Anti-Kasha triplet energy transfer and excitation wavelength dependent persistent luminescence from host-guest doping systems.

Anti-Kasha's process in organic luminogens has attracted many attentions since its discovery. However, only limited examples of anti-Kasha's rule have been reported and anti-Kasha triplet energy transfer (ET) is even less-touched. Benefiting from anti-Kasha's rule, this work provided an efficient strategy to realize excitation wavelength dependent (Ex-De) afterglow in a host-guest system. The host has almost imperceptible RTP upon 365 nm excitation and guest is totally RTP inactive, while the doping host-guest system exhibits Ex-De afterglow with improved quantum yields. Anti-Kasha triplet ET process is realized from the higher excited triplet state T2 of host to the lowest excited singlet state S1 of the aggregated/unimolecular guest. ET efficiency in the doping system could be tuned by simply changing its processing methods to guide host and guest to adopt denser or looser intermolecular packing. The strategy of anti-Kasha triplet ET endows the host-guest doping system with multiple stimuli-responsive properties, including Ex-De afterglow, mechano-, and thermal-triggered afterglow behaviors. The corresponding applications of these properties are also realized in multiple information anti-counterfeiting and display.

Correction: In situ synthesis of chiral AuNCs with aggregation-induced emission using glutathione and ceria precursor nanosheets for glutathione biosensing.

Correction for 'In situ synthesis of chiral AuNCs with aggregation-induced emission using glutathione and ceria precursor nanosheets for glutathione biosensing' by Mohamed Ibrahim Halawa et al., Analyst, 2022, https://doi.org/10.1039/d2an00939k.

In situ synthesis of chiral AuNCs with aggregation-induced emission using glutathione and ceria precursor nanosheets for glutathione biosensing.

In the present study, a mediator release test (MRT) strategy has been designed for the photoluminescent sensing of glutathione (GSH). On the basis of the redox reaction of GSH and cerium-based nanosheets (Ce(CO3)2 NSs), Ce3+ ions were released to act as a mediator for the photoluminescence emission of the Au-thiolate complexes through an aggregation-induced emission (AIE) process. Remarkably, AIE was also accompanied by high chirality for the in situ synthesis of AuNCs using Ce(CO3)2 NSs as a template and GSH as a releaser for oligomeric Au-thiolate complexes. Multiple characterization techniques, including high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), selected-area electron diffraction (SAED), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were employed to check the structure and morphology of the Ce(CO3)2 NSs as well as the successful in situ fabrication of the AuNCs. Using this new MRT strategy, an eco-friendly, selective, biocompatible and label-free AIE probe was established for the sensitive sensing of GSH with a limit of detection (LOD) of 1.02 µM. Moreover, this switch-on luminescent nanoplatform of the conjugate probe of Au-thiolate/Ce-based NSs was successfully applied for the selective and reliable GSH detection in human serum samples.

Two Cholesterol-Containing Pyrene Derivatives: Subtle Spacer Difference, Diverse Stimuli-Responsive Luminescence, Chirality, and Self-Assembly Behaviors.

Two chiral molecules 1 and 2 were designed and synthesized with a pyrene moiety directly linked to a chiral cholesterol moiety and connected through a methylene spacer, respectively. Influence of the spacer on their stimuli-responsive luminescence, chirality, and self-assembly behaviors was systematically investigated. Molecules 1 and 2 had similar aggregation-induced emission enhancement (AIEE) in solution, because of carrying the same fluorescence moiety. Both molecules displayed mechanochromism (MC) property but with different color contrast, whereas only 2 showed mechanoluminescence (ML) activity. When doping in liquid crystal molecule 5CB, both molecules induced the formation of chiral nematic liquid crystals (N*-LCs) with strong circularly polarized luminescence (CPL). Molecule 2 induced single handedness signal, irrespective of doping ratios, while 1-doped N*-LCs showed an inversion of CPL signal from negative to positive upon the increase of doping ratios. Molecules 1 and 2 also self-assembled into different coassemblies with 5CB. Their distinct behaviors were attributed to the influence of the methylene spacer, which caused different molecular conformation and steric bulkiness; accordingly, it changed intermolecular interactions and molecular packing of the two molecules and led to diverse chirality and luminescence. This work provided important model molecules to better understand the molecular structure-property relationship and guide the design of novel functional molecules.

Insight into Isomeric Effect on the Photoluminescence and Mechanoluminescence of Cyanostilbene Derivatives.

Molecular structures, packings, and intermolecular interactions significantly affect the photophysical properties of organic luminogens. In this work, the photoluminescence (PL) and mechanoluminescence (ML) of two pairs of isomers, 1/2 and 3/4, were systematically explored. The fluorescence of crystals 1c and 4c is much brighter than that of their isomers 2c and 3c, respectively. Only 1c is ML-active among all four molecules. Single-crystal structural analysis revealed that isomerization of a substituent group affected their molecular packing and intermolecular interactions. Stronger intermolecular interaction and intact three-dimensional hydrogen-bonded networks were formed only in crystal 1c, which were essential for preventing slippage of molecular layers and generating ML; the other molecules were either lacking π-π interactions or C-H···π interactions. Theoretical calculation suggested that the energy barrier between the Franck-Condon (FC) structure and minimum energy crossing point (MECP) structure of 2/3 was much lower than that of 1/4. Nonradiative decay channels of molecules 2 and 3 were thus more easily activated, which led to their lower quantum yield.

Controllable room temperature phosphorescence, mechanoluminescence and polymorphism of a carbazole derivative.

Room temperature phosphorescence (RTP) and mechanoluminescence (ML) materials are in high demand because of their promising applications in optoelectronic devices. However, most materials bear only one of these properties and molecules bearing both of them are rarely reported. Here, we report a carbazole derivative 1, which displays both RTP activity and near-ultraviolet ML properties. These properties are highly related to the packing modes and molecular configuration as revealed by the analysis of their crystal structures and theoretical calculations. The near-ultraviolet ML of 1 can further serve as the exciting light source to transfer its energy to luminescent dyes to realize colorful ML. The thermal-responsive RTP of 1 can be utilized to prepare anti-counterfeiting tags for simple security protection. This work has put forward a simple but efficient strategy to prepare multifunctional molecular systems bearing both RTP and ML properties.

An ultrasensitive chemiluminescent biosensor for tracing glutathione in human serum using BSA@AuNCs as a peroxidase-mimetic nanozyme on a luminol/artesunate system.

In this work, a nanosensor chemiluminescent (CL) probe for sensing glutathione (GSH) was developed, for the first time, based on its inhibition of the intrinsic peroxidase-mimetic effect of BSA@AuNCs. The endoperoxide linkage of artesunate could be hydrolyzed by BSA@AuNCs resulting in the release of reactive oxygen species (ROS), and the consequent generation of strong CL emission. By virtue of the strong covalent interactions of -S⋯Au-, GSH could greatly suppress the peroxidase-mimetic effect of BSA@AuNCs, leading to a drastic CL quenching. The CL quenching efficiency increased proportionally to the logarithm of GSH concentration through the linearity range of 50.0-5000.0 nM with a limit of detection of 5.2 nM. This CL-based strategy for GSH tracing demonstrated the advantages of ultrasensitivity, high selectivity and simplicity. This strategy was successfully utilized to measure GSH levels in human serum with reasonable recovery results of 98.71%, 103.18%, and 101.68%, suggesting that this turn-off CL sensor is a promising candidate for GSH in biological and clinical samples.

Direct Visualization of Chiral Amplification of Chiral Aggregation Induced Emission Molecules in Nematic Liquid Crystals.

Chiral amplification in liquid crystals (LCs) is a well-known strategy. However, current knowledge about the underlying mechanism was still lacking; in particular, how it was realized at the nano scale still remained to be revealed. Here, we provide systematical exploration of chiral amplification of chiral aggregation induced emission (AIE) molecules in LCs from direct visualization of their co-assemblies at the nano scale to theoretical calculation of the molecular packing modes on a single molecular level. Using AFM imaging,we directly visualized the co-assembly formed by chiral AIE molecules/LCs at the nano scale: the chiral AIE molecules self-assembled into helical fibers to serve as the helical template for LCs to bind, while the LCs helically bound to the helical fibers to form the co-assembly, giving the morphology of pearled necklaces or thick rods. Theoretical calculation suggested that chiral AIE molecules were packed into left-handed helical fibers with a large volume of empty space between neighboring molecules, which provided the binding cites for LCs. Structural analysis showed that the π-π stacking between aromatic groups from LCs and TPE groups and the σ-π hyperconjugation between LC aromatic groups and cholesterol aliphatic groups play an important role in stabilizing the binding of LCs in the confined space on the surface of the helical assemblies.

Development of luminol-based chemiluminescence approach for ultrasensitive sensing of Hg(II) using povidone-I2 protected gold nanoparticles as an efficient coreactant.

In this work, we fabricated gold nanoparticles (AuNPs) capped with both polyvinyl pyrrolidone (PVP) and iodine (I2) to act as efficient chemiluminescent coreactants for luminol. AuNPs synthesis was based on the direct chemical reduction of Au3+ with NaBH4 in the presence of PVP-I2 complex. The successful synthesis of PVP-I2@AuNPs was confirmed with scanning electron microscopy (SEM) and UV-vis spectrophotometry. Chemiluminescence (CL) intensity of luminol was greatly enhanced, upon its chemical reaction with chemisorbed I2 on AuNPs surfaces owing to the excellent catalytic activity of AuNPs. The PVP-I2@AuNPs/luminol CL sensing system was successfully applied for determination of Hg2+ ions and the results displayed linearity in a wide range from 0.5 to 2000 nM and an ultrasensitive response to 1.0 nM Hg2+. The detection limit of Hg2+ ions was 0.1 nM, which was 100 times lower than the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. This ultrasensitive luminogenic system for Hg2+ detection also exhibited excellent selectivity among 13 types of metals, suggesting that the luminol/PVP-I2@AuNPs system is a promising sensor for real-time detection of Hg2+. Graphical abstract.

Novel Synthesis of Thiolated Gold Nanoclusters Induced by Lanthanides for Ultrasensitive and Luminescent Detection of the Potential Anthrax Spores' Biomarker.

In this study, we reported a facile, one-pot, and "green" synthesis of glutathione-protected gold nanoclusters (GSH@AuNCs) initiated by samarium (Sm3+) lanthanides for the first time. Sm3+ lanthanides more efficiently induced the formation of GSH@AuNCs with significantly enhanced luminescence than other lanthanides or heavy metal ions (Cd2+, Pb2+) did. Using this strategy, a detection for Sm3+ was made with a linearity range of (10.0-100.0 µM) and a limit of detection (LOD) of 0.5 µM. The Sm3+-based GSH@AuNCs were characterized by eco-friendliness, photostability, and low-cost synthesis with low biological toxicity and had great potential in the application for biosensing and bioimaging. They were successfully employed in the detection of dipicolinic acid (DPA), a well-reported biomarker for sensing potential infection by strongly hazardous anthrax spores. A good linear response was obtained for DPA detection ranging from 1.0 to 120.0 µM with a low LOD of 0.1 µM, which was much lower (600 times) than the infectious dosage of anthrax spores (6 × 10-5 M). The detection was due to the strong binding affinity and strong chelation capability of DPA to Sm3+ lanthanides, which caused the dissociation of the aggregates with an obvious decrease or even a turning-off effect of their luminescence.

Multiple Anti-Counterfeiting Guarantees from a Simple Tetraphenylethylene Derivative - High-Contrasted and Multi-State Mechanochromism and Photochromism.

Herein the novel tetraphenylethylene (TPE) derivative 1 was designed with an integration of aggregation-induced emission (AIE), multi-state mechanochromism and self-recovery photochromism. The molecule was susceptible to grinding, heating and vapor fuming and showed corresponding transition of its emission colors. The heated powder or single crystal of 1 exhibited reversible photochromism. After a short period of UV irradiation, it showed a bright red color, but recovered to its original white appearance within 1 min. The photochromism is due to the formation of photocyclization intermediates upon UV irradiation, while the eversible mechanochromism is attributed to the weak molecular interactions derived from head-to-tail stacking of the molecules. This reversible multi-state, high-contrasted and rapid responsive mechanochromic and photochromic property cooperatively provide double enhancement of a multimode guarantee in advanced anti-counterfeiting.

Real-Time Monitoring of Hierarchical Self-Assembly and Induction of Circularly Polarized Luminescence from Achiral Luminogens.

Constructing artificial helical structures through hierarchical self-assembly and exploring the underlying mechanism are important, and they help gain insight from the structures, processes, and functions from the biological helices and facilitate the development of material science and nanotechnology. Herein, the two enantiomers of chiral Au(I) complexes ( S)-1 and ( R)-1 were synthesized, and they exhibited impressive spontaneous hierarchical self-assembly transitions from vesicles to helical fibers. An impressive chirality inversion and amplification was accompanied by the assembly transition, as elucidated by the results of in situ and time-dependent circular dichroism spectroscopy and scanning electron microscope imaging. The two enantiomers could serve as ideal chiral templates to co-assemble with other achiral luminogens to efficiently induce the resulting co-assembly systems to show circularly polarized luminescence (CPL). Our work has provided a simple but efficient way to explore the sophisticated self-assembly process and presented a facile and effective strategy to fabricate architectures with CPL properties.

Solvent and Surface/Interface Effect on the Hierarchical Assemblies of Chiral Aggregation-Induced Emitting Molecules.

The core of aggregation-induced emitting (AIE) molecules was their aggregation behavior. It was, in essence, a self-assembly process driven by noncovalent interactions, which were governed not only by the chemical structures of the molecules but also by the conditions where the self-assemblies were formed. The self-assemblies of two AIE molecules, tetraphenylethene (TPE) derivatives carrying one valine attachment (TPE-Val) and two valine attachments (TPE-2Val), were studied. Both kinds of molecules self-assembled into supramolecular helical fibers with different handedness upon the addition of poor solvent to their solution. However, when deposited on air/water interface, both kinds of molecules formed aligned elementary helical fibers instead of supramolecular fibers. The lateral solvophobic effect exerted by water molecules caused a shift of the original noncovalent balance between molecules and solvent; thus, the supramolecular helical assemblies were unraveled into aligned helical elementary fibers. Similar elementary assemblies were formed on the surface of 3-aminopropyl triethoxysilane-modified mica, confirming the lateral solvophobic effect on the self-assemblies of the molecules.

Molecular Design, Circularly Polarized Luminescence, and Helical Self-Assembly of Chiral Aggregation-Induced Emission Molecules.

Aggregation-induced emission luminogens (AIEgens) are a new class of luminophors, which are non-emissive in solution, but emit intensively upon aggregation. By properly designing the chemical structures of the AIEgens, their aggregation process can be tuned towards a desired direction to give diverse novel luminescent architectures of micelles, rods, and helical fibers. AIEgens represent a kind of promising building block for the fabrication of luminescent micro/nanostructures with controllable morphologies. In this review, we describe our recent work in this research area, focusing on the molecular design, circularly polarized luminescence properties, and helical self-assembly behavior of AIEgens.

Ovarian Fibrosis: A Phenomenon of Concern / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>Ovarian fibrosis is characterized by excessive proliferation of ovarian fibroblasts and deposition of extracellular matrix (ECM) and it is one of the principal reasons for ovarian dysfunction. This review aimed to investigate the pathogenetic mechanism of ovarian fibrosis and to clarify the relationship between ovarian diseases and fibrosis.</p><p><b>DATA SOURCES</b>We searched PubMed for English language articles published up to November 2016. The search terms included ovarian fibrosis OR fibrosis, ovarian chocolate cyst OR ovarian endometrioma, polycystic ovarian syndrome (PCOS), premature ovarian failure, ECM, matrix metalloproteinases (MMPs), tissue inhibitors of matrix metalloproteinases (TIMPs), transforming growth factor-beta 1 (TGF-β1), connective tissue growth factor (CTGF), peroxisome proliferator-activated receptor gamma (PPAR-γ), vascular endothelial growth factor (VEGF), endothelin-1 (ET-1), and combinations of these terms.</p><p><b>STUDY SELECTION</b>Articles were obtained and reviewed to analyze the pathogenic mechanism of ovarian fibrosis and related ovarian diseases.</p><p><b>RESULTS</b>Many cytokines, such as MMPs, TIMPs, TGF-β1, CTGF, PPAR-γ, VEGF, and ET-1, are involved in ovarian fibrogenesis. Ovarian fibrogenesis is associated with various ovarian diseases, including ovarian chocolate cyst, PCOS, and premature ovarian failure. One finding of particular interest is that fibrogenesis in peripheral tissues around an ovarian chocolate cyst commonly causes ovarian function diminution, and therefore, this medical problem should arouse widespread concern in clinicians worldwide.</p><p><b>CONCLUSIONS</b>Patients with ovarian fibrosis are susceptible to infertility and tend to have decreased responses to assisted fertility treatment. Thus, protection of ovarian function should be a priority for women who wish to reproduce when making therapeutic decisions about ovarian fibrosis-related diseases.</p>

Click Synthesis, Aggregation-Induced Emission and Chirality, Circularly Polarized Luminescence, and Helical Self-Assembly of a Leucine-Containing Silole.

By introducing chiral leucine pendants to silole scaffold, leucine-containing silole (Silole-Leu) is synthesized and it is endowed with not only aggregation-induced emission and circular dichroism, but excellent chiral polarized luminescence as well. Silole-Leu also has the capacity to self-assemble into nano/micro helical luminescent fibers and the dimension of the fibers can be tuned by adjusting the ratio and volume of mixed solvents for evaporation as revealed by atomic force microscope, scanning electron microscope, and fluorescence microscope. The characteristic helicity of microfibers is directly visualized for the first time by using fluorescence microscope.

Synthesis, optical properties, and helical self-assembly of a bivaline-containing tetraphenylethene.

A chiral tetraphenylethene derivative with two valine-containing attachments (TPE-DVAL), was synthesized by Cu(I)-catalyzed azide-alkyne "click" reaction. The optical properties and self-assembling behaviours of TPE-DVAL were investigated. The molecule is non-emissive and circular dichroism (CD)-silent in solution, but shows strong fluorescence and Cotton effects in the aggregation state, demonstrating aggregation-induced emission (AIE) and CD (AICD) characteristics. TPE-DVAL exhibits good circularly polarized luminescence (CPL) when depositing on the surface of quartz to allow the evaporation of its 1,2-dichloroethane solution. SEM and TEM images of the molecule show that the molecule readily self-assembles into right-handed helical nanofibers upon the evaporation of its solvent of DCE. The molecular alignments and interactions in assembling process are further explored through XRD analysis and computational simulation. The driving forces for the formation of the helical fibers were from the cooperative effects of intermolecular hydrogen bonding, π-π interactions and steric effect.

Direct visualization of the formation of RecA/dsDNA complexes at the single-molecule level.

The assembly of RecA on linear dsDNA with ATPγS in the reaction was elucidated using atomic force microscopy (AFM) on a single-molecule level. It was found that assembly generally (∼95%) proceeded from a single nucleation site that started from one end of the DNA strand. About 5% of the complexes were formed starting either from both ends or from the middle of dsDNA strand. In all these cases, the RecA coating was contiguous for each region suggesting the binding of RecA to DNA is cooperative. The AFM observation provides direct experimental evidence to show how RecA binds to linear dsDNA in the presence of ATPγS.

Tunable helical assemblies of L-alanine methyl ester-containing polyphenylacetylene.

The self-assemblying behaviors of L-alanine methyl ester-containing polyphenylacetylene (PPA-Ala, in Chart 1 ) were investigated upon the evaporation of its solvent on mica and on air/water interfaces. The introduction of chiral amino acid attachments to the polyphenylacetylene backbone induced a helical conformation of the backbone, which was stabilized by various noncovalent interactions, especially hydrophobic effect and hydrogen bonds. The helicity of the polymer was further amplified in its higher-order self-assemblies as the formation of helical fibers on the surface of mica upon natural evaporation of its THF solution. By LB technique, the polymer chains were guided to form ordered parallel ridges and highly aligned, with their helical conformation still remaining. The reorganization of the chiral polymer chains on air/water interface was associated with the additional hydrophobic effect of PPA-Ala on an air/water interface. The polymer backbones had to adopt different arrangements to minimize their contact with water, and this adjustment led to the formation of aligned polymer ridges under proper surface pressure.

Direct evidence of the role of ATPγS in the binding of single-stranded binding protein (Escherichia coli) and RecA to single-stranded DNA.

To gain insight into the influence of ATPγS on the competitive binding of RecA and single-stranded binding protein (SSB) on single-stranded DNA (ssDNA), AFM imaging was used to examine the three-dimensional structures of the different complexes formed by the binding of the two proteins on ssDNA in the presence and absence of ATPγS. In the presence of ATPγS, RecA attaches to ssDNA, displacing SSB, to form continuous binding regions that caused considerable elongation of the strand. When ATPγS is absent, RecA could not compete with SSB and only binds at a few sites that correspond to the vacancy in ssDNA left when SSB unbinds. These results provide direct evidence that, while SSB binding affinity to DNA is substantially higher than that of RecA, the presence of ATPγS is sufficient to alter the events and enable RecA coating of DNA.