of an immunochromatographic sensing platform, where it enables bright fluorescent labeling after magnetically enriching and separating procalcitonin and lipoarabinomannan in clinical human serum and urine, respectively, for the clinical diagnosis of bacterial infections-caused inflammation and tuberculosis. This study not only inspires the rational design of magnetic-fluorescent nanoemitter, but also highlights promising potential in magneto-assisted point-of-care test and biomedicine applications.

Photoresponsive supramolecular materials have been fabricated by controlling the density of reversible cross-links or the distribution of movable cross-links. This study prepared photoresponsive polyurethane (CD-Azo-PU) based on controlling the crystallization of the hard segments in polyurethane (PU) by complexation between azobenzene (Azo) and cyclodextrins (CDs). CD-Azo-PU incorporated polyurethane as the main chain and a 1:2 inclusion complex between Azo and γCD as a movable crosslink point. Upon ultraviolet light (UV, λ = 365 nm) irradiation, the photoresponsiveness of CD-Azo-PU bent toward the light source (defined as positive), while that of the linear Azo polyurethane (Azo-LPU) without TAcγCD-diOH as a movable crosslinker bent in the direction opposite the light source. The bending rates were determined to be 0.058°/s for CD-Azo-PU and 0.027°/s for Azo-LPU, indicating that the bending rate for CD-Azo-PU was faster than that for Azo-LPU. By incorporating movable cross-links into CD-Azo-PU, we successfully achieved specific photoresponsive actuation with an enhanced rate.

The efficacy of nanoparticle (NP)-based drug delivery technology is hampered by aberrant tumor stromal microenvironments (TSMs) that hinder NP transportation. Therefore, the promotion of NP permeation into deep tumor sites via the regulation of tumor microenvironments is of critical importance. Herein, we propose a potential solution using a dihydrazidine (HDZ)-loaded nanoparticle drug delivery system containing a pH-responsive, cyclic RGD peptide-modified prodrug based on doxorubicin (cRGD-Dex-DOX). With a combined experimental and theoretical approach, we find that the designed NP system can recognize the acid tumor environments and precisely release the encapsulated HDZ into tumor tissues. HDZ can notably downregulate the expression levels of hypoxia-inducible factor 1α (HIF1α), α-smooth muscle actin, and fibronectin through the dilation of tumor blood vessels. These changes in the TSMs enhance the enrichment and penetration of NPs and also unexpectedly promote the infiltration of activated T cells into tumors, suggesting that such a system may offer an effective “multifunctional therapy” through both improving the chemotherapeutic effect and enhancing the immune response to tumors. In vivo experiments on 4T1 breast cancer bearing mice indeed validate that this therapy has the most outstanding antitumor effects over all the other tested control regimens, with the lowest side effects as well.

Centrifugal and shear forces are produced when solids or liquids rotate. Rotary systems and devices that use these forces, such as dynamic thin-film flow technology, are evolving continuously, improving material structure-property relationships at the nanoscale, representing a rapidly thriving and expanding field of research high with green chemistry metrics, consolidated at the inception of science. The vortex fluidic device (VFD) provides many advantages, with fluidic waves causing high shear and producing large surface areas for micro-mixing as well as rapid mass and heat transfer, enabling reactions beyond diffusion control in the processing. Combining these abilities allows for a green and innovative approach to altering materials for various research and industry applications by controlling small-scale flows and regulating molecular and macromolecular chemical reactivity, self-organization phenomena, and the synthesis of novel materials. This review highlights the aptitude of the VFD as clean technology, with an increase in efficiency for a diversity of top-down, bottom-up, and novel material transformations, benefiting from effective vortex-based processing for the transformation of material structure-property relationships.

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.

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.

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.

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.

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.

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.

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.

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.