Supramolecular Metal Halide Complexes for High-Temperature Nonlinear Optical Switches.

Nonlinear optical (NLO) switching materials, which exhibit reversible intensity modulation in response to thermal stimuli, have found extensive applications across diverse fields including sensing, photoelectronics, and photonic applications. While significant progress has been made in solid-state NLO switching materials, these materials typically showcase their highest NLO performance near room temperature. However, this performance drastically deteriorates upon heating, primarily due to the phase transition undergone by the materials from noncentrosymmetric to centrosymmetric phase. Here, we introduce a new class of NLO switching materials, solid-state supramolecular compounds 18-Crown-6 ether@Cu2Cl4·4H2O (1·4H2O), exhibiting reversible and stable NLO switching when subjected to near-infrared (NIR) photoexcitation and/or thermal stimuli. The reversible crystal structure in response to external stimuli is attributed to the presence of a weakly coordinated bridging water molecule facilitated by hydrogen bonding/chelation interactions between the metal halide and crown-ether supramolecules. We observed an exceptionally high second-harmonic generation (SHG) signal under continuous photoexcitation, even at temperatures exceeding 110 °C. In addition, the bridging water molecules within the complex can be released and recaptured in a fully reversible manner, all without requiring excessive energy input. This feature allows for precise control of SHG signal activation and deactivation through structural transformations, resulting in a high-contrast off/on ratio, reaching values in the million-fold range.

Photoinduced Dynamic Ligation in Metal-Organic Frameworks.

Metal organic frameworks (MOFs), a class of porous crystalline materials consisting of metal-based nodes and organic linkers, have emerged as a promising platform for photocatalysis due to their ultrahigh functional surface area, customizable topologies, and tunable energetics. While interesting photochemistry has been reported, the related photoinduced structural dynamics of MOFs remains unclear. The consensus is that the coordination bonds between MOF nodes and linkers are considered static during photoexcitation, while the open-metal sites on the nodes are taken as the key active sites for catalysis. In this work, through a complementary time-resolved visible and infrared (IR) spectroscopic investigation, along with computational studies, we report for the first time light-induced structural bond dissociation (COO-M) and reformation in an iron-oxo framework, MIL-101(Fe). The probed excited state displayed ligand-to-metal charge transfer (LMCT) characteristics and exhibited a ca. 30 µs lifetime. The incredibly long excited-state lifetime led us to probe potential structural rearrangements that facilitated charge separation in MIL-101(Fe). By probing the vibrational fingerprints of the carboxylate linker upon LMCT photoexcitation, we observed the reversible transition of the carboxylate-Fe bond from a bidentate bridging mode to a monodentate mode, indicating the partial dissociation of the carboxylate ligand. Importantly, the bidentate configuration is recovered on the same time scale of the excited state lifetimes as probed via visible transient absorption spectroscopy. The elucidated photoinduced configurational dynamics provides a foundation for an in-depth understanding of MOF-based photocatalytic mechanisms.

Pyridine Functionalized Carbon Nanotubes: Unveiling the Role of External Pyridinic Nitrogen Sites for Oxygen Reduction Reaction.

Pyridinic nitrogen has been recognized as the primary active site in nitrogen-doped carbon electrocatalysts for the oxygen reduction reaction (ORR), which is a critical process in many renewable energy devices. However, the preparation of nitrogen-doped carbon catalysts comprised of exclusively pyridinic nitrogen remains challenging, as well as understanding the precise ORR mechanisms on the catalyst. Herein, a novel process is developed using pyridyne reactive intermediates to functionalize carbon nanotubes (CNTs) exclusively with pyridine rings for ORR electrocatalysis. The relationship between the structure and ORR performance of the prepared materials is studied in combination with density functional theory calculations to probe the ORR mechanism on the catalyst. Pyridinic nitrogen can contribute to a more efficient 4-electron reaction pathway, while high level of pyridyne functionalization result in negative structural effects, such as poor electrical conductivity, reduced surface area, and small pore diameters, that suppressed the ORR performance. This study provides insights into pyridine-doped CNTs-functionalized for the first time via pyridyne intermediates-as applied in the ORR and is expected to serve as valuable inspiration in designing high-performance electrocatalysts for energy applications.

Improved FCOS for Detecting Breast Cancers.

PURPOSE: Breast cancer ranks first among cancers affecting women's health. Our goal is to develop a fast, high-precision, and fully automated breast cancer detection algorithm to improve the early detection rate of breast cancer. METHODS: We compare different object detection algorithms, including anchor-based and anchor-free object detection algorithms for detecting breast lesions. Finally, we find that the fully convolutional onestage object detection (FCOS) showed the best performance in the detection of breast lesions, which is an anchor-free algorithm. 1) Considering that the detection of breast lesions requires the context information of the ultrasound images, we introduce the non-local technique, which models long-range dependency between pixels to the FCOS algorithm, providing the global context information for the detection of the breast lesions. 2) The variety of shapes and sizes of breast lesions makes detection difficult. We propose a new deformable spatial attention (DSA) module and add it to the FCOS algorithm. RESULTS: The detection performance of the original FCOS is that the average precision (AP) for benign lesions is 0.818, and for malignant lesions is 0.888. The FCOS with a non-local module improves the performance of the breast detection; the AP of benign lesions was 0.819, and that of malignant lesions was 0.894. Combining the DSA module with the FCOS improves the performance of breast detection; the AP for benign lesions and malignant lesions is 0.840 and 0.899, respectively. CONCLUSION: We propose two methods to improve the FCOS algorithm from different perspectives to improve its performance in detecting breast lesions. We find that FCOS combined with DSA is beneficial in improving the localization and classification of breast tumors and can provide auxiliary diagnostic advice for ultrasound physicians, which has a certain clinical application value.

Feiyanning Formula Induces Apoptosis of Lung Adenocarcinoma Cells by Activating the Mitochondrial Pathway.

Feiyanning formula (FYN) is a traditional Chinese medicine (TCM) prescription used for more than 20 years in the treatment of lung cancer. FYN is composed of Astragalus membranaceus, Polygonatum sibiricum, Atractylodes macrocephala, Cornus officinalis, Paris polyphylla, and Polistes olivaceous, etc. All of them have been proved to have anti-tumor effect. In this study, we used the TCM network pharmacological analysis to perform the collection of compound and disease target, the prediction of compound target and biological signal and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. It was found that the activation of mitochondrial pathway might be the molecular mechanism of the anti-lung cancer effect of FYN. The experimental results showed that FYN had an inhibitory effect on the growth of lung cancer cells in a dose-dependent and time-dependent manner. Moreover, FYN induced G2/M cell cycle arrest and apoptotic cell death as early as 6 h after treatment. In addition, FYN significantly induced mitochondrial membrane depolarization and increased calreticulin expression. Metabolomics analysis showed the increase of ATP utilization (assessed by a significant increase of the AMP/ATP and ADP/ATP ratio, necessary for apoptosis induction) and decrease of polyamines (that reflects growth potential). Taken together, our study suggested that FYN induced apoptosis of lung adenocarcinoma cells by promoting metabolism and changing the mitochondrial membrane potential, further supporting the validity of network pharmacological prediction.

DNA-driven dynamic assembly of MoS2 nanosheets.

Controlling the assembly of molybdenum disulfide (MoS2) layers into static and dynamic superstructures can impact on their use in optoelectronics, energy, and drug delivery. Toward this goal, we present a strategy to drive the assembly of MoS2 layers via the hybridization of complementary DNA linkers. By functionalizing the MoS2 surface with thiolated DNA, MoS2 nanosheets were assembled into mulitlayered superstructures, and the complementary DNA strands were used as linkers. A disassembly process was triggered by the formation of an intramolecular i-motif structure at a cystosine-rich sequence in the DNA linker at acidic pH values. We tested the versatility of our approach by driving the disassembly of the MoS2 superstructures through a different DNA-based mechanism, namely strand displacement. This study demonstrates how DNA can be employed to drive the static and dynamic assembly of MoS2 nanosheets in aqueous solution.

A One-Step Chemical Strategy for the Formation of Carbon Nanotube Junctions in Aqueous Solution: Reaction of DNA-Wrapped Carbon Nanotubes with Diazonium Salts.

A single-step chemical strategy allows the formation of single-walled carbon nanotube (SWCNT) molecular junctions in aqueous solution. SWCNTs were first wrapped with DNA to be water soluble and solution processable. Diazonium salts, which have been shown to react spontaneously with carbon nanotubes in water at room temperature, were then employed to covalently link SWCNT segments. The DNA wrapping of the nanotubes acted as a protective layer that limits the functionalization predominantly to the nanotube terminal ends, therefore allowing the assembly of linear SWCNT junctions. Upon increasing the concentration of the linker, we observed first the formation of side-to-end junctions, and eventually the assembly, through side-to-side interactions, of SWCNTs into bundles. This approach demonstrates the possibility of tuning the formation of linear and branched carbon nanotube junctions that in turn is of importance for the sustainable fabrication of solution-processable CNT-based nanoscale systems and devices.

Formation of Cyclopenta[c]pyridine Derivatives from 2,5-Disubstituted Pyrroles and 1,4-Dibromo-1,3-butadienes via Pyrrole-Ring One-Carbon Expansion.

Reactions between 1,4-dibromo-1,3-butadienes and 2,5-disubstituted pyrroles afforded cyclopenta[c]pyridine derivatives in high yield, catalyzed by palladium and a cyclopentadiene-phosphine ligand (L1). Insertion of one terminal carbon of the butadienyl skeleton into one C═C double bond in the pyrrole ring resulted in ring expansion, along with a 1,2-shift of an alkyl or an aryl substituent on the butadienes.

Cyclopentadiene-Phosphine/Palladium-Catalyzed Synthesis of Indolizines from Pyrrole and 1,4-Dibromo-1,3-butadienes.

The cyclopentadiene-phosphine ligand (L1) and palladium were found to be an efficient catalyst system to activate the α-C(sp(2))-H bond of pyrrole and indole derivatives. Various alkenyl or aryl dibromides could be used to react with pyrrole and indole derivatives to afford multisubstituted indolizines in high yields.